1 /* $XConsortium: jdtrans.c /main/2 1996/05/09 03:50:06 drk $ */
5 * Copyright (C) 1995-1996, Thomas G. Lane.
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 library routines for transcoding decompression,
10 * that is, reading raw DCT coefficient arrays from an input JPEG file.
11 * The routines in jdapimin.c will also be needed by a transcoder.
14 #define JPEG_INTERNALS
19 /* Forward declarations */
20 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
24 * Read the coefficient arrays from a JPEG file.
25 * jpeg_read_header must be completed before calling this.
27 * The entire image is read into a set of virtual coefficient-block arrays,
28 * one per component. The return value is a pointer to the array of
29 * virtual-array descriptors. These can be manipulated directly via the
30 * JPEG memory manager, or handed off to jpeg_write_coefficients().
31 * To release the memory occupied by the virtual arrays, call
32 * jpeg_finish_decompress() when done with the data.
34 * Returns NULL if suspended. This case need be checked only if
35 * a suspending data source is used.
38 GLOBAL(jvirt_barray_ptr *)
39 jpeg_read_coefficients (j_decompress_ptr cinfo)
41 if (cinfo->global_state == DSTATE_READY) {
42 /* First call: initialize active modules */
43 transdecode_master_selection(cinfo);
44 cinfo->global_state = DSTATE_RDCOEFS;
45 } else if (cinfo->global_state != DSTATE_RDCOEFS)
46 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
47 /* Absorb whole file into the coef buffer */
50 /* Call progress monitor hook if present */
51 if (cinfo->progress != NULL)
52 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
53 /* Absorb some more input */
54 retcode = (*cinfo->inputctl->consume_input) (cinfo);
55 if (retcode == JPEG_SUSPENDED)
57 if (retcode == JPEG_REACHED_EOI)
59 /* Advance progress counter if appropriate */
60 if (cinfo->progress != NULL &&
61 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
62 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
63 /* startup underestimated number of scans; ratchet up one scan */
64 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
68 /* Set state so that jpeg_finish_decompress does the right thing */
69 cinfo->global_state = DSTATE_STOPPING;
70 return cinfo->coef->coef_arrays;
75 * Master selection of decompression modules for transcoding.
76 * This substitutes for jdmaster.c's initialization of the full decompressor.
80 transdecode_master_selection (j_decompress_ptr cinfo)
82 /* Entropy decoding: either Huffman or arithmetic coding. */
83 if (cinfo->arith_code) {
84 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
86 if (cinfo->progressive_mode) {
87 #ifdef D_PROGRESSIVE_SUPPORTED
88 jinit_phuff_decoder(cinfo);
90 ERREXIT(cinfo, JERR_NOT_COMPILED);
93 jinit_huff_decoder(cinfo);
96 /* Always get a full-image coefficient buffer. */
97 jinit_d_coef_controller(cinfo, TRUE);
99 /* We can now tell the memory manager to allocate virtual arrays. */
100 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
102 /* Initialize input side of decompressor to consume first scan. */
103 (*cinfo->inputctl->start_input_pass) (cinfo);
105 /* Initialize progress monitoring. */
106 if (cinfo->progress != NULL) {
108 /* Estimate number of scans to set pass_limit. */
109 if (cinfo->progressive_mode) {
110 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
111 nscans = 2 + 3 * cinfo->num_components;
112 } else if (cinfo->inputctl->has_multiple_scans) {
113 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
114 nscans = cinfo->num_components;
118 cinfo->progress->pass_counter = 0L;
119 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
120 cinfo->progress->completed_passes = 0;
121 cinfo->progress->total_passes = 1;