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annotate libs/libjpeg/jcprepct.c @ 0:b2f14e535253

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author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 01 Feb 2014 19:58:19 +0200
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nuclear@0 1 /*
nuclear@0 2 * jcprepct.c
nuclear@0 3 *
nuclear@0 4 * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@0 5 * This file is part of the Independent JPEG Group's software.
nuclear@0 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@0 7 *
nuclear@0 8 * This file contains the compression preprocessing controller.
nuclear@0 9 * This controller manages the color conversion, downsampling,
nuclear@0 10 * and edge expansion steps.
nuclear@0 11 *
nuclear@0 12 * Most of the complexity here is associated with buffering input rows
nuclear@0 13 * as required by the downsampler. See the comments at the head of
nuclear@0 14 * jcsample.c for the downsampler's needs.
nuclear@0 15 */
nuclear@0 16
nuclear@0 17 #define JPEG_INTERNALS
nuclear@0 18 #include "jinclude.h"
nuclear@0 19 #include "jpeglib.h"
nuclear@0 20
nuclear@0 21
nuclear@0 22 /* At present, jcsample.c can request context rows only for smoothing.
nuclear@0 23 * In the future, we might also need context rows for CCIR601 sampling
nuclear@0 24 * or other more-complex downsampling procedures. The code to support
nuclear@0 25 * context rows should be compiled only if needed.
nuclear@0 26 */
nuclear@0 27 #ifdef INPUT_SMOOTHING_SUPPORTED
nuclear@0 28 #define CONTEXT_ROWS_SUPPORTED
nuclear@0 29 #endif
nuclear@0 30
nuclear@0 31
nuclear@0 32 /*
nuclear@0 33 * For the simple (no-context-row) case, we just need to buffer one
nuclear@0 34 * row group's worth of pixels for the downsampling step. At the bottom of
nuclear@0 35 * the image, we pad to a full row group by replicating the last pixel row.
nuclear@0 36 * The downsampler's last output row is then replicated if needed to pad
nuclear@0 37 * out to a full iMCU row.
nuclear@0 38 *
nuclear@0 39 * When providing context rows, we must buffer three row groups' worth of
nuclear@0 40 * pixels. Three row groups are physically allocated, but the row pointer
nuclear@0 41 * arrays are made five row groups high, with the extra pointers above and
nuclear@0 42 * below "wrapping around" to point to the last and first real row groups.
nuclear@0 43 * This allows the downsampler to access the proper context rows.
nuclear@0 44 * At the top and bottom of the image, we create dummy context rows by
nuclear@0 45 * copying the first or last real pixel row. This copying could be avoided
nuclear@0 46 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
nuclear@0 47 * trouble on the compression side.
nuclear@0 48 */
nuclear@0 49
nuclear@0 50
nuclear@0 51 /* Private buffer controller object */
nuclear@0 52
nuclear@0 53 typedef struct {
nuclear@0 54 struct jpeg_c_prep_controller pub; /* public fields */
nuclear@0 55
nuclear@0 56 /* Downsampling input buffer. This buffer holds color-converted data
nuclear@0 57 * until we have enough to do a downsample step.
nuclear@0 58 */
nuclear@0 59 JSAMPARRAY color_buf[MAX_COMPONENTS];
nuclear@0 60
nuclear@0 61 JDIMENSION rows_to_go; /* counts rows remaining in source image */
nuclear@0 62 int next_buf_row; /* index of next row to store in color_buf */
nuclear@0 63
nuclear@0 64 #ifdef CONTEXT_ROWS_SUPPORTED /* only needed for context case */
nuclear@0 65 int this_row_group; /* starting row index of group to process */
nuclear@0 66 int next_buf_stop; /* downsample when we reach this index */
nuclear@0 67 #endif
nuclear@0 68 } my_prep_controller;
nuclear@0 69
nuclear@0 70 typedef my_prep_controller * my_prep_ptr;
nuclear@0 71
nuclear@0 72
nuclear@0 73 /*
nuclear@0 74 * Initialize for a processing pass.
nuclear@0 75 */
nuclear@0 76
nuclear@0 77 METHODDEF(void)
nuclear@0 78 start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
nuclear@0 79 {
nuclear@0 80 my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@0 81
nuclear@0 82 if (pass_mode != JBUF_PASS_THRU)
nuclear@0 83 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
nuclear@0 84
nuclear@0 85 /* Initialize total-height counter for detecting bottom of image */
nuclear@0 86 prep->rows_to_go = cinfo->image_height;
nuclear@0 87 /* Mark the conversion buffer empty */
nuclear@0 88 prep->next_buf_row = 0;
nuclear@0 89 #ifdef CONTEXT_ROWS_SUPPORTED
nuclear@0 90 /* Preset additional state variables for context mode.
nuclear@0 91 * These aren't used in non-context mode, so we needn't test which mode.
nuclear@0 92 */
nuclear@0 93 prep->this_row_group = 0;
nuclear@0 94 /* Set next_buf_stop to stop after two row groups have been read in. */
nuclear@0 95 prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
nuclear@0 96 #endif
nuclear@0 97 }
nuclear@0 98
nuclear@0 99
nuclear@0 100 /*
nuclear@0 101 * Expand an image vertically from height input_rows to height output_rows,
nuclear@0 102 * by duplicating the bottom row.
nuclear@0 103 */
nuclear@0 104
nuclear@0 105 LOCAL(void)
nuclear@0 106 expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
nuclear@0 107 int input_rows, int output_rows)
nuclear@0 108 {
nuclear@0 109 register int row;
nuclear@0 110
nuclear@0 111 for (row = input_rows; row < output_rows; row++) {
nuclear@0 112 jcopy_sample_rows(image_data, input_rows-1, image_data, row,
nuclear@0 113 1, num_cols);
nuclear@0 114 }
nuclear@0 115 }
nuclear@0 116
nuclear@0 117
nuclear@0 118 /*
nuclear@0 119 * Process some data in the simple no-context case.
nuclear@0 120 *
nuclear@0 121 * Preprocessor output data is counted in "row groups". A row group
nuclear@0 122 * is defined to be v_samp_factor sample rows of each component.
nuclear@0 123 * Downsampling will produce this much data from each max_v_samp_factor
nuclear@0 124 * input rows.
nuclear@0 125 */
nuclear@0 126
nuclear@0 127 METHODDEF(void)
nuclear@0 128 pre_process_data (j_compress_ptr cinfo,
nuclear@0 129 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
nuclear@0 130 JDIMENSION in_rows_avail,
nuclear@0 131 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
nuclear@0 132 JDIMENSION out_row_groups_avail)
nuclear@0 133 {
nuclear@0 134 my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@0 135 int numrows, ci;
nuclear@0 136 JDIMENSION inrows;
nuclear@0 137 jpeg_component_info * compptr;
nuclear@0 138
nuclear@0 139 while (*in_row_ctr < in_rows_avail &&
nuclear@0 140 *out_row_group_ctr < out_row_groups_avail) {
nuclear@0 141 /* Do color conversion to fill the conversion buffer. */
nuclear@0 142 inrows = in_rows_avail - *in_row_ctr;
nuclear@0 143 numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
nuclear@0 144 numrows = (int) MIN((JDIMENSION) numrows, inrows);
nuclear@0 145 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
nuclear@0 146 prep->color_buf,
nuclear@0 147 (JDIMENSION) prep->next_buf_row,
nuclear@0 148 numrows);
nuclear@0 149 *in_row_ctr += numrows;
nuclear@0 150 prep->next_buf_row += numrows;
nuclear@0 151 prep->rows_to_go -= numrows;
nuclear@0 152 /* If at bottom of image, pad to fill the conversion buffer. */
nuclear@0 153 if (prep->rows_to_go == 0 &&
nuclear@0 154 prep->next_buf_row < cinfo->max_v_samp_factor) {
nuclear@0 155 for (ci = 0; ci < cinfo->num_components; ci++) {
nuclear@0 156 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
nuclear@0 157 prep->next_buf_row, cinfo->max_v_samp_factor);
nuclear@0 158 }
nuclear@0 159 prep->next_buf_row = cinfo->max_v_samp_factor;
nuclear@0 160 }
nuclear@0 161 /* If we've filled the conversion buffer, empty it. */
nuclear@0 162 if (prep->next_buf_row == cinfo->max_v_samp_factor) {
nuclear@0 163 (*cinfo->downsample->downsample) (cinfo,
nuclear@0 164 prep->color_buf, (JDIMENSION) 0,
nuclear@0 165 output_buf, *out_row_group_ctr);
nuclear@0 166 prep->next_buf_row = 0;
nuclear@0 167 (*out_row_group_ctr)++;
nuclear@0 168 }
nuclear@0 169 /* If at bottom of image, pad the output to a full iMCU height.
nuclear@0 170 * Note we assume the caller is providing a one-iMCU-height output buffer!
nuclear@0 171 */
nuclear@0 172 if (prep->rows_to_go == 0 &&
nuclear@0 173 *out_row_group_ctr < out_row_groups_avail) {
nuclear@0 174 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@0 175 ci++, compptr++) {
nuclear@0 176 expand_bottom_edge(output_buf[ci],
nuclear@0 177 compptr->width_in_blocks * DCTSIZE,
nuclear@0 178 (int) (*out_row_group_ctr * compptr->v_samp_factor),
nuclear@0 179 (int) (out_row_groups_avail * compptr->v_samp_factor));
nuclear@0 180 }
nuclear@0 181 *out_row_group_ctr = out_row_groups_avail;
nuclear@0 182 break; /* can exit outer loop without test */
nuclear@0 183 }
nuclear@0 184 }
nuclear@0 185 }
nuclear@0 186
nuclear@0 187
nuclear@0 188 #ifdef CONTEXT_ROWS_SUPPORTED
nuclear@0 189
nuclear@0 190 /*
nuclear@0 191 * Process some data in the context case.
nuclear@0 192 */
nuclear@0 193
nuclear@0 194 METHODDEF(void)
nuclear@0 195 pre_process_context (j_compress_ptr cinfo,
nuclear@0 196 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
nuclear@0 197 JDIMENSION in_rows_avail,
nuclear@0 198 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
nuclear@0 199 JDIMENSION out_row_groups_avail)
nuclear@0 200 {
nuclear@0 201 my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@0 202 int numrows, ci;
nuclear@0 203 int buf_height = cinfo->max_v_samp_factor * 3;
nuclear@0 204 JDIMENSION inrows;
nuclear@0 205
nuclear@0 206 while (*out_row_group_ctr < out_row_groups_avail) {
nuclear@0 207 if (*in_row_ctr < in_rows_avail) {
nuclear@0 208 /* Do color conversion to fill the conversion buffer. */
nuclear@0 209 inrows = in_rows_avail - *in_row_ctr;
nuclear@0 210 numrows = prep->next_buf_stop - prep->next_buf_row;
nuclear@0 211 numrows = (int) MIN((JDIMENSION) numrows, inrows);
nuclear@0 212 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
nuclear@0 213 prep->color_buf,
nuclear@0 214 (JDIMENSION) prep->next_buf_row,
nuclear@0 215 numrows);
nuclear@0 216 /* Pad at top of image, if first time through */
nuclear@0 217 if (prep->rows_to_go == cinfo->image_height) {
nuclear@0 218 for (ci = 0; ci < cinfo->num_components; ci++) {
nuclear@0 219 int row;
nuclear@0 220 for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
nuclear@0 221 jcopy_sample_rows(prep->color_buf[ci], 0,
nuclear@0 222 prep->color_buf[ci], -row,
nuclear@0 223 1, cinfo->image_width);
nuclear@0 224 }
nuclear@0 225 }
nuclear@0 226 }
nuclear@0 227 *in_row_ctr += numrows;
nuclear@0 228 prep->next_buf_row += numrows;
nuclear@0 229 prep->rows_to_go -= numrows;
nuclear@0 230 } else {
nuclear@0 231 /* Return for more data, unless we are at the bottom of the image. */
nuclear@0 232 if (prep->rows_to_go != 0)
nuclear@0 233 break;
nuclear@0 234 /* When at bottom of image, pad to fill the conversion buffer. */
nuclear@0 235 if (prep->next_buf_row < prep->next_buf_stop) {
nuclear@0 236 for (ci = 0; ci < cinfo->num_components; ci++) {
nuclear@0 237 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
nuclear@0 238 prep->next_buf_row, prep->next_buf_stop);
nuclear@0 239 }
nuclear@0 240 prep->next_buf_row = prep->next_buf_stop;
nuclear@0 241 }
nuclear@0 242 }
nuclear@0 243 /* If we've gotten enough data, downsample a row group. */
nuclear@0 244 if (prep->next_buf_row == prep->next_buf_stop) {
nuclear@0 245 (*cinfo->downsample->downsample) (cinfo,
nuclear@0 246 prep->color_buf,
nuclear@0 247 (JDIMENSION) prep->this_row_group,
nuclear@0 248 output_buf, *out_row_group_ctr);
nuclear@0 249 (*out_row_group_ctr)++;
nuclear@0 250 /* Advance pointers with wraparound as necessary. */
nuclear@0 251 prep->this_row_group += cinfo->max_v_samp_factor;
nuclear@0 252 if (prep->this_row_group >= buf_height)
nuclear@0 253 prep->this_row_group = 0;
nuclear@0 254 if (prep->next_buf_row >= buf_height)
nuclear@0 255 prep->next_buf_row = 0;
nuclear@0 256 prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
nuclear@0 257 }
nuclear@0 258 }
nuclear@0 259 }
nuclear@0 260
nuclear@0 261
nuclear@0 262 /*
nuclear@0 263 * Create the wrapped-around downsampling input buffer needed for context mode.
nuclear@0 264 */
nuclear@0 265
nuclear@0 266 LOCAL(void)
nuclear@0 267 create_context_buffer (j_compress_ptr cinfo)
nuclear@0 268 {
nuclear@0 269 my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@0 270 int rgroup_height = cinfo->max_v_samp_factor;
nuclear@0 271 int ci, i;
nuclear@0 272 jpeg_component_info * compptr;
nuclear@0 273 JSAMPARRAY true_buffer, fake_buffer;
nuclear@0 274
nuclear@0 275 /* Grab enough space for fake row pointers for all the components;
nuclear@0 276 * we need five row groups' worth of pointers for each component.
nuclear@0 277 */
nuclear@0 278 fake_buffer = (JSAMPARRAY)
nuclear@0 279 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@0 280 (cinfo->num_components * 5 * rgroup_height) *
nuclear@0 281 SIZEOF(JSAMPROW));
nuclear@0 282
nuclear@0 283 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@0 284 ci++, compptr++) {
nuclear@0 285 /* Allocate the actual buffer space (3 row groups) for this component.
nuclear@0 286 * We make the buffer wide enough to allow the downsampler to edge-expand
nuclear@0 287 * horizontally within the buffer, if it so chooses.
nuclear@0 288 */
nuclear@0 289 true_buffer = (*cinfo->mem->alloc_sarray)
nuclear@0 290 ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@0 291 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
nuclear@0 292 cinfo->max_h_samp_factor) / compptr->h_samp_factor),
nuclear@0 293 (JDIMENSION) (3 * rgroup_height));
nuclear@0 294 /* Copy true buffer row pointers into the middle of the fake row array */
nuclear@0 295 MEMCOPY(fake_buffer + rgroup_height, true_buffer,
nuclear@0 296 3 * rgroup_height * SIZEOF(JSAMPROW));
nuclear@0 297 /* Fill in the above and below wraparound pointers */
nuclear@0 298 for (i = 0; i < rgroup_height; i++) {
nuclear@0 299 fake_buffer[i] = true_buffer[2 * rgroup_height + i];
nuclear@0 300 fake_buffer[4 * rgroup_height + i] = true_buffer[i];
nuclear@0 301 }
nuclear@0 302 prep->color_buf[ci] = fake_buffer + rgroup_height;
nuclear@0 303 fake_buffer += 5 * rgroup_height; /* point to space for next component */
nuclear@0 304 }
nuclear@0 305 }
nuclear@0 306
nuclear@0 307 #endif /* CONTEXT_ROWS_SUPPORTED */
nuclear@0 308
nuclear@0 309
nuclear@0 310 /*
nuclear@0 311 * Initialize preprocessing controller.
nuclear@0 312 */
nuclear@0 313
nuclear@0 314 GLOBAL(void)
nuclear@0 315 jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
nuclear@0 316 {
nuclear@0 317 my_prep_ptr prep;
nuclear@0 318 int ci;
nuclear@0 319 jpeg_component_info * compptr;
nuclear@0 320
nuclear@0 321 if (need_full_buffer) /* safety check */
nuclear@0 322 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
nuclear@0 323
nuclear@0 324 prep = (my_prep_ptr)
nuclear@0 325 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@0 326 SIZEOF(my_prep_controller));
nuclear@0 327 cinfo->prep = (struct jpeg_c_prep_controller *) prep;
nuclear@0 328 prep->pub.start_pass = start_pass_prep;
nuclear@0 329
nuclear@0 330 /* Allocate the color conversion buffer.
nuclear@0 331 * We make the buffer wide enough to allow the downsampler to edge-expand
nuclear@0 332 * horizontally within the buffer, if it so chooses.
nuclear@0 333 */
nuclear@0 334 if (cinfo->downsample->need_context_rows) {
nuclear@0 335 /* Set up to provide context rows */
nuclear@0 336 #ifdef CONTEXT_ROWS_SUPPORTED
nuclear@0 337 prep->pub.pre_process_data = pre_process_context;
nuclear@0 338 create_context_buffer(cinfo);
nuclear@0 339 #else
nuclear@0 340 ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@0 341 #endif
nuclear@0 342 } else {
nuclear@0 343 /* No context, just make it tall enough for one row group */
nuclear@0 344 prep->pub.pre_process_data = pre_process_data;
nuclear@0 345 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@0 346 ci++, compptr++) {
nuclear@0 347 prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
nuclear@0 348 ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@0 349 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
nuclear@0 350 cinfo->max_h_samp_factor) / compptr->h_samp_factor),
nuclear@0 351 (JDIMENSION) cinfo->max_v_samp_factor);
nuclear@0 352 }
nuclear@0 353 }
nuclear@0 354 }