source: trunk/libjpeg/jdtrans.c @ 15

Last change on this file since 15 was 15, checked in by Eugene Romanenko, 16 years ago

needed libs update

File size: 5.1 KB
RevLine 
[15]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}
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