1 | /* |
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2 | * jddctmgr.c |
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3 | * |
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4 | * Copyright (C) 1994-1996, 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 the inverse-DCT management logic. |
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9 | * This code selects a particular IDCT implementation to be used, |
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10 | * and it performs related housekeeping chores. No code in this file |
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11 | * is executed per IDCT step, only during output pass setup. |
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12 | * |
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13 | * Note that the IDCT routines are responsible for performing coefficient |
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14 | * dequantization as well as the IDCT proper. This module sets up the |
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15 | * dequantization multiplier table needed by the IDCT routine. |
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16 | */ |
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17 | |
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18 | #define JPEG_INTERNALS |
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19 | #include "jinclude.h" |
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20 | #include "jpeglib.h" |
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21 | #include "jdct.h" /* Private declarations for DCT subsystem */ |
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22 | |
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23 | |
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24 | /* |
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25 | * The decompressor input side (jdinput.c) saves away the appropriate |
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26 | * quantization table for each component at the start of the first scan |
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27 | * involving that component. (This is necessary in order to correctly |
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28 | * decode files that reuse Q-table slots.) |
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29 | * When we are ready to make an output pass, the saved Q-table is converted |
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30 | * to a multiplier table that will actually be used by the IDCT routine. |
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31 | * The multiplier table contents are IDCT-method-dependent. To support |
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32 | * application changes in IDCT method between scans, we can remake the |
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33 | * multiplier tables if necessary. |
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34 | * In buffered-image mode, the first output pass may occur before any data |
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35 | * has been seen for some components, and thus before their Q-tables have |
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36 | * been saved away. To handle this case, multiplier tables are preset |
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37 | * to zeroes; the result of the IDCT will be a neutral gray level. |
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38 | */ |
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39 | |
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40 | |
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41 | /* Private subobject for this module */ |
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42 | |
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43 | typedef struct { |
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44 | struct jpeg_inverse_dct pub; /* public fields */ |
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45 | |
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46 | /* This array contains the IDCT method code that each multiplier table |
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47 | * is currently set up for, or -1 if it's not yet set up. |
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48 | * The actual multiplier tables are pointed to by dct_table in the |
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49 | * per-component comp_info structures. |
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50 | */ |
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51 | int cur_method[MAX_COMPONENTS]; |
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52 | } my_idct_controller; |
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53 | |
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54 | typedef my_idct_controller * my_idct_ptr; |
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55 | |
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56 | |
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57 | /* Allocated multiplier tables: big enough for any supported variant */ |
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58 | |
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59 | typedef union { |
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60 | ISLOW_MULT_TYPE islow_array[DCTSIZE2]; |
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61 | #ifdef DCT_IFAST_SUPPORTED |
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62 | IFAST_MULT_TYPE ifast_array[DCTSIZE2]; |
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63 | #endif |
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64 | #ifdef DCT_FLOAT_SUPPORTED |
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65 | FLOAT_MULT_TYPE float_array[DCTSIZE2]; |
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66 | #endif |
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67 | } multiplier_table; |
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68 | |
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69 | |
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70 | /* The current scaled-IDCT routines require ISLOW-style multiplier tables, |
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71 | * so be sure to compile that code if either ISLOW or SCALING is requested. |
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72 | */ |
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73 | #ifdef DCT_ISLOW_SUPPORTED |
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74 | #define PROVIDE_ISLOW_TABLES |
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75 | #else |
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76 | #ifdef IDCT_SCALING_SUPPORTED |
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77 | #define PROVIDE_ISLOW_TABLES |
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78 | #endif |
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79 | #endif |
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80 | |
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81 | |
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82 | /* |
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83 | * Prepare for an output pass. |
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84 | * Here we select the proper IDCT routine for each component and build |
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85 | * a matching multiplier table. |
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86 | */ |
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87 | |
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88 | METHODDEF(void) |
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89 | start_pass (j_decompress_ptr cinfo) |
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90 | { |
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91 | my_idct_ptr idct = (my_idct_ptr) cinfo->idct; |
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92 | int ci, i; |
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93 | jpeg_component_info *compptr; |
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94 | int method = 0; |
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95 | inverse_DCT_method_ptr method_ptr = NULL; |
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96 | JQUANT_TBL * qtbl; |
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97 | |
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98 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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99 | ci++, compptr++) { |
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100 | /* Select the proper IDCT routine for this component's scaling */ |
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101 | switch (compptr->DCT_scaled_size) { |
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102 | #ifdef IDCT_SCALING_SUPPORTED |
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103 | case 1: |
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104 | method_ptr = jpeg_idct_1x1; |
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105 | method = JDCT_ISLOW; /* jidctred uses islow-style table */ |
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106 | break; |
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107 | case 2: |
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108 | method_ptr = jpeg_idct_2x2; |
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109 | method = JDCT_ISLOW; /* jidctred uses islow-style table */ |
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110 | break; |
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111 | case 4: |
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112 | method_ptr = jpeg_idct_4x4; |
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113 | method = JDCT_ISLOW; /* jidctred uses islow-style table */ |
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114 | break; |
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115 | #endif |
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116 | case DCTSIZE: |
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117 | switch (cinfo->dct_method) { |
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118 | #ifdef DCT_ISLOW_SUPPORTED |
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119 | case JDCT_ISLOW: |
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120 | method_ptr = jpeg_idct_islow; |
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121 | method = JDCT_ISLOW; |
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122 | break; |
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123 | #endif |
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124 | #ifdef DCT_IFAST_SUPPORTED |
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125 | case JDCT_IFAST: |
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126 | method_ptr = jpeg_idct_ifast; |
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127 | method = JDCT_IFAST; |
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128 | break; |
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129 | #endif |
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130 | #ifdef DCT_FLOAT_SUPPORTED |
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131 | case JDCT_FLOAT: |
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132 | method_ptr = jpeg_idct_float; |
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133 | method = JDCT_FLOAT; |
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134 | break; |
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135 | #endif |
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136 | default: |
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137 | ERREXIT(cinfo, JERR_NOT_COMPILED); |
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138 | break; |
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139 | } |
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140 | break; |
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141 | default: |
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142 | ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->DCT_scaled_size); |
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143 | break; |
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144 | } |
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145 | idct->pub.inverse_DCT[ci] = method_ptr; |
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146 | /* Create multiplier table from quant table. |
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147 | * However, we can skip this if the component is uninteresting |
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148 | * or if we already built the table. Also, if no quant table |
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149 | * has yet been saved for the component, we leave the |
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150 | * multiplier table all-zero; we'll be reading zeroes from the |
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151 | * coefficient controller's buffer anyway. |
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152 | */ |
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153 | if (! compptr->component_needed || idct->cur_method[ci] == method) |
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154 | continue; |
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155 | qtbl = compptr->quant_table; |
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156 | if (qtbl == NULL) /* happens if no data yet for component */ |
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157 | continue; |
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158 | idct->cur_method[ci] = method; |
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159 | switch (method) { |
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160 | #ifdef PROVIDE_ISLOW_TABLES |
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161 | case JDCT_ISLOW: |
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162 | { |
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163 | /* For LL&M IDCT method, multipliers are equal to raw quantization |
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164 | * coefficients, but are stored as ints to ensure access efficiency. |
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165 | */ |
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166 | ISLOW_MULT_TYPE * ismtbl = (ISLOW_MULT_TYPE *) compptr->dct_table; |
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167 | for (i = 0; i < DCTSIZE2; i++) { |
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168 | ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i]; |
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169 | } |
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170 | } |
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171 | break; |
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172 | #endif |
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173 | #ifdef DCT_IFAST_SUPPORTED |
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174 | case JDCT_IFAST: |
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175 | { |
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176 | /* For AA&N IDCT method, multipliers are equal to quantization |
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177 | * coefficients scaled by scalefactor[row]*scalefactor[col], where |
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178 | * scalefactor[0] = 1 |
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179 | * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |
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180 | * For integer operation, the multiplier table is to be scaled by |
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181 | * IFAST_SCALE_BITS. |
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182 | */ |
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183 | IFAST_MULT_TYPE * ifmtbl = (IFAST_MULT_TYPE *) compptr->dct_table; |
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184 | #define CONST_BITS 14 |
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185 | static const INT16 aanscales[DCTSIZE2] = { |
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186 | /* precomputed values scaled up by 14 bits */ |
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187 | 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |
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188 | 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270, |
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189 | 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906, |
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190 | 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315, |
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191 | 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |
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192 | 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552, |
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193 | 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446, |
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194 | 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247 |
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195 | }; |
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196 | SHIFT_TEMPS |
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197 | |
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198 | for (i = 0; i < DCTSIZE2; i++) { |
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199 | ifmtbl[i] = (IFAST_MULT_TYPE) |
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200 | DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i], |
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201 | (INT32) aanscales[i]), |
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202 | CONST_BITS-IFAST_SCALE_BITS); |
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203 | } |
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204 | } |
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205 | break; |
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206 | #endif |
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207 | #ifdef DCT_FLOAT_SUPPORTED |
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208 | case JDCT_FLOAT: |
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209 | { |
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210 | /* For float AA&N IDCT method, multipliers are equal to quantization |
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211 | * coefficients scaled by scalefactor[row]*scalefactor[col], where |
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212 | * scalefactor[0] = 1 |
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213 | * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |
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214 | */ |
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215 | FLOAT_MULT_TYPE * fmtbl = (FLOAT_MULT_TYPE *) compptr->dct_table; |
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216 | int row, col; |
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217 | static const double aanscalefactor[DCTSIZE] = { |
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218 | 1.0, 1.387039845, 1.306562965, 1.175875602, |
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219 | 1.0, 0.785694958, 0.541196100, 0.275899379 |
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220 | }; |
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221 | |
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222 | i = 0; |
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223 | for (row = 0; row < DCTSIZE; row++) { |
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224 | for (col = 0; col < DCTSIZE; col++) { |
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225 | fmtbl[i] = (FLOAT_MULT_TYPE) |
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226 | ((double) qtbl->quantval[i] * |
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227 | aanscalefactor[row] * aanscalefactor[col]); |
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228 | i++; |
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229 | } |
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230 | } |
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231 | } |
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232 | break; |
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233 | #endif |
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234 | default: |
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235 | ERREXIT(cinfo, JERR_NOT_COMPILED); |
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236 | break; |
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237 | } |
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238 | } |
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239 | } |
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240 | |
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241 | |
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242 | /* |
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243 | * Initialize IDCT manager. |
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244 | */ |
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245 | |
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246 | GLOBAL(void) |
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247 | jinit_inverse_dct (j_decompress_ptr cinfo) |
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248 | { |
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249 | my_idct_ptr idct; |
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250 | int ci; |
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251 | jpeg_component_info *compptr; |
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252 | |
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253 | idct = (my_idct_ptr) |
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254 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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255 | SIZEOF(my_idct_controller)); |
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256 | cinfo->idct = (struct jpeg_inverse_dct *) idct; |
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257 | idct->pub.start_pass = start_pass; |
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258 | |
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259 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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260 | ci++, compptr++) { |
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261 | /* Allocate and pre-zero a multiplier table for each component */ |
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262 | compptr->dct_table = |
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263 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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264 | SIZEOF(multiplier_table)); |
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265 | MEMZERO(compptr->dct_table, SIZEOF(multiplier_table)); |
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266 | /* Mark multiplier table not yet set up for any method */ |
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267 | idct->cur_method[ci] = -1; |
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268 | } |
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269 | } |
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