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145 lines
4.7 KiB
C
145 lines
4.7 KiB
C
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/*
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* jdapistd.c
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*
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* Copyright (C) 1994-1996, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains application interface code for the decompression half
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* of the JPEG library. These are the "standard" API routines that are
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* used in the normal full-decompression case. They are not used by a
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* transcoding-only application. Note that if an application links in
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* jpeg_start_decompress, it will end up linking in the entire decompressor.
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* We thus must separate this file from jdapimin.c to avoid linking the
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* whole decompression library into a transcoder.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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/* Forward declarations */
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LOCAL(boolean) output_pass_setup JPP((j_decompress_ptr cinfo));
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/*
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* Decompression initialization.
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* jpeg_read_header must be completed before calling this.
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*
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* If a multipass operating mode was selected, this will do all but the
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* last pass, and thus may take a great deal of time.
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*
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* Returns FALSE if suspended. The return value need be inspected only if
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* a suspending data source is used.
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*/
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GLOBAL(boolean)
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jpeg_start_decompress (j_decompress_ptr cinfo)
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{
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if (cinfo->global_state == DSTATE_READY) {
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/* First call: initialize master control, select active modules */
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jinit_master_decompress(cinfo);
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cinfo->global_state = DSTATE_PRELOAD;
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}
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if (cinfo->global_state == DSTATE_PRELOAD) {
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/* If file has multiple scans, absorb them all into the coef buffer */
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if (cinfo->inputctl->has_multiple_scans) {
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#ifdef D_MULTISCAN_FILES_SUPPORTED
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for (;;) {
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int retcode;
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/* Call progress monitor hook if present */
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if (cinfo->progress != NULL)
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(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
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/* Absorb some more input */
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retcode = (*cinfo->inputctl->consume_input) (cinfo);
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if (retcode == JPEG_SUSPENDED)
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return FALSE;
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if (retcode == JPEG_REACHED_EOI)
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break;
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/* Advance progress counter if appropriate */
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if (cinfo->progress != NULL &&
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(retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
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if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
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/* jdmaster underestimated number of scans; ratchet up one scan */
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cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
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}
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}
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}
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#else
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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#endif /* D_MULTISCAN_FILES_SUPPORTED */
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}
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cinfo->output_scan_number = cinfo->input_scan_number;
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} else if (cinfo->global_state != DSTATE_PRESCAN)
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ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
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/* Perform any dummy output passes, and set up for the final pass */
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return output_pass_setup(cinfo);
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}
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/*
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* Set up for an output pass, and perform any dummy pass(es) needed.
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* Common subroutine for jpeg_start_decompress and jpeg_start_output.
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* Entry: global_state = DSTATE_PRESCAN only if previously suspended.
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* Exit: If done, returns TRUE and sets global_state for proper output mode.
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* If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
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*/
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LOCAL(boolean)
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output_pass_setup (j_decompress_ptr cinfo)
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{
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if (cinfo->global_state != DSTATE_PRESCAN) {
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/* First call: do pass setup */
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(*cinfo->master->prepare_for_output_pass) (cinfo);
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cinfo->output_scanline = 0;
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cinfo->global_state = DSTATE_PRESCAN;
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}
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/* Ready for application to drive output pass through
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* jpeg_read_scanlines or jpeg_read_raw_data.
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*/
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cinfo->global_state = DSTATE_SCANNING;
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return TRUE;
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}
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/*
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* Read some scanlines of data from the JPEG decompressor.
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*
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* The return value will be the number of lines actually read.
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* This may be less than the number requested in several cases,
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* including bottom of image, data source suspension, and operating
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* modes that emit multiple scanlines at a time.
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*
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* Note: we warn about excess calls to jpeg_read_scanlines() since
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* this likely signals an application programmer error. However,
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* an oversize buffer (max_lines > scanlines remaining) is not an error.
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*/
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GLOBAL(JDIMENSION)
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jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,
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JDIMENSION max_lines)
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{
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JDIMENSION row_ctr;
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if (cinfo->global_state != DSTATE_SCANNING)
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ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
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if (cinfo->output_scanline >= cinfo->output_height) {
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WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
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return 0;
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}
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/* Call progress monitor hook if present */
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if (cinfo->progress != NULL) {
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cinfo->progress->pass_counter = (long) cinfo->output_scanline;
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cinfo->progress->pass_limit = (long) cinfo->output_height;
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(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
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}
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/* Process some data */
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row_ctr = 0;
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(*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
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cinfo->output_scanline += row_ctr;
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return row_ctr;
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}
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