4 * Copyright (C) 1995, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
8 * This file contains library routines for transcoding decompression,
9 * that is, reading raw DCT coefficient arrays from an input JPEG file.
10 * The routines in jdapimin.c will also be needed by a transcoder.
13 #define JPEG_INTERNALS
15 #include "radiant_jpeglib.h"
18 /* Forward declarations */
19 LOCAL void transdecode_master_selection JPP((j_decompress_ptr cinfo));
23 * Read the coefficient arrays from a JPEG file.
24 * jpeg_read_header must be completed before calling this.
26 * The entire image is read into a set of virtual coefficient-block arrays,
27 * one per component. The return value is a pointer to the array of
28 * virtual-array descriptors. These can be manipulated directly via the
29 * JPEG memory manager, or handed off to jpeg_write_coefficients().
30 * To release the memory occupied by the virtual arrays, call
31 * jpeg_finish_decompress() when done with the data.
33 * Returns NULL if suspended. This case need be checked only if
34 * a suspending data source is used.
37 GLOBAL jvirt_barray_ptr *
38 jpeg_read_coefficients (j_decompress_ptr cinfo)
40 if (cinfo->global_state == DSTATE_READY) {
41 /* First call: initialize active modules */
42 transdecode_master_selection(cinfo);
43 cinfo->global_state = DSTATE_RDCOEFS;
44 } else if (cinfo->global_state != DSTATE_RDCOEFS)
45 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
46 /* Absorb whole file into the coef buffer */
49 /* Call progress monitor hook if present */
50 if (cinfo->progress != NULL)
51 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
52 /* Absorb some more input */
53 retcode = (*cinfo->inputctl->consume_input) (cinfo);
54 if (retcode == JPEG_SUSPENDED)
56 if (retcode == JPEG_REACHED_EOI)
58 /* Advance progress counter if appropriate */
59 if (cinfo->progress != NULL &&
60 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
61 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
62 /* startup underestimated number of scans; ratchet up one scan */
63 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
67 /* Set state so that jpeg_finish_decompress does the right thing */
68 cinfo->global_state = DSTATE_STOPPING;
69 return cinfo->coef->coef_arrays;
74 * Master selection of decompression modules for transcoding.
75 * This substitutes for jdmaster.c's initialization of the full decompressor.
79 transdecode_master_selection (j_decompress_ptr cinfo)
81 /* Entropy decoding: either Huffman or arithmetic coding. */
82 if (cinfo->arith_code) {
83 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
85 if (cinfo->progressive_mode) {
86 #ifdef D_PROGRESSIVE_SUPPORTED
87 jinit_phuff_decoder(cinfo);
89 ERREXIT(cinfo, JERR_NOT_COMPILED);
92 jinit_huff_decoder(cinfo);
95 /* Always get a full-image coefficient buffer. */
96 jinit_d_coef_controller(cinfo, TRUE);
98 /* We can now tell the memory manager to allocate virtual arrays. */
99 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
101 /* Initialize input side of decompressor to consume first scan. */
102 (*cinfo->inputctl->start_input_pass) (cinfo);
104 /* Initialize progress monitoring. */
105 if (cinfo->progress != NULL) {
107 /* Estimate number of scans to set pass_limit. */
108 if (cinfo->progressive_mode) {
109 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
110 nscans = 2 + 3 * cinfo->num_components;
111 } else if (cinfo->inputctl->has_multiple_scans) {
112 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
113 nscans = cinfo->num_components;
117 cinfo->progress->pass_counter = 0L;
118 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
119 cinfo->progress->completed_passes = 0;
120 cinfo->progress->total_passes = 1;