7 * <setjmp.h> is used for the optional error recovery mechanism shown in
8 * the second part of the example.
12 * Include file for users of JPEG library.
13 * You will need to have included system headers that define at least
14 * the typedefs FILE and size_t before you can include jpeglib.h.
15 * (stdio.h is sufficient on ANSI-conforming systems.)
16 * You may also wish to include "jerror.h".
24 /******************** JPEG DECOMPRESSION SAMPLE INTERFACE *******************/
26 /* This half of the example shows how to read data from the JPEG decompressor.
27 * It's a bit more refined than the above, in that we show:
28 * (a) how to modify the JPEG library's standard error-reporting behavior;
29 * (b) how to allocate workspace using the library's memory manager.
31 * Just to make this example a little different from the first one, we'll
32 * assume that we do not intend to put the whole image into an in-memory
33 * buffer, but to send it line-by-line someplace else. We need a one-
34 * scanline-high JSAMPLE array as a work buffer, and we will let the JPEG
35 * memory manager allocate it for us. This approach is actually quite useful
36 * because we don't need to remember to deallocate the buffer separately: it
37 * will go away automatically when the JPEG object is cleaned up.
43 * The JPEG library's standard error handler (jerror.c) is divided into
44 * several "methods" which you can override individually. This lets you
45 * adjust the behavior without duplicating a lot of code, which you might
46 * have to update with each future release.
48 * Our example here shows how to override the "error_exit" method so that
49 * control is returned to the library's caller when a fatal error occurs,
50 * rather than calling exit() as the standard error_exit method does.
52 * We use C's setjmp/longjmp facility to return control. This means that the
53 * routine which calls the JPEG library must first execute a setjmp() call to
54 * establish the return point. We want the replacement error_exit to do a
55 * longjmp(). But we need to make the setjmp buffer accessible to the
56 * error_exit routine. To do this, we make a private extension of the
57 * standard JPEG error handler object. (If we were using C++, we'd say we
58 * were making a subclass of the regular error handler.)
60 * Here's the extended error handler struct:
64 struct jpeg_error_mgr pub; /* "public" fields */
65 jmp_buf setjmp_buffer; /* for return to caller */
68 typedef struct my_error_mgr * my_error_ptr;
71 * Here's the routine that will replace the standard error_exit method:
75 my_error_exit (j_common_ptr cinfo) {
76 /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
77 my_error_ptr myerr = (my_error_ptr) cinfo->err;
79 /* Always display the message. */
80 /* We could postpone this until after returning, if we chose. */
81 (*cinfo->err->output_message) (cinfo);
83 /* Return control to the setjmp point */
84 longjmp(myerr->setjmp_buffer, 1);
89 * Sample routine for JPEG decompression. We assume that the source file name
90 * is passed in. We want to return 1 on success, 0 on error.
96 gdcmFile::gdcm_read_JPEG_file (void * image_buffer) {
100 /* This struct contains the JPEG decompression parameters and pointers to
101 * working space (which is allocated as needed by the JPEG library).
104 struct jpeg_decompress_struct cinfo;
106 /* -------------- inside, we found :
107 JDIMENSION image_width; // input image width
108 JDIMENSION image_height; // input image height
109 int input_components; // nb of color components in input image
110 J_COLOR_SPACE in_color_space; // colorspace of input image
111 double input_gamma; // image gamma of input image
114 /* We use our private extension JPEG error handler.
115 * Note that this struct must live as long as the main JPEG parameter
116 * struct, to avoid dangling-pointer problems.
118 struct my_error_mgr jerr;
121 JSAMPARRAY buffer; /* Output row buffer */
124 // typedef unsigned char JSAMPLE;
125 // typedef JSAMPLE FAR *JSAMPROW; /* ptr to one image row of pixel samples. */
126 // typedef JSAMPROW *JSAMPARRAY; /* ptr to some rows (a 2-D sample array) */
127 // typedef JSAMPARRAY *JSAMPIMAGE; /* a 3-D sample array: top index is color */
130 int row_stride; /* physical row width in output buffer */
132 if (DEBUG) printf("entree dans gdcmFile::gdcm_read_JPEG_file, depuis gdcmJpeg\n");
135 /* In this example we want to open the input file before doing anything else,
136 * so that the setjmp() error recovery below can assume the file is open.
137 * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
138 * requires it in order to read binary files.
141 /* Step 1: allocate and initialize JPEG decompression object */
143 if (DEBUG)printf("Entree Step 1\n");
145 /* We set up the normal JPEG error routines, then override error_exit. */
147 cinfo.err = jpeg_std_error(&jerr.pub);
148 jerr.pub.error_exit = my_error_exit;
150 /* Establish the setjmp return context for my_error_exit to use. */
152 if (setjmp(jerr.setjmp_buffer)) {
153 /* If we get here, the JPEG code has signaled an error.
154 * We need to clean up the JPEG object, close the input file, and return.
156 jpeg_destroy_decompress(&cinfo);
159 /* Now we can initialize the JPEG decompression object. */
160 jpeg_create_decompress(&cinfo);
162 /* Step 2: specify data source (eg, a file) */
164 if (DEBUG) printf("Entree Step 2\n");
166 jpeg_stdio_src(&cinfo, fp);
168 /* Step 3: read file parameters with jpeg_read_header() */
170 if (DEBUG) printf("Entree Step 3\n");
172 (void) jpeg_read_header(&cinfo, TRUE);
174 /* We can ignore the return value from jpeg_read_header since
175 * (a) suspension is not possible with the stdio data source, and
176 * (b) we passed TRUE to reject a tables-only JPEG file as an error.
177 * See libjpeg.doc for more info.
181 printf("--------------Header contents :----------------\n");
182 printf("image_width %d image_height %d\n",
183 cinfo.image_width , cinfo.image_height);
184 printf("bits of precision in image data %d \n",
185 cinfo.output_components);
186 printf("nb of color components returned %d \n",
187 cinfo.data_precision);
192 JDIMENSION image_width; // input image width
193 JDIMENSION image_height; // input image height
194 int output_components; // # of color components returned
195 J_COLOR_SPACE in_color_space; // colorspace of input image
196 double input_gamma; // image gamma of input image
197 int data_precision; // bits of precision in image data
201 /* Step 4: set parameters for decompression */
203 if (DEBUG) printf("Entree Step 4\n");
205 /* In this example, we don't need to change any of the defaults set by
206 * jpeg_read_header(), so we do nothing here.
209 /* Step 5: Start decompressor */
211 if (DEBUG) printf("Entree Step 5\n");
213 (void) jpeg_start_decompress(&cinfo);
214 /* We can ignore the return value since suspension is not possible
215 * with the stdio data source.
218 /* We may need to do some setup of our own at this point before reading
219 * the data. After jpeg_start_decompress() we have the correct scaled
220 * output image dimensions available, as well as the output colormap
221 * if we asked for color quantization.
222 * In this example, we need to make an output work buffer of the right size.
224 /* JSAMPLEs per row in output buffer */
225 row_stride = cinfo.output_width * cinfo.output_components;
227 if (DEBUG) printf ("cinfo.output_width %d cinfo.output_components %d row_stride %d\n",
228 cinfo.output_width, cinfo.output_components,row_stride);
230 /* Make a one-row-high sample array that will go away when done with image */
231 buffer = (*cinfo.mem->alloc_sarray)
232 ((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
234 /* Step 6: while (scan lines remain to be read) */
236 if (DEBUG) printf("Entree Step 6\n");
238 /* jpeg_read_scanlines(...); */
240 /* Here we use the library's state variable cinfo.output_scanline as the
241 * loop counter, so that we don't have to keep track ourselves.
244 if (DEBUG) printf ("cinfo.output_height %d cinfo.output_width %d\n",
245 cinfo.output_height,cinfo.output_width);
247 pimage=(char *)image_buffer;
250 while (cinfo.output_scanline < cinfo.output_height) {
251 /* jpeg_read_scanlines expects an array of pointers to scanlines.
252 * Here the array is only one element long, but you could ask for
253 * more than one scanline at a time if that's more convenient.
256 // l'image est deja allouée (et passée en param)
257 // on ecrit directement les pixels
258 // (on DEVRAIT pouvoir)
260 //(void) jpeg_read_scanlines(&cinfo, pimage, 1);
262 (void) jpeg_read_scanlines(&cinfo, buffer, 1);
263 memcpy( pimage, buffer[0],row_stride*2 ); // FIXME : *2 car 16 bits?!?
265 pimage+=row_stride*2; // FIXME : *2 car 16 bits?!?
268 /* Step 7: Finish decompression */
270 if (DEBUG) printf("Entree Step 7\n");
272 (void) jpeg_finish_decompress(&cinfo);
273 /* We can ignore the return value since suspension is not possible
274 * with the stdio data source.
277 /* Step 8: Release JPEG decompression object */
279 if (DEBUG) printf("Entree Step 8\n");
281 /* This is an important step since it will release a good deal of memory. */
283 jpeg_destroy_decompress(&cinfo);
285 /* After finish_decompress, we can close the input file.
286 * Here we postpone it until after no more JPEG errors are possible,
287 * so as to simplify the setjmp error logic above. (Actually, I don't
288 * think that jpeg_destroy can do an error exit, but why assume anything...)
291 /* At this point you may want to check to see whether any corrupt-data
292 * warnings occurred (test whether jerr.pub.num_warnings is nonzero).
295 /* And we're done! */
303 * In the above code, we ignored the return value of jpeg_read_scanlines,
304 * which is the number of scanlines actually read. We could get away with
305 * this because we asked for only one line at a time and we weren't using
306 * a suspending data source. See libjpeg.doc for more info.
308 * We cheated a bit by calling alloc_sarray() after jpeg_start_decompress();
309 * we should have done it beforehand to ensure that the space would be
310 * counted against the JPEG max_memory setting. In some systems the above
311 * code would risk an out-of-memory error. However, in general we don't
312 * know the output image dimensions before jpeg_start_decompress(), unless we
313 * call jpeg_calc_output_dimensions(). See libjpeg.doc for more about this.
315 * Scanlines are returned in the same order as they appear in the JPEG file,
316 * which is standardly top-to-bottom. If you must emit data bottom-to-top,
317 * you can use one of the virtual arrays provided by the JPEG memory manager
318 * to invert the data. See wrbmp.c for an example.
320 * As with compression, some operating modes may require temporary files.
321 * On some systems you may need to set up a signal handler to ensure that
322 * temporary files are deleted if the program is interrupted. See libjpeg.doc.