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1 /* |
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2 * jcdctmgr.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 forward-DCT management logic. |
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9 * This code selects a particular DCT implementation to be used, |
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10 * and it performs related housekeeping chores including coefficient |
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11 * quantization. |
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12 */ |
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13 |
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14 #define JPEG_INTERNALS |
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15 #include "jinclude.h" |
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16 #include "jpeglib.h" |
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17 #include "jdct.h" /* Private declarations for DCT subsystem */ |
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18 |
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19 |
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20 /* Private subobject for this module */ |
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21 |
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22 typedef struct { |
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23 struct jpeg_forward_dct pub; /* public fields */ |
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24 |
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25 /* Pointer to the DCT routine actually in use */ |
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26 forward_DCT_method_ptr do_dct; |
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27 |
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28 /* The actual post-DCT divisors --- not identical to the quant table |
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29 * entries, because of scaling (especially for an unnormalized DCT). |
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30 * Each table is given in normal array order. |
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31 */ |
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32 DCTELEM * divisors[NUM_QUANT_TBLS]; |
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33 |
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34 #ifdef DCT_FLOAT_SUPPORTED |
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35 /* Same as above for the floating-point case. */ |
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36 float_DCT_method_ptr do_float_dct; |
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37 FAST_FLOAT * float_divisors[NUM_QUANT_TBLS]; |
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38 #endif |
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39 } my_fdct_controller; |
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40 |
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41 typedef my_fdct_controller * my_fdct_ptr; |
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42 |
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43 |
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44 /* |
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45 * Initialize for a processing pass. |
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46 * Verify that all referenced Q-tables are present, and set up |
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47 * the divisor table for each one. |
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48 * In the current implementation, DCT of all components is done during |
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49 * the first pass, even if only some components will be output in the |
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50 * first scan. Hence all components should be examined here. |
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51 */ |
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52 |
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53 METHODDEF(void) |
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54 start_pass_fdctmgr (j_compress_ptr cinfo) |
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55 { |
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56 my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |
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57 int ci, qtblno, i; |
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58 jpeg_component_info *compptr; |
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59 JQUANT_TBL * qtbl; |
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60 DCTELEM * dtbl; |
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61 |
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62 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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63 ci++, compptr++) { |
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64 qtblno = compptr->quant_tbl_no; |
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65 /* Make sure specified quantization table is present */ |
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66 if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS || |
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67 cinfo->quant_tbl_ptrs[qtblno] == NULL) |
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68 ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno); |
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69 qtbl = cinfo->quant_tbl_ptrs[qtblno]; |
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70 /* Compute divisors for this quant table */ |
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71 /* We may do this more than once for same table, but it's not a big deal */ |
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72 switch (cinfo->dct_method) { |
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73 #ifdef DCT_ISLOW_SUPPORTED |
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74 case JDCT_ISLOW: |
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75 /* For LL&M IDCT method, divisors are equal to raw quantization |
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76 * coefficients multiplied by 8 (to counteract scaling). |
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77 */ |
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78 if (fdct->divisors[qtblno] == NULL) { |
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79 fdct->divisors[qtblno] = (DCTELEM *) |
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80 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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81 DCTSIZE2 * SIZEOF(DCTELEM)); |
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82 } |
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83 dtbl = fdct->divisors[qtblno]; |
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84 for (i = 0; i < DCTSIZE2; i++) { |
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85 dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3; |
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86 } |
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87 break; |
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88 #endif |
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89 #ifdef DCT_IFAST_SUPPORTED |
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90 case JDCT_IFAST: |
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91 { |
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92 /* For AA&N IDCT method, divisors are equal to quantization |
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93 * coefficients scaled by scalefactor[row]*scalefactor[col], where |
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94 * scalefactor[0] = 1 |
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95 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |
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96 * We apply a further scale factor of 8. |
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97 */ |
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98 #define CONST_BITS 14 |
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99 static const INT16 aanscales[DCTSIZE2] = { |
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100 /* precomputed values scaled up by 14 bits */ |
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101 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |
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102 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270, |
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103 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906, |
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104 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315, |
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105 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |
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106 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552, |
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107 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446, |
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108 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247 |
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109 }; |
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110 SHIFT_TEMPS |
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111 |
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112 if (fdct->divisors[qtblno] == NULL) { |
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113 fdct->divisors[qtblno] = (DCTELEM *) |
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114 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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115 DCTSIZE2 * SIZEOF(DCTELEM)); |
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116 } |
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117 dtbl = fdct->divisors[qtblno]; |
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118 for (i = 0; i < DCTSIZE2; i++) { |
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119 dtbl[i] = (DCTELEM) |
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120 DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i], |
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121 (INT32) aanscales[i]), |
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122 CONST_BITS-3); |
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123 } |
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124 } |
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125 break; |
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126 #endif |
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127 #ifdef DCT_FLOAT_SUPPORTED |
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128 case JDCT_FLOAT: |
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129 { |
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130 /* For float AA&N IDCT method, divisors are equal to quantization |
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131 * coefficients scaled by scalefactor[row]*scalefactor[col], where |
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132 * scalefactor[0] = 1 |
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133 * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |
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134 * We apply a further scale factor of 8. |
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135 * What's actually stored is 1/divisor so that the inner loop can |
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136 * use a multiplication rather than a division. |
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137 */ |
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138 FAST_FLOAT * fdtbl; |
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139 int row, col; |
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140 static const double aanscalefactor[DCTSIZE] = { |
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141 1.0, 1.387039845, 1.306562965, 1.175875602, |
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142 1.0, 0.785694958, 0.541196100, 0.275899379 |
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143 }; |
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144 |
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145 if (fdct->float_divisors[qtblno] == NULL) { |
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146 fdct->float_divisors[qtblno] = (FAST_FLOAT *) |
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147 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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148 DCTSIZE2 * SIZEOF(FAST_FLOAT)); |
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149 } |
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150 fdtbl = fdct->float_divisors[qtblno]; |
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151 i = 0; |
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152 for (row = 0; row < DCTSIZE; row++) { |
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153 for (col = 0; col < DCTSIZE; col++) { |
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154 fdtbl[i] = (FAST_FLOAT) |
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155 (1.0 / (((double) qtbl->quantval[i] * |
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156 aanscalefactor[row] * aanscalefactor[col] * 8.0))); |
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157 i++; |
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158 } |
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159 } |
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160 } |
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161 break; |
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162 #endif |
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163 default: |
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164 ERREXIT(cinfo, JERR_NOT_COMPILED); |
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165 break; |
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166 } |
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167 } |
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168 } |
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169 |
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170 |
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171 /* |
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172 * Perform forward DCT on one or more blocks of a component. |
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173 * |
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174 * The input samples are taken from the sample_data[] array starting at |
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175 * position start_row/start_col, and moving to the right for any additional |
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176 * blocks. The quantized coefficients are returned in coef_blocks[]. |
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177 */ |
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178 |
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179 METHODDEF(void) |
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180 forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr, |
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181 JSAMPARRAY sample_data, JBLOCKROW coef_blocks, |
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182 JDIMENSION start_row, JDIMENSION start_col, |
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183 JDIMENSION num_blocks) |
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184 /* This version is used for integer DCT implementations. */ |
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185 { |
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186 /* This routine is heavily used, so it's worth coding it tightly. */ |
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187 my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |
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188 forward_DCT_method_ptr do_dct = fdct->do_dct; |
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189 DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no]; |
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190 DCTELEM workspace[DCTSIZE2]; /* work area for FDCT subroutine */ |
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191 JDIMENSION bi; |
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192 |
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193 sample_data += start_row; /* fold in the vertical offset once */ |
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194 |
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195 for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) { |
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196 /* Load data into workspace, applying unsigned->signed conversion */ |
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197 { register DCTELEM *workspaceptr; |
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198 register JSAMPROW elemptr; |
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199 register int elemr; |
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200 |
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201 workspaceptr = workspace; |
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202 for (elemr = 0; elemr < DCTSIZE; elemr++) { |
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203 elemptr = sample_data[elemr] + start_col; |
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204 #if DCTSIZE == 8 /* unroll the inner loop */ |
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205 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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206 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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207 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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208 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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209 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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210 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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211 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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212 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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213 #else |
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214 { register int elemc; |
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215 for (elemc = DCTSIZE; elemc > 0; elemc--) { |
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216 *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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217 } |
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218 } |
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219 #endif |
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220 } |
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221 } |
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222 |
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223 /* Perform the DCT */ |
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224 (*do_dct) (workspace); |
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225 |
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226 /* Quantize/descale the coefficients, and store into coef_blocks[] */ |
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227 { register DCTELEM temp, qval; |
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228 register int i; |
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229 register JCOEFPTR output_ptr = coef_blocks[bi]; |
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230 |
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231 for (i = 0; i < DCTSIZE2; i++) { |
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232 qval = divisors[i]; |
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233 temp = workspace[i]; |
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234 /* Divide the coefficient value by qval, ensuring proper rounding. |
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235 * Since C does not specify the direction of rounding for negative |
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236 * quotients, we have to force the dividend positive for portability. |
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237 * |
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238 * In most files, at least half of the output values will be zero |
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239 * (at default quantization settings, more like three-quarters...) |
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240 * so we should ensure that this case is fast. On many machines, |
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241 * a comparison is enough cheaper than a divide to make a special test |
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242 * a win. Since both inputs will be nonnegative, we need only test |
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243 * for a < b to discover whether a/b is 0. |
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244 * If your machine's division is fast enough, define FAST_DIVIDE. |
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245 */ |
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246 #ifdef FAST_DIVIDE |
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247 #define DIVIDE_BY(a,b) a /= b |
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248 #else |
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249 #define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0 |
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250 #endif |
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251 if (temp < 0) { |
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252 temp = -temp; |
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253 temp += qval>>1; /* for rounding */ |
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254 DIVIDE_BY(temp, qval); |
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255 temp = -temp; |
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256 } else { |
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257 temp += qval>>1; /* for rounding */ |
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258 DIVIDE_BY(temp, qval); |
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259 } |
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260 output_ptr[i] = (JCOEF) temp; |
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261 } |
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262 } |
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263 } |
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264 } |
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265 |
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266 |
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267 #ifdef DCT_FLOAT_SUPPORTED |
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268 |
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269 METHODDEF(void) |
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270 forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr, |
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271 JSAMPARRAY sample_data, JBLOCKROW coef_blocks, |
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272 JDIMENSION start_row, JDIMENSION start_col, |
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273 JDIMENSION num_blocks) |
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274 /* This version is used for floating-point DCT implementations. */ |
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275 { |
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276 /* This routine is heavily used, so it's worth coding it tightly. */ |
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277 my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |
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278 float_DCT_method_ptr do_dct = fdct->do_float_dct; |
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279 FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no]; |
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280 FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */ |
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281 JDIMENSION bi; |
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282 |
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283 sample_data += start_row; /* fold in the vertical offset once */ |
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284 |
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285 for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) { |
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286 /* Load data into workspace, applying unsigned->signed conversion */ |
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287 { register FAST_FLOAT *workspaceptr; |
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288 register JSAMPROW elemptr; |
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289 register int elemr; |
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290 |
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291 workspaceptr = workspace; |
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292 for (elemr = 0; elemr < DCTSIZE; elemr++) { |
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293 elemptr = sample_data[elemr] + start_col; |
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294 #if DCTSIZE == 8 /* unroll the inner loop */ |
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295 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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296 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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297 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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298 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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299 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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300 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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301 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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302 *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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303 #else |
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304 { register int elemc; |
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305 for (elemc = DCTSIZE; elemc > 0; elemc--) { |
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306 *workspaceptr++ = (FAST_FLOAT) |
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307 (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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308 } |
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309 } |
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310 #endif |
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311 } |
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312 } |
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313 |
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314 /* Perform the DCT */ |
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315 (*do_dct) (workspace); |
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316 |
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317 /* Quantize/descale the coefficients, and store into coef_blocks[] */ |
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318 { register FAST_FLOAT temp; |
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319 register int i; |
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320 register JCOEFPTR output_ptr = coef_blocks[bi]; |
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321 |
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322 for (i = 0; i < DCTSIZE2; i++) { |
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323 /* Apply the quantization and scaling factor */ |
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324 temp = workspace[i] * divisors[i]; |
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325 /* Round to nearest integer. |
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326 * Since C does not specify the direction of rounding for negative |
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327 * quotients, we have to force the dividend positive for portability. |
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328 * The maximum coefficient size is +-16K (for 12-bit data), so this |
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329 * code should work for either 16-bit or 32-bit ints. |
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330 */ |
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331 output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384); |
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332 } |
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333 } |
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334 } |
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335 } |
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336 |
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337 #endif /* DCT_FLOAT_SUPPORTED */ |
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338 |
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339 |
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340 /* |
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341 * Initialize FDCT manager. |
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342 */ |
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343 |
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344 GLOBAL(void) |
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345 jinit_forward_dct (j_compress_ptr cinfo) |
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346 { |
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347 my_fdct_ptr fdct; |
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348 int i; |
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349 |
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350 fdct = (my_fdct_ptr) |
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351 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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352 SIZEOF(my_fdct_controller)); |
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353 cinfo->fdct = (struct jpeg_forward_dct *) fdct; |
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354 fdct->pub.start_pass = start_pass_fdctmgr; |
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355 |
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356 switch (cinfo->dct_method) { |
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357 #ifdef DCT_ISLOW_SUPPORTED |
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358 case JDCT_ISLOW: |
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359 fdct->pub.forward_DCT = forward_DCT; |
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360 fdct->do_dct = jpeg_fdct_islow; |
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361 break; |
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362 #endif |
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363 #ifdef DCT_IFAST_SUPPORTED |
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364 case JDCT_IFAST: |
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365 fdct->pub.forward_DCT = forward_DCT; |
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366 fdct->do_dct = jpeg_fdct_ifast; |
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367 break; |
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368 #endif |
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369 #ifdef DCT_FLOAT_SUPPORTED |
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370 case JDCT_FLOAT: |
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371 fdct->pub.forward_DCT = forward_DCT_float; |
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372 fdct->do_float_dct = jpeg_fdct_float; |
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373 break; |
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374 #endif |
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375 default: |
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376 ERREXIT(cinfo, JERR_NOT_COMPILED); |
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377 break; |
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378 } |
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379 |
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380 /* Mark divisor tables unallocated */ |
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381 for (i = 0; i < NUM_QUANT_TBLS; i++) { |
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382 fdct->divisors[i] = NULL; |
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383 #ifdef DCT_FLOAT_SUPPORTED |
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384 fdct->float_divisors[i] = NULL; |
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385 #endif |
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386 } |
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387 } |