ReactOS 0.4.15-dev-8236-g99f0937
example.c File Reference
#include <stdio.h>
#include "jpeglib.h"
#include <setjmp.h>
Include dependency graph for example.c:

Go to the source code of this file.

Classes

struct  my_error_mgr
 

Typedefs

typedef struct my_error_mgrmy_error_ptr
 

Functions

 write_JPEG_file (char *filename, int quality)
 
 my_error_exit (j_common_ptr cinfo)
 
 read_JPEG_file (char *filename)
 

Variables

JSAMPLEimage_buffer
 
int image_height
 
int image_width
 

Typedef Documentation

◆ my_error_ptr

Definition at line 256 of file example.c.

Function Documentation

◆ my_error_exit()

my_error_exit ( j_common_ptr  cinfo)

Definition at line 263 of file example.c.

264{
265 /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
266 my_error_ptr myerr = (my_error_ptr) cinfo->err;
267
268 /* Always display the message. */
269 /* We could postpone this until after returning, if we chose. */
270 (*cinfo->err->output_message) (cinfo);
271
272 /* Return control to the setjmp point */
273 longjmp(myerr->setjmp_buffer, 1);
274}
struct my_error_mgr * my_error_ptr
Definition: example.c:256
jmp_buf setjmp_buffer
Definition: example.c:253

Referenced by read_JPEG_file().

◆ read_JPEG_file()

read_JPEG_file ( char filename)

Definition at line 284 of file example.c.

285{
286 /* This struct contains the JPEG decompression parameters and pointers to
287 * working space (which is allocated as needed by the JPEG library).
288 */
289 struct jpeg_decompress_struct cinfo;
290 /* We use our private extension JPEG error handler.
291 * Note that this struct must live as long as the main JPEG parameter
292 * struct, to avoid dangling-pointer problems.
293 */
294 struct my_error_mgr jerr;
295 /* More stuff */
296 FILE * infile; /* source file */
297 JSAMPARRAY buffer; /* Output row buffer */
298 int row_stride; /* physical row width in output buffer */
299
300 /* In this example we want to open the input file before doing anything else,
301 * so that the setjmp() error recovery below can assume the file is open.
302 * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
303 * requires it in order to read binary files.
304 */
305
306 if ((infile = fopen(filename, "rb")) == NULL) {
307 fprintf(stderr, "can't open %s\n", filename);
308 return 0;
309 }
310
311 /* Step 1: allocate and initialize JPEG decompression object */
312
313 /* We set up the normal JPEG error routines, then override error_exit. */
314 cinfo.err = jpeg_std_error(&jerr.pub);
315 jerr.pub.error_exit = my_error_exit;
316 /* Establish the setjmp return context for my_error_exit to use. */
317 if (setjmp(jerr.setjmp_buffer)) {
318 /* If we get here, the JPEG code has signaled an error.
319 * We need to clean up the JPEG object, close the input file, and return.
320 */
322 fclose(infile);
323 return 0;
324 }
325 /* Now we can initialize the JPEG decompression object. */
327
328 /* Step 2: specify data source (eg, a file) */
329
330 jpeg_stdio_src(&cinfo, infile);
331
332 /* Step 3: read file parameters with jpeg_read_header() */
333
334 (void) jpeg_read_header(&cinfo, TRUE);
335 /* We can ignore the return value from jpeg_read_header since
336 * (a) suspension is not possible with the stdio data source, and
337 * (b) we passed TRUE to reject a tables-only JPEG file as an error.
338 * See libjpeg.txt for more info.
339 */
340
341 /* Step 4: set parameters for decompression */
342
343 /* In this example, we don't need to change any of the defaults set by
344 * jpeg_read_header(), so we do nothing here.
345 */
346
347 /* Step 5: Start decompressor */
348
349 (void) jpeg_start_decompress(&cinfo);
350 /* We can ignore the return value since suspension is not possible
351 * with the stdio data source.
352 */
353
354 /* We may need to do some setup of our own at this point before reading
355 * the data. After jpeg_start_decompress() we have the correct scaled
356 * output image dimensions available, as well as the output colormap
357 * if we asked for color quantization.
358 * In this example, we need to make an output work buffer of the right size.
359 */
360 /* JSAMPLEs per row in output buffer */
361 row_stride = cinfo.output_width * cinfo.output_components;
362 /* Make a one-row-high sample array that will go away when done with image */
363 buffer = (*cinfo.mem->alloc_sarray)
364 ((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
365
366 /* Step 6: while (scan lines remain to be read) */
367 /* jpeg_read_scanlines(...); */
368
369 /* Here we use the library's state variable cinfo.output_scanline as the
370 * loop counter, so that we don't have to keep track ourselves.
371 */
372 while (cinfo.output_scanline < cinfo.output_height) {
373 /* jpeg_read_scanlines expects an array of pointers to scanlines.
374 * Here the array is only one element long, but you could ask for
375 * more than one scanline at a time if that's more convenient.
376 */
377 (void) jpeg_read_scanlines(&cinfo, buffer, 1);
378 /* Assume put_scanline_someplace wants a pointer and sample count. */
379 put_scanline_someplace(buffer[0], row_stride);
380 }
381
382 /* Step 7: Finish decompression */
383
385 /* We can ignore the return value since suspension is not possible
386 * with the stdio data source.
387 */
388
389 /* Step 8: Release JPEG decompression object */
390
391 /* This is an important step since it will release a good deal of memory. */
393
394 /* After finish_decompress, we can close the input file.
395 * Here we postpone it until after no more JPEG errors are possible,
396 * so as to simplify the setjmp error logic above. (Actually, I don't
397 * think that jpeg_destroy can do an error exit, but why assume anything...)
398 */
399 fclose(infile);
400
401 /* At this point you may want to check to see whether any corrupt-data
402 * warnings occurred (test whether jerr.pub.num_warnings is nonzero).
403 */
404
405 /* And we're done! */
406 return 1;
407}
#define setjmp
Definition: setjmp.h:209
#define NULL
Definition: types.h:112
#define TRUE
Definition: types.h:120
GLuint buffer
Definition: glext.h:5915
#define stderr
Definition: stdio.h:100
_Check_return_opt_ _CRTIMP int __cdecl fprintf(_Inout_ FILE *_File, _In_z_ _Printf_format_string_ const char *_Format,...)
_Check_return_ _CRTIMP FILE *__cdecl fopen(_In_z_ const char *_Filename, _In_z_ const char *_Mode)
_Check_return_opt_ _CRTIMP int __cdecl fclose(_Inout_ FILE *_File)
const char * filename
Definition: ioapi.h:137
jpeg_destroy_decompress(j_decompress_ptr cinfo)
Definition: jdapimin.c:92
jpeg_finish_decompress(j_decompress_ptr cinfo)
Definition: jdapimin.c:373
jpeg_read_header(j_decompress_ptr cinfo, boolean require_image)
Definition: jdapimin.c:245
jpeg_read_scanlines(j_decompress_ptr cinfo, JSAMPARRAY scanlines, JDIMENSION max_lines)
Definition: jdapistd.c:153
jpeg_stdio_src(j_decompress_ptr cinfo, FILE *infile)
Definition: jdatasrc.c:212
jpeg_std_error(struct jpeg_error_mgr *err)
Definition: jerror.c:232
#define jpeg_create_decompress(cinfo)
Definition: jpeglib.h:962
JSAMPROW * JSAMPARRAY
Definition: jpeglib.h:76
#define JPOOL_IMAGE
Definition: jpeglib.h:808
my_error_exit(j_common_ptr cinfo)
Definition: example.c:263
static FILE * infile
Definition: rdjpgcom.c:65

◆ write_JPEG_file()

write_JPEG_file ( char filename,
int  quality 
)

Definition at line 72 of file example.c.

73{
74 /* This struct contains the JPEG compression parameters and pointers to
75 * working space (which is allocated as needed by the JPEG library).
76 * It is possible to have several such structures, representing multiple
77 * compression/decompression processes, in existence at once. We refer
78 * to any one struct (and its associated working data) as a "JPEG object".
79 */
80 struct jpeg_compress_struct cinfo;
81 /* This struct represents a JPEG error handler. It is declared separately
82 * because applications often want to supply a specialized error handler
83 * (see the second half of this file for an example). But here we just
84 * take the easy way out and use the standard error handler, which will
85 * print a message on stderr and call exit() if compression fails.
86 * Note that this struct must live as long as the main JPEG parameter
87 * struct, to avoid dangling-pointer problems.
88 */
89 struct jpeg_error_mgr jerr;
90 /* More stuff */
91 FILE * outfile; /* target file */
92 JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
93 int row_stride; /* physical row width in image buffer */
94
95 /* Step 1: allocate and initialize JPEG compression object */
96
97 /* We have to set up the error handler first, in case the initialization
98 * step fails. (Unlikely, but it could happen if you are out of memory.)
99 * This routine fills in the contents of struct jerr, and returns jerr's
100 * address which we place into the link field in cinfo.
101 */
102 cinfo.err = jpeg_std_error(&jerr);
103 /* Now we can initialize the JPEG compression object. */
104 jpeg_create_compress(&cinfo);
105
106 /* Step 2: specify data destination (eg, a file) */
107 /* Note: steps 2 and 3 can be done in either order. */
108
109 /* Here we use the library-supplied code to send compressed data to a
110 * stdio stream. You can also write your own code to do something else.
111 * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
112 * requires it in order to write binary files.
113 */
114 if ((outfile = fopen(filename, "wb")) == NULL) {
115 fprintf(stderr, "can't open %s\n", filename);
116 exit(1);
117 }
118 jpeg_stdio_dest(&cinfo, outfile);
119
120 /* Step 3: set parameters for compression */
121
122 /* First we supply a description of the input image.
123 * Four fields of the cinfo struct must be filled in:
124 */
125 cinfo.image_width = image_width; /* image width and height, in pixels */
126 cinfo.image_height = image_height;
127 cinfo.input_components = 3; /* # of color components per pixel */
128 cinfo.in_color_space = JCS_RGB; /* colorspace of input image */
129 /* Now use the library's routine to set default compression parameters.
130 * (You must set at least cinfo.in_color_space before calling this,
131 * since the defaults depend on the source color space.)
132 */
133 jpeg_set_defaults(&cinfo);
134 /* Now you can set any non-default parameters you wish to.
135 * Here we just illustrate the use of quality (quantization table) scaling:
136 */
137 jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);
138
139 /* Step 4: Start compressor */
140
141 /* TRUE ensures that we will write a complete interchange-JPEG file.
142 * Pass TRUE unless you are very sure of what you're doing.
143 */
144 jpeg_start_compress(&cinfo, TRUE);
145
146 /* Step 5: while (scan lines remain to be written) */
147 /* jpeg_write_scanlines(...); */
148
149 /* Here we use the library's state variable cinfo.next_scanline as the
150 * loop counter, so that we don't have to keep track ourselves.
151 * To keep things simple, we pass one scanline per call; you can pass
152 * more if you wish, though.
153 */
154 row_stride = image_width * 3; /* JSAMPLEs per row in image_buffer */
155
156 while (cinfo.next_scanline < cinfo.image_height) {
157 /* jpeg_write_scanlines expects an array of pointers to scanlines.
158 * Here the array is only one element long, but you could pass
159 * more than one scanline at a time if that's more convenient.
160 */
161 row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride];
162 (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
163 }
164
165 /* Step 6: Finish compression */
166
167 jpeg_finish_compress(&cinfo);
168 /* After finish_compress, we can close the output file. */
170
171 /* Step 7: release JPEG compression object */
172
173 /* This is an important step since it will release a good deal of memory. */
174 jpeg_destroy_compress(&cinfo);
175
176 /* And we're done! */
177}
jpeg_destroy_compress(j_compress_ptr cinfo)
Definition: jcapimin.c:96
jpeg_finish_compress(j_compress_ptr cinfo)
Definition: jcapimin.c:155
jpeg_write_scanlines(j_compress_ptr cinfo, JSAMPARRAY scanlines, JDIMENSION num_lines)
Definition: jcapistd.c:78
jpeg_start_compress(j_compress_ptr cinfo, boolean write_all_tables)
Definition: jcapistd.c:39
jpeg_set_quality(j_compress_ptr cinfo, int quality, boolean force_baseline)
Definition: jcparam.c:149
jpeg_set_defaults(j_compress_ptr cinfo)
Definition: jcparam.c:196
jpeg_stdio_dest(j_compress_ptr cinfo, FILE *outfile)
Definition: jdatadst.c:195
@ JCS_RGB
Definition: jpeglib.h:223
#define jpeg_create_compress(cinfo)
Definition: jpeglib.h:959
int quality
Definition: jpeglib.h:992
JSAMPLE FAR * JSAMPROW
Definition: jpeglib.h:75
int image_height
int image_width
JSAMPLE * image_buffer
#define exit(n)
Definition: config.h:202
static FILE * outfile
Definition: wrjpgcom.c:81

Variable Documentation

◆ image_buffer

JSAMPLE* image_buffer
extern

Referenced by write_JPEG_file().

◆ image_height

int image_height
extern

Referenced by process_SOFn(), and write_JPEG_file().

◆ image_width

int image_width
extern