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