1 /*
2 * jdtrans.c
3 *
4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1995-1997, Thomas G. Lane.
6 * It was modified by The libjpeg-turbo Project to include only code relevant
7 * to libjpeg-turbo.
8 * For conditions of distribution and use, see the accompanying README.ijg
9 * file.
10 *
11 * This file contains library routines for transcoding decompression,
12 * that is, reading raw DCT coefficient arrays from an input JPEG file.
13 * The routines in jdapimin.c will also be needed by a transcoder.
14 */
15
16 #define JPEG_INTERNALS
17 #include "jinclude.h"
18 #include "jpeglib.h"
19
20
21 /* Forward declarations */
22 LOCAL(void) transdecode_master_selection (j_decompress_ptr cinfo);
23
24
25 /*
26 * Read the coefficient arrays from a JPEG file.
27 * jpeg_read_header must be completed before calling this.
28 *
29 * The entire image is read into a set of virtual coefficient-block arrays,
30 * one per component. The return value is a pointer to the array of
31 * virtual-array descriptors. These can be manipulated directly via the
32 * JPEG memory manager, or handed off to jpeg_write_coefficients().
33 * To release the memory occupied by the virtual arrays, call
34 * jpeg_finish_decompress() when done with the data.
35 *
36 * An alternative usage is to simply obtain access to the coefficient arrays
37 * during a buffered-image-mode decompression operation. This is allowed
38 * after any jpeg_finish_output() call. The arrays can be accessed until
39 * jpeg_finish_decompress() is called. (Note that any call to the library
40 * may reposition the arrays, so don't rely on access_virt_barray() results
41 * to stay valid across library calls.)
42 *
43 * Returns NULL if suspended. This case need be checked only if
44 * a suspending data source is used.
45 */
46
47 GLOBAL(jvirt_barray_ptr *)
jpeg_read_coefficients(j_decompress_ptr cinfo)48 jpeg_read_coefficients (j_decompress_ptr cinfo)
49 {
50 if (cinfo->global_state == DSTATE_READY) {
51 /* First call: initialize active modules */
52 transdecode_master_selection(cinfo);
53 cinfo->global_state = DSTATE_RDCOEFS;
54 }
55 if (cinfo->global_state == DSTATE_RDCOEFS) {
56 /* Absorb whole file into the coef buffer */
57 for (;;) {
58 int retcode;
59 /* Call progress monitor hook if present */
60 if (cinfo->progress != NULL)
61 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
62 /* Absorb some more input */
63 retcode = (*cinfo->inputctl->consume_input) (cinfo);
64 if (retcode == JPEG_SUSPENDED)
65 return NULL;
66 if (retcode == JPEG_REACHED_EOI)
67 break;
68 /* Advance progress counter if appropriate */
69 if (cinfo->progress != NULL &&
70 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
71 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
72 /* startup underestimated number of scans; ratchet up one scan */
73 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
74 }
75 }
76 }
77 /* Set state so that jpeg_finish_decompress does the right thing */
78 cinfo->global_state = DSTATE_STOPPING;
79 }
80 /* At this point we should be in state DSTATE_STOPPING if being used
81 * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
82 * to the coefficients during a full buffered-image-mode decompression.
83 */
84 if ((cinfo->global_state == DSTATE_STOPPING ||
85 cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
86 return cinfo->coef->coef_arrays;
87 }
88 /* Oops, improper usage */
89 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
90 return NULL; /* keep compiler happy */
91 }
92
93
94 /*
95 * Master selection of decompression modules for transcoding.
96 * This substitutes for jdmaster.c's initialization of the full decompressor.
97 */
98
99 LOCAL(void)
transdecode_master_selection(j_decompress_ptr cinfo)100 transdecode_master_selection (j_decompress_ptr cinfo)
101 {
102 /* This is effectively a buffered-image operation. */
103 cinfo->buffered_image = TRUE;
104
105 #if JPEG_LIB_VERSION >= 80
106 /* Compute output image dimensions and related values. */
107 jpeg_core_output_dimensions(cinfo);
108 #endif
109
110 /* Entropy decoding: either Huffman or arithmetic coding. */
111 if (cinfo->arith_code) {
112 #ifdef D_ARITH_CODING_SUPPORTED
113 jinit_arith_decoder(cinfo);
114 #else
115 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
116 #endif
117 } else {
118 if (cinfo->progressive_mode) {
119 #ifdef D_PROGRESSIVE_SUPPORTED
120 jinit_phuff_decoder(cinfo);
121 #else
122 ERREXIT(cinfo, JERR_NOT_COMPILED);
123 #endif
124 } else
125 jinit_huff_decoder(cinfo);
126 }
127
128 /* Always get a full-image coefficient buffer. */
129 jinit_d_coef_controller(cinfo, TRUE);
130
131 /* We can now tell the memory manager to allocate virtual arrays. */
132 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
133
134 /* Initialize input side of decompressor to consume first scan. */
135 (*cinfo->inputctl->start_input_pass) (cinfo);
136
137 /* Initialize progress monitoring. */
138 if (cinfo->progress != NULL) {
139 int nscans;
140 /* Estimate number of scans to set pass_limit. */
141 if (cinfo->progressive_mode) {
142 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
143 nscans = 2 + 3 * cinfo->num_components;
144 } else if (cinfo->inputctl->has_multiple_scans) {
145 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
146 nscans = cinfo->num_components;
147 } else {
148 nscans = 1;
149 }
150 cinfo->progress->pass_counter = 0L;
151 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
152 cinfo->progress->completed_passes = 0;
153 cinfo->progress->total_passes = 1;
154 }
155 }
156