4 * Copyright (C) 1991-1998, Thomas G. Lane.
5 * Modified 2003-2022 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
9 * This file contains optional default-setting code for the JPEG compressor.
10 * Applications do not have to use this file, but those that don't use it
11 * must know a lot more about the innards of the JPEG code.
14 #define JPEG_INTERNALS
20 * Quantization table setup routines
24 jpeg_add_quant_table (j_compress_ptr cinfo
, int which_tbl
,
25 const unsigned int *basic_table
,
26 int scale_factor
, boolean force_baseline
)
27 /* Define a quantization table equal to the basic_table times
28 * a scale factor (given as a percentage).
29 * If force_baseline is TRUE, the computed quantization table entries
30 * are limited to 1..255 for JPEG baseline compatibility.
33 JQUANT_TBL
** qtblptr
;
37 /* Safety check to ensure start_compress not called yet. */
38 if (cinfo
->global_state
!= CSTATE_START
)
39 ERREXIT1(cinfo
, JERR_BAD_STATE
, cinfo
->global_state
);
41 if (which_tbl
< 0 || which_tbl
>= NUM_QUANT_TBLS
)
42 ERREXIT1(cinfo
, JERR_DQT_INDEX
, which_tbl
);
44 qtblptr
= & cinfo
->quant_tbl_ptrs
[which_tbl
];
47 *qtblptr
= jpeg_alloc_quant_table((j_common_ptr
) cinfo
);
49 for (i
= 0; i
< DCTSIZE2
; i
++) {
50 temp
= ((long) basic_table
[i
] * scale_factor
+ 50L) / 100L;
51 /* limit the values to the valid range */
52 if (temp
<= 0L) temp
= 1L;
53 if (temp
> 32767L) temp
= 32767L; /* max quantizer needed for 12 bits */
54 if (force_baseline
&& temp
> 255L)
55 temp
= 255L; /* limit to baseline range if requested */
56 (*qtblptr
)->quantval
[i
] = (UINT16
) temp
;
59 /* Initialize sent_table FALSE so table will be written to JPEG file. */
60 (*qtblptr
)->sent_table
= FALSE
;
64 /* These are the sample quantization tables given in JPEG spec section K.1.
65 * NOTE: chrominance DC value is changed from 17 to 16 for lossless support.
66 * The spec says that the values given produce "good" quality,
67 * and when divided by 2, "very good" quality.
69 static const unsigned int std_luminance_quant_tbl
[DCTSIZE2
] = {
70 16, 11, 10, 16, 24, 40, 51, 61,
71 12, 12, 14, 19, 26, 58, 60, 55,
72 14, 13, 16, 24, 40, 57, 69, 56,
73 14, 17, 22, 29, 51, 87, 80, 62,
74 18, 22, 37, 56, 68, 109, 103, 77,
75 24, 35, 55, 64, 81, 104, 113, 92,
76 49, 64, 78, 87, 103, 121, 120, 101,
77 72, 92, 95, 98, 112, 100, 103, 99
79 static const unsigned int std_chrominance_quant_tbl
[DCTSIZE2
] = {
80 16, 18, 24, 47, 99, 99, 99, 99,
81 18, 21, 26, 66, 99, 99, 99, 99,
82 24, 26, 56, 99, 99, 99, 99, 99,
83 47, 66, 99, 99, 99, 99, 99, 99,
84 99, 99, 99, 99, 99, 99, 99, 99,
85 99, 99, 99, 99, 99, 99, 99, 99,
86 99, 99, 99, 99, 99, 99, 99, 99,
87 99, 99, 99, 99, 99, 99, 99, 99
92 jpeg_default_qtables (j_compress_ptr cinfo
, boolean force_baseline
)
93 /* Set or change the 'quality' (quantization) setting, using default tables
94 * and straight percentage-scaling quality scales.
95 * This entry point allows different scalings for luminance and chrominance.
98 /* Set up two quantization tables using the specified scaling */
99 jpeg_add_quant_table(cinfo
, 0, std_luminance_quant_tbl
,
100 cinfo
->q_scale_factor
[0], force_baseline
);
101 jpeg_add_quant_table(cinfo
, 1, std_chrominance_quant_tbl
,
102 cinfo
->q_scale_factor
[1], force_baseline
);
107 jpeg_set_linear_quality (j_compress_ptr cinfo
, int scale_factor
,
108 boolean force_baseline
)
109 /* Set or change the 'quality' (quantization) setting, using default tables
110 * and a straight percentage-scaling quality scale. In most cases it's better
111 * to use jpeg_set_quality (below); this entry point is provided for
112 * applications that insist on a linear percentage scaling.
115 /* Set up two quantization tables using the specified scaling */
116 jpeg_add_quant_table(cinfo
, 0, std_luminance_quant_tbl
,
117 scale_factor
, force_baseline
);
118 jpeg_add_quant_table(cinfo
, 1, std_chrominance_quant_tbl
,
119 scale_factor
, force_baseline
);
124 jpeg_quality_scaling (int quality
)
125 /* Convert a user-specified quality rating to a percentage scaling factor
126 * for an underlying quantization table, using our recommended scaling curve.
127 * The input 'quality' factor should be 0 (terrible) to 100 (very good).
130 /* Safety limit on quality factor. Convert 0 to 1 to avoid zero divide. */
131 if (quality
<= 0) quality
= 1;
132 if (quality
> 100) quality
= 100;
134 /* The basic table is used as-is (scaling 100) for a quality of 50.
135 * Qualities 50..100 are converted to scaling percentage 200 - 2*Q;
136 * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table
137 * to make all the table entries 1 (hence, minimum quantization loss).
138 * Qualities 1..50 are converted to scaling percentage 5000/Q.
141 quality
= 5000 / quality
;
143 quality
= 200 - quality
*2;
150 jpeg_set_quality (j_compress_ptr cinfo
, int quality
, boolean force_baseline
)
151 /* Set or change the 'quality' (quantization) setting, using default tables.
152 * This is the standard quality-adjusting entry point for typical user
153 * interfaces; only those who want detailed control over quantization tables
154 * would use the preceding routines directly.
157 /* Convert user 0-100 rating to percentage scaling */
158 quality
= jpeg_quality_scaling(quality
);
160 /* Set up standard quality tables */
161 jpeg_set_linear_quality(cinfo
, quality
, force_baseline
);
166 * Reset standard Huffman tables
170 std_huff_tables (j_compress_ptr cinfo
)
172 if (cinfo
->dc_huff_tbl_ptrs
[0] != NULL
)
173 (void) jpeg_std_huff_table((j_common_ptr
) cinfo
, TRUE
, 0);
175 if (cinfo
->ac_huff_tbl_ptrs
[0] != NULL
)
176 (void) jpeg_std_huff_table((j_common_ptr
) cinfo
, FALSE
, 0);
178 if (cinfo
->dc_huff_tbl_ptrs
[1] != NULL
)
179 (void) jpeg_std_huff_table((j_common_ptr
) cinfo
, TRUE
, 1);
181 if (cinfo
->ac_huff_tbl_ptrs
[1] != NULL
)
182 (void) jpeg_std_huff_table((j_common_ptr
) cinfo
, FALSE
, 1);
187 * Default parameter setup for compression.
189 * Applications that don't choose to use this routine must do their
190 * own setup of all these parameters. Alternately, you can call this
191 * to establish defaults and then alter parameters selectively. This
192 * is the recommended approach since, if we add any new parameters,
193 * your code will still work (they'll be set to reasonable defaults).
197 jpeg_set_defaults (j_compress_ptr cinfo
)
201 /* Safety check to ensure start_compress not called yet. */
202 if (cinfo
->global_state
!= CSTATE_START
)
203 ERREXIT1(cinfo
, JERR_BAD_STATE
, cinfo
->global_state
);
205 /* Allocate comp_info array large enough for maximum component count.
206 * Array is made permanent in case application wants to compress
207 * multiple images at same param settings.
209 if (cinfo
->comp_info
== NULL
)
210 cinfo
->comp_info
= (jpeg_component_info
*)
211 (*cinfo
->mem
->alloc_small
) ((j_common_ptr
) cinfo
, JPOOL_PERMANENT
,
212 MAX_COMPONENTS
* SIZEOF(jpeg_component_info
));
214 /* Initialize everything not dependent on the color space */
216 cinfo
->scale_num
= 1; /* 1:1 scaling */
217 cinfo
->scale_denom
= 1;
218 cinfo
->data_precision
= BITS_IN_JSAMPLE
;
219 /* Set up two quantization tables using default quality of 75 */
220 jpeg_set_quality(cinfo
, 75, TRUE
);
221 /* Reset standard Huffman tables */
222 std_huff_tables(cinfo
);
224 /* Initialize default arithmetic coding conditioning */
225 for (i
= 0; i
< NUM_ARITH_TBLS
; i
++) {
226 cinfo
->arith_dc_L
[i
] = 0;
227 cinfo
->arith_dc_U
[i
] = 1;
228 cinfo
->arith_ac_K
[i
] = 5;
231 /* Default is no multiple-scan output */
232 cinfo
->scan_info
= NULL
;
233 cinfo
->num_scans
= 0;
235 /* Expect normal source image, not raw downsampled data */
236 cinfo
->raw_data_in
= FALSE
;
238 /* The standard Huffman tables are only valid for 8-bit data precision.
239 * If the precision is higher, use arithmetic coding.
240 * (Alternatively, using Huffman coding would be possible with forcing
241 * optimization on so that usable tables will be computed, or by
242 * supplying default tables that are valid for the desired precision.)
243 * Otherwise, use Huffman coding by default.
245 cinfo
->arith_code
= cinfo
->data_precision
> 8 ? TRUE
: FALSE
;
247 /* By default, don't do extra passes to optimize entropy coding */
248 cinfo
->optimize_coding
= FALSE
;
250 /* By default, use the simpler non-cosited sampling alignment */
251 cinfo
->CCIR601_sampling
= FALSE
;
253 /* By default, apply fancy downsampling */
254 cinfo
->do_fancy_downsampling
= TRUE
;
256 /* No input smoothing */
257 cinfo
->smoothing_factor
= 0;
259 /* DCT algorithm preference */
260 cinfo
->dct_method
= JDCT_DEFAULT
;
262 /* No restart markers */
263 cinfo
->restart_interval
= 0;
264 cinfo
->restart_in_rows
= 0;
266 /* Fill in default JFIF marker parameters. Note that whether the marker
267 * will actually be written is determined by jpeg_set_colorspace.
269 * By default, the library emits JFIF version code 1.01.
270 * An application that wants to emit JFIF 1.02 extension markers should set
271 * JFIF_minor_version to 2. We could probably get away with just defaulting
272 * to 1.02, but there may still be some decoders in use that will complain
273 * about that; saying 1.01 should minimize compatibility problems.
275 * For wide gamut colorspaces (BG_RGB and BG_YCC), the major version will be
276 * overridden by jpeg_set_colorspace and set to 2.
278 cinfo
->JFIF_major_version
= 1; /* Default JFIF version = 1.01 */
279 cinfo
->JFIF_minor_version
= 1;
280 cinfo
->density_unit
= 0; /* Pixel size is unknown by default */
281 cinfo
->X_density
= 1; /* Pixel aspect ratio is square by default */
282 cinfo
->Y_density
= 1;
284 /* No color transform */
285 cinfo
->color_transform
= JCT_NONE
;
287 /* Choose JPEG colorspace based on input space, set defaults accordingly */
289 jpeg_default_colorspace(cinfo
);
294 * Select an appropriate JPEG colorspace for in_color_space.
298 jpeg_default_colorspace (j_compress_ptr cinfo
)
300 switch (cinfo
->in_color_space
) {
302 jpeg_set_colorspace(cinfo
, JCS_UNKNOWN
);
305 jpeg_set_colorspace(cinfo
, JCS_GRAYSCALE
);
308 jpeg_set_colorspace(cinfo
, JCS_YCbCr
);
311 jpeg_set_colorspace(cinfo
, JCS_YCbCr
);
314 jpeg_set_colorspace(cinfo
, JCS_CMYK
); /* By default, no translation */
317 jpeg_set_colorspace(cinfo
, JCS_YCCK
);
320 /* No translation for now -- conversion to BG_YCC not yet supportet */
321 jpeg_set_colorspace(cinfo
, JCS_BG_RGB
);
324 jpeg_set_colorspace(cinfo
, JCS_BG_YCC
);
327 ERREXIT(cinfo
, JERR_BAD_IN_COLORSPACE
);
333 * Set the JPEG colorspace, and choose colorspace-dependent default values.
337 jpeg_set_colorspace (j_compress_ptr cinfo
, J_COLOR_SPACE colorspace
)
339 jpeg_component_info
* compptr
;
342 #define SET_COMP(index,id,hsamp,vsamp,quant,dctbl,actbl) \
343 (compptr = &cinfo->comp_info[index], \
344 compptr->component_id = (id), \
345 compptr->h_samp_factor = (hsamp), \
346 compptr->v_samp_factor = (vsamp), \
347 compptr->quant_tbl_no = (quant), \
348 compptr->dc_tbl_no = (dctbl), \
349 compptr->ac_tbl_no = (actbl) )
351 /* Safety check to ensure start_compress not called yet. */
352 if (cinfo
->global_state
!= CSTATE_START
)
353 ERREXIT1(cinfo
, JERR_BAD_STATE
, cinfo
->global_state
);
355 /* For all colorspaces, we use Q and Huff tables 0 for luminance components,
356 * tables 1 for chrominance components.
359 cinfo
->jpeg_color_space
= colorspace
;
361 cinfo
->write_JFIF_header
= FALSE
; /* No marker for non-JFIF colorspaces */
362 cinfo
->write_Adobe_marker
= FALSE
; /* write no Adobe marker by default */
364 switch (colorspace
) {
366 cinfo
->num_components
= cinfo
->input_components
;
367 if (cinfo
->num_components
< 1 || cinfo
->num_components
> MAX_COMPONENTS
)
368 ERREXIT2(cinfo
, JERR_COMPONENT_COUNT
, cinfo
->num_components
,
370 for (ci
= 0; ci
< cinfo
->num_components
; ci
++) {
371 SET_COMP(ci
, ci
, 1,1, 0, 0,0);
375 cinfo
->write_JFIF_header
= TRUE
; /* Write a JFIF marker */
376 cinfo
->num_components
= 1;
377 /* JFIF specifies component ID 1 */
378 SET_COMP(0, 0x01, 1,1, 0, 0,0);
381 cinfo
->write_Adobe_marker
= TRUE
; /* write Adobe marker to flag RGB */
382 cinfo
->num_components
= 3;
383 SET_COMP(0, 0x52 /* 'R' */, 1,1,
384 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
385 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
386 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0);
387 SET_COMP(1, 0x47 /* 'G' */, 1,1, 0, 0,0);
388 SET_COMP(2, 0x42 /* 'B' */, 1,1,
389 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
390 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
391 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0);
394 cinfo
->write_JFIF_header
= TRUE
; /* Write a JFIF marker */
395 cinfo
->num_components
= 3;
396 /* JFIF specifies component IDs 1,2,3 */
397 /* We default to 2x2 subsamples of chrominance */
398 SET_COMP(0, 0x01, 2,2, 0, 0,0);
399 SET_COMP(1, 0x02, 1,1, 1, 1,1);
400 SET_COMP(2, 0x03, 1,1, 1, 1,1);
403 cinfo
->write_Adobe_marker
= TRUE
; /* write Adobe marker to flag CMYK */
404 cinfo
->num_components
= 4;
405 SET_COMP(0, 0x43 /* 'C' */, 1,1, 0, 0,0);
406 SET_COMP(1, 0x4D /* 'M' */, 1,1, 0, 0,0);
407 SET_COMP(2, 0x59 /* 'Y' */, 1,1, 0, 0,0);
408 SET_COMP(3, 0x4B /* 'K' */, 1,1, 0, 0,0);
411 cinfo
->write_Adobe_marker
= TRUE
; /* write Adobe marker to flag YCCK */
412 cinfo
->num_components
= 4;
413 SET_COMP(0, 0x01, 2,2, 0, 0,0);
414 SET_COMP(1, 0x02, 1,1, 1, 1,1);
415 SET_COMP(2, 0x03, 1,1, 1, 1,1);
416 SET_COMP(3, 0x04, 2,2, 0, 0,0);
419 cinfo
->write_JFIF_header
= TRUE
; /* Write a JFIF marker */
420 cinfo
->JFIF_major_version
= 2; /* Set JFIF major version = 2 */
421 cinfo
->num_components
= 3;
422 /* Add offset 0x20 to the normal R/G/B component IDs */
423 SET_COMP(0, 0x72 /* 'r' */, 1,1,
424 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
425 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
426 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0);
427 SET_COMP(1, 0x67 /* 'g' */, 1,1, 0, 0,0);
428 SET_COMP(2, 0x62 /* 'b' */, 1,1,
429 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
430 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0,
431 cinfo
->color_transform
== JCT_SUBTRACT_GREEN
? 1 : 0);
434 cinfo
->write_JFIF_header
= TRUE
; /* Write a JFIF marker */
435 cinfo
->JFIF_major_version
= 2; /* Set JFIF major version = 2 */
436 cinfo
->num_components
= 3;
437 /* Add offset 0x20 to the normal Cb/Cr component IDs */
438 /* We default to 2x2 subsamples of chrominance */
439 SET_COMP(0, 0x01, 2,2, 0, 0,0);
440 SET_COMP(1, 0x22, 1,1, 1, 1,1);
441 SET_COMP(2, 0x23, 1,1, 1, 1,1);
444 ERREXIT(cinfo
, JERR_BAD_J_COLORSPACE
);
449 #ifdef C_PROGRESSIVE_SUPPORTED
451 LOCAL(jpeg_scan_info
*)
452 fill_a_scan (jpeg_scan_info
* scanptr
, int ci
,
453 int Ss
, int Se
, int Ah
, int Al
)
454 /* Support routine: generate one scan for specified component */
456 scanptr
->comps_in_scan
= 1;
457 scanptr
->component_index
[0] = ci
;
466 LOCAL(jpeg_scan_info
*)
467 fill_scans (jpeg_scan_info
* scanptr
, int ncomps
,
468 int Ss
, int Se
, int Ah
, int Al
)
469 /* Support routine: generate one scan for each component */
473 for (ci
= 0; ci
< ncomps
; ci
++) {
474 scanptr
->comps_in_scan
= 1;
475 scanptr
->component_index
[0] = ci
;
485 LOCAL(jpeg_scan_info
*)
486 fill_dc_scans (jpeg_scan_info
* scanptr
, int ncomps
, int Ah
, int Al
)
487 /* Support routine: generate interleaved DC scan if possible, else N scans */
491 if (ncomps
<= MAX_COMPS_IN_SCAN
) {
492 /* Single interleaved DC scan */
493 scanptr
->comps_in_scan
= ncomps
;
494 for (ci
= 0; ci
< ncomps
; ci
++)
495 scanptr
->component_index
[ci
] = ci
;
496 scanptr
->Ss
= scanptr
->Se
= 0;
501 /* Noninterleaved DC scan for each component */
502 scanptr
= fill_scans(scanptr
, ncomps
, 0, 0, Ah
, Al
);
509 * Create a recommended progressive-JPEG script.
510 * cinfo->num_components and cinfo->jpeg_color_space must be correct.
514 jpeg_simple_progression (j_compress_ptr cinfo
)
516 int ncomps
= cinfo
->num_components
;
518 jpeg_scan_info
* scanptr
;
520 /* Safety check to ensure start_compress not called yet. */
521 if (cinfo
->global_state
!= CSTATE_START
)
522 ERREXIT1(cinfo
, JERR_BAD_STATE
, cinfo
->global_state
);
524 /* Figure space needed for script. Calculation must match code below! */
526 (cinfo
->jpeg_color_space
== JCS_YCbCr
||
527 cinfo
->jpeg_color_space
== JCS_BG_YCC
)) {
528 /* Custom script for YCC color images. */
531 /* All-purpose script for other color spaces. */
532 if (ncomps
> MAX_COMPS_IN_SCAN
)
533 nscans
= 6 * ncomps
; /* 2 DC + 4 AC scans per component */
535 nscans
= 2 + 4 * ncomps
; /* 2 DC scans; 4 AC scans per component */
538 /* Allocate space for script.
539 * We need to put it in the permanent pool in case the application performs
540 * multiple compressions without changing the settings. To avoid a memory
541 * leak if jpeg_simple_progression is called repeatedly for the same JPEG
542 * object, we try to re-use previously allocated space, and we allocate
543 * enough space to handle YCC even if initially asked for grayscale.
545 if (cinfo
->script_space
== NULL
|| cinfo
->script_space_size
< nscans
) {
546 cinfo
->script_space_size
= MAX(nscans
, 10);
547 cinfo
->script_space
= (jpeg_scan_info
*)
548 (*cinfo
->mem
->alloc_small
) ((j_common_ptr
) cinfo
, JPOOL_PERMANENT
,
549 cinfo
->script_space_size
* SIZEOF(jpeg_scan_info
));
551 scanptr
= cinfo
->script_space
;
552 cinfo
->scan_info
= scanptr
;
553 cinfo
->num_scans
= nscans
;
556 (cinfo
->jpeg_color_space
== JCS_YCbCr
||
557 cinfo
->jpeg_color_space
== JCS_BG_YCC
)) {
558 /* Custom script for YCC color images. */
559 /* Initial DC scan */
560 scanptr
= fill_dc_scans(scanptr
, ncomps
, 0, 1);
561 /* Initial AC scan: get some luma data out in a hurry */
562 scanptr
= fill_a_scan(scanptr
, 0, 1, 5, 0, 2);
563 /* Chroma data is too small to be worth expending many scans on */
564 scanptr
= fill_a_scan(scanptr
, 2, 1, 63, 0, 1);
565 scanptr
= fill_a_scan(scanptr
, 1, 1, 63, 0, 1);
566 /* Complete spectral selection for luma AC */
567 scanptr
= fill_a_scan(scanptr
, 0, 6, 63, 0, 2);
568 /* Refine next bit of luma AC */
569 scanptr
= fill_a_scan(scanptr
, 0, 1, 63, 2, 1);
570 /* Finish DC successive approximation */
571 scanptr
= fill_dc_scans(scanptr
, ncomps
, 1, 0);
572 /* Finish AC successive approximation */
573 scanptr
= fill_a_scan(scanptr
, 2, 1, 63, 1, 0);
574 scanptr
= fill_a_scan(scanptr
, 1, 1, 63, 1, 0);
575 /* Luma bottom bit comes last since it's usually largest scan */
576 scanptr
= fill_a_scan(scanptr
, 0, 1, 63, 1, 0);
578 /* All-purpose script for other color spaces. */
579 /* Successive approximation first pass */
580 scanptr
= fill_dc_scans(scanptr
, ncomps
, 0, 1);
581 scanptr
= fill_scans(scanptr
, ncomps
, 1, 5, 0, 2);
582 scanptr
= fill_scans(scanptr
, ncomps
, 6, 63, 0, 2);
583 /* Successive approximation second pass */
584 scanptr
= fill_scans(scanptr
, ncomps
, 1, 63, 2, 1);
585 /* Successive approximation final pass */
586 scanptr
= fill_dc_scans(scanptr
, ncomps
, 1, 0);
587 scanptr
= fill_scans(scanptr
, ncomps
, 1, 63, 1, 0);
591 #endif /* C_PROGRESSIVE_SUPPORTED */