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6417 | ashmew2 | 1 | /* |
2 | * jdmainct.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 main buffer controller for decompression. |
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9 | * The main buffer lies between the JPEG decompressor proper and the |
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10 | * post-processor; it holds downsampled data in the JPEG colorspace. |
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11 | * |
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12 | * Note that this code is bypassed in raw-data mode, since the application |
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13 | * supplies the equivalent of the main buffer in that case. |
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14 | */ |
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15 | |||
16 | #define JPEG_INTERNALS |
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17 | #include "jinclude.h" |
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18 | #include "jpeglib.h" |
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19 | |||
20 | |||
21 | /* |
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22 | * In the current system design, the main buffer need never be a full-image |
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23 | * buffer; any full-height buffers will be found inside the coefficient or |
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24 | * postprocessing controllers. Nonetheless, the main controller is not |
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25 | * trivial. Its responsibility is to provide context rows for upsampling/ |
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26 | * rescaling, and doing this in an efficient fashion is a bit tricky. |
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27 | * |
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28 | * Postprocessor input data is counted in "row groups". A row group |
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29 | * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size) |
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30 | * sample rows of each component. (We require DCT_scaled_size values to be |
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31 | * chosen such that these numbers are integers. In practice DCT_scaled_size |
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32 | * values will likely be powers of two, so we actually have the stronger |
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33 | * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.) |
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34 | * Upsampling will typically produce max_v_samp_factor pixel rows from each |
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35 | * row group (times any additional scale factor that the upsampler is |
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36 | * applying). |
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37 | * |
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38 | * The coefficient controller will deliver data to us one iMCU row at a time; |
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39 | * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or |
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40 | * exactly min_DCT_scaled_size row groups. (This amount of data corresponds |
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41 | * to one row of MCUs when the image is fully interleaved.) Note that the |
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42 | * number of sample rows varies across components, but the number of row |
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43 | * groups does not. Some garbage sample rows may be included in the last iMCU |
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44 | * row at the bottom of the image. |
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45 | * |
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46 | * Depending on the vertical scaling algorithm used, the upsampler may need |
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47 | * access to the sample row(s) above and below its current input row group. |
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48 | * The upsampler is required to set need_context_rows TRUE at global selection |
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49 | * time if so. When need_context_rows is FALSE, this controller can simply |
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50 | * obtain one iMCU row at a time from the coefficient controller and dole it |
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51 | * out as row groups to the postprocessor. |
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52 | * |
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53 | * When need_context_rows is TRUE, this controller guarantees that the buffer |
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54 | * passed to postprocessing contains at least one row group's worth of samples |
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55 | * above and below the row group(s) being processed. Note that the context |
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56 | * rows "above" the first passed row group appear at negative row offsets in |
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57 | * the passed buffer. At the top and bottom of the image, the required |
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58 | * context rows are manufactured by duplicating the first or last real sample |
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59 | * row; this avoids having special cases in the upsampling inner loops. |
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60 | * |
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61 | * The amount of context is fixed at one row group just because that's a |
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62 | * convenient number for this controller to work with. The existing |
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63 | * upsamplers really only need one sample row of context. An upsampler |
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64 | * supporting arbitrary output rescaling might wish for more than one row |
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65 | * group of context when shrinking the image; tough, we don't handle that. |
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66 | * (This is justified by the assumption that downsizing will be handled mostly |
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67 | * by adjusting the DCT_scaled_size values, so that the actual scale factor at |
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68 | * the upsample step needn't be much less than one.) |
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69 | * |
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70 | * To provide the desired context, we have to retain the last two row groups |
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71 | * of one iMCU row while reading in the next iMCU row. (The last row group |
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72 | * can't be processed until we have another row group for its below-context, |
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73 | * and so we have to save the next-to-last group too for its above-context.) |
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74 | * We could do this most simply by copying data around in our buffer, but |
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75 | * that'd be very slow. We can avoid copying any data by creating a rather |
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76 | * strange pointer structure. Here's how it works. We allocate a workspace |
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77 | * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number |
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78 | * of row groups per iMCU row). We create two sets of redundant pointers to |
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79 | * the workspace. Labeling the physical row groups 0 to M+1, the synthesized |
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80 | * pointer lists look like this: |
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81 | * M+1 M-1 |
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82 | * master pointer --> 0 master pointer --> 0 |
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83 | * 1 1 |
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84 | * ... ... |
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85 | * M-3 M-3 |
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86 | * M-2 M |
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87 | * M-1 M+1 |
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88 | * M M-2 |
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89 | * M+1 M-1 |
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90 | * 0 0 |
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91 | * We read alternate iMCU rows using each master pointer; thus the last two |
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92 | * row groups of the previous iMCU row remain un-overwritten in the workspace. |
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93 | * The pointer lists are set up so that the required context rows appear to |
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94 | * be adjacent to the proper places when we pass the pointer lists to the |
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95 | * upsampler. |
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96 | * |
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97 | * The above pictures describe the normal state of the pointer lists. |
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98 | * At top and bottom of the image, we diddle the pointer lists to duplicate |
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99 | * the first or last sample row as necessary (this is cheaper than copying |
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100 | * sample rows around). |
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101 | * |
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102 | * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1. In that |
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103 | * situation each iMCU row provides only one row group so the buffering logic |
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104 | * must be different (eg, we must read two iMCU rows before we can emit the |
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105 | * first row group). For now, we simply do not support providing context |
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106 | * rows when min_DCT_scaled_size is 1. That combination seems unlikely to |
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107 | * be worth providing --- if someone wants a 1/8th-size preview, they probably |
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108 | * want it quick and dirty, so a context-free upsampler is sufficient. |
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109 | */ |
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110 | |||
111 | |||
112 | /* Private buffer controller object */ |
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113 | |||
114 | typedef struct { |
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115 | struct jpeg_d_main_controller pub; /* public fields */ |
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116 | |||
117 | /* Pointer to allocated workspace (M or M+2 row groups). */ |
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118 | JSAMPARRAY buffer[MAX_COMPONENTS]; |
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119 | |||
120 | boolean buffer_full; /* Have we gotten an iMCU row from decoder? */ |
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121 | JDIMENSION rowgroup_ctr; /* counts row groups output to postprocessor */ |
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122 | |||
123 | /* Remaining fields are only used in the context case. */ |
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124 | |||
125 | /* These are the master pointers to the funny-order pointer lists. */ |
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126 | JSAMPIMAGE xbuffer[2]; /* pointers to weird pointer lists */ |
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127 | |||
128 | int whichptr; /* indicates which pointer set is now in use */ |
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129 | int context_state; /* process_data state machine status */ |
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130 | JDIMENSION rowgroups_avail; /* row groups available to postprocessor */ |
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131 | JDIMENSION iMCU_row_ctr; /* counts iMCU rows to detect image top/bot */ |
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132 | } my_main_controller; |
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133 | |||
134 | typedef my_main_controller * my_main_ptr; |
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135 | |||
136 | /* context_state values: */ |
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137 | #define CTX_PREPARE_FOR_IMCU 0 /* need to prepare for MCU row */ |
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138 | #define CTX_PROCESS_IMCU 1 /* feeding iMCU to postprocessor */ |
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139 | #define CTX_POSTPONED_ROW 2 /* feeding postponed row group */ |
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140 | |||
141 | |||
142 | /* Forward declarations */ |
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143 | METHODDEF(void) process_data_simple_main |
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144 | JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf, |
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145 | JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)); |
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146 | METHODDEF(void) process_data_context_main |
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147 | JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf, |
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148 | JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)); |
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149 | #ifdef QUANT_2PASS_SUPPORTED |
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150 | METHODDEF(void) process_data_crank_post |
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151 | JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf, |
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152 | JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)); |
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153 | #endif |
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154 | |||
155 | |||
156 | LOCAL(void) |
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157 | alloc_funny_pointers (j_decompress_ptr cinfo) |
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158 | /* Allocate space for the funny pointer lists. |
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159 | * This is done only once, not once per pass. |
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160 | */ |
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161 | { |
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162 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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163 | int ci, rgroup; |
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164 | int M = cinfo->min_DCT_scaled_size; |
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165 | jpeg_component_info *compptr; |
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166 | JSAMPARRAY xbuf; |
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167 | |||
168 | /* Get top-level space for component array pointers. |
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169 | * We alloc both arrays with one call to save a few cycles. |
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170 | */ |
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171 | main->xbuffer[0] = (JSAMPIMAGE) |
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172 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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173 | cinfo->num_components * 2 * SIZEOF(JSAMPARRAY)); |
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174 | main->xbuffer[1] = main->xbuffer[0] + cinfo->num_components; |
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175 | |||
176 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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177 | ci++, compptr++) { |
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178 | rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) / |
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179 | cinfo->min_DCT_scaled_size; /* height of a row group of component */ |
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180 | /* Get space for pointer lists --- M+4 row groups in each list. |
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181 | * We alloc both pointer lists with one call to save a few cycles. |
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182 | */ |
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183 | xbuf = (JSAMPARRAY) |
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184 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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185 | 2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW)); |
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186 | xbuf += rgroup; /* want one row group at negative offsets */ |
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187 | main->xbuffer[0][ci] = xbuf; |
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188 | xbuf += rgroup * (M + 4); |
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189 | main->xbuffer[1][ci] = xbuf; |
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190 | } |
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191 | } |
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192 | |||
193 | |||
194 | LOCAL(void) |
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195 | make_funny_pointers (j_decompress_ptr cinfo) |
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196 | /* Create the funny pointer lists discussed in the comments above. |
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197 | * The actual workspace is already allocated (in main->buffer), |
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198 | * and the space for the pointer lists is allocated too. |
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199 | * This routine just fills in the curiously ordered lists. |
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200 | * This will be repeated at the beginning of each pass. |
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201 | */ |
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202 | { |
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203 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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204 | int ci, i, rgroup; |
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205 | int M = cinfo->min_DCT_scaled_size; |
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206 | jpeg_component_info *compptr; |
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207 | JSAMPARRAY buf, xbuf0, xbuf1; |
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208 | |||
209 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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210 | ci++, compptr++) { |
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211 | rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) / |
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212 | cinfo->min_DCT_scaled_size; /* height of a row group of component */ |
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213 | xbuf0 = main->xbuffer[0][ci]; |
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214 | xbuf1 = main->xbuffer[1][ci]; |
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215 | /* First copy the workspace pointers as-is */ |
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216 | buf = main->buffer[ci]; |
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217 | for (i = 0; i < rgroup * (M + 2); i++) { |
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218 | xbuf0[i] = xbuf1[i] = buf[i]; |
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219 | } |
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220 | /* In the second list, put the last four row groups in swapped order */ |
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221 | for (i = 0; i < rgroup * 2; i++) { |
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222 | xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i]; |
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223 | xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i]; |
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224 | } |
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225 | /* The wraparound pointers at top and bottom will be filled later |
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226 | * (see set_wraparound_pointers, below). Initially we want the "above" |
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227 | * pointers to duplicate the first actual data line. This only needs |
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228 | * to happen in xbuffer[0]. |
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229 | */ |
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230 | for (i = 0; i < rgroup; i++) { |
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231 | xbuf0[i - rgroup] = xbuf0[0]; |
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232 | } |
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233 | } |
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234 | } |
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235 | |||
236 | |||
237 | LOCAL(void) |
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238 | set_wraparound_pointers (j_decompress_ptr cinfo) |
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239 | /* Set up the "wraparound" pointers at top and bottom of the pointer lists. |
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240 | * This changes the pointer list state from top-of-image to the normal state. |
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241 | */ |
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242 | { |
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243 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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244 | int ci, i, rgroup; |
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245 | int M = cinfo->min_DCT_scaled_size; |
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246 | jpeg_component_info *compptr; |
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247 | JSAMPARRAY xbuf0, xbuf1; |
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248 | |||
249 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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250 | ci++, compptr++) { |
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251 | rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) / |
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252 | cinfo->min_DCT_scaled_size; /* height of a row group of component */ |
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253 | xbuf0 = main->xbuffer[0][ci]; |
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254 | xbuf1 = main->xbuffer[1][ci]; |
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255 | for (i = 0; i < rgroup; i++) { |
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256 | xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i]; |
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257 | xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i]; |
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258 | xbuf0[rgroup*(M+2) + i] = xbuf0[i]; |
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259 | xbuf1[rgroup*(M+2) + i] = xbuf1[i]; |
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260 | } |
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261 | } |
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262 | } |
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263 | |||
264 | |||
265 | LOCAL(void) |
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266 | set_bottom_pointers (j_decompress_ptr cinfo) |
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267 | /* Change the pointer lists to duplicate the last sample row at the bottom |
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268 | * of the image. whichptr indicates which xbuffer holds the final iMCU row. |
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269 | * Also sets rowgroups_avail to indicate number of nondummy row groups in row. |
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270 | */ |
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271 | { |
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272 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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273 | int ci, i, rgroup, iMCUheight, rows_left; |
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274 | jpeg_component_info *compptr; |
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275 | JSAMPARRAY xbuf; |
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276 | |||
277 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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278 | ci++, compptr++) { |
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279 | /* Count sample rows in one iMCU row and in one row group */ |
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280 | iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size; |
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281 | rgroup = iMCUheight / cinfo->min_DCT_scaled_size; |
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282 | /* Count nondummy sample rows remaining for this component */ |
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283 | rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight); |
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284 | if (rows_left == 0) rows_left = iMCUheight; |
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285 | /* Count nondummy row groups. Should get same answer for each component, |
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286 | * so we need only do it once. |
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287 | */ |
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288 | if (ci == 0) { |
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289 | main->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1); |
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290 | } |
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291 | /* Duplicate the last real sample row rgroup*2 times; this pads out the |
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292 | * last partial rowgroup and ensures at least one full rowgroup of context. |
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293 | */ |
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294 | xbuf = main->xbuffer[main->whichptr][ci]; |
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295 | for (i = 0; i < rgroup * 2; i++) { |
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296 | xbuf[rows_left + i] = xbuf[rows_left-1]; |
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297 | } |
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298 | } |
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299 | } |
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300 | |||
301 | |||
302 | /* |
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303 | * Initialize for a processing pass. |
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304 | */ |
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305 | |||
306 | METHODDEF(void) |
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307 | start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode) |
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308 | { |
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309 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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310 | |||
311 | switch (pass_mode) { |
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312 | case JBUF_PASS_THRU: |
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313 | if (cinfo->upsample->need_context_rows) { |
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314 | main->pub.process_data = process_data_context_main; |
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315 | make_funny_pointers(cinfo); /* Create the xbuffer[] lists */ |
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316 | main->whichptr = 0; /* Read first iMCU row into xbuffer[0] */ |
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317 | main->context_state = CTX_PREPARE_FOR_IMCU; |
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318 | main->iMCU_row_ctr = 0; |
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319 | } else { |
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320 | /* Simple case with no context needed */ |
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321 | main->pub.process_data = process_data_simple_main; |
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322 | } |
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323 | main->buffer_full = FALSE; /* Mark buffer empty */ |
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324 | main->rowgroup_ctr = 0; |
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325 | break; |
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326 | #ifdef QUANT_2PASS_SUPPORTED |
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327 | case JBUF_CRANK_DEST: |
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328 | /* For last pass of 2-pass quantization, just crank the postprocessor */ |
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329 | main->pub.process_data = process_data_crank_post; |
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330 | break; |
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331 | #endif |
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332 | default: |
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333 | ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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334 | break; |
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335 | } |
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336 | } |
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337 | |||
338 | |||
339 | /* |
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340 | * Process some data. |
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341 | * This handles the simple case where no context is required. |
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342 | */ |
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343 | |||
344 | METHODDEF(void) |
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345 | process_data_simple_main (j_decompress_ptr cinfo, |
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346 | JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
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347 | JDIMENSION out_rows_avail) |
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348 | { |
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349 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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350 | JDIMENSION rowgroups_avail; |
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351 | |||
352 | /* Read input data if we haven't filled the main buffer yet */ |
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353 | if (! main->buffer_full) { |
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354 | if (! (*cinfo->coef->decompress_data) (cinfo, main->buffer)) |
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355 | return; /* suspension forced, can do nothing more */ |
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356 | main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */ |
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357 | } |
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358 | |||
359 | /* There are always min_DCT_scaled_size row groups in an iMCU row. */ |
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360 | rowgroups_avail = (JDIMENSION) cinfo->min_DCT_scaled_size; |
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361 | /* Note: at the bottom of the image, we may pass extra garbage row groups |
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362 | * to the postprocessor. The postprocessor has to check for bottom |
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363 | * of image anyway (at row resolution), so no point in us doing it too. |
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364 | */ |
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365 | |||
366 | /* Feed the postprocessor */ |
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367 | (*cinfo->post->post_process_data) (cinfo, main->buffer, |
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368 | &main->rowgroup_ctr, rowgroups_avail, |
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369 | output_buf, out_row_ctr, out_rows_avail); |
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370 | |||
371 | /* Has postprocessor consumed all the data yet? If so, mark buffer empty */ |
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372 | if (main->rowgroup_ctr >= rowgroups_avail) { |
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373 | main->buffer_full = FALSE; |
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374 | main->rowgroup_ctr = 0; |
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375 | } |
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376 | } |
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377 | |||
378 | |||
379 | /* |
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380 | * Process some data. |
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381 | * This handles the case where context rows must be provided. |
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382 | */ |
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383 | |||
384 | METHODDEF(void) |
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385 | process_data_context_main (j_decompress_ptr cinfo, |
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386 | JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
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387 | JDIMENSION out_rows_avail) |
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388 | { |
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389 | my_main_ptr main = (my_main_ptr) cinfo->main; |
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390 | |||
391 | /* Read input data if we haven't filled the main buffer yet */ |
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392 | if (! main->buffer_full) { |
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393 | if (! (*cinfo->coef->decompress_data) (cinfo, |
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394 | main->xbuffer[main->whichptr])) |
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395 | return; /* suspension forced, can do nothing more */ |
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396 | main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */ |
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397 | main->iMCU_row_ctr++; /* count rows received */ |
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398 | } |
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399 | |||
400 | /* Postprocessor typically will not swallow all the input data it is handed |
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401 | * in one call (due to filling the output buffer first). Must be prepared |
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402 | * to exit and restart. This switch lets us keep track of how far we got. |
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403 | * Note that each case falls through to the next on successful completion. |
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404 | */ |
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405 | switch (main->context_state) { |
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406 | case CTX_POSTPONED_ROW: |
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407 | /* Call postprocessor using previously set pointers for postponed row */ |
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408 | (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr], |
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409 | &main->rowgroup_ctr, main->rowgroups_avail, |
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410 | output_buf, out_row_ctr, out_rows_avail); |
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411 | if (main->rowgroup_ctr < main->rowgroups_avail) |
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412 | return; /* Need to suspend */ |
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413 | main->context_state = CTX_PREPARE_FOR_IMCU; |
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414 | if (*out_row_ctr >= out_rows_avail) |
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415 | return; /* Postprocessor exactly filled output buf */ |
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416 | /*FALLTHROUGH*/ |
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417 | case CTX_PREPARE_FOR_IMCU: |
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418 | /* Prepare to process first M-1 row groups of this iMCU row */ |
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419 | main->rowgroup_ctr = 0; |
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420 | main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size - 1); |
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421 | /* Check for bottom of image: if so, tweak pointers to "duplicate" |
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422 | * the last sample row, and adjust rowgroups_avail to ignore padding rows. |
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423 | */ |
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424 | if (main->iMCU_row_ctr == cinfo->total_iMCU_rows) |
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425 | set_bottom_pointers(cinfo); |
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426 | main->context_state = CTX_PROCESS_IMCU; |
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427 | /*FALLTHROUGH*/ |
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428 | case CTX_PROCESS_IMCU: |
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429 | /* Call postprocessor using previously set pointers */ |
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430 | (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr], |
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431 | &main->rowgroup_ctr, main->rowgroups_avail, |
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432 | output_buf, out_row_ctr, out_rows_avail); |
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433 | if (main->rowgroup_ctr < main->rowgroups_avail) |
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434 | return; /* Need to suspend */ |
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435 | /* After the first iMCU, change wraparound pointers to normal state */ |
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436 | if (main->iMCU_row_ctr == 1) |
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437 | set_wraparound_pointers(cinfo); |
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438 | /* Prepare to load new iMCU row using other xbuffer list */ |
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439 | main->whichptr ^= 1; /* 0=>1 or 1=>0 */ |
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440 | main->buffer_full = FALSE; |
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441 | /* Still need to process last row group of this iMCU row, */ |
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442 | /* which is saved at index M+1 of the other xbuffer */ |
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443 | main->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1); |
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444 | main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2); |
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445 | main->context_state = CTX_POSTPONED_ROW; |
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446 | } |
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447 | } |
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448 | |||
449 | |||
450 | /* |
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451 | * Process some data. |
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452 | * Final pass of two-pass quantization: just call the postprocessor. |
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453 | * Source data will be the postprocessor controller's internal buffer. |
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454 | */ |
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455 | |||
456 | #ifdef QUANT_2PASS_SUPPORTED |
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457 | |||
458 | METHODDEF(void) |
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459 | process_data_crank_post (j_decompress_ptr cinfo, |
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460 | JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, |
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461 | JDIMENSION out_rows_avail) |
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462 | { |
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463 | (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL, |
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464 | (JDIMENSION *) NULL, (JDIMENSION) 0, |
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465 | output_buf, out_row_ctr, out_rows_avail); |
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466 | } |
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467 | |||
468 | #endif /* QUANT_2PASS_SUPPORTED */ |
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469 | |||
470 | |||
471 | /* |
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472 | * Initialize main buffer controller. |
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473 | */ |
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474 | |||
475 | GLOBAL(void) |
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476 | jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer) |
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477 | { |
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478 | my_main_ptr main; |
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479 | int ci, rgroup, ngroups; |
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480 | jpeg_component_info *compptr; |
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481 | |||
482 | main = (my_main_ptr) |
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483 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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484 | SIZEOF(my_main_controller)); |
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485 | cinfo->main = (struct jpeg_d_main_controller *) main; |
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486 | main->pub.start_pass = start_pass_main; |
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487 | |||
488 | if (need_full_buffer) /* shouldn't happen */ |
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489 | ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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490 | |||
491 | /* Allocate the workspace. |
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492 | * ngroups is the number of row groups we need. |
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493 | */ |
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494 | if (cinfo->upsample->need_context_rows) { |
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495 | if (cinfo->min_DCT_scaled_size < 2) /* unsupported, see comments above */ |
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496 | ERREXIT(cinfo, JERR_NOTIMPL); |
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497 | alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */ |
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498 | ngroups = cinfo->min_DCT_scaled_size + 2; |
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499 | } else { |
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500 | ngroups = cinfo->min_DCT_scaled_size; |
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501 | } |
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502 | |||
503 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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504 | ci++, compptr++) { |
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505 | rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) / |
||
506 | cinfo->min_DCT_scaled_size; /* height of a row group of component */ |
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507 | main->buffer[ci] = (*cinfo->mem->alloc_sarray) |
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508 | ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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509 | compptr->width_in_blocks * compptr->DCT_scaled_size, |
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510 | (JDIMENSION) (rgroup * ngroups)); |
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511 | } |
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512 | }>>>>>>>>>>>>>> |