Details | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 6417 | ashmew2 | 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 | jpeg_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 | |||
| 96 | LOCAL(void) |
||
| 97 | transdecode_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 | } |