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1 /* |
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2 * jccoefct.c |
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3 * |
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4 * Copyright (C) 1994-1997, Thomas G. Lane. |
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5 * This file is part of the Independent JPEG Group's software. |
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6 * For conditions of distribution and use, see the accompanying README file. |
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7 * |
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8 * This file contains the coefficient buffer controller for compression. |
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9 * This controller is the top level of the JPEG compressor proper. |
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10 * The coefficient buffer lies between forward-DCT and entropy encoding steps. |
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11 */ |
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12 |
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13 #define JPEG_INTERNALS |
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14 #include "jinclude.h" |
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15 #include "jpeglib.h" |
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16 |
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17 |
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18 /* We use a full-image coefficient buffer when doing Huffman optimization, |
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19 * and also for writing multiple-scan JPEG files. In all cases, the DCT |
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20 * step is run during the first pass, and subsequent passes need only read |
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21 * the buffered coefficients. |
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22 */ |
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23 #ifdef ENTROPY_OPT_SUPPORTED |
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24 #define FULL_COEF_BUFFER_SUPPORTED |
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25 #else |
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26 #ifdef C_MULTISCAN_FILES_SUPPORTED |
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27 #define FULL_COEF_BUFFER_SUPPORTED |
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28 #endif |
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29 #endif |
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30 |
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31 |
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32 /* Private buffer controller object */ |
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33 |
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34 typedef struct { |
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35 struct jpeg_c_coef_controller pub; /* public fields */ |
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36 |
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37 JDIMENSION iMCU_row_num; /* iMCU row # within image */ |
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38 JDIMENSION mcu_ctr; /* counts MCUs processed in current row */ |
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39 int MCU_vert_offset; /* counts MCU rows within iMCU row */ |
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40 int MCU_rows_per_iMCU_row; /* number of such rows needed */ |
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41 |
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42 /* For single-pass compression, it's sufficient to buffer just one MCU |
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43 * (although this may prove a bit slow in practice). We allocate a |
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44 * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each |
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45 * MCU constructed and sent. (On 80x86, the workspace is FAR even though |
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46 * it's not really very big; this is to keep the module interfaces unchanged |
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47 * when a large coefficient buffer is necessary.) |
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48 * In multi-pass modes, this array points to the current MCU's blocks |
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49 * within the virtual arrays. |
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50 */ |
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51 JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU]; |
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52 |
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53 /* In multi-pass modes, we need a virtual block array for each component. */ |
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54 jvirt_barray_ptr whole_image[MAX_COMPONENTS]; |
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55 } my_coef_controller; |
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56 |
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57 typedef my_coef_controller * my_coef_ptr; |
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58 |
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59 |
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60 /* Forward declarations */ |
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61 METHODDEF(boolean) compress_data |
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62 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf)); |
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63 #ifdef FULL_COEF_BUFFER_SUPPORTED |
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64 METHODDEF(boolean) compress_first_pass |
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65 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf)); |
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66 METHODDEF(boolean) compress_output |
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67 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf)); |
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68 #endif |
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69 |
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70 |
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71 LOCAL(void) |
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72 start_iMCU_row (j_compress_ptr cinfo) |
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73 /* Reset within-iMCU-row counters for a new row */ |
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74 { |
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75 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; |
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76 |
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77 /* In an interleaved scan, an MCU row is the same as an iMCU row. |
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78 * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows. |
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79 * But at the bottom of the image, process only what's left. |
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80 */ |
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81 if (cinfo->comps_in_scan > 1) { |
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82 coef->MCU_rows_per_iMCU_row = 1; |
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83 } else { |
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84 if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1)) |
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85 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor; |
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86 else |
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87 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height; |
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88 } |
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89 |
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90 coef->mcu_ctr = 0; |
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91 coef->MCU_vert_offset = 0; |
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92 } |
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93 |
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94 |
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95 /* |
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96 * Initialize for a processing pass. |
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97 */ |
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98 |
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99 METHODDEF(void) |
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100 start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode) |
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101 { |
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102 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; |
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103 |
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104 coef->iMCU_row_num = 0; |
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105 start_iMCU_row(cinfo); |
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106 |
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107 switch (pass_mode) { |
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108 case JBUF_PASS_THRU: |
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109 if (coef->whole_image[0] != NULL) |
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110 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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111 coef->pub.compress_data = compress_data; |
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112 break; |
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113 #ifdef FULL_COEF_BUFFER_SUPPORTED |
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114 case JBUF_SAVE_AND_PASS: |
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115 if (coef->whole_image[0] == NULL) |
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116 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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117 coef->pub.compress_data = compress_first_pass; |
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118 break; |
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119 case JBUF_CRANK_DEST: |
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120 if (coef->whole_image[0] == NULL) |
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121 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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122 coef->pub.compress_data = compress_output; |
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123 break; |
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124 #endif |
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125 default: |
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126 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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127 break; |
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128 } |
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129 } |
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130 |
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131 |
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132 /* |
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133 * Process some data in the single-pass case. |
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134 * We process the equivalent of one fully interleaved MCU row ("iMCU" row) |
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135 * per call, ie, v_samp_factor block rows for each component in the image. |
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136 * Returns TRUE if the iMCU row is completed, FALSE if suspended. |
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137 * |
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138 * NB: input_buf contains a plane for each component in image, |
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139 * which we index according to the component's SOF position. |
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140 */ |
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141 |
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142 METHODDEF(boolean) |
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143 compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf) |
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144 { |
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145 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; |
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146 JDIMENSION MCU_col_num; /* index of current MCU within row */ |
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147 JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1; |
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148 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1; |
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149 int blkn, bi, ci, yindex, yoffset, blockcnt; |
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150 JDIMENSION ypos, xpos; |
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151 jpeg_component_info *compptr; |
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152 |
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153 /* Loop to write as much as one whole iMCU row */ |
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154 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row; |
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155 yoffset++) { |
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156 for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col; |
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157 MCU_col_num++) { |
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158 /* Determine where data comes from in input_buf and do the DCT thing. |
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159 * Each call on forward_DCT processes a horizontal row of DCT blocks |
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160 * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks |
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161 * sequentially. Dummy blocks at the right or bottom edge are filled in |
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162 * specially. The data in them does not matter for image reconstruction, |
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163 * so we fill them with values that will encode to the smallest amount of |
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164 * data, viz: all zeroes in the AC entries, DC entries equal to previous |
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165 * block's DC value. (Thanks to Thomas Kinsman for this idea.) |
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166 */ |
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167 blkn = 0; |
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168 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
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169 compptr = cinfo->cur_comp_info[ci]; |
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170 blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width |
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171 : compptr->last_col_width; |
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172 xpos = MCU_col_num * compptr->MCU_sample_width; |
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173 ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */ |
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174 for (yindex = 0; yindex < compptr->MCU_height; yindex++) { |
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175 if (coef->iMCU_row_num < last_iMCU_row || |
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176 yoffset+yindex < compptr->last_row_height) { |
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177 (*cinfo->fdct->forward_DCT) (cinfo, compptr, |
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178 input_buf[compptr->component_index], |
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179 coef->MCU_buffer[blkn], |
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180 ypos, xpos, (JDIMENSION) blockcnt); |
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181 if (blockcnt < compptr->MCU_width) { |
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182 /* Create some dummy blocks at the right edge of the image. */ |
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183 jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt], |
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184 (compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK)); |
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185 for (bi = blockcnt; bi < compptr->MCU_width; bi++) { |
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186 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0]; |
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187 } |
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188 } |
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189 } else { |
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190 /* Create a row of dummy blocks at the bottom of the image. */ |
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191 jzero_far((void FAR *) coef->MCU_buffer[blkn], |
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192 compptr->MCU_width * SIZEOF(JBLOCK)); |
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193 for (bi = 0; bi < compptr->MCU_width; bi++) { |
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194 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0]; |
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195 } |
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196 } |
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197 blkn += compptr->MCU_width; |
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198 ypos += DCTSIZE; |
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199 } |
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200 } |
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201 /* Try to write the MCU. In event of a suspension failure, we will |
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202 * re-DCT the MCU on restart (a bit inefficient, could be fixed...) |
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203 */ |
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204 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) { |
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205 /* Suspension forced; update state counters and exit */ |
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206 coef->MCU_vert_offset = yoffset; |
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207 coef->mcu_ctr = MCU_col_num; |
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208 return FALSE; |
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209 } |
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210 } |
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211 /* Completed an MCU row, but perhaps not an iMCU row */ |
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212 coef->mcu_ctr = 0; |
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213 } |
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214 /* Completed the iMCU row, advance counters for next one */ |
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215 coef->iMCU_row_num++; |
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216 start_iMCU_row(cinfo); |
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217 return TRUE; |
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218 } |
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219 |
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220 |
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221 #ifdef FULL_COEF_BUFFER_SUPPORTED |
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222 |
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223 /* |
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224 * Process some data in the first pass of a multi-pass case. |
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225 * We process the equivalent of one fully interleaved MCU row ("iMCU" row) |
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226 * per call, ie, v_samp_factor block rows for each component in the image. |
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227 * This amount of data is read from the source buffer, DCT'd and quantized, |
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228 * and saved into the virtual arrays. We also generate suitable dummy blocks |
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229 * as needed at the right and lower edges. (The dummy blocks are constructed |
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230 * in the virtual arrays, which have been padded appropriately.) This makes |
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231 * it possible for subsequent passes not to worry about real vs. dummy blocks. |
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232 * |
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233 * We must also emit the data to the entropy encoder. This is conveniently |
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234 * done by calling compress_output() after we've loaded the current strip |
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235 * of the virtual arrays. |
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236 * |
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237 * NB: input_buf contains a plane for each component in image. All |
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238 * components are DCT'd and loaded into the virtual arrays in this pass. |
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239 * However, it may be that only a subset of the components are emitted to |
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240 * the entropy encoder during this first pass; be careful about looking |
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241 * at the scan-dependent variables (MCU dimensions, etc). |
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242 */ |
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243 |
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244 METHODDEF(boolean) |
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245 compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf) |
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246 { |
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247 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; |
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248 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1; |
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249 JDIMENSION blocks_across, MCUs_across, MCUindex; |
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250 int bi, ci, h_samp_factor, block_row, block_rows, ndummy; |
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251 JCOEF lastDC; |
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252 jpeg_component_info *compptr; |
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253 JBLOCKARRAY buffer; |
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254 JBLOCKROW thisblockrow, lastblockrow; |
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255 |
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256 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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257 ci++, compptr++) { |
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258 /* Align the virtual buffer for this component. */ |
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259 buffer = (*cinfo->mem->access_virt_barray) |
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260 ((j_common_ptr) cinfo, coef->whole_image[ci], |
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261 coef->iMCU_row_num * compptr->v_samp_factor, |
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262 (JDIMENSION) compptr->v_samp_factor, TRUE); |
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263 /* Count non-dummy DCT block rows in this iMCU row. */ |
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264 if (coef->iMCU_row_num < last_iMCU_row) |
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265 block_rows = compptr->v_samp_factor; |
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266 else { |
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267 /* NB: can't use last_row_height here, since may not be set! */ |
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268 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor); |
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269 if (block_rows == 0) block_rows = compptr->v_samp_factor; |
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270 } |
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271 blocks_across = compptr->width_in_blocks; |
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272 h_samp_factor = compptr->h_samp_factor; |
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273 /* Count number of dummy blocks to be added at the right margin. */ |
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274 ndummy = (int) (blocks_across % h_samp_factor); |
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275 if (ndummy > 0) |
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276 ndummy = h_samp_factor - ndummy; |
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277 /* Perform DCT for all non-dummy blocks in this iMCU row. Each call |
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278 * on forward_DCT processes a complete horizontal row of DCT blocks. |
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279 */ |
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280 for (block_row = 0; block_row < block_rows; block_row++) { |
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281 thisblockrow = buffer[block_row]; |
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282 (*cinfo->fdct->forward_DCT) (cinfo, compptr, |
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283 input_buf[ci], thisblockrow, |
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284 (JDIMENSION) (block_row * DCTSIZE), |
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285 (JDIMENSION) 0, blocks_across); |
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286 if (ndummy > 0) { |
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287 /* Create dummy blocks at the right edge of the image. */ |
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288 thisblockrow += blocks_across; /* => first dummy block */ |
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289 jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK)); |
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290 lastDC = thisblockrow[-1][0]; |
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291 for (bi = 0; bi < ndummy; bi++) { |
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292 thisblockrow[bi][0] = lastDC; |
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293 } |
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294 } |
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295 } |
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296 /* If at end of image, create dummy block rows as needed. |
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297 * The tricky part here is that within each MCU, we want the DC values |
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298 * of the dummy blocks to match the last real block's DC value. |
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299 * This squeezes a few more bytes out of the resulting file... |
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300 */ |
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301 if (coef->iMCU_row_num == last_iMCU_row) { |
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302 blocks_across += ndummy; /* include lower right corner */ |
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303 MCUs_across = blocks_across / h_samp_factor; |
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304 for (block_row = block_rows; block_row < compptr->v_samp_factor; |
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305 block_row++) { |
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306 thisblockrow = buffer[block_row]; |
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307 lastblockrow = buffer[block_row-1]; |
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308 jzero_far((void FAR *) thisblockrow, |
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309 (size_t) (blocks_across * SIZEOF(JBLOCK))); |
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310 for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) { |
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311 lastDC = lastblockrow[h_samp_factor-1][0]; |
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312 for (bi = 0; bi < h_samp_factor; bi++) { |
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313 thisblockrow[bi][0] = lastDC; |
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314 } |
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315 thisblockrow += h_samp_factor; /* advance to next MCU in row */ |
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316 lastblockrow += h_samp_factor; |
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317 } |
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318 } |
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319 } |
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320 } |
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321 /* NB: compress_output will increment iMCU_row_num if successful. |
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322 * A suspension return will result in redoing all the work above next time. |
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323 */ |
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324 |
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325 /* Emit data to the entropy encoder, sharing code with subsequent passes */ |
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326 return compress_output(cinfo, input_buf); |
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327 } |
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328 |
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329 |
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330 /* |
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331 * Process some data in subsequent passes of a multi-pass case. |
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332 * We process the equivalent of one fully interleaved MCU row ("iMCU" row) |
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333 * per call, ie, v_samp_factor block rows for each component in the scan. |
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334 * The data is obtained from the virtual arrays and fed to the entropy coder. |
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335 * Returns TRUE if the iMCU row is completed, FALSE if suspended. |
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336 * |
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337 * NB: input_buf is ignored; it is likely to be a NULL pointer. |
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338 */ |
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339 |
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340 METHODDEF(boolean) |
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341 compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf) |
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342 { |
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343 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; |
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344 JDIMENSION MCU_col_num; /* index of current MCU within row */ |
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345 int blkn, ci, xindex, yindex, yoffset; |
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346 JDIMENSION start_col; |
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347 JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN]; |
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348 JBLOCKROW buffer_ptr; |
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349 jpeg_component_info *compptr; |
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350 |
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351 /* Align the virtual buffers for the components used in this scan. |
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352 * NB: during first pass, this is safe only because the buffers will |
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353 * already be aligned properly, so jmemmgr.c won't need to do any I/O. |
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354 */ |
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355 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
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356 compptr = cinfo->cur_comp_info[ci]; |
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357 buffer[ci] = (*cinfo->mem->access_virt_barray) |
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358 ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index], |
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359 coef->iMCU_row_num * compptr->v_samp_factor, |
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360 (JDIMENSION) compptr->v_samp_factor, FALSE); |
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361 } |
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362 |
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363 /* Loop to process one whole iMCU row */ |
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364 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row; |
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365 yoffset++) { |
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366 for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row; |
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367 MCU_col_num++) { |
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368 /* Construct list of pointers to DCT blocks belonging to this MCU */ |
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369 blkn = 0; /* index of current DCT block within MCU */ |
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370 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
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371 compptr = cinfo->cur_comp_info[ci]; |
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372 start_col = MCU_col_num * compptr->MCU_width; |
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373 for (yindex = 0; yindex < compptr->MCU_height; yindex++) { |
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374 buffer_ptr = buffer[ci][yindex+yoffset] + start_col; |
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375 for (xindex = 0; xindex < compptr->MCU_width; xindex++) { |
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376 coef->MCU_buffer[blkn++] = buffer_ptr++; |
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377 } |
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378 } |
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379 } |
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380 /* Try to write the MCU. */ |
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381 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) { |
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382 /* Suspension forced; update state counters and exit */ |
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383 coef->MCU_vert_offset = yoffset; |
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384 coef->mcu_ctr = MCU_col_num; |
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385 return FALSE; |
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386 } |
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387 } |
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388 /* Completed an MCU row, but perhaps not an iMCU row */ |
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389 coef->mcu_ctr = 0; |
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390 } |
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391 /* Completed the iMCU row, advance counters for next one */ |
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392 coef->iMCU_row_num++; |
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393 start_iMCU_row(cinfo); |
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394 return TRUE; |
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395 } |
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396 |
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397 #endif /* FULL_COEF_BUFFER_SUPPORTED */ |
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398 |
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399 |
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400 /* |
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401 * Initialize coefficient buffer controller. |
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402 */ |
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403 |
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404 GLOBAL(void) |
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405 jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer) |
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406 { |
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407 my_coef_ptr coef; |
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408 |
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409 coef = (my_coef_ptr) |
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410 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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411 SIZEOF(my_coef_controller)); |
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412 cinfo->coef = (struct jpeg_c_coef_controller *) coef; |
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413 coef->pub.start_pass = start_pass_coef; |
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414 |
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415 /* Create the coefficient buffer. */ |
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416 if (need_full_buffer) { |
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417 #ifdef FULL_COEF_BUFFER_SUPPORTED |
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418 /* Allocate a full-image virtual array for each component, */ |
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419 /* padded to a multiple of samp_factor DCT blocks in each direction. */ |
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420 int ci; |
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421 jpeg_component_info *compptr; |
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422 |
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423 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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424 ci++, compptr++) { |
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425 coef->whole_image[ci] = (*cinfo->mem->request_virt_barray) |
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426 ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE, |
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427 (JDIMENSION) jround_up((long) compptr->width_in_blocks, |
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428 (long) compptr->h_samp_factor), |
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429 (JDIMENSION) jround_up((long) compptr->height_in_blocks, |
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430 (long) compptr->v_samp_factor), |
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431 (JDIMENSION) compptr->v_samp_factor); |
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432 } |
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433 #else |
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434 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); |
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435 #endif |
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436 } else { |
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437 /* We only need a single-MCU buffer. */ |
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438 JBLOCKROW buffer; |
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439 int i; |
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440 |
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441 buffer = (JBLOCKROW) |
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442 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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443 C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK)); |
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444 for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) { |
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445 coef->MCU_buffer[i] = buffer + i; |
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446 } |
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447 coef->whole_image[0] = NULL; /* flag for no virtual arrays */ |
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448 } |
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449 } |