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1 /* |
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2 * jcprepct.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 compression preprocessing controller. |
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9 * This controller manages the color conversion, downsampling, |
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10 * and edge expansion steps. |
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11 * |
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12 * Most of the complexity here is associated with buffering input rows |
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13 * as required by the downsampler. See the comments at the head of |
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14 * jcsample.c for the downsampler's needs. |
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15 */ |
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16 |
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17 #define JPEG_INTERNALS |
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18 #include "jinclude.h" |
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19 #include "jpeglib.h" |
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20 |
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21 |
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22 /* At present, jcsample.c can request context rows only for smoothing. |
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23 * In the future, we might also need context rows for CCIR601 sampling |
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24 * or other more-complex downsampling procedures. The code to support |
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25 * context rows should be compiled only if needed. |
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26 */ |
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27 #ifdef INPUT_SMOOTHING_SUPPORTED |
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28 #define CONTEXT_ROWS_SUPPORTED |
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29 #endif |
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30 |
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31 |
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32 /* |
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33 * For the simple (no-context-row) case, we just need to buffer one |
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34 * row group's worth of pixels for the downsampling step. At the bottom of |
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35 * the image, we pad to a full row group by replicating the last pixel row. |
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36 * The downsampler's last output row is then replicated if needed to pad |
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37 * out to a full iMCU row. |
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38 * |
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39 * When providing context rows, we must buffer three row groups' worth of |
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40 * pixels. Three row groups are physically allocated, but the row pointer |
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41 * arrays are made five row groups high, with the extra pointers above and |
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42 * below "wrapping around" to point to the last and first real row groups. |
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43 * This allows the downsampler to access the proper context rows. |
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44 * At the top and bottom of the image, we create dummy context rows by |
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45 * copying the first or last real pixel row. This copying could be avoided |
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46 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the |
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47 * trouble on the compression side. |
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48 */ |
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49 |
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50 |
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51 /* Private buffer controller object */ |
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52 |
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53 typedef struct { |
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54 struct jpeg_c_prep_controller pub; /* public fields */ |
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55 |
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56 /* Downsampling input buffer. This buffer holds color-converted data |
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57 * until we have enough to do a downsample step. |
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58 */ |
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59 JSAMPARRAY color_buf[MAX_COMPONENTS]; |
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60 |
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61 JDIMENSION rows_to_go; /* counts rows remaining in source image */ |
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62 int next_buf_row; /* index of next row to store in color_buf */ |
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63 |
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64 #ifdef CONTEXT_ROWS_SUPPORTED /* only needed for context case */ |
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65 int this_row_group; /* starting row index of group to process */ |
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66 int next_buf_stop; /* downsample when we reach this index */ |
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67 #endif |
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68 } my_prep_controller; |
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69 |
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70 typedef my_prep_controller * my_prep_ptr; |
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71 |
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72 |
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73 /* |
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74 * Initialize for a processing pass. |
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75 */ |
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76 |
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77 METHODDEF(void) |
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78 start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode) |
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79 { |
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80 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; |
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81 |
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82 if (pass_mode != JBUF_PASS_THRU) |
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83 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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84 |
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85 /* Initialize total-height counter for detecting bottom of image */ |
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86 prep->rows_to_go = cinfo->image_height; |
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87 /* Mark the conversion buffer empty */ |
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88 prep->next_buf_row = 0; |
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89 #ifdef CONTEXT_ROWS_SUPPORTED |
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90 /* Preset additional state variables for context mode. |
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91 * These aren't used in non-context mode, so we needn't test which mode. |
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92 */ |
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93 prep->this_row_group = 0; |
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94 /* Set next_buf_stop to stop after two row groups have been read in. */ |
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95 prep->next_buf_stop = 2 * cinfo->max_v_samp_factor; |
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96 #endif |
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97 } |
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98 |
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99 |
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100 /* |
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101 * Expand an image vertically from height input_rows to height output_rows, |
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102 * by duplicating the bottom row. |
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103 */ |
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104 |
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105 LOCAL(void) |
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106 expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols, |
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107 int input_rows, int output_rows) |
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108 { |
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109 register int row; |
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110 |
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111 for (row = input_rows; row < output_rows; row++) { |
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112 jcopy_sample_rows(image_data, input_rows-1, image_data, row, |
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113 1, num_cols); |
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114 } |
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115 } |
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116 |
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117 |
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118 /* |
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119 * Process some data in the simple no-context case. |
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120 * |
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121 * Preprocessor output data is counted in "row groups". A row group |
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122 * is defined to be v_samp_factor sample rows of each component. |
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123 * Downsampling will produce this much data from each max_v_samp_factor |
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124 * input rows. |
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125 */ |
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126 |
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127 METHODDEF(void) |
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128 pre_process_data (j_compress_ptr cinfo, |
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129 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, |
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130 JDIMENSION in_rows_avail, |
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131 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, |
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132 JDIMENSION out_row_groups_avail) |
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133 { |
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134 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; |
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135 int numrows, ci; |
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136 JDIMENSION inrows; |
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137 jpeg_component_info * compptr; |
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138 |
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139 while (*in_row_ctr < in_rows_avail && |
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140 *out_row_group_ctr < out_row_groups_avail) { |
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141 /* Do color conversion to fill the conversion buffer. */ |
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142 inrows = in_rows_avail - *in_row_ctr; |
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143 numrows = cinfo->max_v_samp_factor - prep->next_buf_row; |
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144 numrows = (int) MIN((JDIMENSION) numrows, inrows); |
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145 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, |
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146 prep->color_buf, |
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147 (JDIMENSION) prep->next_buf_row, |
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148 numrows); |
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149 *in_row_ctr += numrows; |
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150 prep->next_buf_row += numrows; |
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151 prep->rows_to_go -= numrows; |
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152 /* If at bottom of image, pad to fill the conversion buffer. */ |
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153 if (prep->rows_to_go == 0 && |
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154 prep->next_buf_row < cinfo->max_v_samp_factor) { |
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155 for (ci = 0; ci < cinfo->num_components; ci++) { |
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156 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, |
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157 prep->next_buf_row, cinfo->max_v_samp_factor); |
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158 } |
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159 prep->next_buf_row = cinfo->max_v_samp_factor; |
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160 } |
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161 /* If we've filled the conversion buffer, empty it. */ |
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162 if (prep->next_buf_row == cinfo->max_v_samp_factor) { |
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163 (*cinfo->downsample->downsample) (cinfo, |
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164 prep->color_buf, (JDIMENSION) 0, |
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165 output_buf, *out_row_group_ctr); |
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166 prep->next_buf_row = 0; |
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167 (*out_row_group_ctr)++; |
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168 } |
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169 /* If at bottom of image, pad the output to a full iMCU height. |
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170 * Note we assume the caller is providing a one-iMCU-height output buffer! |
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171 */ |
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172 if (prep->rows_to_go == 0 && |
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173 *out_row_group_ctr < out_row_groups_avail) { |
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174 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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175 ci++, compptr++) { |
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176 expand_bottom_edge(output_buf[ci], |
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177 compptr->width_in_blocks * DCTSIZE, |
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178 (int) (*out_row_group_ctr * compptr->v_samp_factor), |
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179 (int) (out_row_groups_avail * compptr->v_samp_factor)); |
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180 } |
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181 *out_row_group_ctr = out_row_groups_avail; |
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182 break; /* can exit outer loop without test */ |
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183 } |
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184 } |
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185 } |
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186 |
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187 |
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188 #ifdef CONTEXT_ROWS_SUPPORTED |
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189 |
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190 /* |
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191 * Process some data in the context case. |
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192 */ |
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193 |
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194 METHODDEF(void) |
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195 pre_process_context (j_compress_ptr cinfo, |
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196 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, |
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197 JDIMENSION in_rows_avail, |
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198 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, |
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199 JDIMENSION out_row_groups_avail) |
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200 { |
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201 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; |
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202 int numrows, ci; |
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203 int buf_height = cinfo->max_v_samp_factor * 3; |
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204 JDIMENSION inrows; |
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205 |
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206 while (*out_row_group_ctr < out_row_groups_avail) { |
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207 if (*in_row_ctr < in_rows_avail) { |
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208 /* Do color conversion to fill the conversion buffer. */ |
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209 inrows = in_rows_avail - *in_row_ctr; |
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210 numrows = prep->next_buf_stop - prep->next_buf_row; |
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211 numrows = (int) MIN((JDIMENSION) numrows, inrows); |
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212 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, |
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213 prep->color_buf, |
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214 (JDIMENSION) prep->next_buf_row, |
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215 numrows); |
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216 /* Pad at top of image, if first time through */ |
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217 if (prep->rows_to_go == cinfo->image_height) { |
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218 for (ci = 0; ci < cinfo->num_components; ci++) { |
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219 int row; |
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220 for (row = 1; row <= cinfo->max_v_samp_factor; row++) { |
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221 jcopy_sample_rows(prep->color_buf[ci], 0, |
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222 prep->color_buf[ci], -row, |
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223 1, cinfo->image_width); |
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224 } |
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225 } |
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226 } |
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227 *in_row_ctr += numrows; |
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228 prep->next_buf_row += numrows; |
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229 prep->rows_to_go -= numrows; |
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230 } else { |
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231 /* Return for more data, unless we are at the bottom of the image. */ |
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232 if (prep->rows_to_go != 0) |
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233 break; |
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234 /* When at bottom of image, pad to fill the conversion buffer. */ |
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235 if (prep->next_buf_row < prep->next_buf_stop) { |
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236 for (ci = 0; ci < cinfo->num_components; ci++) { |
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237 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, |
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238 prep->next_buf_row, prep->next_buf_stop); |
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239 } |
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240 prep->next_buf_row = prep->next_buf_stop; |
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241 } |
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242 } |
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243 /* If we've gotten enough data, downsample a row group. */ |
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244 if (prep->next_buf_row == prep->next_buf_stop) { |
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245 (*cinfo->downsample->downsample) (cinfo, |
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246 prep->color_buf, |
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247 (JDIMENSION) prep->this_row_group, |
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248 output_buf, *out_row_group_ctr); |
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249 (*out_row_group_ctr)++; |
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250 /* Advance pointers with wraparound as necessary. */ |
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251 prep->this_row_group += cinfo->max_v_samp_factor; |
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252 if (prep->this_row_group >= buf_height) |
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253 prep->this_row_group = 0; |
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254 if (prep->next_buf_row >= buf_height) |
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255 prep->next_buf_row = 0; |
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256 prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor; |
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257 } |
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258 } |
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259 } |
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260 |
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261 |
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262 /* |
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263 * Create the wrapped-around downsampling input buffer needed for context mode. |
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264 */ |
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265 |
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266 LOCAL(void) |
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267 create_context_buffer (j_compress_ptr cinfo) |
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268 { |
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269 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; |
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270 int rgroup_height = cinfo->max_v_samp_factor; |
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271 int ci, i; |
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272 jpeg_component_info * compptr; |
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273 JSAMPARRAY true_buffer, fake_buffer; |
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274 |
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275 /* Grab enough space for fake row pointers for all the components; |
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276 * we need five row groups' worth of pointers for each component. |
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277 */ |
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278 fake_buffer = (JSAMPARRAY) |
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279 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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280 (cinfo->num_components * 5 * rgroup_height) * |
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281 SIZEOF(JSAMPROW)); |
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282 |
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283 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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284 ci++, compptr++) { |
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285 /* Allocate the actual buffer space (3 row groups) for this component. |
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286 * We make the buffer wide enough to allow the downsampler to edge-expand |
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287 * horizontally within the buffer, if it so chooses. |
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288 */ |
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289 true_buffer = (*cinfo->mem->alloc_sarray) |
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290 ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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291 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * |
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292 cinfo->max_h_samp_factor) / compptr->h_samp_factor), |
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293 (JDIMENSION) (3 * rgroup_height)); |
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294 /* Copy true buffer row pointers into the middle of the fake row array */ |
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295 MEMCOPY(fake_buffer + rgroup_height, true_buffer, |
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296 3 * rgroup_height * SIZEOF(JSAMPROW)); |
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297 /* Fill in the above and below wraparound pointers */ |
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298 for (i = 0; i < rgroup_height; i++) { |
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299 fake_buffer[i] = true_buffer[2 * rgroup_height + i]; |
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300 fake_buffer[4 * rgroup_height + i] = true_buffer[i]; |
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301 } |
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302 prep->color_buf[ci] = fake_buffer + rgroup_height; |
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303 fake_buffer += 5 * rgroup_height; /* point to space for next component */ |
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304 } |
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305 } |
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306 |
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307 #endif /* CONTEXT_ROWS_SUPPORTED */ |
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308 |
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309 |
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310 /* |
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311 * Initialize preprocessing controller. |
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312 */ |
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313 |
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314 GLOBAL(void) |
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315 jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer) |
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316 { |
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317 my_prep_ptr prep; |
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318 int ci; |
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319 jpeg_component_info * compptr; |
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320 |
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321 if (need_full_buffer) /* safety check */ |
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322 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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323 |
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324 prep = (my_prep_ptr) |
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325 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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326 SIZEOF(my_prep_controller)); |
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327 cinfo->prep = (struct jpeg_c_prep_controller *) prep; |
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328 prep->pub.start_pass = start_pass_prep; |
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329 |
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330 /* Allocate the color conversion buffer. |
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331 * We make the buffer wide enough to allow the downsampler to edge-expand |
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332 * horizontally within the buffer, if it so chooses. |
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333 */ |
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334 if (cinfo->downsample->need_context_rows) { |
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335 /* Set up to provide context rows */ |
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336 #ifdef CONTEXT_ROWS_SUPPORTED |
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337 prep->pub.pre_process_data = pre_process_context; |
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338 create_context_buffer(cinfo); |
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339 #else |
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340 ERREXIT(cinfo, JERR_NOT_COMPILED); |
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341 #endif |
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342 } else { |
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343 /* No context, just make it tall enough for one row group */ |
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344 prep->pub.pre_process_data = pre_process_data; |
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345 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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346 ci++, compptr++) { |
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347 prep->color_buf[ci] = (*cinfo->mem->alloc_sarray) |
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348 ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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349 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * |
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350 cinfo->max_h_samp_factor) / compptr->h_samp_factor), |
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351 (JDIMENSION) cinfo->max_v_samp_factor); |
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352 } |
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353 } |
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354 } |