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 */
19 : LOCAL(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 :
44 : GLOBAL(jvirt_barray_ptr *)
45 0 : jpeg_read_coefficients (j_decompress_ptr cinfo)
46 : {
47 0 : if (cinfo->global_state == DSTATE_READY) {
48 : /* First call: initialize active modules */
49 0 : transdecode_master_selection(cinfo);
50 0 : cinfo->global_state = DSTATE_RDCOEFS;
51 : }
52 0 : 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 0 : if (cinfo->progress != NULL)
58 0 : (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
59 : /* Absorb some more input */
60 0 : retcode = (*cinfo->inputctl->consume_input) (cinfo);
61 0 : if (retcode == JPEG_SUSPENDED)
62 0 : return NULL;
63 0 : if (retcode == JPEG_REACHED_EOI)
64 : break;
65 : /* Advance progress counter if appropriate */
66 0 : if (cinfo->progress != NULL &&
67 0 : (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
68 0 : if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
69 : /* startup underestimated number of scans; ratchet up one scan */
70 0 : cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
71 : }
72 : }
73 0 : }
74 : /* Set state so that jpeg_finish_decompress does the right thing */
75 0 : 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 0 : if ((cinfo->global_state == DSTATE_STOPPING ||
82 0 : cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
83 0 : return cinfo->coef->coef_arrays;
84 : }
85 : /* Oops, improper usage */
86 0 : ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
87 0 : 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 :
96 : LOCAL(void)
97 0 : transdecode_master_selection (j_decompress_ptr cinfo)
98 : {
99 : /* This is effectively a buffered-image operation. */
100 0 : cinfo->buffered_image = TRUE;
101 :
102 : #if JPEG_LIB_VERSION >= 80
103 : /* Compute output image dimensions and related values. */
104 : jpeg_core_output_dimensions(cinfo);
105 : #endif
106 :
107 : /* Entropy decoding: either Huffman or arithmetic coding. */
108 0 : if (cinfo->arith_code) {
109 : #ifdef D_ARITH_CODING_SUPPORTED
110 : jinit_arith_decoder(cinfo);
111 : #else
112 0 : ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
113 : #endif
114 : } else {
115 0 : if (cinfo->progressive_mode) {
116 : #ifdef D_PROGRESSIVE_SUPPORTED
117 0 : jinit_phuff_decoder(cinfo);
118 : #else
119 : ERREXIT(cinfo, JERR_NOT_COMPILED);
120 : #endif
121 : } else
122 0 : jinit_huff_decoder(cinfo);
123 : }
124 :
125 : /* Always get a full-image coefficient buffer. */
126 0 : jinit_d_coef_controller(cinfo, TRUE);
127 :
128 : /* We can now tell the memory manager to allocate virtual arrays. */
129 0 : (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
130 :
131 : /* Initialize input side of decompressor to consume first scan. */
132 0 : (*cinfo->inputctl->start_input_pass) (cinfo);
133 :
134 : /* Initialize progress monitoring. */
135 0 : if (cinfo->progress != NULL) {
136 : int nscans;
137 : /* Estimate number of scans to set pass_limit. */
138 0 : if (cinfo->progressive_mode) {
139 : /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
140 0 : nscans = 2 + 3 * cinfo->num_components;
141 0 : } else if (cinfo->inputctl->has_multiple_scans) {
142 : /* For a nonprogressive multiscan file, estimate 1 scan per component. */
143 0 : nscans = cinfo->num_components;
144 : } else {
145 0 : nscans = 1;
146 : }
147 0 : cinfo->progress->pass_counter = 0L;
148 0 : cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
149 0 : cinfo->progress->completed_passes = 0;
150 0 : cinfo->progress->total_passes = 1;
151 : }
152 0 : }
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