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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 } |