1 #if !defined(_FX_JPEG_TURBO_) 2 /* 3 * jcprepct.c 4 * 5 * Copyright (C) 1994-1996, Thomas G. Lane. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains the compression preprocessing controller. 10 * This controller manages the color conversion, downsampling, 11 * and edge expansion steps. 12 * 13 * Most of the complexity here is associated with buffering input rows 14 * as required by the downsampler. See the comments at the head of 15 * jcsample.c for the downsampler's needs. 16 */ 17 18 #define JPEG_INTERNALS 19 #include "jinclude.h" 20 #include "jpeglib.h" 21 22 23 /* At present, jcsample.c can request context rows only for smoothing. 24 * In the future, we might also need context rows for CCIR601 sampling 25 * or other more-complex downsampling procedures. The code to support 26 * context rows should be compiled only if needed. 27 */ 28 #ifdef INPUT_SMOOTHING_SUPPORTED 29 #define CONTEXT_ROWS_SUPPORTED 30 #endif 31 32 33 /* 34 * For the simple (no-context-row) case, we just need to buffer one 35 * row group's worth of pixels for the downsampling step. At the bottom of 36 * the image, we pad to a full row group by replicating the last pixel row. 37 * The downsampler's last output row is then replicated if needed to pad 38 * out to a full iMCU row. 39 * 40 * When providing context rows, we must buffer three row groups' worth of 41 * pixels. Three row groups are physically allocated, but the row pointer 42 * arrays are made five row groups high, with the extra pointers above and 43 * below "wrapping around" to point to the last and first real row groups. 44 * This allows the downsampler to access the proper context rows. 45 * At the top and bottom of the image, we create dummy context rows by 46 * copying the first or last real pixel row. This copying could be avoided 47 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the 48 * trouble on the compression side. 49 */ 50 51 52 /* Private buffer controller object */ 53 54 typedef struct { 55 struct jpeg_c_prep_controller pub; /* public fields */ 56 57 /* Downsampling input buffer. This buffer holds color-converted data 58 * until we have enough to do a downsample step. 59 */ 60 JSAMPARRAY color_buf[MAX_COMPONENTS]; 61 62 JDIMENSION rows_to_go; /* counts rows remaining in source image */ 63 int next_buf_row; /* index of next row to store in color_buf */ 64 65 #ifdef CONTEXT_ROWS_SUPPORTED /* only needed for context case */ 66 int this_row_group; /* starting row index of group to process */ 67 int next_buf_stop; /* downsample when we reach this index */ 68 #endif 69 } my_prep_controller; 70 71 typedef my_prep_controller * my_prep_ptr; 72 73 74 /* 75 * Initialize for a processing pass. 76 */ 77 78 METHODDEF(void) 79 start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode) 80 { 81 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; 82 83 if (pass_mode != JBUF_PASS_THRU) 84 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 85 86 /* Initialize total-height counter for detecting bottom of image */ 87 prep->rows_to_go = cinfo->image_height; 88 /* Mark the conversion buffer empty */ 89 prep->next_buf_row = 0; 90 #ifdef CONTEXT_ROWS_SUPPORTED 91 /* Preset additional state variables for context mode. 92 * These aren't used in non-context mode, so we needn't test which mode. 93 */ 94 prep->this_row_group = 0; 95 /* Set next_buf_stop to stop after two row groups have been read in. */ 96 prep->next_buf_stop = 2 * cinfo->max_v_samp_factor; 97 #endif 98 } 99 100 101 /* 102 * Expand an image vertically from height input_rows to height output_rows, 103 * by duplicating the bottom row. 104 */ 105 106 LOCAL(void) 107 expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols, 108 int input_rows, int output_rows) 109 { 110 register int row; 111 112 for (row = input_rows; row < output_rows; row++) { 113 jcopy_sample_rows(image_data, input_rows-1, image_data, row, 114 1, num_cols); 115 } 116 } 117 118 119 /* 120 * Process some data in the simple no-context case. 121 * 122 * Preprocessor output data is counted in "row groups". A row group 123 * is defined to be v_samp_factor sample rows of each component. 124 * Downsampling will produce this much data from each max_v_samp_factor 125 * input rows. 126 */ 127 128 METHODDEF(void) 129 pre_process_data (j_compress_ptr cinfo, 130 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, 131 JDIMENSION in_rows_avail, 132 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, 133 JDIMENSION out_row_groups_avail) 134 { 135 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; 136 int numrows, ci; 137 JDIMENSION inrows; 138 jpeg_component_info * compptr; 139 140 while (*in_row_ctr < in_rows_avail && 141 *out_row_group_ctr < out_row_groups_avail) { 142 /* Do color conversion to fill the conversion buffer. */ 143 inrows = in_rows_avail - *in_row_ctr; 144 numrows = cinfo->max_v_samp_factor - prep->next_buf_row; 145 numrows = (int) MIN((JDIMENSION) numrows, inrows); 146 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, 147 prep->color_buf, 148 (JDIMENSION) prep->next_buf_row, 149 numrows); 150 *in_row_ctr += numrows; 151 prep->next_buf_row += numrows; 152 prep->rows_to_go -= numrows; 153 /* If at bottom of image, pad to fill the conversion buffer. */ 154 if (prep->rows_to_go == 0 && 155 prep->next_buf_row < cinfo->max_v_samp_factor) { 156 for (ci = 0; ci < cinfo->num_components; ci++) { 157 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, 158 prep->next_buf_row, cinfo->max_v_samp_factor); 159 } 160 prep->next_buf_row = cinfo->max_v_samp_factor; 161 } 162 /* If we've filled the conversion buffer, empty it. */ 163 if (prep->next_buf_row == cinfo->max_v_samp_factor) { 164 (*cinfo->downsample->downsample) (cinfo, 165 prep->color_buf, (JDIMENSION) 0, 166 output_buf, *out_row_group_ctr); 167 prep->next_buf_row = 0; 168 (*out_row_group_ctr)++; 169 } 170 /* If at bottom of image, pad the output to a full iMCU height. 171 * Note we assume the caller is providing a one-iMCU-height output buffer! 172 */ 173 if (prep->rows_to_go == 0 && 174 *out_row_group_ctr < out_row_groups_avail) { 175 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 176 ci++, compptr++) { 177 expand_bottom_edge(output_buf[ci], 178 compptr->width_in_blocks * DCTSIZE, 179 (int) (*out_row_group_ctr * compptr->v_samp_factor), 180 (int) (out_row_groups_avail * compptr->v_samp_factor)); 181 } 182 *out_row_group_ctr = out_row_groups_avail; 183 break; /* can exit outer loop without test */ 184 } 185 } 186 } 187 188 189 #ifdef CONTEXT_ROWS_SUPPORTED 190 191 /* 192 * Process some data in the context case. 193 */ 194 195 METHODDEF(void) 196 pre_process_context (j_compress_ptr cinfo, 197 JSAMPARRAY input_buf, JDIMENSION *in_row_ctr, 198 JDIMENSION in_rows_avail, 199 JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr, 200 JDIMENSION out_row_groups_avail) 201 { 202 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; 203 int numrows, ci; 204 int buf_height = cinfo->max_v_samp_factor * 3; 205 JDIMENSION inrows; 206 207 while (*out_row_group_ctr < out_row_groups_avail) { 208 if (*in_row_ctr < in_rows_avail) { 209 /* Do color conversion to fill the conversion buffer. */ 210 inrows = in_rows_avail - *in_row_ctr; 211 numrows = prep->next_buf_stop - prep->next_buf_row; 212 numrows = (int) MIN((JDIMENSION) numrows, inrows); 213 (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr, 214 prep->color_buf, 215 (JDIMENSION) prep->next_buf_row, 216 numrows); 217 /* Pad at top of image, if first time through */ 218 if (prep->rows_to_go == cinfo->image_height) { 219 for (ci = 0; ci < cinfo->num_components; ci++) { 220 int row; 221 for (row = 1; row <= cinfo->max_v_samp_factor; row++) { 222 jcopy_sample_rows(prep->color_buf[ci], 0, 223 prep->color_buf[ci], -row, 224 1, cinfo->image_width); 225 } 226 } 227 } 228 *in_row_ctr += numrows; 229 prep->next_buf_row += numrows; 230 prep->rows_to_go -= numrows; 231 } else { 232 /* Return for more data, unless we are at the bottom of the image. */ 233 if (prep->rows_to_go != 0) 234 break; 235 /* When at bottom of image, pad to fill the conversion buffer. */ 236 if (prep->next_buf_row < prep->next_buf_stop) { 237 for (ci = 0; ci < cinfo->num_components; ci++) { 238 expand_bottom_edge(prep->color_buf[ci], cinfo->image_width, 239 prep->next_buf_row, prep->next_buf_stop); 240 } 241 prep->next_buf_row = prep->next_buf_stop; 242 } 243 } 244 /* If we've gotten enough data, downsample a row group. */ 245 if (prep->next_buf_row == prep->next_buf_stop) { 246 (*cinfo->downsample->downsample) (cinfo, 247 prep->color_buf, 248 (JDIMENSION) prep->this_row_group, 249 output_buf, *out_row_group_ctr); 250 (*out_row_group_ctr)++; 251 /* Advance pointers with wraparound as necessary. */ 252 prep->this_row_group += cinfo->max_v_samp_factor; 253 if (prep->this_row_group >= buf_height) 254 prep->this_row_group = 0; 255 if (prep->next_buf_row >= buf_height) 256 prep->next_buf_row = 0; 257 prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor; 258 } 259 } 260 } 261 262 263 /* 264 * Create the wrapped-around downsampling input buffer needed for context mode. 265 */ 266 267 LOCAL(void) 268 create_context_buffer (j_compress_ptr cinfo) 269 { 270 my_prep_ptr prep = (my_prep_ptr) cinfo->prep; 271 int rgroup_height = cinfo->max_v_samp_factor; 272 int ci, i; 273 jpeg_component_info * compptr; 274 JSAMPARRAY true_buffer, fake_buffer; 275 276 /* Grab enough space for fake row pointers for all the components; 277 * we need five row groups' worth of pointers for each component. 278 */ 279 fake_buffer = (JSAMPARRAY) 280 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 281 (cinfo->num_components * 5 * rgroup_height) * 282 SIZEOF(JSAMPROW)); 283 284 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 285 ci++, compptr++) { 286 /* Allocate the actual buffer space (3 row groups) for this component. 287 * We make the buffer wide enough to allow the downsampler to edge-expand 288 * horizontally within the buffer, if it so chooses. 289 */ 290 true_buffer = (*cinfo->mem->alloc_sarray) 291 ((j_common_ptr) cinfo, JPOOL_IMAGE, 292 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * 293 cinfo->max_h_samp_factor) / compptr->h_samp_factor), 294 (JDIMENSION) (3 * rgroup_height)); 295 /* Copy true buffer row pointers into the middle of the fake row array */ 296 MEMCOPY(fake_buffer + rgroup_height, true_buffer, 297 3 * rgroup_height * SIZEOF(JSAMPROW)); 298 /* Fill in the above and below wraparound pointers */ 299 for (i = 0; i < rgroup_height; i++) { 300 fake_buffer[i] = true_buffer[2 * rgroup_height + i]; 301 fake_buffer[4 * rgroup_height + i] = true_buffer[i]; 302 } 303 prep->color_buf[ci] = fake_buffer + rgroup_height; 304 fake_buffer += 5 * rgroup_height; /* point to space for next component */ 305 } 306 } 307 308 #endif /* CONTEXT_ROWS_SUPPORTED */ 309 310 311 /* 312 * Initialize preprocessing controller. 313 */ 314 315 GLOBAL(void) 316 jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer) 317 { 318 my_prep_ptr prep; 319 int ci; 320 jpeg_component_info * compptr; 321 322 if (need_full_buffer) /* safety check */ 323 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 324 325 prep = (my_prep_ptr) 326 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 327 SIZEOF(my_prep_controller)); 328 cinfo->prep = (struct jpeg_c_prep_controller *) prep; 329 prep->pub.start_pass = start_pass_prep; 330 331 /* Allocate the color conversion buffer. 332 * We make the buffer wide enough to allow the downsampler to edge-expand 333 * horizontally within the buffer, if it so chooses. 334 */ 335 if (cinfo->downsample->need_context_rows) { 336 /* Set up to provide context rows */ 337 #ifdef CONTEXT_ROWS_SUPPORTED 338 prep->pub.pre_process_data = pre_process_context; 339 create_context_buffer(cinfo); 340 #else 341 ERREXIT(cinfo, JERR_NOT_COMPILED); 342 #endif 343 } else { 344 /* No context, just make it tall enough for one row group */ 345 prep->pub.pre_process_data = pre_process_data; 346 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 347 ci++, compptr++) { 348 prep->color_buf[ci] = (*cinfo->mem->alloc_sarray) 349 ((j_common_ptr) cinfo, JPOOL_IMAGE, 350 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE * 351 cinfo->max_h_samp_factor) / compptr->h_samp_factor), 352 (JDIMENSION) cinfo->max_v_samp_factor); 353 } 354 } 355 } 356 357 #endif //_FX_JPEG_TURBO_ 358
