| 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 | } |