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