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| 1 /* | |
| 2 * jcprepct.c | |
| 3 * | |
| 4 * Copyright (C) 1994-1996, Thomas G. Lane. | |
| 5 * This file is part of the Independent JPEG Group's software. | |
| 6 * For conditions of distribution and use, see the accompanying README file. | |
| 7 * | |
| 8 * This file contains the compression preprocessing controller. | |
| 9 * This controller manages the color conversion, downsampling, | |
| 10 * and edge expansion steps. | |
| 11 * | |
| 12 * Most of the complexity here is associated with buffering input rows | |
| 13 * as required by the downsampler. See the comments at the head of | |
| 14 * jcsample.c for the downsampler's needs. | |
| 15 */ | |
| 16 | |
| 17 #define JPEG_INTERNALS | |
| 18 #include "jinclude.h" | |
| 19 #include "jpeglib.h" | |
| 20 | |
| 21 | |
| 22 /* At present, jcsample.c can request context rows only for smoothing. | |
| 23 * In the future, we might also need context rows for CCIR601 sampling | |
| 24 * or other more-complex downsampling procedures. The code to support | |
| 25 * context rows should be compiled only if needed. | |
| 26 */ | |
| 27 #ifdef INPUT_SMOOTHING_SUPPORTED | |
| 28 #define CONTEXT_ROWS_SUPPORTED | |
| 29 #endif | |
| 30 | |
| 31 | |
| 32 /* | |
| 33 * For the simple (no-context-row) case, we just need to buffer one | |
| 34 * row group's worth of pixels for the downsampling step. At the bottom of | |
| 35 * the image, we pad to a full row group by replicating the last pixel row. | |
| 36 * The downsampler's last output row is then replicated if needed to pad | |
| 37 * out to a full iMCU row. | |
| 38 * | |
| 39 * When providing context rows, we must buffer three row groups' worth of | |
| 40 * pixels. Three row groups are physically allocated, but the row pointer | |
| 41 * arrays are made five row groups high, with the extra pointers above and | |
| 42 * below "wrapping around" to point to the last and first real row groups. | |
| 43 * This allows the downsampler to access the proper context rows. | |
| 44 * At the top and bottom of the image, we create dummy context rows by | |
| 45 * copying the first or last real pixel row. This copying could be avoided | |
| 46 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the | |
| 47 * trouble on the compression side. | |
| 48 */ | |
| 49 | |
| 50 | |
| 51 /* Private buffer controller object */ | |
| 52 | |
| 53 typedef struct { | |
| 54 struct jpeg_c_prep_controller pub; /* public fields */ | |
| 55 | |
| 56 /* Downsampling input buffer. This buffer holds color-converted data | |
| 57 * until we have enough to do a downsample step. | |
| 58 */ | |
| 59 JSAMPARRAY color_buf[MAX_COMPONENTS]; | |
| 60 | |
| 61 JDIMENSION rows_to_go; /* counts rows remaining in source image */ | |
| 62 int next_buf_row; /* index of next row to store in color_buf */ | |
| 63 | |
| 64 #ifdef CONTEXT_ROWS_SUPPORTED /* only needed for context case */ | |
| 65 int this_row_group; /* starting row index of group to process */ | |
| 66 int next_buf_stop; /* downsample when we reach this index */ | |
| 67 #endif | |
| 68 } my_prep_controller; | |
| 69 | |
| 70 typedef my_prep_controller * my_prep_ptr; | |
| 71 | |
| 72 | |
| 73 /* | |
| 74 * Initialize for a processing pass. | |
| 75 */ | |
| 76 | |
| 77 METHODDEF(void) | |
| 78 start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode) | |
| 79 { | |
| 80 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; | |
| 81 | |
| 82 if (pass_mode != JBUF_PASS_THRU) | |
| 83 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); | |
| 84 | |
| 85 /* Initialize total-height counter for detecting bottom of image */ | |
| 86 prep->rows_to_go = cinfo->image_height; | |
| 87 /* Mark the conversion buffer empty */ | |
| 88 prep->next_buf_row = 0; | |
| 89 #ifdef CONTEXT_ROWS_SUPPORTED | |
| 90 /* Preset additional state variables for context mode. | |
| 91 * These aren't used in non-context mode, so we needn't test which mode. | |
| 92 */ | |
| 93 prep->this_row_group = 0; | |
| 94 /* Set next_buf_stop to stop after two row groups have been read in. */ | |
| 95 prep->next_buf_stop = 2 * cinfo->max_v_samp_factor; | |
| 96 #endif | |
| 97 } | |
| 98 | |
| 99 | |
| 100 /* | |
| 101 * Expand an image vertically from height input_rows to height output_rows, | |
| 102 * by duplicating the bottom row. | |
| 103 */ | |
| 104 | |
| 105 LOCAL(void) | |
| 106 expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols, | |
| 107 int input_rows, int output_rows) | |
| 108 { | |
| 109 register int row; | |
| 110 | |
| 111 for (row = input_rows; row < output_rows; row++) { | |
| 112 jcopy_sample_rows(image_data, input_rows-1, image_data, row, | |
| 113 1, num_cols); | |
| 114 } | |
| 115 } | |
| 116 | |
| 117 | |
| 118 /* | |
| 119 * Process some data in the simple no-context case. | |
| 120 * | |
| 121 * Preprocessor output data is counted in "row groups". A row group | |
| 122 * is defined to be v_samp_factor sample rows of each component. | |
| 123 * Downsampling will produce this much data from each max_v_samp_factor | |
| 124 * input rows. | |
| 125 */ | |
| 126 | |
| 127 METHODDEF(void) | |
| 128 pre_process_data (j_compress_ptr cinfo, | |
| 129 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, | |
| 130 JDIMENSION in_rows_avail, | |
| 131 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, | |
| 132 JDIMENSION out_row_groups_avail) | |
| 133 { | |
| 134 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; | |
| 135 int numrows, ci; | |
| 136 JDIMENSION inrows; | |
| 137 jpeg_component_info * compptr; | |
| 138 | |
| 139 while (*in_row_ctr < in_rows_avail && | |
| 140 *out_row_group_ctr < out_row_groups_avail) { | |
| 141 /* Do color conversion to fill the conversion buffer. */ | |
| 142 inrows = in_rows_avail - *in_row_ctr; | |
| 143 numrows = cinfo->max_v_samp_factor - prep->next_buf_row; | |
| 144 numrows = (int) MIN((JDIMENSION) numrows, inrows); | |
| 145 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, | |
| 146 prep->color_buf, | |
| 147 (JDIMENSION) prep->next_buf_row, | |
| 148 numrows); | |
| 149 *in_row_ctr += numrows; | |
| 150 prep->next_buf_row += numrows; | |
| 151 prep->rows_to_go -= numrows; | |
| 152 /* If at bottom of image, pad to fill the conversion buffer. */ | |
| 153 if (prep->rows_to_go == 0 && | |
| 154 prep->next_buf_row < cinfo->max_v_samp_factor) { | |
| 155 for (ci = 0; ci < cinfo->num_components; ci++) { | |
| 156 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, | |
| 157 prep->next_buf_row, cinfo->max_v_samp_factor); | |
| 158 } | |
| 159 prep->next_buf_row = cinfo->max_v_samp_factor; | |
| 160 } | |
| 161 /* If we've filled the conversion buffer, empty it. */ | |
| 162 if (prep->next_buf_row == cinfo->max_v_samp_factor) { | |
| 163 (*cinfo->downsample->downsample) (cinfo, | |
| 164 prep->color_buf, (JDIMENSION) 0, | |
| 165 output_buf, *out_row_group_ctr); | |
| 166 prep->next_buf_row = 0; | |
| 167 (*out_row_group_ctr)++; | |
| 168 } | |
| 169 /* If at bottom of image, pad the output to a full iMCU height. | |
| 170 * Note we assume the caller is providing a one-iMCU-height output buffer! | |
| 171 */ | |
| 172 if (prep->rows_to_go == 0 && | |
| 173 *out_row_group_ctr < out_row_groups_avail) { | |
| 174 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; | |
| 175 ci++, compptr++) { | |
| 176 expand_bottom_edge(output_buf[ci], | |
| 177 compptr->width_in_blocks * DCTSIZE, | |
| 178 (int) (*out_row_group_ctr * compptr->v_samp_factor), | |
| 179 (int) (out_row_groups_avail * compptr->v_samp_factor)
); | |
| 180 } | |
| 181 *out_row_group_ctr = out_row_groups_avail; | |
| 182 break; /* can exit outer loop without test */ | |
| 183 } | |
| 184 } | |
| 185 } | |
| 186 | |
| 187 | |
| 188 #ifdef CONTEXT_ROWS_SUPPORTED | |
| 189 | |
| 190 /* | |
| 191 * Process some data in the context case. | |
| 192 */ | |
| 193 | |
| 194 METHODDEF(void) | |
| 195 pre_process_context (j_compress_ptr cinfo, | |
| 196 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, | |
| 197 JDIMENSION in_rows_avail, | |
| 198 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, | |
| 199 JDIMENSION out_row_groups_avail) | |
| 200 { | |
| 201 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; | |
| 202 int numrows, ci; | |
| 203 int buf_height = cinfo->max_v_samp_factor * 3; | |
| 204 JDIMENSION inrows; | |
| 205 | |
| 206 while (*out_row_group_ctr < out_row_groups_avail) { | |
| 207 if (*in_row_ctr < in_rows_avail) { | |
| 208 /* Do color conversion to fill the conversion buffer. */ | |
| 209 inrows = in_rows_avail - *in_row_ctr; | |
| 210 numrows = prep->next_buf_stop - prep->next_buf_row; | |
| 211 numrows = (int) MIN((JDIMENSION) numrows, inrows); | |
| 212 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, | |
| 213 prep->color_buf, | |
| 214 (JDIMENSION) prep->next_buf_row, | |
| 215 numrows); | |
| 216 /* Pad at top of image, if first time through */ | |
| 217 if (prep->rows_to_go == cinfo->image_height) { | |
| 218 for (ci = 0; ci < cinfo->num_components; ci++) { | |
| 219 int row; | |
| 220 for (row = 1; row <= cinfo->max_v_samp_factor; row++) { | |
| 221 jcopy_sample_rows(prep->color_buf[ci], 0, | |
| 222 prep->color_buf[ci], -row, | |
| 223 1, cinfo->image_width); | |
| 224 } | |
| 225 } | |
| 226 } | |
| 227 *in_row_ctr += numrows; | |
| 228 prep->next_buf_row += numrows; | |
| 229 prep->rows_to_go -= numrows; | |
| 230 } else { | |
| 231 /* Return for more data, unless we are at the bottom of the image. */ | |
| 232 if (prep->rows_to_go != 0) | |
| 233 break; | |
| 234 /* When at bottom of image, pad to fill the conversion buffer. */ | |
| 235 if (prep->next_buf_row < prep->next_buf_stop) { | |
| 236 for (ci = 0; ci < cinfo->num_components; ci++) { | |
| 237 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, | |
| 238 prep->next_buf_row, prep->next_buf_stop); | |
| 239 } | |
| 240 prep->next_buf_row = prep->next_buf_stop; | |
| 241 } | |
| 242 } | |
| 243 /* If we've gotten enough data, downsample a row group. */ | |
| 244 if (prep->next_buf_row == prep->next_buf_stop) { | |
| 245 (*cinfo->downsample->downsample) (cinfo, | |
| 246 prep->color_buf, | |
| 247 (JDIMENSION) prep->this_row_group, | |
| 248 output_buf, *out_row_group_ctr); | |
| 249 (*out_row_group_ctr)++; | |
| 250 /* Advance pointers with wraparound as necessary. */ | |
| 251 prep->this_row_group += cinfo->max_v_samp_factor; | |
| 252 if (prep->this_row_group >= buf_height) | |
| 253 prep->this_row_group = 0; | |
| 254 if (prep->next_buf_row >= buf_height) | |
| 255 prep->next_buf_row = 0; | |
| 256 prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor; | |
| 257 } | |
| 258 } | |
| 259 } | |
| 260 | |
| 261 | |
| 262 /* | |
| 263 * Create the wrapped-around downsampling input buffer needed for context mode. | |
| 264 */ | |
| 265 | |
| 266 LOCAL(void) | |
| 267 create_context_buffer (j_compress_ptr cinfo) | |
| 268 { | |
| 269 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; | |
| 270 int rgroup_height = cinfo->max_v_samp_factor; | |
| 271 int ci, i; | |
| 272 jpeg_component_info * compptr; | |
| 273 JSAMPARRAY true_buffer, fake_buffer; | |
| 274 | |
| 275 /* Grab enough space for fake row pointers for all the components; | |
| 276 * we need five row groups' worth of pointers for each component. | |
| 277 */ | |
| 278 fake_buffer = (JSAMPARRAY) | |
| 279 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 280 (cinfo->num_components * 5 * rgroup_height) * | |
| 281 SIZEOF(JSAMPROW)); | |
| 282 | |
| 283 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; | |
| 284 ci++, compptr++) { | |
| 285 /* Allocate the actual buffer space (3 row groups) for this component. | |
| 286 * We make the buffer wide enough to allow the downsampler to edge-expand | |
| 287 * horizontally within the buffer, if it so chooses. | |
| 288 */ | |
| 289 true_buffer = (*cinfo->mem->alloc_sarray) | |
| 290 ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 291 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * | |
| 292 cinfo->max_h_samp_factor) / compptr->h_samp_factor), | |
| 293 (JDIMENSION) (3 * rgroup_height)); | |
| 294 /* Copy true buffer row pointers into the middle of the fake row array */ | |
| 295 MEMCOPY(fake_buffer + rgroup_height, true_buffer, | |
| 296 3 * rgroup_height * SIZEOF(JSAMPROW)); | |
| 297 /* Fill in the above and below wraparound pointers */ | |
| 298 for (i = 0; i < rgroup_height; i++) { | |
| 299 fake_buffer[i] = true_buffer[2 * rgroup_height + i]; | |
| 300 fake_buffer[4 * rgroup_height + i] = true_buffer[i]; | |
| 301 } | |
| 302 prep->color_buf[ci] = fake_buffer + rgroup_height; | |
| 303 fake_buffer += 5 * rgroup_height; /* point to space for next component */ | |
| 304 } | |
| 305 } | |
| 306 | |
| 307 #endif /* CONTEXT_ROWS_SUPPORTED */ | |
| 308 | |
| 309 | |
| 310 /* | |
| 311 * Initialize preprocessing controller. | |
| 312 */ | |
| 313 | |
| 314 GLOBAL(void) | |
| 315 jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer) | |
| 316 { | |
| 317 my_prep_ptr prep; | |
| 318 int ci; | |
| 319 jpeg_component_info * compptr; | |
| 320 | |
| 321 if (need_full_buffer) /* safety check */ | |
| 322 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); | |
| 323 | |
| 324 prep = (my_prep_ptr) | |
| 325 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 326 SIZEOF(my_prep_controller)); | |
| 327 cinfo->prep = (struct jpeg_c_prep_controller *) prep; | |
| 328 prep->pub.start_pass = start_pass_prep; | |
| 329 | |
| 330 /* Allocate the color conversion buffer. | |
| 331 * We make the buffer wide enough to allow the downsampler to edge-expand | |
| 332 * horizontally within the buffer, if it so chooses. | |
| 333 */ | |
| 334 if (cinfo->downsample->need_context_rows) { | |
| 335 /* Set up to provide context rows */ | |
| 336 #ifdef CONTEXT_ROWS_SUPPORTED | |
| 337 prep->pub.pre_process_data = pre_process_context; | |
| 338 create_context_buffer(cinfo); | |
| 339 #else | |
| 340 ERREXIT(cinfo, JERR_NOT_COMPILED); | |
| 341 #endif | |
| 342 } else { | |
| 343 /* No context, just make it tall enough for one row group */ | |
| 344 prep->pub.pre_process_data = pre_process_data; | |
| 345 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; | |
| 346 ci++, compptr++) { | |
| 347 prep->color_buf[ci] = (*cinfo->mem->alloc_sarray) | |
| 348 ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 349 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * | |
| 350 cinfo->max_h_samp_factor) / compptr->h_samp_factor), | |
| 351 (JDIMENSION) cinfo->max_v_samp_factor); | |
| 352 } | |
| 353 } | |
| 354 } | |
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Chromium Code Reviews
Issue 1705523002:
Remove libjpeg and libjpeg_turbo. (Closed)
Base URL: https://github.com/domokit/mojo.git@master