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annotate libs/libjpeg/jdtrans.c @ 35:643f4ab609a4

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added readme and license
author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 31 Oct 2015 05:45:35 +0200
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nuclear@2 1 /*
nuclear@2 2 * jdtrans.c
nuclear@2 3 *
nuclear@2 4 * Copyright (C) 1995-1997, Thomas G. Lane.
nuclear@2 5 * This file is part of the Independent JPEG Group's software.
nuclear@2 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@2 7 *
nuclear@2 8 * This file contains library routines for transcoding decompression,
nuclear@2 9 * that is, reading raw DCT coefficient arrays from an input JPEG file.
nuclear@2 10 * The routines in jdapimin.c will also be needed by a transcoder.
nuclear@2 11 */
nuclear@2 12
nuclear@2 13 #define JPEG_INTERNALS
nuclear@2 14 #include "jinclude.h"
nuclear@2 15 #include "jpeglib.h"
nuclear@2 16
nuclear@2 17
nuclear@2 18 /* Forward declarations */
nuclear@2 19 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
nuclear@2 20
nuclear@2 21
nuclear@2 22 /*
nuclear@2 23 * Read the coefficient arrays from a JPEG file.
nuclear@2 24 * jpeg_read_header must be completed before calling this.
nuclear@2 25 *
nuclear@2 26 * The entire image is read into a set of virtual coefficient-block arrays,
nuclear@2 27 * one per component. The return value is a pointer to the array of
nuclear@2 28 * virtual-array descriptors. These can be manipulated directly via the
nuclear@2 29 * JPEG memory manager, or handed off to jpeg_write_coefficients().
nuclear@2 30 * To release the memory occupied by the virtual arrays, call
nuclear@2 31 * jpeg_finish_decompress() when done with the data.
nuclear@2 32 *
nuclear@2 33 * An alternative usage is to simply obtain access to the coefficient arrays
nuclear@2 34 * during a buffered-image-mode decompression operation. This is allowed
nuclear@2 35 * after any jpeg_finish_output() call. The arrays can be accessed until
nuclear@2 36 * jpeg_finish_decompress() is called. (Note that any call to the library
nuclear@2 37 * may reposition the arrays, so don't rely on access_virt_barray() results
nuclear@2 38 * to stay valid across library calls.)
nuclear@2 39 *
nuclear@2 40 * Returns NULL if suspended. This case need be checked only if
nuclear@2 41 * a suspending data source is used.
nuclear@2 42 */
nuclear@2 43
nuclear@2 44 GLOBAL(jvirt_barray_ptr *)
nuclear@2 45 jpeg_read_coefficients (j_decompress_ptr cinfo)
nuclear@2 46 {
nuclear@2 47 if (cinfo->global_state == DSTATE_READY) {
nuclear@2 48 /* First call: initialize active modules */
nuclear@2 49 transdecode_master_selection(cinfo);
nuclear@2 50 cinfo->global_state = DSTATE_RDCOEFS;
nuclear@2 51 }
nuclear@2 52 if (cinfo->global_state == DSTATE_RDCOEFS) {
nuclear@2 53 /* Absorb whole file into the coef buffer */
nuclear@2 54 for (;;) {
nuclear@2 55 int retcode;
nuclear@2 56 /* Call progress monitor hook if present */
nuclear@2 57 if (cinfo->progress != NULL)
nuclear@2 58 (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
nuclear@2 59 /* Absorb some more input */
nuclear@2 60 retcode = (*cinfo->inputctl->consume_input) (cinfo);
nuclear@2 61 if (retcode == JPEG_SUSPENDED)
nuclear@2 62 return NULL;
nuclear@2 63 if (retcode == JPEG_REACHED_EOI)
nuclear@2 64 break;
nuclear@2 65 /* Advance progress counter if appropriate */
nuclear@2 66 if (cinfo->progress != NULL &&
nuclear@2 67 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
nuclear@2 68 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
nuclear@2 69 /* startup underestimated number of scans; ratchet up one scan */
nuclear@2 70 cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
nuclear@2 71 }
nuclear@2 72 }
nuclear@2 73 }
nuclear@2 74 /* Set state so that jpeg_finish_decompress does the right thing */
nuclear@2 75 cinfo->global_state = DSTATE_STOPPING;
nuclear@2 76 }
nuclear@2 77 /* At this point we should be in state DSTATE_STOPPING if being used
nuclear@2 78 * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
nuclear@2 79 * to the coefficients during a full buffered-image-mode decompression.
nuclear@2 80 */
nuclear@2 81 if ((cinfo->global_state == DSTATE_STOPPING ||
nuclear@2 82 cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
nuclear@2 83 return cinfo->coef->coef_arrays;
nuclear@2 84 }
nuclear@2 85 /* Oops, improper usage */
nuclear@2 86 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
nuclear@2 87 return NULL; /* keep compiler happy */
nuclear@2 88 }
nuclear@2 89
nuclear@2 90
nuclear@2 91 /*
nuclear@2 92 * Master selection of decompression modules for transcoding.
nuclear@2 93 * This substitutes for jdmaster.c's initialization of the full decompressor.
nuclear@2 94 */
nuclear@2 95
nuclear@2 96 LOCAL(void)
nuclear@2 97 transdecode_master_selection (j_decompress_ptr cinfo)
nuclear@2 98 {
nuclear@2 99 /* This is effectively a buffered-image operation. */
nuclear@2 100 cinfo->buffered_image = TRUE;
nuclear@2 101
nuclear@2 102 /* Entropy decoding: either Huffman or arithmetic coding. */
nuclear@2 103 if (cinfo->arith_code) {
nuclear@2 104 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
nuclear@2 105 } else {
nuclear@2 106 if (cinfo->progressive_mode) {
nuclear@2 107 #ifdef D_PROGRESSIVE_SUPPORTED
nuclear@2 108 jinit_phuff_decoder(cinfo);
nuclear@2 109 #else
nuclear@2 110 ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@2 111 #endif
nuclear@2 112 } else
nuclear@2 113 jinit_huff_decoder(cinfo);
nuclear@2 114 }
nuclear@2 115
nuclear@2 116 /* Always get a full-image coefficient buffer. */
nuclear@2 117 jinit_d_coef_controller(cinfo, TRUE);
nuclear@2 118
nuclear@2 119 /* We can now tell the memory manager to allocate virtual arrays. */
nuclear@2 120 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
nuclear@2 121
nuclear@2 122 /* Initialize input side of decompressor to consume first scan. */
nuclear@2 123 (*cinfo->inputctl->start_input_pass) (cinfo);
nuclear@2 124
nuclear@2 125 /* Initialize progress monitoring. */
nuclear@2 126 if (cinfo->progress != NULL) {
nuclear@2 127 int nscans;
nuclear@2 128 /* Estimate number of scans to set pass_limit. */
nuclear@2 129 if (cinfo->progressive_mode) {
nuclear@2 130 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
nuclear@2 131 nscans = 2 + 3 * cinfo->num_components;
nuclear@2 132 } else if (cinfo->inputctl->has_multiple_scans) {
nuclear@2 133 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
nuclear@2 134 nscans = cinfo->num_components;
nuclear@2 135 } else {
nuclear@2 136 nscans = 1;
nuclear@2 137 }
nuclear@2 138 cinfo->progress->pass_counter = 0L;
nuclear@2 139 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
nuclear@2 140 cinfo->progress->completed_passes = 0;
nuclear@2 141 cinfo->progress->total_passes = 1;
nuclear@2 142 }
nuclear@2 143 }