4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * Copyright (C) 2010, D. R. Commander.
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 application interface code for the decompression half
10 * of the JPEG library. These are the "standard" API routines that are
11 * used in the normal full-decompression case. They are not used by a
12 * transcoding-only application. Note that if an application links in
13 * jpeg_start_decompress, it will end up linking in the entire decompressor.
14 * We thus must separate this file from jdapimin.c to avoid linking the
15 * whole decompression library into a transcoder.
18 #define JPEG_INTERNALS
24 /* Forward declarations */
25 LOCAL(boolean) output_pass_setup JPP((j_decompress_ptr cinfo));
29 * Decompression initialization.
30 * jpeg_read_header must be completed before calling this.
32 * If a multipass operating mode was selected, this will do all but the
33 * last pass, and thus may take a great deal of time.
35 * Returns FALSE if suspended. The return value need be inspected only if
36 * a suspending data source is used.
40 jpeg_start_decompress (j_decompress_ptr cinfo)
42 if (cinfo->global_state == DSTATE_READY) {
43 /* First call: initialize master control, select active modules */
44 jinit_master_decompress(cinfo);
45 if (cinfo->buffered_image) {
46 /* No more work here; expecting jpeg_start_output next */
47 cinfo->global_state = DSTATE_BUFIMAGE;
50 cinfo->global_state = DSTATE_PRELOAD;
52 if (cinfo->global_state == DSTATE_PRELOAD) {
53 /* If file has multiple scans, absorb them all into the coef buffer */
54 if (cinfo->inputctl->has_multiple_scans) {
55 #ifdef D_MULTISCAN_FILES_SUPPORTED
58 /* Call progress monitor hook if present */
59 if (cinfo->progress != NULL)
60 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
61 /* Absorb some more input */
62 retcode = (*cinfo->inputctl->consume_input) (cinfo);
63 if (retcode == JPEG_SUSPENDED)
65 if (retcode == JPEG_REACHED_EOI)
67 /* Advance progress counter if appropriate */
68 if (cinfo->progress != NULL &&
69 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
70 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
71 /* jdmaster underestimated number of scans; ratchet up one scan */
72 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
77 ERREXIT(cinfo, JERR_NOT_COMPILED);
78 #endif /* D_MULTISCAN_FILES_SUPPORTED */
80 cinfo->output_scan_number = cinfo->input_scan_number;
81 } else if (cinfo->global_state != DSTATE_PRESCAN)
82 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
83 /* Perform any dummy output passes, and set up for the final pass */
84 return output_pass_setup(cinfo);
89 * Set up for an output pass, and perform any dummy pass(es) needed.
90 * Common subroutine for jpeg_start_decompress and jpeg_start_output.
91 * Entry: global_state = DSTATE_PRESCAN only if previously suspended.
92 * Exit: If done, returns TRUE and sets global_state for proper output mode.
93 * If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
97 output_pass_setup (j_decompress_ptr cinfo)
99 if (cinfo->global_state != DSTATE_PRESCAN) {
100 /* First call: do pass setup */
101 (*cinfo->master->prepare_for_output_pass) (cinfo);
102 cinfo->output_scanline = 0;
103 cinfo->global_state = DSTATE_PRESCAN;
105 /* Loop over any required dummy passes */
106 while (cinfo->master->is_dummy_pass) {
107 #ifdef QUANT_2PASS_SUPPORTED
108 /* Crank through the dummy pass */
109 while (cinfo->output_scanline < cinfo->output_height) {
110 JDIMENSION last_scanline;
111 /* Call progress monitor hook if present */
112 if (cinfo->progress != NULL) {
113 cinfo->progress->pass_counter = (long) cinfo->output_scanline;
114 cinfo->progress->pass_limit = (long) cinfo->output_height;
115 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
117 /* Process some data */
118 last_scanline = cinfo->output_scanline;
119 (*cinfo->main->process_data) (cinfo, (JSAMPARRAY) NULL,
120 &cinfo->output_scanline, (JDIMENSION) 0);
121 if (cinfo->output_scanline == last_scanline)
122 return FALSE; /* No progress made, must suspend */
124 /* Finish up dummy pass, and set up for another one */
125 (*cinfo->master->finish_output_pass) (cinfo);
126 (*cinfo->master->prepare_for_output_pass) (cinfo);
127 cinfo->output_scanline = 0;
129 ERREXIT(cinfo, JERR_NOT_COMPILED);
130 #endif /* QUANT_2PASS_SUPPORTED */
132 /* Ready for application to drive output pass through
133 * jpeg_read_scanlines or jpeg_read_raw_data.
135 cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
141 * Read some scanlines of data from the JPEG decompressor.
143 * The return value will be the number of lines actually read.
144 * This may be less than the number requested in several cases,
145 * including bottom of image, data source suspension, and operating
146 * modes that emit multiple scanlines at a time.
148 * Note: we warn about excess calls to jpeg_read_scanlines() since
149 * this likely signals an application programmer error. However,
150 * an oversize buffer (max_lines > scanlines remaining) is not an error.
154 jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,
155 JDIMENSION max_lines)
159 if (cinfo->global_state != DSTATE_SCANNING)
160 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
161 if (cinfo->output_scanline >= cinfo->output_height) {
162 WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
166 /* Call progress monitor hook if present */
167 if (cinfo->progress != NULL) {
168 cinfo->progress->pass_counter = (long) cinfo->output_scanline;
169 cinfo->progress->pass_limit = (long) cinfo->output_height;
170 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
173 /* Process some data */
175 (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
176 cinfo->output_scanline += row_ctr;
182 * Alternate entry point to read raw data.
183 * Processes exactly one iMCU row per call, unless suspended.
187 jpeg_read_raw_data (j_decompress_ptr cinfo, JSAMPIMAGE data,
188 JDIMENSION max_lines)
190 JDIMENSION lines_per_iMCU_row;
192 if (cinfo->global_state != DSTATE_RAW_OK)
193 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
194 if (cinfo->output_scanline >= cinfo->output_height) {
195 WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
199 /* Call progress monitor hook if present */
200 if (cinfo->progress != NULL) {
201 cinfo->progress->pass_counter = (long) cinfo->output_scanline;
202 cinfo->progress->pass_limit = (long) cinfo->output_height;
203 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
206 /* Verify that at least one iMCU row can be returned. */
207 lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size;
208 if (max_lines < lines_per_iMCU_row)
209 ERREXIT(cinfo, JERR_BUFFER_SIZE);
211 /* Decompress directly into user's buffer. */
212 if (! (*cinfo->coef->decompress_data) (cinfo, data))
213 return 0; /* suspension forced, can do nothing more */
215 /* OK, we processed one iMCU row. */
216 cinfo->output_scanline += lines_per_iMCU_row;
217 return lines_per_iMCU_row;
221 /* Additional entry points for buffered-image mode. */
223 #ifdef D_MULTISCAN_FILES_SUPPORTED
226 * Initialize for an output pass in buffered-image mode.
230 jpeg_start_output (j_decompress_ptr cinfo, int scan_number)
232 if (cinfo->global_state != DSTATE_BUFIMAGE &&
233 cinfo->global_state != DSTATE_PRESCAN)
234 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
235 /* Limit scan number to valid range */
236 if (scan_number <= 0)
238 if (cinfo->inputctl->eoi_reached &&
239 scan_number > cinfo->input_scan_number)
240 scan_number = cinfo->input_scan_number;
241 cinfo->output_scan_number = scan_number;
242 /* Perform any dummy output passes, and set up for the real pass */
243 return output_pass_setup(cinfo);
248 * Finish up after an output pass in buffered-image mode.
250 * Returns FALSE if suspended. The return value need be inspected only if
251 * a suspending data source is used.
255 jpeg_finish_output (j_decompress_ptr cinfo)
257 if ((cinfo->global_state == DSTATE_SCANNING ||
258 cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
259 /* Terminate this pass. */
260 /* We do not require the whole pass to have been completed. */
261 (*cinfo->master->finish_output_pass) (cinfo);
262 cinfo->global_state = DSTATE_BUFPOST;
263 } else if (cinfo->global_state != DSTATE_BUFPOST) {
264 /* BUFPOST = repeat call after a suspension, anything else is error */
265 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
267 /* Read markers looking for SOS or EOI */
268 while (cinfo->input_scan_number <= cinfo->output_scan_number &&
269 ! cinfo->inputctl->eoi_reached) {
270 if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
271 return FALSE; /* Suspend, come back later */
273 cinfo->global_state = DSTATE_BUFIMAGE;
277 #endif /* D_MULTISCAN_FILES_SUPPORTED */