1 /* jpeg.c - load JPEG image from file
3 * Raster graphics library
5 * Copyright (c) 1997 Alfredo K. Kojima
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the Free
19 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
25 /* Avoid a compiler warning */
41 * <setjmp.h> is used for the optional error recovery mechanism shown in
42 * the second part of the example.
50 * The JPEG library's standard error handler (jerror.c) is divided into
51 * several "methods" which you can override individually. This lets you
52 * adjust the behavior without duplicating a lot of code, which you might
53 * have to update with each future release.
55 * Our example here shows how to override the "error_exit" method so that
56 * control is returned to the library's caller when a fatal error occurs,
57 * rather than calling exit() as the standard error_exit method does.
59 * We use C's setjmp/longjmp facility to return control. This means that the
60 * routine which calls the JPEG library must first execute a setjmp() call to
61 * establish the return point. We want the replacement error_exit to do a
62 * longjmp(). But we need to make the setjmp buffer accessible to the
63 * error_exit routine. To do this, we make a private extension of the
64 * standard JPEG error handler object. (If we were using C++, we'd say we
65 * were making a subclass of the regular error handler.)
67 * Here's the extended error handler struct:
71 struct jpeg_error_mgr pub
; /* "public" fields */
73 jmp_buf setjmp_buffer
; /* for return to caller */
76 typedef struct my_error_mgr
* my_error_ptr
;
79 * Here's the routine that will replace the standard error_exit method:
83 my_error_exit(j_common_ptr cinfo
)
85 /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
86 my_error_ptr myerr
= (my_error_ptr
) cinfo
->err
;
88 /* Always display the message. */
89 /* We could postpone this until after returning, if we chose. */
90 (*cinfo
->err
->output_message
) (cinfo
);
92 /* Return control to the setjmp point */
93 longjmp(myerr
->setjmp_buffer
, 1);
98 RLoadJPEG(RContext
*context
, char *file_name
, int index
)
100 RImage
*image
= NULL
;
101 struct jpeg_decompress_struct cinfo
;
104 JSAMPROW buffer
[1], bptr
;
106 /* We use our private extension JPEG error handler.
107 * Note that this struct must live as long as the main JPEG parameter
108 * struct, to avoid dangling-pointer problems.
110 struct my_error_mgr jerr
;
112 file
= fopen(file_name
, "r");
114 RErrorCode
= RERR_OPEN
;
118 cinfo
.err
= jpeg_std_error(&jerr
.pub
);
119 jerr
.pub
.error_exit
= my_error_exit
;
120 /* Establish the setjmp return context for my_error_exit to use. */
121 if (setjmp(jerr
.setjmp_buffer
)) {
122 /* If we get here, the JPEG code has signaled an error.
123 * We need to clean up the JPEG object, close the input file, and return.
125 jpeg_destroy_decompress(&cinfo
);
130 jpeg_create_decompress(&cinfo
);
132 jpeg_stdio_src(&cinfo
, file
);
134 jpeg_read_header(&cinfo
, TRUE
);
136 bptr
= buffer
[0] = (JSAMPROW
)malloc(cinfo
.image_width
*cinfo
.num_components
);
138 RErrorCode
= RERR_NOMEMORY
;
142 if(cinfo
.jpeg_color_space
==JCS_GRAYSCALE
) {
143 cinfo
.out_color_space
=JCS_GRAYSCALE
;
145 cinfo
.out_color_space
= JCS_RGB
;
146 cinfo
.quantize_colors
= FALSE
;
147 cinfo
.do_fancy_upsampling
= FALSE
;
148 cinfo
.do_block_smoothing
= FALSE
;
149 jpeg_calc_output_dimensions(&cinfo
);
151 if (context
->flags
.optimize_for_speed
)
152 image
= RCreateImage(cinfo
.image_width
, cinfo
.image_height
, True
);
154 image
= RCreateImage(cinfo
.image_width
, cinfo
.image_height
, False
);
157 RErrorCode
= RERR_NOMEMORY
;
160 jpeg_start_decompress(&cinfo
);
165 if (cinfo
.out_color_space
==JCS_RGB
) {
166 if (context
->flags
.optimize_for_speed
) {
167 while (cinfo
.output_scanline
< cinfo
.output_height
) {
168 jpeg_read_scanlines(&cinfo
, buffer
,(JDIMENSION
) 1);
170 for (i
=0; i
<cinfo
.image_width
; i
++) {
174 ptr
++; /* skip alpha channel */
178 while (cinfo
.output_scanline
< cinfo
.output_height
) {
179 jpeg_read_scanlines(&cinfo
, buffer
,(JDIMENSION
) 1);
181 memcpy(ptr
, bptr
, cinfo
.image_width
*3);
182 ptr
+= cinfo
.image_width
*3;
186 while (cinfo
.output_scanline
< cinfo
.output_height
) {
187 jpeg_read_scanlines(&cinfo
, buffer
,(JDIMENSION
) 1);
189 for (i
=0; i
<cinfo
.image_width
; i
++) {
197 jpeg_finish_decompress(&cinfo
);
200 jpeg_destroy_decompress(&cinfo
);
210 #endif /* USE_JPEG */