2 /* pngread.c - read a PNG file
4 * Copyright (c) 2018-2024 Cosmin Truta
5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6 * Copyright (c) 1996-1997 Andreas Dilger
7 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
13 * This file contains routines that an application calls directly to
14 * read a PNG file or stream.
18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
22 #ifdef PNG_READ_SUPPORTED
24 /* Create a PNG structure for reading, and allocate any memory needed. */
25 PNG_FUNCTION(png_structp
,PNGAPI
26 png_create_read_struct
,(png_const_charp user_png_ver
, png_voidp error_ptr
,
27 png_error_ptr error_fn
, png_error_ptr warn_fn
),PNG_ALLOCATED
)
29 #ifndef PNG_USER_MEM_SUPPORTED
30 png_structp png_ptr
= png_create_png_struct(user_png_ver
, error_ptr
,
31 error_fn
, warn_fn
, NULL
, NULL
, NULL
);
33 return png_create_read_struct_2(user_png_ver
, error_ptr
, error_fn
,
34 warn_fn
, NULL
, NULL
, NULL
);
37 /* Alternate create PNG structure for reading, and allocate any memory
40 PNG_FUNCTION(png_structp
,PNGAPI
41 png_create_read_struct_2
,(png_const_charp user_png_ver
, png_voidp error_ptr
,
42 png_error_ptr error_fn
, png_error_ptr warn_fn
, png_voidp mem_ptr
,
43 png_malloc_ptr malloc_fn
, png_free_ptr free_fn
),PNG_ALLOCATED
)
45 png_structp png_ptr
= png_create_png_struct(user_png_ver
, error_ptr
,
46 error_fn
, warn_fn
, mem_ptr
, malloc_fn
, free_fn
);
51 png_ptr
->mode
= PNG_IS_READ_STRUCT
;
53 /* Added in libpng-1.6.0; this can be used to detect a read structure if
54 * required (it will be zero in a write structure.)
56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
57 png_ptr
->IDAT_read_size
= PNG_IDAT_READ_SIZE
;
60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
61 png_ptr
->flags
|= PNG_FLAG_BENIGN_ERRORS_WARN
;
63 /* In stable builds only warn if an application error can be completely
66 # if PNG_RELEASE_BUILD
67 png_ptr
->flags
|= PNG_FLAG_APP_WARNINGS_WARN
;
71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
72 * do it itself) avoiding setting the default function if it is not
75 png_set_read_fn(png_ptr
, NULL
, NULL
);
82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83 /* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
92 png_read_info(png_structrp png_ptr
, png_inforp info_ptr
)
94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
98 png_debug(1, "in png_read_info");
100 if (png_ptr
== NULL
|| info_ptr
== NULL
)
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr
, info_ptr
);
108 png_uint_32 length
= png_read_chunk_header(png_ptr
);
109 png_uint_32 chunk_name
= png_ptr
->chunk_name
;
111 /* IDAT logic needs to happen here to simplify getting the two flags
114 if (chunk_name
== png_IDAT
)
116 if ((png_ptr
->mode
& PNG_HAVE_IHDR
) == 0)
117 png_chunk_error(png_ptr
, "Missing IHDR before IDAT");
119 else if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
&&
120 (png_ptr
->mode
& PNG_HAVE_PLTE
) == 0)
121 png_chunk_error(png_ptr
, "Missing PLTE before IDAT");
123 else if ((png_ptr
->mode
& PNG_AFTER_IDAT
) != 0)
124 png_chunk_benign_error(png_ptr
, "Too many IDATs found");
126 png_ptr
->mode
|= PNG_HAVE_IDAT
;
129 else if ((png_ptr
->mode
& PNG_HAVE_IDAT
) != 0)
131 png_ptr
->mode
|= PNG_HAVE_CHUNK_AFTER_IDAT
;
132 png_ptr
->mode
|= PNG_AFTER_IDAT
;
135 /* This should be a binary subdivision search or a hash for
136 * matching the chunk name rather than a linear search.
138 if (chunk_name
== png_IHDR
)
139 png_handle_IHDR(png_ptr
, info_ptr
, length
);
141 else if (chunk_name
== png_IEND
)
142 png_handle_IEND(png_ptr
, info_ptr
, length
);
144 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
145 else if ((keep
= png_chunk_unknown_handling(png_ptr
, chunk_name
)) != 0)
147 png_handle_unknown(png_ptr
, info_ptr
, length
, keep
);
149 if (chunk_name
== png_PLTE
)
150 png_ptr
->mode
|= PNG_HAVE_PLTE
;
152 else if (chunk_name
== png_IDAT
)
154 png_ptr
->idat_size
= 0; /* It has been consumed */
159 else if (chunk_name
== png_PLTE
)
160 png_handle_PLTE(png_ptr
, info_ptr
, length
);
162 else if (chunk_name
== png_IDAT
)
164 png_ptr
->idat_size
= length
;
168 #ifdef PNG_READ_bKGD_SUPPORTED
169 else if (chunk_name
== png_bKGD
)
170 png_handle_bKGD(png_ptr
, info_ptr
, length
);
173 #ifdef PNG_READ_cHRM_SUPPORTED
174 else if (chunk_name
== png_cHRM
)
175 png_handle_cHRM(png_ptr
, info_ptr
, length
);
178 #ifdef PNG_READ_eXIf_SUPPORTED
179 else if (chunk_name
== png_eXIf
)
180 png_handle_eXIf(png_ptr
, info_ptr
, length
);
183 #ifdef PNG_READ_gAMA_SUPPORTED
184 else if (chunk_name
== png_gAMA
)
185 png_handle_gAMA(png_ptr
, info_ptr
, length
);
188 #ifdef PNG_READ_hIST_SUPPORTED
189 else if (chunk_name
== png_hIST
)
190 png_handle_hIST(png_ptr
, info_ptr
, length
);
193 #ifdef PNG_READ_oFFs_SUPPORTED
194 else if (chunk_name
== png_oFFs
)
195 png_handle_oFFs(png_ptr
, info_ptr
, length
);
198 #ifdef PNG_READ_pCAL_SUPPORTED
199 else if (chunk_name
== png_pCAL
)
200 png_handle_pCAL(png_ptr
, info_ptr
, length
);
203 #ifdef PNG_READ_sCAL_SUPPORTED
204 else if (chunk_name
== png_sCAL
)
205 png_handle_sCAL(png_ptr
, info_ptr
, length
);
208 #ifdef PNG_READ_pHYs_SUPPORTED
209 else if (chunk_name
== png_pHYs
)
210 png_handle_pHYs(png_ptr
, info_ptr
, length
);
213 #ifdef PNG_READ_sBIT_SUPPORTED
214 else if (chunk_name
== png_sBIT
)
215 png_handle_sBIT(png_ptr
, info_ptr
, length
);
218 #ifdef PNG_READ_sRGB_SUPPORTED
219 else if (chunk_name
== png_sRGB
)
220 png_handle_sRGB(png_ptr
, info_ptr
, length
);
223 #ifdef PNG_READ_iCCP_SUPPORTED
224 else if (chunk_name
== png_iCCP
)
225 png_handle_iCCP(png_ptr
, info_ptr
, length
);
228 #ifdef PNG_READ_sPLT_SUPPORTED
229 else if (chunk_name
== png_sPLT
)
230 png_handle_sPLT(png_ptr
, info_ptr
, length
);
233 #ifdef PNG_READ_tEXt_SUPPORTED
234 else if (chunk_name
== png_tEXt
)
235 png_handle_tEXt(png_ptr
, info_ptr
, length
);
238 #ifdef PNG_READ_tIME_SUPPORTED
239 else if (chunk_name
== png_tIME
)
240 png_handle_tIME(png_ptr
, info_ptr
, length
);
243 #ifdef PNG_READ_tRNS_SUPPORTED
244 else if (chunk_name
== png_tRNS
)
245 png_handle_tRNS(png_ptr
, info_ptr
, length
);
248 #ifdef PNG_READ_zTXt_SUPPORTED
249 else if (chunk_name
== png_zTXt
)
250 png_handle_zTXt(png_ptr
, info_ptr
, length
);
253 #ifdef PNG_READ_iTXt_SUPPORTED
254 else if (chunk_name
== png_iTXt
)
255 png_handle_iTXt(png_ptr
, info_ptr
, length
);
259 png_handle_unknown(png_ptr
, info_ptr
, length
,
260 PNG_HANDLE_CHUNK_AS_DEFAULT
);
263 #endif /* SEQUENTIAL_READ */
265 /* Optional call to update the users info_ptr structure */
267 png_read_update_info(png_structrp png_ptr
, png_inforp info_ptr
)
269 png_debug(1, "in png_read_update_info");
273 if ((png_ptr
->flags
& PNG_FLAG_ROW_INIT
) == 0)
275 png_read_start_row(png_ptr
);
277 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
278 png_read_transform_info(png_ptr
, info_ptr
);
284 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
286 png_app_error(png_ptr
,
287 "png_read_update_info/png_start_read_image: duplicate call");
291 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
292 /* Initialize palette, background, etc, after transformations
293 * are set, but before any reading takes place. This allows
294 * the user to obtain a gamma-corrected palette, for example.
295 * If the user doesn't call this, we will do it ourselves.
298 png_start_read_image(png_structrp png_ptr
)
300 png_debug(1, "in png_start_read_image");
304 if ((png_ptr
->flags
& PNG_FLAG_ROW_INIT
) == 0)
305 png_read_start_row(png_ptr
);
307 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
309 png_app_error(png_ptr
,
310 "png_start_read_image/png_read_update_info: duplicate call");
313 #endif /* SEQUENTIAL_READ */
315 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
316 #ifdef PNG_MNG_FEATURES_SUPPORTED
317 /* Undoes intrapixel differencing,
318 * NOTE: this is apparently only supported in the 'sequential' reader.
321 png_do_read_intrapixel(png_row_infop row_info
, png_bytep row
)
323 png_debug(1, "in png_do_read_intrapixel");
326 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) != 0)
329 png_uint_32 row_width
= row_info
->width
;
331 if (row_info
->bit_depth
== 8)
336 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
)
339 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)
345 for (i
= 0, rp
= row
; i
< row_width
; i
++, rp
+= bytes_per_pixel
)
347 *(rp
) = (png_byte
)((256 + *rp
+ *(rp
+ 1)) & 0xff);
348 *(rp
+2) = (png_byte
)((256 + *(rp
+ 2) + *(rp
+ 1)) & 0xff);
351 else if (row_info
->bit_depth
== 16)
356 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
)
359 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)
365 for (i
= 0, rp
= row
; i
< row_width
; i
++, rp
+= bytes_per_pixel
)
367 png_uint_32 s0
= (png_uint_32
)(*(rp
) << 8) | *(rp
+ 1);
368 png_uint_32 s1
= (png_uint_32
)(*(rp
+ 2) << 8) | *(rp
+ 3);
369 png_uint_32 s2
= (png_uint_32
)(*(rp
+ 4) << 8) | *(rp
+ 5);
370 png_uint_32 red
= (s0
+ s1
+ 65536) & 0xffff;
371 png_uint_32 blue
= (s2
+ s1
+ 65536) & 0xffff;
372 *(rp
) = (png_byte
)((red
>> 8) & 0xff);
373 *(rp
+ 1) = (png_byte
)(red
& 0xff);
374 *(rp
+ 4) = (png_byte
)((blue
>> 8) & 0xff);
375 *(rp
+ 5) = (png_byte
)(blue
& 0xff);
380 #endif /* MNG_FEATURES */
383 png_read_row(png_structrp png_ptr
, png_bytep row
, png_bytep dsp_row
)
385 png_row_info row_info
;
390 png_debug2(1, "in png_read_row (row %lu, pass %d)",
391 (unsigned long)png_ptr
->row_number
, png_ptr
->pass
);
393 /* png_read_start_row sets the information (in particular iwidth) for this
396 if ((png_ptr
->flags
& PNG_FLAG_ROW_INIT
) == 0)
397 png_read_start_row(png_ptr
);
399 /* 1.5.6: row_info moved out of png_struct to a local here. */
400 row_info
.width
= png_ptr
->iwidth
; /* NOTE: width of current interlaced row */
401 row_info
.color_type
= png_ptr
->color_type
;
402 row_info
.bit_depth
= png_ptr
->bit_depth
;
403 row_info
.channels
= png_ptr
->channels
;
404 row_info
.pixel_depth
= png_ptr
->pixel_depth
;
405 row_info
.rowbytes
= PNG_ROWBYTES(row_info
.pixel_depth
, row_info
.width
);
407 #ifdef PNG_WARNINGS_SUPPORTED
408 if (png_ptr
->row_number
== 0 && png_ptr
->pass
== 0)
410 /* Check for transforms that have been set but were defined out */
411 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
412 if ((png_ptr
->transformations
& PNG_INVERT_MONO
) != 0)
413 png_warning(png_ptr
, "PNG_READ_INVERT_SUPPORTED is not defined");
416 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
417 if ((png_ptr
->transformations
& PNG_FILLER
) != 0)
418 png_warning(png_ptr
, "PNG_READ_FILLER_SUPPORTED is not defined");
421 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
422 !defined(PNG_READ_PACKSWAP_SUPPORTED)
423 if ((png_ptr
->transformations
& PNG_PACKSWAP
) != 0)
424 png_warning(png_ptr
, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
427 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
428 if ((png_ptr
->transformations
& PNG_PACK
) != 0)
429 png_warning(png_ptr
, "PNG_READ_PACK_SUPPORTED is not defined");
432 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
433 if ((png_ptr
->transformations
& PNG_SHIFT
) != 0)
434 png_warning(png_ptr
, "PNG_READ_SHIFT_SUPPORTED is not defined");
437 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
438 if ((png_ptr
->transformations
& PNG_BGR
) != 0)
439 png_warning(png_ptr
, "PNG_READ_BGR_SUPPORTED is not defined");
442 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
443 if ((png_ptr
->transformations
& PNG_SWAP_BYTES
) != 0)
444 png_warning(png_ptr
, "PNG_READ_SWAP_SUPPORTED is not defined");
447 #endif /* WARNINGS */
449 #ifdef PNG_READ_INTERLACING_SUPPORTED
450 /* If interlaced and we do not need a new row, combine row and return.
451 * Notice that the pixels we have from previous rows have been transformed
452 * already; we can only combine like with like (transformed or
453 * untransformed) and, because of the libpng API for interlaced images, this
454 * means we must transform before de-interlacing.
456 if (png_ptr
->interlaced
!= 0 &&
457 (png_ptr
->transformations
& PNG_INTERLACE
) != 0)
459 switch (png_ptr
->pass
)
462 if (png_ptr
->row_number
& 0x07)
465 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
466 png_read_finish_row(png_ptr
);
472 if ((png_ptr
->row_number
& 0x07) || png_ptr
->width
< 5)
475 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
477 png_read_finish_row(png_ptr
);
483 if ((png_ptr
->row_number
& 0x07) != 4)
485 if (dsp_row
!= NULL
&& (png_ptr
->row_number
& 4))
486 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
488 png_read_finish_row(png_ptr
);
494 if ((png_ptr
->row_number
& 3) || png_ptr
->width
< 3)
497 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
499 png_read_finish_row(png_ptr
);
505 if ((png_ptr
->row_number
& 3) != 2)
507 if (dsp_row
!= NULL
&& (png_ptr
->row_number
& 2))
508 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
510 png_read_finish_row(png_ptr
);
516 if ((png_ptr
->row_number
& 1) || png_ptr
->width
< 2)
519 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
521 png_read_finish_row(png_ptr
);
528 if ((png_ptr
->row_number
& 1) == 0)
530 png_read_finish_row(png_ptr
);
538 if ((png_ptr
->mode
& PNG_HAVE_IDAT
) == 0)
539 png_error(png_ptr
, "Invalid attempt to read row data");
541 /* Fill the row with IDAT data: */
542 png_ptr
->row_buf
[0]=255; /* to force error if no data was found */
543 png_read_IDAT_data(png_ptr
, png_ptr
->row_buf
, row_info
.rowbytes
+ 1);
545 if (png_ptr
->row_buf
[0] > PNG_FILTER_VALUE_NONE
)
547 if (png_ptr
->row_buf
[0] < PNG_FILTER_VALUE_LAST
)
548 png_read_filter_row(png_ptr
, &row_info
, png_ptr
->row_buf
+ 1,
549 png_ptr
->prev_row
+ 1, png_ptr
->row_buf
[0]);
551 png_error(png_ptr
, "bad adaptive filter value");
554 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
555 * 1.5.6, while the buffer really is this big in current versions of libpng
556 * it may not be in the future, so this was changed just to copy the
559 memcpy(png_ptr
->prev_row
, png_ptr
->row_buf
, row_info
.rowbytes
+ 1);
561 #ifdef PNG_MNG_FEATURES_SUPPORTED
562 if ((png_ptr
->mng_features_permitted
& PNG_FLAG_MNG_FILTER_64
) != 0 &&
563 (png_ptr
->filter_type
== PNG_INTRAPIXEL_DIFFERENCING
))
565 /* Intrapixel differencing */
566 png_do_read_intrapixel(&row_info
, png_ptr
->row_buf
+ 1);
570 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
571 if (png_ptr
->transformations
572 # ifdef PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED
573 || png_ptr
->num_palette_max
>= 0
576 png_do_read_transformations(png_ptr
, &row_info
);
579 /* The transformed pixel depth should match the depth now in row_info. */
580 if (png_ptr
->transformed_pixel_depth
== 0)
582 png_ptr
->transformed_pixel_depth
= row_info
.pixel_depth
;
583 if (row_info
.pixel_depth
> png_ptr
->maximum_pixel_depth
)
584 png_error(png_ptr
, "sequential row overflow");
587 else if (png_ptr
->transformed_pixel_depth
!= row_info
.pixel_depth
)
588 png_error(png_ptr
, "internal sequential row size calculation error");
590 #ifdef PNG_READ_INTERLACING_SUPPORTED
591 /* Expand interlaced rows to full size */
592 if (png_ptr
->interlaced
!= 0 &&
593 (png_ptr
->transformations
& PNG_INTERLACE
) != 0)
595 if (png_ptr
->pass
< 6)
596 png_do_read_interlace(&row_info
, png_ptr
->row_buf
+ 1, png_ptr
->pass
,
597 png_ptr
->transformations
);
600 png_combine_row(png_ptr
, dsp_row
, 1/*display*/);
603 png_combine_row(png_ptr
, row
, 0/*row*/);
610 png_combine_row(png_ptr
, row
, -1/*ignored*/);
613 png_combine_row(png_ptr
, dsp_row
, -1/*ignored*/);
615 png_read_finish_row(png_ptr
);
617 if (png_ptr
->read_row_fn
!= NULL
)
618 (*(png_ptr
->read_row_fn
))(png_ptr
, png_ptr
->row_number
, png_ptr
->pass
);
621 #endif /* SEQUENTIAL_READ */
623 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
624 /* Read one or more rows of image data. If the image is interlaced,
625 * and png_set_interlace_handling() has been called, the rows need to
626 * contain the contents of the rows from the previous pass. If the
627 * image has alpha or transparency, and png_handle_alpha()[*] has been
628 * called, the rows contents must be initialized to the contents of the
631 * "row" holds the actual image, and pixels are placed in it
632 * as they arrive. If the image is displayed after each pass, it will
633 * appear to "sparkle" in. "display_row" can be used to display a
634 * "chunky" progressive image, with finer detail added as it becomes
635 * available. If you do not want this "chunky" display, you may pass
636 * NULL for display_row. If you do not want the sparkle display, and
637 * you have not called png_handle_alpha(), you may pass NULL for rows.
638 * If you have called png_handle_alpha(), and the image has either an
639 * alpha channel or a transparency chunk, you must provide a buffer for
640 * rows. In this case, you do not have to provide a display_row buffer
641 * also, but you may. If the image is not interlaced, or if you have
642 * not called png_set_interlace_handling(), the display_row buffer will
643 * be ignored, so pass NULL to it.
645 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
649 png_read_rows(png_structrp png_ptr
, png_bytepp row
,
650 png_bytepp display_row
, png_uint_32 num_rows
)
656 png_debug(1, "in png_read_rows");
663 if (rp
!= NULL
&& dp
!= NULL
)
664 for (i
= 0; i
< num_rows
; i
++)
666 png_bytep rptr
= *rp
++;
667 png_bytep dptr
= *dp
++;
669 png_read_row(png_ptr
, rptr
, dptr
);
673 for (i
= 0; i
< num_rows
; i
++)
675 png_bytep rptr
= *rp
;
676 png_read_row(png_ptr
, rptr
, NULL
);
681 for (i
= 0; i
< num_rows
; i
++)
683 png_bytep dptr
= *dp
;
684 png_read_row(png_ptr
, NULL
, dptr
);
688 #endif /* SEQUENTIAL_READ */
690 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
691 /* Read the entire image. If the image has an alpha channel or a tRNS
692 * chunk, and you have called png_handle_alpha()[*], you will need to
693 * initialize the image to the current image that PNG will be overlaying.
694 * We set the num_rows again here, in case it was incorrectly set in
695 * png_read_start_row() by a call to png_read_update_info() or
696 * png_start_read_image() if png_set_interlace_handling() wasn't called
697 * prior to either of these functions like it should have been. You can
698 * only call this function once. If you desire to have an image for
699 * each pass of a interlaced image, use png_read_rows() instead.
701 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
704 png_read_image(png_structrp png_ptr
, png_bytepp image
)
706 png_uint_32 i
, image_height
;
710 png_debug(1, "in png_read_image");
715 #ifdef PNG_READ_INTERLACING_SUPPORTED
716 if ((png_ptr
->flags
& PNG_FLAG_ROW_INIT
) == 0)
718 pass
= png_set_interlace_handling(png_ptr
);
719 /* And make sure transforms are initialized. */
720 png_start_read_image(png_ptr
);
724 if (png_ptr
->interlaced
!= 0 &&
725 (png_ptr
->transformations
& PNG_INTERLACE
) == 0)
727 /* Caller called png_start_read_image or png_read_update_info without
728 * first turning on the PNG_INTERLACE transform. We can fix this here,
729 * but the caller should do it!
731 png_warning(png_ptr
, "Interlace handling should be turned on when "
732 "using png_read_image");
733 /* Make sure this is set correctly */
734 png_ptr
->num_rows
= png_ptr
->height
;
737 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
738 * the above error case.
740 pass
= png_set_interlace_handling(png_ptr
);
743 if (png_ptr
->interlaced
)
745 "Cannot read interlaced image -- interlace handler disabled");
750 image_height
=png_ptr
->height
;
752 for (j
= 0; j
< pass
; j
++)
755 for (i
= 0; i
< image_height
; i
++)
757 png_read_row(png_ptr
, *rp
, NULL
);
762 #endif /* SEQUENTIAL_READ */
764 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
765 /* Read the end of the PNG file. Will not read past the end of the
766 * file, will verify the end is accurate, and will read any comments
767 * or time information at the end of the file, if info is not NULL.
770 png_read_end(png_structrp png_ptr
, png_inforp info_ptr
)
772 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
776 png_debug(1, "in png_read_end");
781 /* If png_read_end is called in the middle of reading the rows there may
782 * still be pending IDAT data and an owned zstream. Deal with this here.
784 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
785 if (png_chunk_unknown_handling(png_ptr
, png_IDAT
) == 0)
787 png_read_finish_IDAT(png_ptr
);
789 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
790 /* Report invalid palette index; added at libng-1.5.10 */
791 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
&&
792 png_ptr
->num_palette_max
>= png_ptr
->num_palette
)
793 png_benign_error(png_ptr
, "Read palette index exceeding num_palette");
798 png_uint_32 length
= png_read_chunk_header(png_ptr
);
799 png_uint_32 chunk_name
= png_ptr
->chunk_name
;
801 if (chunk_name
!= png_IDAT
)
802 png_ptr
->mode
|= PNG_HAVE_CHUNK_AFTER_IDAT
;
804 if (chunk_name
== png_IEND
)
805 png_handle_IEND(png_ptr
, info_ptr
, length
);
807 else if (chunk_name
== png_IHDR
)
808 png_handle_IHDR(png_ptr
, info_ptr
, length
);
810 else if (info_ptr
== NULL
)
811 png_crc_finish(png_ptr
, length
);
813 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
814 else if ((keep
= png_chunk_unknown_handling(png_ptr
, chunk_name
)) != 0)
816 if (chunk_name
== png_IDAT
)
818 if ((length
> 0 && !(png_ptr
->flags
& PNG_FLAG_ZSTREAM_ENDED
))
819 || (png_ptr
->mode
& PNG_HAVE_CHUNK_AFTER_IDAT
) != 0)
820 png_benign_error(png_ptr
, ".Too many IDATs found");
822 png_handle_unknown(png_ptr
, info_ptr
, length
, keep
);
823 if (chunk_name
== png_PLTE
)
824 png_ptr
->mode
|= PNG_HAVE_PLTE
;
828 else if (chunk_name
== png_IDAT
)
830 /* Zero length IDATs are legal after the last IDAT has been
831 * read, but not after other chunks have been read. 1.6 does not
832 * always read all the deflate data; specifically it cannot be relied
833 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
834 * chunks which are longer than zero as well:
836 if ((length
> 0 && !(png_ptr
->flags
& PNG_FLAG_ZSTREAM_ENDED
))
837 || (png_ptr
->mode
& PNG_HAVE_CHUNK_AFTER_IDAT
) != 0)
838 png_benign_error(png_ptr
, "..Too many IDATs found");
840 png_crc_finish(png_ptr
, length
);
842 else if (chunk_name
== png_PLTE
)
843 png_handle_PLTE(png_ptr
, info_ptr
, length
);
845 #ifdef PNG_READ_bKGD_SUPPORTED
846 else if (chunk_name
== png_bKGD
)
847 png_handle_bKGD(png_ptr
, info_ptr
, length
);
850 #ifdef PNG_READ_cHRM_SUPPORTED
851 else if (chunk_name
== png_cHRM
)
852 png_handle_cHRM(png_ptr
, info_ptr
, length
);
855 #ifdef PNG_READ_eXIf_SUPPORTED
856 else if (chunk_name
== png_eXIf
)
857 png_handle_eXIf(png_ptr
, info_ptr
, length
);
860 #ifdef PNG_READ_gAMA_SUPPORTED
861 else if (chunk_name
== png_gAMA
)
862 png_handle_gAMA(png_ptr
, info_ptr
, length
);
865 #ifdef PNG_READ_hIST_SUPPORTED
866 else if (chunk_name
== png_hIST
)
867 png_handle_hIST(png_ptr
, info_ptr
, length
);
870 #ifdef PNG_READ_oFFs_SUPPORTED
871 else if (chunk_name
== png_oFFs
)
872 png_handle_oFFs(png_ptr
, info_ptr
, length
);
875 #ifdef PNG_READ_pCAL_SUPPORTED
876 else if (chunk_name
== png_pCAL
)
877 png_handle_pCAL(png_ptr
, info_ptr
, length
);
880 #ifdef PNG_READ_sCAL_SUPPORTED
881 else if (chunk_name
== png_sCAL
)
882 png_handle_sCAL(png_ptr
, info_ptr
, length
);
885 #ifdef PNG_READ_pHYs_SUPPORTED
886 else if (chunk_name
== png_pHYs
)
887 png_handle_pHYs(png_ptr
, info_ptr
, length
);
890 #ifdef PNG_READ_sBIT_SUPPORTED
891 else if (chunk_name
== png_sBIT
)
892 png_handle_sBIT(png_ptr
, info_ptr
, length
);
895 #ifdef PNG_READ_sRGB_SUPPORTED
896 else if (chunk_name
== png_sRGB
)
897 png_handle_sRGB(png_ptr
, info_ptr
, length
);
900 #ifdef PNG_READ_iCCP_SUPPORTED
901 else if (chunk_name
== png_iCCP
)
902 png_handle_iCCP(png_ptr
, info_ptr
, length
);
905 #ifdef PNG_READ_sPLT_SUPPORTED
906 else if (chunk_name
== png_sPLT
)
907 png_handle_sPLT(png_ptr
, info_ptr
, length
);
910 #ifdef PNG_READ_tEXt_SUPPORTED
911 else if (chunk_name
== png_tEXt
)
912 png_handle_tEXt(png_ptr
, info_ptr
, length
);
915 #ifdef PNG_READ_tIME_SUPPORTED
916 else if (chunk_name
== png_tIME
)
917 png_handle_tIME(png_ptr
, info_ptr
, length
);
920 #ifdef PNG_READ_tRNS_SUPPORTED
921 else if (chunk_name
== png_tRNS
)
922 png_handle_tRNS(png_ptr
, info_ptr
, length
);
925 #ifdef PNG_READ_zTXt_SUPPORTED
926 else if (chunk_name
== png_zTXt
)
927 png_handle_zTXt(png_ptr
, info_ptr
, length
);
930 #ifdef PNG_READ_iTXt_SUPPORTED
931 else if (chunk_name
== png_iTXt
)
932 png_handle_iTXt(png_ptr
, info_ptr
, length
);
936 png_handle_unknown(png_ptr
, info_ptr
, length
,
937 PNG_HANDLE_CHUNK_AS_DEFAULT
);
938 } while ((png_ptr
->mode
& PNG_HAVE_IEND
) == 0);
940 #endif /* SEQUENTIAL_READ */
942 /* Free all memory used in the read struct */
944 png_read_destroy(png_structrp png_ptr
)
946 png_debug(1, "in png_read_destroy");
948 #ifdef PNG_READ_GAMMA_SUPPORTED
949 png_destroy_gamma_table(png_ptr
);
952 png_free(png_ptr
, png_ptr
->big_row_buf
);
953 png_ptr
->big_row_buf
= NULL
;
954 png_free(png_ptr
, png_ptr
->big_prev_row
);
955 png_ptr
->big_prev_row
= NULL
;
956 png_free(png_ptr
, png_ptr
->read_buffer
);
957 png_ptr
->read_buffer
= NULL
;
959 #ifdef PNG_READ_QUANTIZE_SUPPORTED
960 png_free(png_ptr
, png_ptr
->palette_lookup
);
961 png_ptr
->palette_lookup
= NULL
;
962 png_free(png_ptr
, png_ptr
->quantize_index
);
963 png_ptr
->quantize_index
= NULL
;
966 if ((png_ptr
->free_me
& PNG_FREE_PLTE
) != 0)
968 png_zfree(png_ptr
, png_ptr
->palette
);
969 png_ptr
->palette
= NULL
;
971 png_ptr
->free_me
&= ~PNG_FREE_PLTE
;
973 #if defined(PNG_tRNS_SUPPORTED) || \
974 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
975 if ((png_ptr
->free_me
& PNG_FREE_TRNS
) != 0)
977 png_free(png_ptr
, png_ptr
->trans_alpha
);
978 png_ptr
->trans_alpha
= NULL
;
980 png_ptr
->free_me
&= ~PNG_FREE_TRNS
;
983 inflateEnd(&png_ptr
->zstream
);
985 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
986 png_free(png_ptr
, png_ptr
->save_buffer
);
987 png_ptr
->save_buffer
= NULL
;
990 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
991 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
992 png_free(png_ptr
, png_ptr
->unknown_chunk
.data
);
993 png_ptr
->unknown_chunk
.data
= NULL
;
996 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
997 png_free(png_ptr
, png_ptr
->chunk_list
);
998 png_ptr
->chunk_list
= NULL
;
1001 #if defined(PNG_READ_EXPAND_SUPPORTED) && \
1002 defined(PNG_ARM_NEON_IMPLEMENTATION)
1003 png_free(png_ptr
, png_ptr
->riffled_palette
);
1004 png_ptr
->riffled_palette
= NULL
;
1007 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1008 * callbacks are still set at this point. They are required to complete the
1009 * destruction of the png_struct itself.
1013 /* Free all memory used by the read */
1015 png_destroy_read_struct(png_structpp png_ptr_ptr
, png_infopp info_ptr_ptr
,
1016 png_infopp end_info_ptr_ptr
)
1018 png_structrp png_ptr
= NULL
;
1020 png_debug(1, "in png_destroy_read_struct");
1022 if (png_ptr_ptr
!= NULL
)
1023 png_ptr
= *png_ptr_ptr
;
1025 if (png_ptr
== NULL
)
1028 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1029 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1030 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1032 png_destroy_info_struct(png_ptr
, end_info_ptr_ptr
);
1033 png_destroy_info_struct(png_ptr
, info_ptr_ptr
);
1035 *png_ptr_ptr
= NULL
;
1036 png_read_destroy(png_ptr
);
1037 png_destroy_png_struct(png_ptr
);
1041 png_set_read_status_fn(png_structrp png_ptr
, png_read_status_ptr read_row_fn
)
1043 if (png_ptr
== NULL
)
1046 png_ptr
->read_row_fn
= read_row_fn
;
1050 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1051 #ifdef PNG_INFO_IMAGE_SUPPORTED
1053 png_read_png(png_structrp png_ptr
, png_inforp info_ptr
,
1054 int transforms
, voidp params
)
1056 png_debug(1, "in png_read_png");
1058 if (png_ptr
== NULL
|| info_ptr
== NULL
)
1061 /* png_read_info() gives us all of the information from the
1062 * PNG file before the first IDAT (image data chunk).
1064 png_read_info(png_ptr
, info_ptr
);
1065 if (info_ptr
->height
> PNG_UINT_32_MAX
/(sizeof (png_bytep
)))
1066 png_error(png_ptr
, "Image is too high to process with png_read_png()");
1068 /* -------------- image transformations start here ------------------- */
1069 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1070 * is not implemented. This will only happen in de-configured (non-default)
1071 * libpng builds. The results can be unexpected - png_read_png may return
1072 * short or mal-formed rows because the transform is skipped.
1075 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1077 if ((transforms
& PNG_TRANSFORM_SCALE_16
) != 0)
1078 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1079 * did in earlier versions, while "scale_16" is now more accurate.
1081 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1082 png_set_scale_16(png_ptr
);
1084 png_app_error(png_ptr
, "PNG_TRANSFORM_SCALE_16 not supported");
1087 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1088 * latter by doing SCALE first. This is ok and allows apps not to check for
1089 * which is supported to get the right answer.
1091 if ((transforms
& PNG_TRANSFORM_STRIP_16
) != 0)
1092 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1093 png_set_strip_16(png_ptr
);
1095 png_app_error(png_ptr
, "PNG_TRANSFORM_STRIP_16 not supported");
1098 /* Strip alpha bytes from the input data without combining with
1099 * the background (not recommended).
1101 if ((transforms
& PNG_TRANSFORM_STRIP_ALPHA
) != 0)
1102 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1103 png_set_strip_alpha(png_ptr
);
1105 png_app_error(png_ptr
, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1108 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1109 * byte into separate bytes (useful for paletted and grayscale images).
1111 if ((transforms
& PNG_TRANSFORM_PACKING
) != 0)
1112 #ifdef PNG_READ_PACK_SUPPORTED
1113 png_set_packing(png_ptr
);
1115 png_app_error(png_ptr
, "PNG_TRANSFORM_PACKING not supported");
1118 /* Change the order of packed pixels to least significant bit first
1119 * (not useful if you are using png_set_packing).
1121 if ((transforms
& PNG_TRANSFORM_PACKSWAP
) != 0)
1122 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1123 png_set_packswap(png_ptr
);
1125 png_app_error(png_ptr
, "PNG_TRANSFORM_PACKSWAP not supported");
1128 /* Expand paletted colors into true RGB triplets
1129 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1130 * Expand paletted or RGB images with transparency to full alpha
1131 * channels so the data will be available as RGBA quartets.
1133 if ((transforms
& PNG_TRANSFORM_EXPAND
) != 0)
1134 #ifdef PNG_READ_EXPAND_SUPPORTED
1135 png_set_expand(png_ptr
);
1137 png_app_error(png_ptr
, "PNG_TRANSFORM_EXPAND not supported");
1140 /* We don't handle background color or gamma transformation or quantizing.
1143 /* Invert monochrome files to have 0 as white and 1 as black
1145 if ((transforms
& PNG_TRANSFORM_INVERT_MONO
) != 0)
1146 #ifdef PNG_READ_INVERT_SUPPORTED
1147 png_set_invert_mono(png_ptr
);
1149 png_app_error(png_ptr
, "PNG_TRANSFORM_INVERT_MONO not supported");
1152 /* If you want to shift the pixel values from the range [0,255] or
1153 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1154 * colors were originally in:
1156 if ((transforms
& PNG_TRANSFORM_SHIFT
) != 0)
1157 #ifdef PNG_READ_SHIFT_SUPPORTED
1158 if ((info_ptr
->valid
& PNG_INFO_sBIT
) != 0)
1159 png_set_shift(png_ptr
, &info_ptr
->sig_bit
);
1161 png_app_error(png_ptr
, "PNG_TRANSFORM_SHIFT not supported");
1164 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1165 if ((transforms
& PNG_TRANSFORM_BGR
) != 0)
1166 #ifdef PNG_READ_BGR_SUPPORTED
1167 png_set_bgr(png_ptr
);
1169 png_app_error(png_ptr
, "PNG_TRANSFORM_BGR not supported");
1172 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1173 if ((transforms
& PNG_TRANSFORM_SWAP_ALPHA
) != 0)
1174 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1175 png_set_swap_alpha(png_ptr
);
1177 png_app_error(png_ptr
, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1180 /* Swap bytes of 16-bit files to least significant byte first */
1181 if ((transforms
& PNG_TRANSFORM_SWAP_ENDIAN
) != 0)
1182 #ifdef PNG_READ_SWAP_SUPPORTED
1183 png_set_swap(png_ptr
);
1185 png_app_error(png_ptr
, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1188 /* Added at libpng-1.2.41 */
1189 /* Invert the alpha channel from opacity to transparency */
1190 if ((transforms
& PNG_TRANSFORM_INVERT_ALPHA
) != 0)
1191 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1192 png_set_invert_alpha(png_ptr
);
1194 png_app_error(png_ptr
, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1197 /* Added at libpng-1.2.41 */
1198 /* Expand grayscale image to RGB */
1199 if ((transforms
& PNG_TRANSFORM_GRAY_TO_RGB
) != 0)
1200 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1201 png_set_gray_to_rgb(png_ptr
);
1203 png_app_error(png_ptr
, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1206 /* Added at libpng-1.5.4 */
1207 if ((transforms
& PNG_TRANSFORM_EXPAND_16
) != 0)
1208 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1209 png_set_expand_16(png_ptr
);
1211 png_app_error(png_ptr
, "PNG_TRANSFORM_EXPAND_16 not supported");
1214 /* We don't handle adding filler bytes */
1216 /* We use png_read_image and rely on that for interlace handling, but we also
1217 * call png_read_update_info therefore must turn on interlace handling now:
1219 (void)png_set_interlace_handling(png_ptr
);
1221 /* Optional call to gamma correct and add the background to the palette
1222 * and update info structure. REQUIRED if you are expecting libpng to
1223 * update the palette for you (i.e., you selected such a transform above).
1225 png_read_update_info(png_ptr
, info_ptr
);
1227 /* -------------- image transformations end here ------------------- */
1229 png_free_data(png_ptr
, info_ptr
, PNG_FREE_ROWS
, 0);
1230 if (info_ptr
->row_pointers
== NULL
)
1234 info_ptr
->row_pointers
= png_voidcast(png_bytepp
, png_malloc(png_ptr
,
1235 info_ptr
->height
* (sizeof (png_bytep
))));
1237 for (iptr
=0; iptr
<info_ptr
->height
; iptr
++)
1238 info_ptr
->row_pointers
[iptr
] = NULL
;
1240 info_ptr
->free_me
|= PNG_FREE_ROWS
;
1242 for (iptr
= 0; iptr
< info_ptr
->height
; iptr
++)
1243 info_ptr
->row_pointers
[iptr
] = png_voidcast(png_bytep
,
1244 png_malloc(png_ptr
, info_ptr
->rowbytes
));
1247 png_read_image(png_ptr
, info_ptr
->row_pointers
);
1248 info_ptr
->valid
|= PNG_INFO_IDAT
;
1250 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1251 png_read_end(png_ptr
, info_ptr
);
1255 #endif /* INFO_IMAGE */
1256 #endif /* SEQUENTIAL_READ */
1258 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1261 * This code currently relies on the sequential reader, though it could easily
1262 * be made to work with the progressive one.
1264 /* Arguments to png_image_finish_read: */
1266 /* Encoding of PNG data (used by the color-map code) */
1267 # define P_NOTSET 0 /* File encoding not yet known */
1268 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1269 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1270 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1271 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1273 /* Color-map processing: after libpng has run on the PNG image further
1274 * processing may be needed to convert the data to color-map indices.
1276 #define PNG_CMAP_NONE 0
1277 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1278 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1279 #define PNG_CMAP_RGB 3 /* Process RGB data */
1280 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1282 /* The following document where the background is for each processing case. */
1283 #define PNG_CMAP_NONE_BACKGROUND 256
1284 #define PNG_CMAP_GA_BACKGROUND 231
1285 #define PNG_CMAP_TRANS_BACKGROUND 254
1286 #define PNG_CMAP_RGB_BACKGROUND 256
1287 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1294 png_int_32 row_stride
;
1296 png_const_colorp background
;
1297 /* Local variables: */
1298 png_voidp local_row
;
1299 png_voidp first_row
;
1300 ptrdiff_t row_bytes
; /* step between rows */
1301 int file_encoding
; /* E_ values above */
1302 png_fixed_point gamma_to_linear
; /* For P_FILE, reciprocal of gamma */
1303 int colormap_processing
; /* PNG_CMAP_ values above */
1304 } png_image_read_control
;
1306 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1307 * called, so setting up the jmp_buf is not required. This means that anything
1308 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1309 * instead so that control is returned safely back to this routine.
1312 png_image_read_init(png_imagep image
)
1314 if (image
->opaque
== NULL
)
1316 png_structp png_ptr
= png_create_read_struct(PNG_LIBPNG_VER_STRING
, image
,
1317 png_safe_error
, png_safe_warning
);
1319 /* And set the rest of the structure to NULL to ensure that the various
1320 * fields are consistent.
1322 memset(image
, 0, (sizeof *image
));
1323 image
->version
= PNG_IMAGE_VERSION
;
1325 if (png_ptr
!= NULL
)
1327 png_infop info_ptr
= png_create_info_struct(png_ptr
);
1329 if (info_ptr
!= NULL
)
1331 png_controlp control
= png_voidcast(png_controlp
,
1332 png_malloc_warn(png_ptr
, (sizeof *control
)));
1334 if (control
!= NULL
)
1336 memset(control
, 0, (sizeof *control
));
1338 control
->png_ptr
= png_ptr
;
1339 control
->info_ptr
= info_ptr
;
1340 control
->for_write
= 0;
1342 image
->opaque
= control
;
1346 /* Error clean up */
1347 png_destroy_info_struct(png_ptr
, &info_ptr
);
1350 png_destroy_read_struct(&png_ptr
, NULL
, NULL
);
1353 return png_image_error(image
, "png_image_read: out of memory");
1356 return png_image_error(image
, "png_image_read: opaque pointer not NULL");
1359 /* Utility to find the base format of a PNG file from a png_struct. */
1361 png_image_format(png_structrp png_ptr
)
1363 png_uint_32 format
= 0;
1365 if ((png_ptr
->color_type
& PNG_COLOR_MASK_COLOR
) != 0)
1366 format
|= PNG_FORMAT_FLAG_COLOR
;
1368 if ((png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0)
1369 format
|= PNG_FORMAT_FLAG_ALPHA
;
1371 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1372 * sets the png_struct fields; that's all we are interested in here. The
1373 * precise interaction with an app call to png_set_tRNS and PNG file reading
1376 else if (png_ptr
->num_trans
> 0)
1377 format
|= PNG_FORMAT_FLAG_ALPHA
;
1379 if (png_ptr
->bit_depth
== 16)
1380 format
|= PNG_FORMAT_FLAG_LINEAR
;
1382 if ((png_ptr
->color_type
& PNG_COLOR_MASK_PALETTE
) != 0)
1383 format
|= PNG_FORMAT_FLAG_COLORMAP
;
1388 /* Is the given gamma significantly different from sRGB? The test is the same
1389 * one used in pngrtran.c when deciding whether to do gamma correction. The
1390 * arithmetic optimizes the division by using the fact that the inverse of the
1391 * file sRGB gamma is 2.2
1394 png_gamma_not_sRGB(png_fixed_point g
)
1398 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1402 return png_gamma_significant((g
* 11 + 2)/5 /* i.e. *2.2, rounded */);
1408 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1409 * header and fill in all the information. This is executed in a safe context,
1410 * unlike the init routine above.
1413 png_image_read_header(png_voidp argument
)
1415 png_imagep image
= png_voidcast(png_imagep
, argument
);
1416 png_structrp png_ptr
= image
->opaque
->png_ptr
;
1417 png_inforp info_ptr
= image
->opaque
->info_ptr
;
1419 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
1420 png_set_benign_errors(png_ptr
, 1/*warn*/);
1422 png_read_info(png_ptr
, info_ptr
);
1424 /* Do this the fast way; just read directly out of png_struct. */
1425 image
->width
= png_ptr
->width
;
1426 image
->height
= png_ptr
->height
;
1429 png_uint_32 format
= png_image_format(png_ptr
);
1431 image
->format
= format
;
1433 #ifdef PNG_COLORSPACE_SUPPORTED
1434 /* Does the colorspace match sRGB? If there is no color endpoint
1435 * (colorant) information assume yes, otherwise require the
1436 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1437 * colorspace has been determined to be invalid ignore it.
1439 if ((format
& PNG_FORMAT_FLAG_COLOR
) != 0 && ((png_ptr
->colorspace
.flags
1440 & (PNG_COLORSPACE_HAVE_ENDPOINTS
|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB
|
1441 PNG_COLORSPACE_INVALID
)) == PNG_COLORSPACE_HAVE_ENDPOINTS
))
1442 image
->flags
|= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB
;
1446 /* We need the maximum number of entries regardless of the format the
1447 * application sets here.
1450 png_uint_32 cmap_entries
;
1452 switch (png_ptr
->color_type
)
1454 case PNG_COLOR_TYPE_GRAY
:
1455 cmap_entries
= 1U << png_ptr
->bit_depth
;
1458 case PNG_COLOR_TYPE_PALETTE
:
1459 cmap_entries
= (png_uint_32
)png_ptr
->num_palette
;
1467 if (cmap_entries
> 256)
1470 image
->colormap_entries
= cmap_entries
;
1476 #ifdef PNG_STDIO_SUPPORTED
1478 png_image_begin_read_from_stdio(png_imagep image
, FILE* file
)
1480 if (image
!= NULL
&& image
->version
== PNG_IMAGE_VERSION
)
1484 if (png_image_read_init(image
) != 0)
1486 /* This is slightly evil, but png_init_io doesn't do anything other
1487 * than this and we haven't changed the standard IO functions so
1488 * this saves a 'safe' function.
1490 image
->opaque
->png_ptr
->io_ptr
= file
;
1491 return png_safe_execute(image
, png_image_read_header
, image
);
1496 return png_image_error(image
,
1497 "png_image_begin_read_from_stdio: invalid argument");
1500 else if (image
!= NULL
)
1501 return png_image_error(image
,
1502 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1508 png_image_begin_read_from_file(png_imagep image
, const char *file_name
)
1510 if (image
!= NULL
&& image
->version
== PNG_IMAGE_VERSION
)
1512 if (file_name
!= NULL
)
1514 FILE *fp
= fopen(file_name
, "rb");
1518 if (png_image_read_init(image
) != 0)
1520 image
->opaque
->png_ptr
->io_ptr
= fp
;
1521 image
->opaque
->owned_file
= 1;
1522 return png_safe_execute(image
, png_image_read_header
, image
);
1525 /* Clean up: just the opened file. */
1530 return png_image_error(image
, strerror(errno
));
1534 return png_image_error(image
,
1535 "png_image_begin_read_from_file: invalid argument");
1538 else if (image
!= NULL
)
1539 return png_image_error(image
,
1540 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1546 static void PNGCBAPI
1547 png_image_memory_read(png_structp png_ptr
, png_bytep out
, size_t need
)
1549 if (png_ptr
!= NULL
)
1551 png_imagep image
= png_voidcast(png_imagep
, png_ptr
->io_ptr
);
1554 png_controlp cp
= image
->opaque
;
1557 png_const_bytep memory
= cp
->memory
;
1558 size_t size
= cp
->size
;
1560 if (memory
!= NULL
&& size
>= need
)
1562 memcpy(out
, memory
, need
);
1563 cp
->memory
= memory
+ need
;
1564 cp
->size
= size
- need
;
1568 png_error(png_ptr
, "read beyond end of data");
1572 png_error(png_ptr
, "invalid memory read");
1576 int PNGAPI
png_image_begin_read_from_memory(png_imagep image
,
1577 png_const_voidp memory
, size_t size
)
1579 if (image
!= NULL
&& image
->version
== PNG_IMAGE_VERSION
)
1581 if (memory
!= NULL
&& size
> 0)
1583 if (png_image_read_init(image
) != 0)
1585 /* Now set the IO functions to read from the memory buffer and
1586 * store it into io_ptr. Again do this in-place to avoid calling a
1587 * libpng function that requires error handling.
1589 image
->opaque
->memory
= png_voidcast(png_const_bytep
, memory
);
1590 image
->opaque
->size
= size
;
1591 image
->opaque
->png_ptr
->io_ptr
= image
;
1592 image
->opaque
->png_ptr
->read_data_fn
= png_image_memory_read
;
1594 return png_safe_execute(image
, png_image_read_header
, image
);
1599 return png_image_error(image
,
1600 "png_image_begin_read_from_memory: invalid argument");
1603 else if (image
!= NULL
)
1604 return png_image_error(image
,
1605 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1610 /* Utility function to skip chunks that are not used by the simplified image
1611 * read functions and an appropriate macro to call it.
1613 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1615 png_image_skip_unused_chunks(png_structrp png_ptr
)
1617 /* Prepare the reader to ignore all recognized chunks whose data will not
1618 * be used, i.e., all chunks recognized by libpng except for those
1619 * involved in basic image reading:
1621 * IHDR, PLTE, IDAT, IEND
1623 * Or image data handling:
1625 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1627 * This provides a small performance improvement and eliminates any
1628 * potential vulnerability to security problems in the unused chunks.
1630 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1631 * too. This allows the simplified API to be compiled without iCCP support,
1632 * however if the support is there the chunk is still checked to detect
1633 * errors (which are unfortunately quite common.)
1636 static const png_byte chunks_to_process
[] = {
1637 98, 75, 71, 68, '\0', /* bKGD */
1638 99, 72, 82, 77, '\0', /* cHRM */
1639 103, 65, 77, 65, '\0', /* gAMA */
1640 # ifdef PNG_READ_iCCP_SUPPORTED
1641 105, 67, 67, 80, '\0', /* iCCP */
1643 115, 66, 73, 84, '\0', /* sBIT */
1644 115, 82, 71, 66, '\0', /* sRGB */
1647 /* Ignore unknown chunks and all other chunks except for the
1648 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1650 png_set_keep_unknown_chunks(png_ptr
, PNG_HANDLE_CHUNK_NEVER
,
1653 /* But do not ignore image data handling chunks */
1654 png_set_keep_unknown_chunks(png_ptr
, PNG_HANDLE_CHUNK_AS_DEFAULT
,
1655 chunks_to_process
, (int)/*SAFE*/(sizeof chunks_to_process
)/5);
1659 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1661 # define PNG_SKIP_CHUNKS(p) ((void)0)
1662 #endif /* HANDLE_AS_UNKNOWN */
1664 /* The following macro gives the exact rounded answer for all values in the
1665 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1666 * the correct numbers 0..5
1668 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1670 /* Utility functions to make particular color-maps */
1672 set_file_encoding(png_image_read_control
*display
)
1674 png_fixed_point g
= display
->image
->opaque
->png_ptr
->colorspace
.gamma
;
1675 if (png_gamma_significant(g
) != 0)
1677 if (png_gamma_not_sRGB(g
) != 0)
1679 display
->file_encoding
= P_FILE
;
1680 display
->gamma_to_linear
= png_reciprocal(g
);
1684 display
->file_encoding
= P_sRGB
;
1688 display
->file_encoding
= P_LINEAR8
;
1692 decode_gamma(png_image_read_control
*display
, png_uint_32 value
, int encoding
)
1694 if (encoding
== P_FILE
) /* double check */
1695 encoding
= display
->file_encoding
;
1697 if (encoding
== P_NOTSET
) /* must be the file encoding */
1699 set_file_encoding(display
);
1700 encoding
= display
->file_encoding
;
1706 value
= png_gamma_16bit_correct(value
*257, display
->gamma_to_linear
);
1710 value
= png_sRGB_table
[value
];
1722 png_error(display
->image
->opaque
->png_ptr
,
1723 "unexpected encoding (internal error)");
1731 png_colormap_compose(png_image_read_control
*display
,
1732 png_uint_32 foreground
, int foreground_encoding
, png_uint_32 alpha
,
1733 png_uint_32 background
, int encoding
)
1735 /* The file value is composed on the background, the background has the given
1736 * encoding and so does the result, the file is encoded with P_FILE and the
1737 * file and alpha are 8-bit values. The (output) encoding will always be
1738 * P_LINEAR or P_sRGB.
1740 png_uint_32 f
= decode_gamma(display
, foreground
, foreground_encoding
);
1741 png_uint_32 b
= decode_gamma(display
, background
, encoding
);
1743 /* The alpha is always an 8-bit value (it comes from the palette), the value
1744 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1746 f
= f
* alpha
+ b
* (255-alpha
);
1748 if (encoding
== P_LINEAR
)
1750 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1751 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1753 f
*= 257; /* Now scaled by 65535 */
1755 f
= (f
+32768) >> 16;
1759 f
= PNG_sRGB_FROM_LINEAR(f
);
1764 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1768 png_create_colormap_entry(png_image_read_control
*display
,
1769 png_uint_32 ip
, png_uint_32 red
, png_uint_32 green
, png_uint_32 blue
,
1770 png_uint_32 alpha
, int encoding
)
1772 png_imagep image
= display
->image
;
1773 int output_encoding
= (image
->format
& PNG_FORMAT_FLAG_LINEAR
) != 0 ?
1775 int convert_to_Y
= (image
->format
& PNG_FORMAT_FLAG_COLOR
) == 0 &&
1776 (red
!= green
|| green
!= blue
);
1779 png_error(image
->opaque
->png_ptr
, "color-map index out of range");
1781 /* Update the cache with whether the file gamma is significantly different
1784 if (encoding
== P_FILE
)
1786 if (display
->file_encoding
== P_NOTSET
)
1787 set_file_encoding(display
);
1789 /* Note that the cached value may be P_FILE too, but if it is then the
1790 * gamma_to_linear member has been set.
1792 encoding
= display
->file_encoding
;
1795 if (encoding
== P_FILE
)
1797 png_fixed_point g
= display
->gamma_to_linear
;
1799 red
= png_gamma_16bit_correct(red
*257, g
);
1800 green
= png_gamma_16bit_correct(green
*257, g
);
1801 blue
= png_gamma_16bit_correct(blue
*257, g
);
1803 if (convert_to_Y
!= 0 || output_encoding
== P_LINEAR
)
1806 encoding
= P_LINEAR
;
1811 red
= PNG_sRGB_FROM_LINEAR(red
* 255);
1812 green
= PNG_sRGB_FROM_LINEAR(green
* 255);
1813 blue
= PNG_sRGB_FROM_LINEAR(blue
* 255);
1818 else if (encoding
== P_LINEAR8
)
1820 /* This encoding occurs quite frequently in test cases because PngSuite
1821 * includes a gAMA 1.0 chunk with most images.
1827 encoding
= P_LINEAR
;
1830 else if (encoding
== P_sRGB
&&
1831 (convert_to_Y
!= 0 || output_encoding
== P_LINEAR
))
1833 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1836 red
= png_sRGB_table
[red
];
1837 green
= png_sRGB_table
[green
];
1838 blue
= png_sRGB_table
[blue
];
1840 encoding
= P_LINEAR
;
1843 /* This is set if the color isn't gray but the output is. */
1844 if (encoding
== P_LINEAR
)
1846 if (convert_to_Y
!= 0)
1848 /* NOTE: these values are copied from png_do_rgb_to_gray */
1849 png_uint_32 y
= (png_uint_32
)6968 * red
+ (png_uint_32
)23434 * green
+
1850 (png_uint_32
)2366 * blue
;
1852 if (output_encoding
== P_LINEAR
)
1853 y
= (y
+ 16384) >> 15;
1857 /* y is scaled by 32768, we need it scaled by 255: */
1860 y
= PNG_sRGB_FROM_LINEAR((y
+ 64) >> 7);
1861 alpha
= PNG_DIV257(alpha
);
1865 blue
= red
= green
= y
;
1868 else if (output_encoding
== P_sRGB
)
1870 red
= PNG_sRGB_FROM_LINEAR(red
* 255);
1871 green
= PNG_sRGB_FROM_LINEAR(green
* 255);
1872 blue
= PNG_sRGB_FROM_LINEAR(blue
* 255);
1873 alpha
= PNG_DIV257(alpha
);
1878 if (encoding
!= output_encoding
)
1879 png_error(image
->opaque
->png_ptr
, "bad encoding (internal error)");
1881 /* Store the value. */
1883 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1884 int afirst
= (image
->format
& PNG_FORMAT_FLAG_AFIRST
) != 0 &&
1885 (image
->format
& PNG_FORMAT_FLAG_ALPHA
) != 0;
1889 # ifdef PNG_FORMAT_BGR_SUPPORTED
1890 int bgr
= (image
->format
& PNG_FORMAT_FLAG_BGR
) != 0 ? 2 : 0;
1895 if (output_encoding
== P_LINEAR
)
1897 png_uint_16p entry
= png_voidcast(png_uint_16p
, display
->colormap
);
1899 entry
+= ip
* PNG_IMAGE_SAMPLE_CHANNELS(image
->format
);
1901 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1902 * value, if less than 65535 (this is, effectively, composite on black
1903 * if the alpha channel is removed.)
1905 switch (PNG_IMAGE_SAMPLE_CHANNELS(image
->format
))
1908 entry
[afirst
? 0 : 3] = (png_uint_16
)alpha
;
1916 blue
= (blue
* alpha
+ 32767U)/65535U;
1917 green
= (green
* alpha
+ 32767U)/65535U;
1918 red
= (red
* alpha
+ 32767U)/65535U;
1922 red
= green
= blue
= 0;
1924 entry
[afirst
+ (2 ^ bgr
)] = (png_uint_16
)blue
;
1925 entry
[afirst
+ 1] = (png_uint_16
)green
;
1926 entry
[afirst
+ bgr
] = (png_uint_16
)red
;
1930 entry
[1 ^ afirst
] = (png_uint_16
)alpha
;
1937 green
= (green
* alpha
+ 32767U)/65535U;
1942 entry
[afirst
] = (png_uint_16
)green
;
1950 else /* output encoding is P_sRGB */
1952 png_bytep entry
= png_voidcast(png_bytep
, display
->colormap
);
1954 entry
+= ip
* PNG_IMAGE_SAMPLE_CHANNELS(image
->format
);
1956 switch (PNG_IMAGE_SAMPLE_CHANNELS(image
->format
))
1959 entry
[afirst
? 0 : 3] = (png_byte
)alpha
;
1962 entry
[afirst
+ (2 ^ bgr
)] = (png_byte
)blue
;
1963 entry
[afirst
+ 1] = (png_byte
)green
;
1964 entry
[afirst
+ bgr
] = (png_byte
)red
;
1968 entry
[1 ^ afirst
] = (png_byte
)alpha
;
1971 entry
[afirst
] = (png_byte
)green
;
1989 make_gray_file_colormap(png_image_read_control
*display
)
1993 for (i
=0; i
<256; ++i
)
1994 png_create_colormap_entry(display
, i
, i
, i
, i
, 255, P_FILE
);
2000 make_gray_colormap(png_image_read_control
*display
)
2004 for (i
=0; i
<256; ++i
)
2005 png_create_colormap_entry(display
, i
, i
, i
, i
, 255, P_sRGB
);
2009 #define PNG_GRAY_COLORMAP_ENTRIES 256
2012 make_ga_colormap(png_image_read_control
*display
)
2016 /* Alpha is retained, the output will be a color-map with entries
2017 * selected by six levels of alpha. One transparent entry, 6 gray
2018 * levels for all the intermediate alpha values, leaving 230 entries
2019 * for the opaque grays. The color-map entries are the six values
2020 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2023 * if (alpha > 229) // opaque
2025 * // The 231 entries are selected to make the math below work:
2027 * entry = (231 * gray + 128) >> 8;
2029 * else if (alpha < 26) // transparent
2034 * else // partially opaque
2036 * base = 226 + 6 * PNG_DIV51(alpha);
2037 * entry = PNG_DIV51(gray);
2043 unsigned int gray
= (i
* 256 + 115) / 231;
2044 png_create_colormap_entry(display
, i
++, gray
, gray
, gray
, 255, P_sRGB
);
2047 /* 255 is used here for the component values for consistency with the code
2048 * that undoes premultiplication in pngwrite.c.
2050 png_create_colormap_entry(display
, i
++, 255, 255, 255, 0, P_sRGB
);
2057 png_create_colormap_entry(display
, i
++, g
*51, g
*51, g
*51, a
*51,
2064 #define PNG_GA_COLORMAP_ENTRIES 256
2067 make_rgb_colormap(png_image_read_control
*display
)
2071 /* Build a 6x6x6 opaque RGB cube */
2072 for (i
=r
=0; r
<6; ++r
)
2081 png_create_colormap_entry(display
, i
++, r
*51, g
*51, b
*51, 255,
2089 #define PNG_RGB_COLORMAP_ENTRIES 216
2091 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2092 #define PNG_RGB_INDEX(r,g,b) \
2093 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2096 png_image_read_colormap(png_voidp argument
)
2098 png_image_read_control
*display
=
2099 png_voidcast(png_image_read_control
*, argument
);
2100 png_imagep image
= display
->image
;
2102 png_structrp png_ptr
= image
->opaque
->png_ptr
;
2103 png_uint_32 output_format
= image
->format
;
2104 int output_encoding
= (output_format
& PNG_FORMAT_FLAG_LINEAR
) != 0 ?
2107 unsigned int cmap_entries
;
2108 unsigned int output_processing
; /* Output processing option */
2109 unsigned int data_encoding
= P_NOTSET
; /* Encoding libpng must produce */
2111 /* Background information; the background color and the index of this color
2112 * in the color-map if it exists (else 256).
2114 unsigned int background_index
= 256;
2115 png_uint_32 back_r
, back_g
, back_b
;
2117 /* Flags to accumulate things that need to be done to the input. */
2118 int expand_tRNS
= 0;
2120 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2121 * very difficult to do, the results look awful, and it is difficult to see
2122 * what possible use it is because the application can't control the
2125 if (((png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0 ||
2126 png_ptr
->num_trans
> 0) /* alpha in input */ &&
2127 ((output_format
& PNG_FORMAT_FLAG_ALPHA
) == 0) /* no alpha in output */)
2129 if (output_encoding
== P_LINEAR
) /* compose on black */
2130 back_b
= back_g
= back_r
= 0;
2132 else if (display
->background
== NULL
/* no way to remove it */)
2134 "background color must be supplied to remove alpha/transparency");
2136 /* Get a copy of the background color (this avoids repeating the checks
2137 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2142 back_g
= display
->background
->green
;
2143 if ((output_format
& PNG_FORMAT_FLAG_COLOR
) != 0)
2145 back_r
= display
->background
->red
;
2146 back_b
= display
->background
->blue
;
2149 back_b
= back_r
= back_g
;
2153 else if (output_encoding
== P_LINEAR
)
2154 back_b
= back_r
= back_g
= 65535;
2157 back_b
= back_r
= back_g
= 255;
2159 /* Default the input file gamma if required - this is necessary because
2160 * libpng assumes that if no gamma information is present the data is in the
2161 * output format, but the simplified API deduces the gamma from the input
2164 if ((png_ptr
->colorspace
.flags
& PNG_COLORSPACE_HAVE_GAMMA
) == 0)
2166 /* Do this directly, not using the png_colorspace functions, to ensure
2167 * that it happens even if the colorspace is invalid (though probably if
2168 * it is the setting will be ignored) Note that the same thing can be
2169 * achieved at the application interface with png_set_gAMA.
2171 if (png_ptr
->bit_depth
== 16 &&
2172 (image
->flags
& PNG_IMAGE_FLAG_16BIT_sRGB
) == 0)
2173 png_ptr
->colorspace
.gamma
= PNG_GAMMA_LINEAR
;
2176 png_ptr
->colorspace
.gamma
= PNG_GAMMA_sRGB_INVERSE
;
2178 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
2181 /* Decide what to do based on the PNG color type of the input data. The
2182 * utility function png_create_colormap_entry deals with most aspects of the
2183 * output transformations; this code works out how to produce bytes of
2184 * color-map entries from the original format.
2186 switch (png_ptr
->color_type
)
2188 case PNG_COLOR_TYPE_GRAY
:
2189 if (png_ptr
->bit_depth
<= 8)
2191 /* There at most 256 colors in the output, regardless of
2194 unsigned int step
, i
, val
, trans
= 256/*ignore*/, back_alpha
= 0;
2196 cmap_entries
= 1U << png_ptr
->bit_depth
;
2197 if (cmap_entries
> image
->colormap_entries
)
2198 png_error(png_ptr
, "gray[8] color-map: too few entries");
2200 step
= 255 / (cmap_entries
- 1);
2201 output_processing
= PNG_CMAP_NONE
;
2203 /* If there is a tRNS chunk then this either selects a transparent
2204 * value or, if the output has no alpha, the background color.
2206 if (png_ptr
->num_trans
> 0)
2208 trans
= png_ptr
->trans_color
.gray
;
2210 if ((output_format
& PNG_FORMAT_FLAG_ALPHA
) == 0)
2211 back_alpha
= output_encoding
== P_LINEAR
? 65535 : 255;
2214 /* png_create_colormap_entry just takes an RGBA and writes the
2215 * corresponding color-map entry using the format from 'image',
2216 * including the required conversion to sRGB or linear as
2217 * appropriate. The input values are always either sRGB (if the
2218 * gamma correction flag is 0) or 0..255 scaled file encoded values
2219 * (if the function must gamma correct them).
2221 for (i
=val
=0; i
<cmap_entries
; ++i
, val
+= step
)
2223 /* 'i' is a file value. While this will result in duplicated
2224 * entries for 8-bit non-sRGB encoded files it is necessary to
2225 * have non-gamma corrected values to do tRNS handling.
2228 png_create_colormap_entry(display
, i
, val
, val
, val
, 255,
2229 P_FILE
/*8-bit with file gamma*/);
2231 /* Else this entry is transparent. The colors don't matter if
2232 * there is an alpha channel (back_alpha == 0), but it does no
2233 * harm to pass them in; the values are not set above so this
2236 * NOTE: this preserves the full precision of the application
2237 * supplied background color when it is used.
2240 png_create_colormap_entry(display
, i
, back_r
, back_g
, back_b
,
2241 back_alpha
, output_encoding
);
2244 /* We need libpng to preserve the original encoding. */
2245 data_encoding
= P_FILE
;
2247 /* The rows from libpng, while technically gray values, are now also
2248 * color-map indices; however, they may need to be expanded to 1
2249 * byte per pixel. This is what png_set_packing does (i.e., it
2250 * unpacks the bit values into bytes.)
2252 if (png_ptr
->bit_depth
< 8)
2253 png_set_packing(png_ptr
);
2256 else /* bit depth is 16 */
2258 /* The 16-bit input values can be converted directly to 8-bit gamma
2259 * encoded values; however, if a tRNS chunk is present 257 color-map
2260 * entries are required. This means that the extra entry requires
2261 * special processing; add an alpha channel, sacrifice gray level
2262 * 254 and convert transparent (alpha==0) entries to that.
2264 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2265 * same time to minimize quality loss. If a tRNS chunk is present
2266 * this means libpng must handle it too; otherwise it is impossible
2267 * to do the exact match on the 16-bit value.
2269 * If the output has no alpha channel *and* the background color is
2270 * gray then it is possible to let libpng handle the substitution by
2271 * ensuring that the corresponding gray level matches the background
2274 data_encoding
= P_sRGB
;
2276 if (PNG_GRAY_COLORMAP_ENTRIES
> image
->colormap_entries
)
2277 png_error(png_ptr
, "gray[16] color-map: too few entries");
2279 cmap_entries
= (unsigned int)make_gray_colormap(display
);
2281 if (png_ptr
->num_trans
> 0)
2283 unsigned int back_alpha
;
2285 if ((output_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
2290 if (back_r
== back_g
&& back_g
== back_b
)
2292 /* Background is gray; no special processing will be
2296 png_uint_32 gray
= back_g
;
2298 if (output_encoding
== P_LINEAR
)
2300 gray
= PNG_sRGB_FROM_LINEAR(gray
* 255);
2302 /* And make sure the corresponding palette entry
2305 png_create_colormap_entry(display
, gray
, back_g
, back_g
,
2306 back_g
, 65535, P_LINEAR
);
2309 /* The background passed to libpng, however, must be the
2312 c
.index
= 0; /*unused*/
2313 c
.gray
= c
.red
= c
.green
= c
.blue
= (png_uint_16
)gray
;
2315 /* NOTE: does this work without expanding tRNS to alpha?
2316 * It should be the color->gray case below apparently
2319 png_set_background_fixed(png_ptr
, &c
,
2320 PNG_BACKGROUND_GAMMA_SCREEN
, 0/*need_expand*/,
2321 0/*gamma: not used*/);
2323 output_processing
= PNG_CMAP_NONE
;
2327 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2332 back_alpha
= output_encoding
== P_LINEAR
? 65535 : 255;
2336 /* output_processing means that the libpng-processed row will be
2337 * 8-bit GA and it has to be processing to single byte color-map
2338 * values. Entry 254 is replaced by either a completely
2339 * transparent entry or by the background color at full
2340 * precision (and the background color is not a simple gray
2341 * level in this case.)
2344 output_processing
= PNG_CMAP_TRANS
;
2345 background_index
= 254;
2347 /* And set (overwrite) color-map entry 254 to the actual
2348 * background color at full precision.
2350 png_create_colormap_entry(display
, 254, back_r
, back_g
, back_b
,
2351 back_alpha
, output_encoding
);
2355 output_processing
= PNG_CMAP_NONE
;
2359 case PNG_COLOR_TYPE_GRAY_ALPHA
:
2360 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2361 * of 65536 combinations. If, however, the alpha channel is to be
2362 * removed there are only 256 possibilities if the background is gray.
2363 * (Otherwise there is a subset of the 65536 possibilities defined by
2364 * the triangle between black, white and the background color.)
2366 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2367 * worry about tRNS matching - tRNS is ignored if there is an alpha
2370 data_encoding
= P_sRGB
;
2372 if ((output_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
2374 if (PNG_GA_COLORMAP_ENTRIES
> image
->colormap_entries
)
2375 png_error(png_ptr
, "gray+alpha color-map: too few entries");
2377 cmap_entries
= (unsigned int)make_ga_colormap(display
);
2379 background_index
= PNG_CMAP_GA_BACKGROUND
;
2380 output_processing
= PNG_CMAP_GA
;
2383 else /* alpha is removed */
2385 /* Alpha must be removed as the PNG data is processed when the
2386 * background is a color because the G and A channels are
2387 * independent and the vector addition (non-parallel vectors) is a
2390 * This can be reduced to the same algorithm as above by making a
2391 * colormap containing gray levels (for the opaque grays), a
2392 * background entry (for a transparent pixel) and a set of four six
2393 * level color values, one set for each intermediate alpha value.
2394 * See the comments in make_ga_colormap for how this works in the
2395 * per-pixel processing.
2397 * If the background is gray, however, we only need a 256 entry gray
2398 * level color map. It is sufficient to make the entry generated
2399 * for the background color be exactly the color specified.
2401 if ((output_format
& PNG_FORMAT_FLAG_COLOR
) == 0 ||
2402 (back_r
== back_g
&& back_g
== back_b
))
2404 /* Background is gray; no special processing will be required. */
2406 png_uint_32 gray
= back_g
;
2408 if (PNG_GRAY_COLORMAP_ENTRIES
> image
->colormap_entries
)
2409 png_error(png_ptr
, "gray-alpha color-map: too few entries");
2411 cmap_entries
= (unsigned int)make_gray_colormap(display
);
2413 if (output_encoding
== P_LINEAR
)
2415 gray
= PNG_sRGB_FROM_LINEAR(gray
* 255);
2417 /* And make sure the corresponding palette entry matches. */
2418 png_create_colormap_entry(display
, gray
, back_g
, back_g
,
2419 back_g
, 65535, P_LINEAR
);
2422 /* The background passed to libpng, however, must be the sRGB
2425 c
.index
= 0; /*unused*/
2426 c
.gray
= c
.red
= c
.green
= c
.blue
= (png_uint_16
)gray
;
2428 png_set_background_fixed(png_ptr
, &c
,
2429 PNG_BACKGROUND_GAMMA_SCREEN
, 0/*need_expand*/,
2430 0/*gamma: not used*/);
2432 output_processing
= PNG_CMAP_NONE
;
2439 /* This is the same as png_make_ga_colormap, above, except that
2440 * the entries are all opaque.
2442 if (PNG_GA_COLORMAP_ENTRIES
> image
->colormap_entries
)
2443 png_error(png_ptr
, "ga-alpha color-map: too few entries");
2448 png_uint_32 gray
= (i
* 256 + 115) / 231;
2449 png_create_colormap_entry(display
, i
++, gray
, gray
, gray
,
2453 /* NOTE: this preserves the full precision of the application
2456 background_index
= i
;
2457 png_create_colormap_entry(display
, i
++, back_r
, back_g
, back_b
,
2459 /* Coverity claims that output_encoding
2460 * cannot be 2 (P_LINEAR) here.
2463 output_encoding
== P_LINEAR
? 65535U : 255U,
2467 /* For non-opaque input composite on the sRGB background - this
2468 * requires inverting the encoding for each component. The input
2469 * is still converted to the sRGB encoding because this is a
2470 * reasonable approximate to the logarithmic curve of human
2471 * visual sensitivity, at least over the narrow range which PNG
2472 * represents. Consequently 'G' is always sRGB encoded, while
2473 * 'A' is linear. We need the linear background colors.
2475 if (output_encoding
== P_sRGB
) /* else already linear */
2477 /* This may produce a value not exactly matching the
2478 * background, but that's ok because these numbers are only
2479 * used when alpha != 0
2481 back_r
= png_sRGB_table
[back_r
];
2482 back_g
= png_sRGB_table
[back_g
];
2483 back_b
= png_sRGB_table
[back_b
];
2490 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2491 * by an 8-bit alpha value (0..255).
2493 png_uint_32 alpha
= 51 * a
;
2494 png_uint_32 back_rx
= (255-alpha
) * back_r
;
2495 png_uint_32 back_gx
= (255-alpha
) * back_g
;
2496 png_uint_32 back_bx
= (255-alpha
) * back_b
;
2500 png_uint_32 gray
= png_sRGB_table
[g
*51] * alpha
;
2502 png_create_colormap_entry(display
, i
++,
2503 PNG_sRGB_FROM_LINEAR(gray
+ back_rx
),
2504 PNG_sRGB_FROM_LINEAR(gray
+ back_gx
),
2505 PNG_sRGB_FROM_LINEAR(gray
+ back_bx
), 255, P_sRGB
);
2510 output_processing
= PNG_CMAP_GA
;
2515 case PNG_COLOR_TYPE_RGB
:
2516 case PNG_COLOR_TYPE_RGB_ALPHA
:
2517 /* Exclude the case where the output is gray; we can always handle this
2518 * with the cases above.
2520 if ((output_format
& PNG_FORMAT_FLAG_COLOR
) == 0)
2522 /* The color-map will be grayscale, so we may as well convert the
2523 * input RGB values to a simple grayscale and use the grayscale
2526 * NOTE: calling this apparently damages the recognition of the
2527 * transparent color in background color handling; call
2528 * png_set_tRNS_to_alpha before png_set_background_fixed.
2530 png_set_rgb_to_gray_fixed(png_ptr
, PNG_ERROR_ACTION_NONE
, -1,
2532 data_encoding
= P_sRGB
;
2534 /* The output will now be one or two 8-bit gray or gray+alpha
2535 * channels. The more complex case arises when the input has alpha.
2537 if ((png_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
2538 png_ptr
->num_trans
> 0) &&
2539 (output_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
2541 /* Both input and output have an alpha channel, so no background
2542 * processing is required; just map the GA bytes to the right
2547 if (PNG_GA_COLORMAP_ENTRIES
> image
->colormap_entries
)
2548 png_error(png_ptr
, "rgb[ga] color-map: too few entries");
2550 cmap_entries
= (unsigned int)make_ga_colormap(display
);
2551 background_index
= PNG_CMAP_GA_BACKGROUND
;
2552 output_processing
= PNG_CMAP_GA
;
2557 /* Either the input or the output has no alpha channel, so there
2558 * will be no non-opaque pixels in the color-map; it will just be
2561 if (PNG_GRAY_COLORMAP_ENTRIES
> image
->colormap_entries
)
2562 png_error(png_ptr
, "rgb[gray] color-map: too few entries");
2564 /* Ideally this code would use libpng to do the gamma correction,
2565 * but if an input alpha channel is to be removed we will hit the
2566 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2567 * correction bug). Fix this by dropping the gamma correction in
2568 * this case and doing it in the palette; this will result in
2569 * duplicate palette entries, but that's better than the
2570 * alternative of double gamma correction.
2572 if ((png_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
2573 png_ptr
->num_trans
> 0) &&
2574 png_gamma_not_sRGB(png_ptr
->colorspace
.gamma
) != 0)
2576 cmap_entries
= (unsigned int)make_gray_file_colormap(display
);
2577 data_encoding
= P_FILE
;
2581 cmap_entries
= (unsigned int)make_gray_colormap(display
);
2583 /* But if the input has alpha or transparency it must be removed
2585 if (png_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
2586 png_ptr
->num_trans
> 0)
2589 png_uint_32 gray
= back_g
;
2591 /* We need to ensure that the application background exists in
2592 * the colormap and that completely transparent pixels map to
2593 * it. Achieve this simply by ensuring that the entry
2594 * selected for the background really is the background color.
2596 if (data_encoding
== P_FILE
) /* from the fixup above */
2598 /* The app supplied a gray which is in output_encoding, we
2599 * need to convert it to a value of the input (P_FILE)
2600 * encoding then set this palette entry to the required
2603 if (output_encoding
== P_sRGB
)
2604 gray
= png_sRGB_table
[gray
]; /* now P_LINEAR */
2606 gray
= PNG_DIV257(png_gamma_16bit_correct(gray
,
2607 png_ptr
->colorspace
.gamma
)); /* now P_FILE */
2609 /* And make sure the corresponding palette entry contains
2610 * exactly the required sRGB value.
2612 png_create_colormap_entry(display
, gray
, back_g
, back_g
,
2613 back_g
, 0/*unused*/, output_encoding
);
2616 else if (output_encoding
== P_LINEAR
)
2618 gray
= PNG_sRGB_FROM_LINEAR(gray
* 255);
2620 /* And make sure the corresponding palette entry matches.
2622 png_create_colormap_entry(display
, gray
, back_g
, back_g
,
2623 back_g
, 0/*unused*/, P_LINEAR
);
2626 /* The background passed to libpng, however, must be the
2627 * output (normally sRGB) value.
2629 c
.index
= 0; /*unused*/
2630 c
.gray
= c
.red
= c
.green
= c
.blue
= (png_uint_16
)gray
;
2632 /* NOTE: the following is apparently a bug in libpng. Without
2633 * it the transparent color recognition in
2634 * png_set_background_fixed seems to go wrong.
2637 png_set_background_fixed(png_ptr
, &c
,
2638 PNG_BACKGROUND_GAMMA_SCREEN
, 0/*need_expand*/,
2639 0/*gamma: not used*/);
2642 output_processing
= PNG_CMAP_NONE
;
2646 else /* output is color */
2648 /* We could use png_quantize here so long as there is no transparent
2649 * color or alpha; png_quantize ignores alpha. Easier overall just
2650 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2651 * Consequently we always want libpng to produce sRGB data.
2653 data_encoding
= P_sRGB
;
2655 /* Is there any transparency or alpha? */
2656 if (png_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
2657 png_ptr
->num_trans
> 0)
2659 /* Is there alpha in the output too? If so all four channels are
2660 * processed into a special RGB cube with alpha support.
2662 if ((output_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
2666 if (PNG_RGB_COLORMAP_ENTRIES
+1+27 > image
->colormap_entries
)
2667 png_error(png_ptr
, "rgb+alpha color-map: too few entries");
2669 cmap_entries
= (unsigned int)make_rgb_colormap(display
);
2671 /* Add a transparent entry. */
2672 png_create_colormap_entry(display
, cmap_entries
, 255, 255,
2675 /* This is stored as the background index for the processing
2678 background_index
= cmap_entries
++;
2680 /* Add 27 r,g,b entries each with alpha 0.5. */
2681 for (r
=0; r
<256; r
= (r
<< 1) | 0x7f)
2685 for (g
=0; g
<256; g
= (g
<< 1) | 0x7f)
2689 /* This generates components with the values 0, 127 and
2692 for (b
=0; b
<256; b
= (b
<< 1) | 0x7f)
2693 png_create_colormap_entry(display
, cmap_entries
++,
2694 r
, g
, b
, 128, P_sRGB
);
2699 output_processing
= PNG_CMAP_RGB_ALPHA
;
2704 /* Alpha/transparency must be removed. The background must
2705 * exist in the color map (achieved by setting adding it after
2706 * the 666 color-map). If the standard processing code will
2707 * pick up this entry automatically that's all that is
2708 * required; libpng can be called to do the background
2711 unsigned int sample_size
=
2712 PNG_IMAGE_SAMPLE_SIZE(output_format
);
2713 png_uint_32 r
, g
, b
; /* sRGB background */
2715 if (PNG_RGB_COLORMAP_ENTRIES
+1+27 > image
->colormap_entries
)
2716 png_error(png_ptr
, "rgb-alpha color-map: too few entries");
2718 cmap_entries
= (unsigned int)make_rgb_colormap(display
);
2720 png_create_colormap_entry(display
, cmap_entries
, back_r
,
2721 back_g
, back_b
, 0/*unused*/, output_encoding
);
2723 if (output_encoding
== P_LINEAR
)
2725 r
= PNG_sRGB_FROM_LINEAR(back_r
* 255);
2726 g
= PNG_sRGB_FROM_LINEAR(back_g
* 255);
2727 b
= PNG_sRGB_FROM_LINEAR(back_b
* 255);
2737 /* Compare the newly-created color-map entry with the one the
2738 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2739 * match, add the new one and set this as the background
2742 if (memcmp((png_const_bytep
)display
->colormap
+
2743 sample_size
* cmap_entries
,
2744 (png_const_bytep
)display
->colormap
+
2745 sample_size
* PNG_RGB_INDEX(r
,g
,b
),
2748 /* The background color must be added. */
2749 background_index
= cmap_entries
++;
2751 /* Add 27 r,g,b entries each with created by composing with
2752 * the background at alpha 0.5.
2754 for (r
=0; r
<256; r
= (r
<< 1) | 0x7f)
2756 for (g
=0; g
<256; g
= (g
<< 1) | 0x7f)
2758 /* This generates components with the values 0, 127
2761 for (b
=0; b
<256; b
= (b
<< 1) | 0x7f)
2762 png_create_colormap_entry(display
, cmap_entries
++,
2763 png_colormap_compose(display
, r
, P_sRGB
, 128,
2764 back_r
, output_encoding
),
2765 png_colormap_compose(display
, g
, P_sRGB
, 128,
2766 back_g
, output_encoding
),
2767 png_colormap_compose(display
, b
, P_sRGB
, 128,
2768 back_b
, output_encoding
),
2769 0/*unused*/, output_encoding
);
2774 output_processing
= PNG_CMAP_RGB_ALPHA
;
2777 else /* background color is in the standard color-map */
2781 c
.index
= 0; /*unused*/
2782 c
.red
= (png_uint_16
)back_r
;
2783 c
.gray
= c
.green
= (png_uint_16
)back_g
;
2784 c
.blue
= (png_uint_16
)back_b
;
2786 png_set_background_fixed(png_ptr
, &c
,
2787 PNG_BACKGROUND_GAMMA_SCREEN
, 0/*need_expand*/,
2788 0/*gamma: not used*/);
2790 output_processing
= PNG_CMAP_RGB
;
2795 else /* no alpha or transparency in the input */
2797 /* Alpha in the output is irrelevant, simply map the opaque input
2798 * pixels to the 6x6x6 color-map.
2800 if (PNG_RGB_COLORMAP_ENTRIES
> image
->colormap_entries
)
2801 png_error(png_ptr
, "rgb color-map: too few entries");
2803 cmap_entries
= (unsigned int)make_rgb_colormap(display
);
2804 output_processing
= PNG_CMAP_RGB
;
2809 case PNG_COLOR_TYPE_PALETTE
:
2810 /* It's already got a color-map. It may be necessary to eliminate the
2811 * tRNS entries though.
2814 unsigned int num_trans
= png_ptr
->num_trans
;
2815 png_const_bytep trans
= num_trans
> 0 ? png_ptr
->trans_alpha
: NULL
;
2816 png_const_colorp colormap
= png_ptr
->palette
;
2817 int do_background
= trans
!= NULL
&&
2818 (output_format
& PNG_FORMAT_FLAG_ALPHA
) == 0;
2825 output_processing
= PNG_CMAP_NONE
;
2826 data_encoding
= P_FILE
; /* Don't change from color-map indices */
2827 cmap_entries
= (unsigned int)png_ptr
->num_palette
;
2828 if (cmap_entries
> 256)
2831 if (cmap_entries
> (unsigned int)image
->colormap_entries
)
2832 png_error(png_ptr
, "palette color-map: too few entries");
2834 for (i
=0; i
< cmap_entries
; ++i
)
2836 if (do_background
!= 0 && i
< num_trans
&& trans
[i
] < 255)
2839 png_create_colormap_entry(display
, i
, back_r
, back_g
,
2840 back_b
, 0, output_encoding
);
2844 /* Must compose the PNG file color in the color-map entry
2845 * on the sRGB color in 'back'.
2847 png_create_colormap_entry(display
, i
,
2848 png_colormap_compose(display
, colormap
[i
].red
,
2849 P_FILE
, trans
[i
], back_r
, output_encoding
),
2850 png_colormap_compose(display
, colormap
[i
].green
,
2851 P_FILE
, trans
[i
], back_g
, output_encoding
),
2852 png_colormap_compose(display
, colormap
[i
].blue
,
2853 P_FILE
, trans
[i
], back_b
, output_encoding
),
2854 output_encoding
== P_LINEAR
? trans
[i
] * 257U :
2861 png_create_colormap_entry(display
, i
, colormap
[i
].red
,
2862 colormap
[i
].green
, colormap
[i
].blue
,
2863 i
< num_trans
? trans
[i
] : 255U, P_FILE
/*8-bit*/);
2866 /* The PNG data may have indices packed in fewer than 8 bits, it
2867 * must be expanded if so.
2869 if (png_ptr
->bit_depth
< 8)
2870 png_set_packing(png_ptr
);
2875 png_error(png_ptr
, "invalid PNG color type");
2879 /* Now deal with the output processing */
2880 if (expand_tRNS
!= 0 && png_ptr
->num_trans
> 0 &&
2881 (png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) == 0)
2882 png_set_tRNS_to_alpha(png_ptr
);
2884 switch (data_encoding
)
2887 /* Change to 8-bit sRGB */
2888 png_set_alpha_mode_fixed(png_ptr
, PNG_ALPHA_PNG
, PNG_GAMMA_sRGB
);
2892 if (png_ptr
->bit_depth
> 8)
2893 png_set_scale_16(png_ptr
);
2898 png_error(png_ptr
, "bad data option (internal error)");
2902 if (cmap_entries
> 256 || cmap_entries
> image
->colormap_entries
)
2903 png_error(png_ptr
, "color map overflow (BAD internal error)");
2905 image
->colormap_entries
= cmap_entries
;
2907 /* Double check using the recorded background index */
2908 switch (output_processing
)
2911 if (background_index
!= PNG_CMAP_NONE_BACKGROUND
)
2912 goto bad_background
;
2916 if (background_index
!= PNG_CMAP_GA_BACKGROUND
)
2917 goto bad_background
;
2920 case PNG_CMAP_TRANS
:
2921 if (background_index
>= cmap_entries
||
2922 background_index
!= PNG_CMAP_TRANS_BACKGROUND
)
2923 goto bad_background
;
2927 if (background_index
!= PNG_CMAP_RGB_BACKGROUND
)
2928 goto bad_background
;
2931 case PNG_CMAP_RGB_ALPHA
:
2932 if (background_index
!= PNG_CMAP_RGB_ALPHA_BACKGROUND
)
2933 goto bad_background
;
2937 png_error(png_ptr
, "bad processing option (internal error)");
2940 png_error(png_ptr
, "bad background index (internal error)");
2943 display
->colormap_processing
= (int)output_processing
;
2948 /* The final part of the color-map read called from png_image_finish_read. */
2950 png_image_read_and_map(png_voidp argument
)
2952 png_image_read_control
*display
= png_voidcast(png_image_read_control
*,
2954 png_imagep image
= display
->image
;
2955 png_structrp png_ptr
= image
->opaque
->png_ptr
;
2958 /* Called when the libpng data must be transformed into the color-mapped
2959 * form. There is a local row buffer in display->local and this routine must
2960 * do the interlace handling.
2962 switch (png_ptr
->interlaced
)
2964 case PNG_INTERLACE_NONE
:
2968 case PNG_INTERLACE_ADAM7
:
2969 passes
= PNG_INTERLACE_ADAM7_PASSES
;
2973 png_error(png_ptr
, "unknown interlace type");
2977 png_uint_32 height
= image
->height
;
2978 png_uint_32 width
= image
->width
;
2979 int proc
= display
->colormap_processing
;
2980 png_bytep first_row
= png_voidcast(png_bytep
, display
->first_row
);
2981 ptrdiff_t step_row
= display
->row_bytes
;
2984 for (pass
= 0; pass
< passes
; ++pass
)
2986 unsigned int startx
, stepx
, stepy
;
2989 if (png_ptr
->interlaced
== PNG_INTERLACE_ADAM7
)
2991 /* The row may be empty for a short image: */
2992 if (PNG_PASS_COLS(width
, pass
) == 0)
2995 startx
= PNG_PASS_START_COL(pass
);
2996 stepx
= PNG_PASS_COL_OFFSET(pass
);
2997 y
= PNG_PASS_START_ROW(pass
);
2998 stepy
= PNG_PASS_ROW_OFFSET(pass
);
3008 for (; y
<height
; y
+= stepy
)
3010 png_bytep inrow
= png_voidcast(png_bytep
, display
->local_row
);
3011 png_bytep outrow
= first_row
+ y
* step_row
;
3012 png_const_bytep end_row
= outrow
+ width
;
3014 /* Read read the libpng data into the temporary buffer. */
3015 png_read_row(png_ptr
, inrow
, NULL
);
3017 /* Now process the row according to the processing option, note
3018 * that the caller verifies that the format of the libpng output
3019 * data is as required.
3025 for (; outrow
< end_row
; outrow
+= stepx
)
3027 /* The data is always in the PNG order */
3028 unsigned int gray
= *inrow
++;
3029 unsigned int alpha
= *inrow
++;
3032 /* NOTE: this code is copied as a comment in
3033 * make_ga_colormap above. Please update the
3034 * comment if you change this code!
3036 if (alpha
> 229) /* opaque */
3038 entry
= (231 * gray
+ 128) >> 8;
3040 else if (alpha
< 26) /* transparent */
3044 else /* partially opaque */
3046 entry
= 226 + 6 * PNG_DIV51(alpha
) + PNG_DIV51(gray
);
3049 *outrow
= (png_byte
)entry
;
3053 case PNG_CMAP_TRANS
:
3054 for (; outrow
< end_row
; outrow
+= stepx
)
3056 png_byte gray
= *inrow
++;
3057 png_byte alpha
= *inrow
++;
3060 *outrow
= PNG_CMAP_TRANS_BACKGROUND
;
3062 else if (gray
!= PNG_CMAP_TRANS_BACKGROUND
)
3066 *outrow
= (png_byte
)(PNG_CMAP_TRANS_BACKGROUND
+1);
3071 for (; outrow
< end_row
; outrow
+= stepx
)
3073 *outrow
= PNG_RGB_INDEX(inrow
[0], inrow
[1], inrow
[2]);
3078 case PNG_CMAP_RGB_ALPHA
:
3079 for (; outrow
< end_row
; outrow
+= stepx
)
3081 unsigned int alpha
= inrow
[3];
3083 /* Because the alpha entries only hold alpha==0.5 values
3084 * split the processing at alpha==0.25 (64) and 0.75
3089 *outrow
= PNG_RGB_INDEX(inrow
[0], inrow
[1],
3092 else if (alpha
< 64)
3093 *outrow
= PNG_CMAP_RGB_ALPHA_BACKGROUND
;
3097 /* Likewise there are three entries for each of r, g
3098 * and b. We could select the entry by popcount on
3099 * the top two bits on those architectures that
3100 * support it, this is what the code below does,
3103 unsigned int back_i
= PNG_CMAP_RGB_ALPHA_BACKGROUND
+1;
3105 /* Here are how the values map:
3111 * So, as above with the explicit alpha checks, the
3112 * breakpoints are at 64 and 196.
3114 if (inrow
[0] & 0x80) back_i
+= 9; /* red */
3115 if (inrow
[0] & 0x40) back_i
+= 9;
3116 if (inrow
[0] & 0x80) back_i
+= 3; /* green */
3117 if (inrow
[0] & 0x40) back_i
+= 3;
3118 if (inrow
[0] & 0x80) back_i
+= 1; /* blue */
3119 if (inrow
[0] & 0x40) back_i
+= 1;
3121 *outrow
= (png_byte
)back_i
;
3139 png_image_read_colormapped(png_voidp argument
)
3141 png_image_read_control
*display
= png_voidcast(png_image_read_control
*,
3143 png_imagep image
= display
->image
;
3144 png_controlp control
= image
->opaque
;
3145 png_structrp png_ptr
= control
->png_ptr
;
3146 png_inforp info_ptr
= control
->info_ptr
;
3148 int passes
= 0; /* As a flag */
3150 PNG_SKIP_CHUNKS(png_ptr
);
3152 /* Update the 'info' structure and make sure the result is as required; first
3153 * make sure to turn on the interlace handling if it will be required
3154 * (because it can't be turned on *after* the call to png_read_update_info!)
3156 if (display
->colormap_processing
== PNG_CMAP_NONE
)
3157 passes
= png_set_interlace_handling(png_ptr
);
3159 png_read_update_info(png_ptr
, info_ptr
);
3161 /* The expected output can be deduced from the colormap_processing option. */
3162 switch (display
->colormap_processing
)
3165 /* Output must be one channel and one byte per pixel, the output
3166 * encoding can be anything.
3168 if ((info_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
||
3169 info_ptr
->color_type
== PNG_COLOR_TYPE_GRAY
) &&
3170 info_ptr
->bit_depth
== 8)
3175 case PNG_CMAP_TRANS
:
3177 /* Output must be two channels and the 'G' one must be sRGB, the latter
3178 * can be checked with an exact number because it should have been set
3179 * to this number above!
3181 if (info_ptr
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
&&
3182 info_ptr
->bit_depth
== 8 &&
3183 png_ptr
->screen_gamma
== PNG_GAMMA_sRGB
&&
3184 image
->colormap_entries
== 256)
3190 /* Output must be 8-bit sRGB encoded RGB */
3191 if (info_ptr
->color_type
== PNG_COLOR_TYPE_RGB
&&
3192 info_ptr
->bit_depth
== 8 &&
3193 png_ptr
->screen_gamma
== PNG_GAMMA_sRGB
&&
3194 image
->colormap_entries
== 216)
3199 case PNG_CMAP_RGB_ALPHA
:
3200 /* Output must be 8-bit sRGB encoded RGBA */
3201 if (info_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
&&
3202 info_ptr
->bit_depth
== 8 &&
3203 png_ptr
->screen_gamma
== PNG_GAMMA_sRGB
&&
3204 image
->colormap_entries
== 244 /* 216 + 1 + 27 */)
3211 png_error(png_ptr
, "bad color-map processing (internal error)");
3214 /* Now read the rows. Do this here if it is possible to read directly into
3215 * the output buffer, otherwise allocate a local row buffer of the maximum
3216 * size libpng requires and call the relevant processing routine safely.
3219 png_voidp first_row
= display
->buffer
;
3220 ptrdiff_t row_bytes
= display
->row_stride
;
3222 /* The following expression is designed to work correctly whether it gives
3223 * a signed or an unsigned result.
3227 char *ptr
= png_voidcast(char*, first_row
);
3228 ptr
+= (image
->height
-1) * (-row_bytes
);
3229 first_row
= png_voidcast(png_voidp
, ptr
);
3232 display
->first_row
= first_row
;
3233 display
->row_bytes
= row_bytes
;
3239 png_voidp row
= png_malloc(png_ptr
, png_get_rowbytes(png_ptr
, info_ptr
));
3241 display
->local_row
= row
;
3242 result
= png_safe_execute(image
, png_image_read_and_map
, display
);
3243 display
->local_row
= NULL
;
3244 png_free(png_ptr
, row
);
3251 png_alloc_size_t row_bytes
= (png_alloc_size_t
)display
->row_bytes
;
3253 while (--passes
>= 0)
3255 png_uint_32 y
= image
->height
;
3256 png_bytep row
= png_voidcast(png_bytep
, display
->first_row
);
3260 png_read_row(png_ptr
, row
, NULL
);
3269 /* Just the row reading part of png_image_read. */
3271 png_image_read_composite(png_voidp argument
)
3273 png_image_read_control
*display
= png_voidcast(png_image_read_control
*,
3275 png_imagep image
= display
->image
;
3276 png_structrp png_ptr
= image
->opaque
->png_ptr
;
3279 switch (png_ptr
->interlaced
)
3281 case PNG_INTERLACE_NONE
:
3285 case PNG_INTERLACE_ADAM7
:
3286 passes
= PNG_INTERLACE_ADAM7_PASSES
;
3290 png_error(png_ptr
, "unknown interlace type");
3294 png_uint_32 height
= image
->height
;
3295 png_uint_32 width
= image
->width
;
3296 ptrdiff_t step_row
= display
->row_bytes
;
3297 unsigned int channels
=
3298 (image
->format
& PNG_FORMAT_FLAG_COLOR
) != 0 ? 3 : 1;
3301 for (pass
= 0; pass
< passes
; ++pass
)
3303 unsigned int startx
, stepx
, stepy
;
3306 if (png_ptr
->interlaced
== PNG_INTERLACE_ADAM7
)
3308 /* The row may be empty for a short image: */
3309 if (PNG_PASS_COLS(width
, pass
) == 0)
3312 startx
= PNG_PASS_START_COL(pass
) * channels
;
3313 stepx
= PNG_PASS_COL_OFFSET(pass
) * channels
;
3314 y
= PNG_PASS_START_ROW(pass
);
3315 stepy
= PNG_PASS_ROW_OFFSET(pass
);
3326 for (; y
<height
; y
+= stepy
)
3328 png_bytep inrow
= png_voidcast(png_bytep
, display
->local_row
);
3330 png_const_bytep end_row
;
3332 /* Read the row, which is packed: */
3333 png_read_row(png_ptr
, inrow
, NULL
);
3335 outrow
= png_voidcast(png_bytep
, display
->first_row
);
3336 outrow
+= y
* step_row
;
3337 end_row
= outrow
+ width
* channels
;
3339 /* Now do the composition on each pixel in this row. */
3341 for (; outrow
< end_row
; outrow
+= stepx
)
3343 png_byte alpha
= inrow
[channels
];
3345 if (alpha
> 0) /* else no change to the output */
3349 for (c
=0; c
<channels
; ++c
)
3351 png_uint_32 component
= inrow
[c
];
3353 if (alpha
< 255) /* else just use component */
3355 /* This is PNG_OPTIMIZED_ALPHA, the component value
3356 * is a linear 8-bit value. Combine this with the
3357 * current outrow[c] value which is sRGB encoded.
3358 * Arithmetic here is 16-bits to preserve the output
3361 component
*= 257*255; /* =65535 */
3362 component
+= (255-alpha
)*png_sRGB_table
[outrow
[c
]];
3364 /* So 'component' is scaled by 255*65535 and is
3365 * therefore appropriate for the sRGB to linear
3368 component
= PNG_sRGB_FROM_LINEAR(component
);
3371 outrow
[c
] = (png_byte
)component
;
3375 inrow
+= channels
+1; /* components and alpha channel */
3384 /* The do_local_background case; called when all the following transforms are to
3391 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3392 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3393 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3394 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3395 * row and handles the removal or pre-multiplication of the alpha channel.
3398 png_image_read_background(png_voidp argument
)
3400 png_image_read_control
*display
= png_voidcast(png_image_read_control
*,
3402 png_imagep image
= display
->image
;
3403 png_structrp png_ptr
= image
->opaque
->png_ptr
;
3404 png_inforp info_ptr
= image
->opaque
->info_ptr
;
3405 png_uint_32 height
= image
->height
;
3406 png_uint_32 width
= image
->width
;
3409 /* Double check the convoluted logic below. We expect to get here with
3410 * libpng doing rgb to gray and gamma correction but background processing
3411 * left to the png_image_read_background function. The rows libpng produce
3412 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3414 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) == 0)
3415 png_error(png_ptr
, "lost rgb to gray");
3417 if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0)
3418 png_error(png_ptr
, "unexpected compose");
3420 if (png_get_channels(png_ptr
, info_ptr
) != 2)
3421 png_error(png_ptr
, "lost/gained channels");
3423 /* Expect the 8-bit case to always remove the alpha channel */
3424 if ((image
->format
& PNG_FORMAT_FLAG_LINEAR
) == 0 &&
3425 (image
->format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3426 png_error(png_ptr
, "unexpected 8-bit transformation");
3428 switch (png_ptr
->interlaced
)
3430 case PNG_INTERLACE_NONE
:
3434 case PNG_INTERLACE_ADAM7
:
3435 passes
= PNG_INTERLACE_ADAM7_PASSES
;
3439 png_error(png_ptr
, "unknown interlace type");
3442 /* Use direct access to info_ptr here because otherwise the simplified API
3443 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3444 * checking the value after libpng expansions, not the original value in the
3447 switch (info_ptr
->bit_depth
)
3450 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3451 * to be removed by composing on a background: either the row if
3452 * display->background is NULL or display->background->green if not.
3453 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3456 png_bytep first_row
= png_voidcast(png_bytep
, display
->first_row
);
3457 ptrdiff_t step_row
= display
->row_bytes
;
3459 for (pass
= 0; pass
< passes
; ++pass
)
3461 unsigned int startx
, stepx
, stepy
;
3464 if (png_ptr
->interlaced
== PNG_INTERLACE_ADAM7
)
3466 /* The row may be empty for a short image: */
3467 if (PNG_PASS_COLS(width
, pass
) == 0)
3470 startx
= PNG_PASS_START_COL(pass
);
3471 stepx
= PNG_PASS_COL_OFFSET(pass
);
3472 y
= PNG_PASS_START_ROW(pass
);
3473 stepy
= PNG_PASS_ROW_OFFSET(pass
);
3483 if (display
->background
== NULL
)
3485 for (; y
<height
; y
+= stepy
)
3487 png_bytep inrow
= png_voidcast(png_bytep
,
3488 display
->local_row
);
3489 png_bytep outrow
= first_row
+ y
* step_row
;
3490 png_const_bytep end_row
= outrow
+ width
;
3492 /* Read the row, which is packed: */
3493 png_read_row(png_ptr
, inrow
, NULL
);
3495 /* Now do the composition on each pixel in this row. */
3497 for (; outrow
< end_row
; outrow
+= stepx
)
3499 png_byte alpha
= inrow
[1];
3501 if (alpha
> 0) /* else no change to the output */
3503 png_uint_32 component
= inrow
[0];
3505 if (alpha
< 255) /* else just use component */
3507 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3508 * necessary to invert the sRGB transfer
3509 * function and multiply the alpha out.
3511 component
= png_sRGB_table
[component
] * alpha
;
3512 component
+= png_sRGB_table
[outrow
[0]] *
3514 component
= PNG_sRGB_FROM_LINEAR(component
);
3517 outrow
[0] = (png_byte
)component
;
3520 inrow
+= 2; /* gray and alpha channel */
3525 else /* constant background value */
3527 png_byte background8
= display
->background
->green
;
3528 png_uint_16 background
= png_sRGB_table
[background8
];
3530 for (; y
<height
; y
+= stepy
)
3532 png_bytep inrow
= png_voidcast(png_bytep
,
3533 display
->local_row
);
3534 png_bytep outrow
= first_row
+ y
* step_row
;
3535 png_const_bytep end_row
= outrow
+ width
;
3537 /* Read the row, which is packed: */
3538 png_read_row(png_ptr
, inrow
, NULL
);
3540 /* Now do the composition on each pixel in this row. */
3542 for (; outrow
< end_row
; outrow
+= stepx
)
3544 png_byte alpha
= inrow
[1];
3546 if (alpha
> 0) /* else use background */
3548 png_uint_32 component
= inrow
[0];
3550 if (alpha
< 255) /* else just use component */
3552 component
= png_sRGB_table
[component
] * alpha
;
3553 component
+= background
* (255-alpha
);
3554 component
= PNG_sRGB_FROM_LINEAR(component
);
3557 outrow
[0] = (png_byte
)component
;
3561 outrow
[0] = background8
;
3563 inrow
+= 2; /* gray and alpha channel */
3572 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3573 * still be done and, maybe, the alpha channel removed. This code also
3574 * handles the alpha-first option.
3577 png_uint_16p first_row
= png_voidcast(png_uint_16p
,
3578 display
->first_row
);
3579 /* The division by two is safe because the caller passed in a
3580 * stride which was multiplied by 2 (below) to get row_bytes.
3582 ptrdiff_t step_row
= display
->row_bytes
/ 2;
3583 unsigned int preserve_alpha
= (image
->format
&
3584 PNG_FORMAT_FLAG_ALPHA
) != 0;
3585 unsigned int outchannels
= 1U+preserve_alpha
;
3588 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3589 if (preserve_alpha
!= 0 &&
3590 (image
->format
& PNG_FORMAT_FLAG_AFIRST
) != 0)
3594 for (pass
= 0; pass
< passes
; ++pass
)
3596 unsigned int startx
, stepx
, stepy
;
3599 /* The 'x' start and step are adjusted to output components here.
3601 if (png_ptr
->interlaced
== PNG_INTERLACE_ADAM7
)
3603 /* The row may be empty for a short image: */
3604 if (PNG_PASS_COLS(width
, pass
) == 0)
3607 startx
= PNG_PASS_START_COL(pass
) * outchannels
;
3608 stepx
= PNG_PASS_COL_OFFSET(pass
) * outchannels
;
3609 y
= PNG_PASS_START_ROW(pass
);
3610 stepy
= PNG_PASS_ROW_OFFSET(pass
);
3617 stepx
= outchannels
;
3621 for (; y
<height
; y
+= stepy
)
3623 png_const_uint_16p inrow
;
3624 png_uint_16p outrow
= first_row
+ y
*step_row
;
3625 png_uint_16p end_row
= outrow
+ width
* outchannels
;
3627 /* Read the row, which is packed: */
3628 png_read_row(png_ptr
, png_voidcast(png_bytep
,
3629 display
->local_row
), NULL
);
3630 inrow
= png_voidcast(png_const_uint_16p
, display
->local_row
);
3632 /* Now do the pre-multiplication on each pixel in this row.
3635 for (; outrow
< end_row
; outrow
+= stepx
)
3637 png_uint_32 component
= inrow
[0];
3638 png_uint_16 alpha
= inrow
[1];
3640 if (alpha
> 0) /* else 0 */
3642 if (alpha
< 65535) /* else just use component */
3653 outrow
[swap_alpha
] = (png_uint_16
)component
;
3654 if (preserve_alpha
!= 0)
3655 outrow
[1 ^ swap_alpha
] = alpha
;
3657 inrow
+= 2; /* components and alpha channel */
3666 png_error(png_ptr
, "unexpected bit depth");
3673 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3675 png_image_read_direct(png_voidp argument
)
3677 png_image_read_control
*display
= png_voidcast(png_image_read_control
*,
3679 png_imagep image
= display
->image
;
3680 png_structrp png_ptr
= image
->opaque
->png_ptr
;
3681 png_inforp info_ptr
= image
->opaque
->info_ptr
;
3683 png_uint_32 format
= image
->format
;
3684 int linear
= (format
& PNG_FORMAT_FLAG_LINEAR
) != 0;
3685 int do_local_compose
= 0;
3686 int do_local_background
= 0; /* to avoid double gamma correction bug */
3689 /* Add transforms to ensure the correct output format is produced then check
3690 * that the required implementation support is there. Always expand; always
3691 * need 8 bits minimum, no palette and expanded tRNS.
3693 png_set_expand(png_ptr
);
3695 /* Now check the format to see if it was modified. */
3697 png_uint_32 base_format
= png_image_format(png_ptr
) &
3698 ~PNG_FORMAT_FLAG_COLORMAP
/* removed by png_set_expand */;
3699 png_uint_32 change
= format
^ base_format
;
3700 png_fixed_point output_gamma
;
3701 int mode
; /* alpha mode */
3703 /* Do this first so that we have a record if rgb to gray is happening. */
3704 if ((change
& PNG_FORMAT_FLAG_COLOR
) != 0)
3706 /* gray<->color transformation required. */
3707 if ((format
& PNG_FORMAT_FLAG_COLOR
) != 0)
3708 png_set_gray_to_rgb(png_ptr
);
3712 /* libpng can't do both rgb to gray and
3713 * background/pre-multiplication if there is also significant gamma
3714 * correction, because both operations require linear colors and
3715 * the code only supports one transform doing the gamma correction.
3716 * Handle this by doing the pre-multiplication or background
3717 * operation in this code, if necessary.
3719 * TODO: fix this by rewriting pngrtran.c (!)
3721 * For the moment (given that fixing this in pngrtran.c is an
3722 * enormous change) 'do_local_background' is used to indicate that
3723 * the problem exists.
3725 if ((base_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3726 do_local_background
= 1/*maybe*/;
3728 png_set_rgb_to_gray_fixed(png_ptr
, PNG_ERROR_ACTION_NONE
,
3729 PNG_RGB_TO_GRAY_DEFAULT
, PNG_RGB_TO_GRAY_DEFAULT
);
3732 change
&= ~PNG_FORMAT_FLAG_COLOR
;
3735 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3738 png_fixed_point input_gamma_default
;
3740 if ((base_format
& PNG_FORMAT_FLAG_LINEAR
) != 0 &&
3741 (image
->flags
& PNG_IMAGE_FLAG_16BIT_sRGB
) == 0)
3742 input_gamma_default
= PNG_GAMMA_LINEAR
;
3744 input_gamma_default
= PNG_DEFAULT_sRGB
;
3746 /* Call png_set_alpha_mode to set the default for the input gamma; the
3747 * output gamma is set by a second call below.
3749 png_set_alpha_mode_fixed(png_ptr
, PNG_ALPHA_PNG
, input_gamma_default
);
3754 /* If there *is* an alpha channel in the input it must be multiplied
3755 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3757 if ((base_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3758 mode
= PNG_ALPHA_STANDARD
; /* associated alpha */
3761 mode
= PNG_ALPHA_PNG
;
3763 output_gamma
= PNG_GAMMA_LINEAR
;
3768 mode
= PNG_ALPHA_PNG
;
3769 output_gamma
= PNG_DEFAULT_sRGB
;
3772 if ((change
& PNG_FORMAT_FLAG_ASSOCIATED_ALPHA
) != 0)
3774 mode
= PNG_ALPHA_OPTIMIZED
;
3775 change
&= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA
;
3778 /* If 'do_local_background' is set check for the presence of gamma
3779 * correction; this is part of the work-round for the libpng bug
3782 * TODO: fix libpng and remove this.
3784 if (do_local_background
!= 0)
3786 png_fixed_point gtest
;
3788 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3789 * gamma correction, the screen gamma hasn't been set on png_struct
3790 * yet; it's set below. png_struct::gamma, however, is set to the
3793 if (png_muldiv(>est
, output_gamma
, png_ptr
->colorspace
.gamma
,
3794 PNG_FP_1
) != 0 && png_gamma_significant(gtest
) == 0)
3795 do_local_background
= 0;
3797 else if (mode
== PNG_ALPHA_STANDARD
)
3799 do_local_background
= 2/*required*/;
3800 mode
= PNG_ALPHA_PNG
; /* prevent libpng doing it */
3803 /* else leave as 1 for the checks below */
3806 /* If the bit-depth changes then handle that here. */
3807 if ((change
& PNG_FORMAT_FLAG_LINEAR
) != 0)
3809 if (linear
!= 0 /*16-bit output*/)
3810 png_set_expand_16(png_ptr
);
3812 else /* 8-bit output */
3813 png_set_scale_16(png_ptr
);
3815 change
&= ~PNG_FORMAT_FLAG_LINEAR
;
3818 /* Now the background/alpha channel changes. */
3819 if ((change
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3821 /* Removing an alpha channel requires composition for the 8-bit
3822 * formats; for the 16-bit it is already done, above, by the
3823 * pre-multiplication and the channel just needs to be stripped.
3825 if ((base_format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3827 /* If RGB->gray is happening the alpha channel must be left and the
3828 * operation completed locally.
3830 * TODO: fix libpng and remove this.
3832 if (do_local_background
!= 0)
3833 do_local_background
= 2/*required*/;
3835 /* 16-bit output: just remove the channel */
3836 else if (linear
!= 0) /* compose on black (well, pre-multiply) */
3837 png_set_strip_alpha(png_ptr
);
3839 /* 8-bit output: do an appropriate compose */
3840 else if (display
->background
!= NULL
)
3844 c
.index
= 0; /*unused*/
3845 c
.red
= display
->background
->red
;
3846 c
.green
= display
->background
->green
;
3847 c
.blue
= display
->background
->blue
;
3848 c
.gray
= display
->background
->green
;
3850 /* This is always an 8-bit sRGB value, using the 'green' channel
3851 * for gray is much better than calculating the luminance here;
3852 * we can get off-by-one errors in that calculation relative to
3853 * the app expectations and that will show up in transparent
3856 png_set_background_fixed(png_ptr
, &c
,
3857 PNG_BACKGROUND_GAMMA_SCREEN
, 0/*need_expand*/,
3858 0/*gamma: not used*/);
3861 else /* compose on row: implemented below. */
3863 do_local_compose
= 1;
3864 /* This leaves the alpha channel in the output, so it has to be
3865 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3866 * one so the code only has to hack on the pixels that require
3869 mode
= PNG_ALPHA_OPTIMIZED
;
3873 else /* output needs an alpha channel */
3875 /* This is tricky because it happens before the swap operation has
3876 * been accomplished; however, the swap does *not* swap the added
3877 * alpha channel (weird API), so it must be added in the correct
3880 png_uint_32 filler
; /* opaque filler */
3889 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3890 if ((format
& PNG_FORMAT_FLAG_AFIRST
) != 0)
3892 where
= PNG_FILLER_BEFORE
;
3893 change
&= ~PNG_FORMAT_FLAG_AFIRST
;
3898 where
= PNG_FILLER_AFTER
;
3900 png_set_add_alpha(png_ptr
, filler
, where
);
3903 /* This stops the (irrelevant) call to swap_alpha below. */
3904 change
&= ~PNG_FORMAT_FLAG_ALPHA
;
3907 /* Now set the alpha mode correctly; this is always done, even if there is
3908 * no alpha channel in either the input or the output because it correctly
3909 * sets the output gamma.
3911 png_set_alpha_mode_fixed(png_ptr
, mode
, output_gamma
);
3913 # ifdef PNG_FORMAT_BGR_SUPPORTED
3914 if ((change
& PNG_FORMAT_FLAG_BGR
) != 0)
3916 /* Check only the output format; PNG is never BGR; don't do this if
3917 * the output is gray, but fix up the 'format' value in that case.
3919 if ((format
& PNG_FORMAT_FLAG_COLOR
) != 0)
3920 png_set_bgr(png_ptr
);
3923 format
&= ~PNG_FORMAT_FLAG_BGR
;
3925 change
&= ~PNG_FORMAT_FLAG_BGR
;
3929 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3930 if ((change
& PNG_FORMAT_FLAG_AFIRST
) != 0)
3932 /* Only relevant if there is an alpha channel - it's particularly
3933 * important to handle this correctly because do_local_compose may
3934 * be set above and then libpng will keep the alpha channel for this
3937 if ((format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3939 /* Disable this if doing a local background,
3940 * TODO: remove this when local background is no longer required.
3942 if (do_local_background
!= 2)
3943 png_set_swap_alpha(png_ptr
);
3947 format
&= ~PNG_FORMAT_FLAG_AFIRST
;
3949 change
&= ~PNG_FORMAT_FLAG_AFIRST
;
3953 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3958 png_uint_16 le
= 0x0001;
3960 if ((*(png_const_bytep
) & le
) != 0)
3961 png_set_swap(png_ptr
);
3964 /* If change is not now 0 some transformation is missing - error out. */
3966 png_error(png_ptr
, "png_read_image: unsupported transformation");
3969 PNG_SKIP_CHUNKS(png_ptr
);
3971 /* Update the 'info' structure and make sure the result is as required; first
3972 * make sure to turn on the interlace handling if it will be required
3973 * (because it can't be turned on *after* the call to png_read_update_info!)
3975 * TODO: remove the do_local_background fixup below.
3977 if (do_local_compose
== 0 && do_local_background
!= 2)
3978 passes
= png_set_interlace_handling(png_ptr
);
3980 png_read_update_info(png_ptr
, info_ptr
);
3983 png_uint_32 info_format
= 0;
3985 if ((info_ptr
->color_type
& PNG_COLOR_MASK_COLOR
) != 0)
3986 info_format
|= PNG_FORMAT_FLAG_COLOR
;
3988 if ((info_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0)
3990 /* do_local_compose removes this channel below. */
3991 if (do_local_compose
== 0)
3993 /* do_local_background does the same if required. */
3994 if (do_local_background
!= 2 ||
3995 (format
& PNG_FORMAT_FLAG_ALPHA
) != 0)
3996 info_format
|= PNG_FORMAT_FLAG_ALPHA
;
4000 else if (do_local_compose
!= 0) /* internal error */
4001 png_error(png_ptr
, "png_image_read: alpha channel lost");
4003 if ((format
& PNG_FORMAT_FLAG_ASSOCIATED_ALPHA
) != 0) {
4004 info_format
|= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA
;
4007 if (info_ptr
->bit_depth
== 16)
4008 info_format
|= PNG_FORMAT_FLAG_LINEAR
;
4010 #ifdef PNG_FORMAT_BGR_SUPPORTED
4011 if ((png_ptr
->transformations
& PNG_BGR
) != 0)
4012 info_format
|= PNG_FORMAT_FLAG_BGR
;
4015 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
4016 if (do_local_background
== 2)
4018 if ((format
& PNG_FORMAT_FLAG_AFIRST
) != 0)
4019 info_format
|= PNG_FORMAT_FLAG_AFIRST
;
4022 if ((png_ptr
->transformations
& PNG_SWAP_ALPHA
) != 0 ||
4023 ((png_ptr
->transformations
& PNG_ADD_ALPHA
) != 0 &&
4024 (png_ptr
->flags
& PNG_FLAG_FILLER_AFTER
) == 0))
4026 if (do_local_background
== 2)
4027 png_error(png_ptr
, "unexpected alpha swap transformation");
4029 info_format
|= PNG_FORMAT_FLAG_AFIRST
;
4033 /* This is actually an internal error. */
4034 if (info_format
!= format
)
4035 png_error(png_ptr
, "png_read_image: invalid transformations");
4038 /* Now read the rows. If do_local_compose is set then it is necessary to use
4039 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4040 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4041 * display acts as a flag.
4044 png_voidp first_row
= display
->buffer
;
4045 ptrdiff_t row_bytes
= display
->row_stride
;
4050 /* The following expression is designed to work correctly whether it gives
4051 * a signed or an unsigned result.
4055 char *ptr
= png_voidcast(char*, first_row
);
4056 ptr
+= (image
->height
-1) * (-row_bytes
);
4057 first_row
= png_voidcast(png_voidp
, ptr
);
4060 display
->first_row
= first_row
;
4061 display
->row_bytes
= row_bytes
;
4064 if (do_local_compose
!= 0)
4067 png_voidp row
= png_malloc(png_ptr
, png_get_rowbytes(png_ptr
, info_ptr
));
4069 display
->local_row
= row
;
4070 result
= png_safe_execute(image
, png_image_read_composite
, display
);
4071 display
->local_row
= NULL
;
4072 png_free(png_ptr
, row
);
4077 else if (do_local_background
== 2)
4080 png_voidp row
= png_malloc(png_ptr
, png_get_rowbytes(png_ptr
, info_ptr
));
4082 display
->local_row
= row
;
4083 result
= png_safe_execute(image
, png_image_read_background
, display
);
4084 display
->local_row
= NULL
;
4085 png_free(png_ptr
, row
);
4092 png_alloc_size_t row_bytes
= (png_alloc_size_t
)display
->row_bytes
;
4094 while (--passes
>= 0)
4096 png_uint_32 y
= image
->height
;
4097 png_bytep row
= png_voidcast(png_bytep
, display
->first_row
);
4101 png_read_row(png_ptr
, row
, NULL
);
4111 png_image_finish_read(png_imagep image
, png_const_colorp background
,
4112 void *buffer
, png_int_32 row_stride
, void *colormap
)
4114 if (image
!= NULL
&& image
->version
== PNG_IMAGE_VERSION
)
4116 /* Check for row_stride overflow. This check is not performed on the
4117 * original PNG format because it may not occur in the output PNG format
4118 * and libpng deals with the issues of reading the original.
4120 unsigned int channels
= PNG_IMAGE_PIXEL_CHANNELS(image
->format
);
4122 /* The following checks just the 'row_stride' calculation to ensure it
4123 * fits in a signed 32-bit value. Because channels/components can be
4124 * either 1 or 2 bytes in size the length of a row can still overflow 32
4125 * bits; this is just to verify that the 'row_stride' argument can be
4128 if (image
->width
<= 0x7fffffffU
/channels
) /* no overflow */
4131 png_uint_32 png_row_stride
= image
->width
* channels
;
4133 if (row_stride
== 0)
4134 row_stride
= (png_int_32
)/*SAFE*/png_row_stride
;
4137 check
= (png_uint_32
)(-row_stride
);
4140 check
= (png_uint_32
)row_stride
;
4142 /* This verifies 'check', the absolute value of the actual stride
4143 * passed in and detects overflow in the application calculation (i.e.
4144 * if the app did actually pass in a non-zero 'row_stride'.
4146 if (image
->opaque
!= NULL
&& buffer
!= NULL
&& check
>= png_row_stride
)
4148 /* Now check for overflow of the image buffer calculation; this
4149 * limits the whole image size to 32 bits for API compatibility with
4150 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4152 * The PNG_IMAGE_BUFFER_SIZE macro is:
4154 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4156 * And the component size is always 1 or 2, so make sure that the
4157 * number of *bytes* that the application is saying are available
4158 * does actually fit into a 32-bit number.
4160 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4161 * will be changed to use png_alloc_size_t; bigger images can be
4162 * accommodated on 64-bit systems.
4164 if (image
->height
<=
4165 0xffffffffU
/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image
->format
)/check
)
4167 if ((image
->format
& PNG_FORMAT_FLAG_COLORMAP
) == 0 ||
4168 (image
->colormap_entries
> 0 && colormap
!= NULL
))
4171 png_image_read_control display
;
4173 memset(&display
, 0, (sizeof display
));
4174 display
.image
= image
;
4175 display
.buffer
= buffer
;
4176 display
.row_stride
= row_stride
;
4177 display
.colormap
= colormap
;
4178 display
.background
= background
;
4179 display
.local_row
= NULL
;
4181 /* Choose the correct 'end' routine; for the color-map case
4182 * all the setup has already been done.
4184 if ((image
->format
& PNG_FORMAT_FLAG_COLORMAP
) != 0)
4186 png_safe_execute(image
,
4187 png_image_read_colormap
, &display
) &&
4188 png_safe_execute(image
,
4189 png_image_read_colormapped
, &display
);
4193 png_safe_execute(image
,
4194 png_image_read_direct
, &display
);
4196 png_image_free(image
);
4201 return png_image_error(image
,
4202 "png_image_finish_read[color-map]: no color-map");
4206 return png_image_error(image
,
4207 "png_image_finish_read: image too large");
4211 return png_image_error(image
,
4212 "png_image_finish_read: invalid argument");
4216 return png_image_error(image
,
4217 "png_image_finish_read: row_stride too large");
4220 else if (image
!= NULL
)
4221 return png_image_error(image
,
4222 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4227 #endif /* SIMPLIFIED_READ */