1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * jdtrans.c
7 *
8 * Copyright (C) 1995-1997, Thomas G. Lane.
9 * This file is part of the Independent JPEG Group's software.
10 * For conditions of distribution and use, see the accompanying README file.
11 *
12 * This file contains library routines for transcoding decompression,
13 * that is, reading raw DCT coefficient arrays from an input JPEG file.
14 * The routines in jdapimin.c will also be needed by a transcoder.
15 */
16
17#define JPEG_INTERNALS
18#include "jinclude.h"
19#include "jpeglib.h"
20
21
22/* Forward declarations */
23LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
24
25
26/*
27 * Read the coefficient arrays from a JPEG file.
28 * jpeg_read_header must be completed before calling this.
29 *
30 * The entire image is read into a set of virtual coefficient-block arrays,
31 * one per component. The return value is a pointer to the array of
32 * virtual-array descriptors. These can be manipulated directly via the
33 * JPEG memory manager, or handed off to jpeg_write_coefficients().
34 * To release the memory occupied by the virtual arrays, call
35 * jpeg_finish_decompress() when done with the data.
36 *
37 * An alternative usage is to simply obtain access to the coefficient arrays
38 * during a buffered-image-mode decompression operation. This is allowed
39 * after any jpeg_finish_output() call. The arrays can be accessed until
40 * jpeg_finish_decompress() is called. (Note that any call to the library
41 * may reposition the arrays, so don't rely on access_virt_barray() results
42 * to stay valid across library calls.)
43 *
44 * Returns NULL if suspended. This case need be checked only if
45 * a suspending data source is used.
46 */
47
48GLOBAL(jvirt_barray_ptr *)
49jpeg_read_coefficients (j_decompress_ptr cinfo)
50{
51 if (cinfo->global_state == DSTATE_READY) {
52 /* First call: initialize active modules */
53 transdecode_master_selection(cinfo);
54 cinfo->global_state = DSTATE_RDCOEFS;
55 }
56 if (cinfo->global_state == DSTATE_RDCOEFS) {
57 /* Absorb whole file into the coef buffer */
58 for (;;) {
59 int retcode;
60 /* Call progress monitor hook if present */
61 if (cinfo->progress != NULL)
62 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
63 /* Absorb some more input */
64 retcode = (*cinfo->inputctl->consume_input) (cinfo);
65 if (retcode == JPEG_SUSPENDED)
66 return NULL;
67 if (retcode == JPEG_REACHED_EOI)
68 break;
69 /* Advance progress counter if appropriate */
70 if (cinfo->progress != NULL &&
71 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
72 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
73 /* startup underestimated number of scans; ratchet up one scan */
74 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
75 }
76 }
77 }
78 /* Set state so that jpeg_finish_decompress does the right thing */
79 cinfo->global_state = DSTATE_STOPPING;
80 }
81 /* At this point we should be in state DSTATE_STOPPING if being used
82 * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
83 * to the coefficients during a full buffered-image-mode decompression.
84 */
85 if ((cinfo->global_state == DSTATE_STOPPING ||
86 cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
87 return cinfo->coef->coef_arrays;
88 }
89 /* Oops, improper usage */
90 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
91 return NULL; /* keep compiler happy */
92}
93
94
95/*
96 * Master selection of decompression modules for transcoding.
97 * This substitutes for jdmaster.c's initialization of the full decompressor.
98 */
99
100LOCAL(void)
101transdecode_master_selection (j_decompress_ptr cinfo)
102{
103 /* This is effectively a buffered-image operation. */
104 cinfo->buffered_image = TRUE;
105
106 /* Entropy decoding: either Huffman or arithmetic coding. */
107 if (cinfo->arith_code) {
108 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
109 } else {
110 if (cinfo->progressive_mode) {
111#ifdef D_PROGRESSIVE_SUPPORTED
112 jinit_phuff_decoder(cinfo);
113#else
114 ERREXIT(cinfo, JERR_NOT_COMPILED);
115#endif
116 } else
117 jinit_huff_decoder(cinfo);
118 }
119
120 /* Always get a full-image coefficient buffer. */
121 jinit_d_coef_controller(cinfo, TRUE);
122
123 /* We can now tell the memory manager to allocate virtual arrays. */
124 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
125
126 /* Initialize input side of decompressor to consume first scan. */
127 (*cinfo->inputctl->start_input_pass) (cinfo);
128
129 /* Initialize progress monitoring. */
130 if (cinfo->progress != NULL) {
131 int nscans;
132 /* Estimate number of scans to set pass_limit. */
133 if (cinfo->progressive_mode) {
134 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
135 nscans = 2 + 3 * cinfo->num_components;
136 } else if (cinfo->inputctl->has_multiple_scans) {
137 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
138 nscans = cinfo->num_components;
139 } else {
140 nscans = 1;
141 }
142 cinfo->progress->pass_counter = 0L;
143 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
144 cinfo->progress->completed_passes = 0;
145 cinfo->progress->total_passes = 1;
146 }
147}
148