2 Copyright (c) 2001, Loki software, inc.
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32 // Functions to load JPEG files from a buffer, based on jdatasrc.c
34 // Leonardo Zide (leo@lokigames.com)
45 /* Expanded data source object for stdio input */
48 struct jpeg_source_mgr pub; /* public fields */
53 JOCTET * buffer; /* start of buffer */
54 boolean start_of_file; /* have we gotten any data yet? */
57 typedef my_source_mgr * my_src_ptr;
59 #define INPUT_BUF_SIZE 4096 /* choose an efficiently fread'able size */
63 * Initialize source --- called by jpeg_read_header
64 * before any data is actually read.
67 static void my_init_source (j_decompress_ptr cinfo)
69 my_src_ptr src = (my_src_ptr) cinfo->src;
71 /* We reset the empty-input-file flag for each image,
72 * but we don't clear the input buffer.
73 * This is correct behavior for reading a series of images from one source.
75 src->start_of_file = TRUE;
80 * Fill the input buffer --- called whenever buffer is emptied.
82 * In typical applications, this should read fresh data into the buffer
83 * (ignoring the current state of next_input_byte & bytes_in_buffer),
84 * reset the pointer & count to the start of the buffer, and return TRUE
85 * indicating that the buffer has been reloaded. It is not necessary to
86 * fill the buffer entirely, only to obtain at least one more byte.
88 * There is no such thing as an EOF return. If the end of the file has been
89 * reached, the routine has a choice of ERREXIT() or inserting fake data into
90 * the buffer. In most cases, generating a warning message and inserting a
91 * fake EOI marker is the best course of action --- this will allow the
92 * decompressor to output however much of the image is there. However,
93 * the resulting error message is misleading if the real problem is an empty
94 * input file, so we handle that case specially.
96 * In applications that need to be able to suspend compression due to input
97 * not being available yet, a FALSE return indicates that no more data can be
98 * obtained right now, but more may be forthcoming later. In this situation,
99 * the decompressor will return to its caller (with an indication of the
100 * number of scanlines it has read, if any). The application should resume
101 * decompression after it has loaded more data into the input buffer. Note
102 * that there are substantial restrictions on the use of suspension --- see
105 * When suspending, the decompressor will back up to a convenient restart point
106 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
107 * indicate where the restart point will be if the current call returns FALSE.
108 * Data beyond this point must be rescanned after resumption, so move it to
109 * the front of the buffer rather than discarding it.
112 static boolean my_fill_input_buffer (j_decompress_ptr cinfo)
114 my_src_ptr src = (my_src_ptr) cinfo->src;
117 if (src->src_size > INPUT_BUF_SIZE)
118 nbytes = INPUT_BUF_SIZE;
120 nbytes = src->src_size;
122 memcpy (src->buffer, src->src_buffer, nbytes);
123 src->src_buffer += nbytes;
124 src->src_size -= nbytes;
127 if (src->start_of_file) /* Treat empty input file as fatal error */
128 ERREXIT(cinfo, JERR_INPUT_EMPTY);
129 WARNMS(cinfo, JWRN_JPEG_EOF);
130 /* Insert a fake EOI marker */
131 src->buffer[0] = (JOCTET) 0xFF;
132 src->buffer[1] = (JOCTET) JPEG_EOI;
136 src->pub.next_input_byte = src->buffer;
137 src->pub.bytes_in_buffer = nbytes;
138 src->start_of_file = FALSE;
145 * Skip data --- used to skip over a potentially large amount of
146 * uninteresting data (such as an APPn marker).
148 * Writers of suspendable-input applications must note that skip_input_data
149 * is not granted the right to give a suspension return. If the skip extends
150 * beyond the data currently in the buffer, the buffer can be marked empty so
151 * that the next read will cause a fill_input_buffer call that can suspend.
152 * Arranging for additional bytes to be discarded before reloading the input
153 * buffer is the application writer's problem.
156 static void my_skip_input_data (j_decompress_ptr cinfo, long num_bytes)
158 my_src_ptr src = (my_src_ptr) cinfo->src;
160 /* Just a dumb implementation for now. Could use fseek() except
161 * it doesn't work on pipes. Not clear that being smart is worth
162 * any trouble anyway --- large skips are infrequent.
165 while (num_bytes > (long) src->pub.bytes_in_buffer) {
166 num_bytes -= (long) src->pub.bytes_in_buffer;
167 (void) my_fill_input_buffer(cinfo);
168 /* note we assume that fill_input_buffer will never return FALSE,
169 * so suspension need not be handled.
172 src->pub.next_input_byte += (size_t) num_bytes;
173 src->pub.bytes_in_buffer -= (size_t) num_bytes;
179 * An additional method that can be provided by data source modules is the
180 * resync_to_restart method for error recovery in the presence of RST markers.
181 * For the moment, this source module just uses the default resync method
182 * provided by the JPEG library. That method assumes that no backtracking
188 * Terminate source --- called by jpeg_finish_decompress
189 * after all data has been read. Often a no-op.
191 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
192 * application must deal with any cleanup that should happen even
196 static void my_term_source (j_decompress_ptr cinfo)
198 /* no work necessary here */
203 * Prepare for input from a stdio stream.
204 * The caller must have already opened the stream, and is responsible
205 * for closing it after finishing decompression.
208 static void jpeg_buffer_src (j_decompress_ptr cinfo, void* buffer, int bufsize)
212 /* The source object and input buffer are made permanent so that a series
213 * of JPEG images can be read from the same file by calling jpeg_stdio_src
214 * only before the first one. (If we discarded the buffer at the end of
215 * one image, we'd likely lose the start of the next one.)
216 * This makes it unsafe to use this manager and a different source
217 * manager serially with the same JPEG object. Caveat programmer.
219 if (cinfo->src == NULL) { /* first time for this JPEG object? */
220 cinfo->src = (struct jpeg_source_mgr *)
221 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
222 sizeof (my_source_mgr));
223 src = (my_src_ptr) cinfo->src;
224 src->buffer = (JOCTET *)
225 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
226 INPUT_BUF_SIZE * sizeof (JOCTET));
229 src = (my_src_ptr) cinfo->src;
230 src->pub.init_source = my_init_source;
231 src->pub.fill_input_buffer = my_fill_input_buffer;
232 src->pub.skip_input_data = my_skip_input_data;
233 src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
234 src->pub.term_source = my_term_source;
235 src->src_buffer = (JOCTET *)buffer;
236 src->src_size = bufsize;
237 src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
238 src->pub.next_input_byte = NULL; /* until buffer loaded */
241 // =============================================================================
243 static char errormsg[JMSG_LENGTH_MAX];
245 typedef struct my_jpeg_error_mgr
247 struct jpeg_error_mgr pub; // "public" fields
248 jmp_buf setjmp_buffer; // for return to caller
251 static void my_jpeg_error_exit (j_common_ptr cinfo)
253 bt_jpeg_error_mgr* myerr = (bt_jpeg_error_mgr*) cinfo->err;
255 (*cinfo->err->format_message) (cinfo, errormsg);
257 longjmp (myerr->setjmp_buffer, 1);
261 static void j_putRGBScanline (unsigned char* jpegline, int widthPix, unsigned char* outBuf, int row)
263 int offset = row * widthPix * 4;
266 for (count = 0; count < widthPix; count++)
268 unsigned char iRed, iBlu, iGrn;
269 unsigned char *oRed, *oBlu, *oGrn, *oAlp;
271 iRed = *(jpegline + count * 3 + 0);
272 iGrn = *(jpegline + count * 3 + 1);
273 iBlu = *(jpegline + count * 3 + 2);
275 oRed = outBuf + offset + count * 4 + 0;
276 oGrn = outBuf + offset + count * 4 + 1;
277 oBlu = outBuf + offset + count * 4 + 2;
278 oAlp = outBuf + offset + count * 4 + 3;
288 static void j_putRGBAScanline (unsigned char* jpegline, int widthPix, unsigned char* outBuf, int row)
290 int offset = row * widthPix * 4;
293 for (count = 0; count < widthPix; count++)
295 unsigned char iRed, iBlu, iGrn, iAlp;
296 unsigned char *oRed, *oBlu, *oGrn, *oAlp;
298 iRed = *(jpegline + count * 4 + 0);
299 iGrn = *(jpegline + count * 4 + 1);
300 iBlu = *(jpegline + count * 4 + 2);
301 iAlp = *(jpegline + count * 4 + 3);
303 oRed = outBuf + offset + count * 4 + 0;
304 oGrn = outBuf + offset + count * 4 + 1;
305 oBlu = outBuf + offset + count * 4 + 2;
306 oAlp = outBuf + offset + count * 4 + 3;
311 // ydnar: see bug 900
312 *oAlp = 255; //% iAlp;
316 // stash a gray scanline
317 static void j_putGrayScanlineToRGB (unsigned char* jpegline, int widthPix, unsigned char* outBuf, int row)
319 int offset = row * widthPix * 4;
322 for (count = 0; count < widthPix; count++)
325 unsigned char *oRed, *oBlu, *oGrn, *oAlp;
327 // get our grayscale value
328 iGray = *(jpegline + count);
330 oRed = outBuf + offset + count * 4;
331 oGrn = outBuf + offset + count * 4 + 1;
332 oBlu = outBuf + offset + count * 4 + 2;
333 oAlp = outBuf + offset + count * 4 + 3;
342 int LoadJPGBuff( void *src_buffer, int src_size, unsigned char **pic, int *width, int *height ) {
343 struct jpeg_decompress_struct cinfo;
344 struct my_jpeg_error_mgr jerr;
346 int row_stride, size;
348 cinfo.err = jpeg_std_error (&jerr.pub);
349 jerr.pub.error_exit = my_jpeg_error_exit;
351 if (setjmp (jerr.setjmp_buffer))
353 *pic = (unsigned char*)errormsg;
354 jpeg_destroy_decompress (&cinfo);
358 jpeg_create_decompress (&cinfo);
359 jpeg_buffer_src (&cinfo, src_buffer, src_size);
360 jpeg_read_header (&cinfo, TRUE);
361 jpeg_start_decompress (&cinfo);
363 row_stride = cinfo.output_width * cinfo.output_components;
365 size = cinfo.output_width * cinfo.output_height * 4;
366 *width = cinfo.output_width;
367 *height = cinfo.output_height;
368 *pic = (unsigned char*)( malloc( size+1 ) );
369 memset (*pic, 0, size+1);
371 buffer = (*cinfo.mem->alloc_sarray) ((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
373 while (cinfo.output_scanline < cinfo.output_height)
375 jpeg_read_scanlines (&cinfo, buffer, 1);
377 if (cinfo.out_color_components == 4)
378 j_putRGBAScanline (buffer[0], cinfo.output_width, *pic, cinfo.output_scanline-1);
379 else if (cinfo.out_color_components == 3)
380 j_putRGBScanline (buffer[0], cinfo.output_width, *pic, cinfo.output_scanline-1);
381 else if (cinfo.out_color_components == 1)
382 j_putGrayScanlineToRGB (buffer[0], cinfo.output_width, *pic, cinfo.output_scanline-1);
385 jpeg_finish_decompress (&cinfo);
386 jpeg_destroy_decompress (&cinfo);