1 #if !defined(_FX_JPEG_TURBO_) 2 /* 3 * jcsample.c 4 * 5 * Copyright (C) 1991-1996, 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 downsampling routines. 10 * 11 * Downsampling input data is counted in "row groups". A row group 12 * is defined to be max_v_samp_factor pixel rows of each component, 13 * from which the downsampler produces v_samp_factor sample rows. 14 * A single row group is processed in each call to the downsampler module. 15 * 16 * The downsampler is responsible for edge-expansion of its output data 17 * to fill an integral number of DCT blocks horizontally. The source buffer 18 * may be modified if it is helpful for this purpose (the source buffer is 19 * allocated wide enough to correspond to the desired output width). 20 * The caller (the prep controller) is responsible for vertical padding. 21 * 22 * The downsampler may request "context rows" by setting need_context_rows 23 * during startup. In this case, the input arrays will contain at least 24 * one row group's worth of pixels above and below the passed-in data; 25 * the caller will create dummy rows at image top and bottom by replicating 26 * the first or last real pixel row. 27 * 28 * An excellent reference for image resampling is 29 * Digital Image Warping, George Wolberg, 1990. 30 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7. 31 * 32 * The downsampling algorithm used here is a simple average of the source 33 * pixels covered by the output pixel. The hi-falutin sampling literature 34 * refers to this as a "box filter". In general the characteristics of a box 35 * filter are not very good, but for the specific cases we normally use (1:1 36 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not 37 * nearly so bad. If you intend to use other sampling ratios, you'd be well 38 * advised to improve this code. 39 * 40 * A simple input-smoothing capability is provided. This is mainly intended 41 * for cleaning up color-dithered GIF input files (if you find it inadequate, 42 * we suggest using an external filtering program such as pnmconvol). When 43 * enabled, each input pixel P is replaced by a weighted sum of itself and its 44 * eight neighbors. P's weight is 1-8*SF and each neighbor's weight is SF, 45 * where SF = (smoothing_factor / 1024). 46 * Currently, smoothing is only supported for 2h2v sampling factors. 47 */ 48 49 #define JPEG_INTERNALS 50 #include "jinclude.h" 51 #include "jpeglib.h" 52 53 54 /* Pointer to routine to downsample a single component */ 55 typedef JMETHOD(void, downsample1_ptr, 56 (j_compress_ptr cinfo, jpeg_component_info * compptr, 57 JSAMPARRAY input_data, JSAMPARRAY output_data)); 58 59 /* Private subobject */ 60 61 typedef struct { 62 struct jpeg_downsampler pub; /* public fields */ 63 64 /* Downsampling method pointers, one per component */ 65 downsample1_ptr methods[MAX_COMPONENTS]; 66 } my_downsampler; 67 68 typedef my_downsampler * my_downsample_ptr; 69 70 71 /* 72 * Initialize for a downsampling pass. 73 */ 74 75 METHODDEF(void) 76 start_pass_downsample (j_compress_ptr cinfo) 77 { 78 /* no work for now */ 79 } 80 81 82 /* 83 * Expand a component horizontally from width input_cols to width output_cols, 84 * by duplicating the rightmost samples. 85 */ 86 87 LOCAL(void) 88 expand_right_edge (JSAMPARRAY image_data, int num_rows, 89 JDIMENSION input_cols, JDIMENSION output_cols) 90 { 91 register JSAMPROW ptr; 92 register JSAMPLE pixval; 93 register int count; 94 int row; 95 int numcols = (int) (output_cols - input_cols); 96 97 if (numcols > 0) { 98 for (row = 0; row < num_rows; row++) { 99 ptr = image_data[row] + input_cols; 100 pixval = ptr[-1]; /* don't need GETJSAMPLE() here */ 101 for (count = numcols; count > 0; count--) 102 *ptr++ = pixval; 103 } 104 } 105 } 106 107 108 /* 109 * Do downsampling for a whole row group (all components). 110 * 111 * In this version we simply downsample each component independently. 112 */ 113 114 METHODDEF(void) 115 sep_downsample (j_compress_ptr cinfo, 116 JSAMPIMAGE input_buf, JDIMENSION in_row_index, 117 JSAMPIMAGE output_buf, JDIMENSION out_row_group_index) 118 { 119 my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample; 120 int ci; 121 jpeg_component_info * compptr; 122 JSAMPARRAY in_ptr, out_ptr; 123 124 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 125 ci++, compptr++) { 126 in_ptr = input_buf[ci] + in_row_index; 127 out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor); 128 (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr); 129 } 130 } 131 132 133 /* 134 * Downsample pixel values of a single component. 135 * One row group is processed per call. 136 * This version handles arbitrary integral sampling ratios, without smoothing. 137 * Note that this version is not actually used for customary sampling ratios. 138 */ 139 140 METHODDEF(void) 141 int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, 142 JSAMPARRAY input_data, JSAMPARRAY output_data) 143 { 144 int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v; 145 JDIMENSION outcol, outcol_h; /* outcol_h == outcol*h_expand */ 146 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; 147 JSAMPROW inptr, outptr; 148 INT32 outvalue; 149 150 h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor; 151 v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor; 152 numpix = h_expand * v_expand; 153 numpix2 = numpix/2; 154 155 /* Expand input data enough to let all the output samples be generated 156 * by the standard loop. Special-casing padded output would be more 157 * efficient. 158 */ 159 expand_right_edge(input_data, cinfo->max_v_samp_factor, 160 cinfo->image_width, output_cols * h_expand); 161 162 inrow = 0; 163 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { 164 outptr = output_data[outrow]; 165 for (outcol = 0, outcol_h = 0; outcol < output_cols; 166 outcol++, outcol_h += h_expand) { 167 outvalue = 0; 168 for (v = 0; v < v_expand; v++) { 169 inptr = input_data[inrow+v] + outcol_h; 170 for (h = 0; h < h_expand; h++) { 171 outvalue += (INT32) GETJSAMPLE(*inptr++); 172 } 173 } 174 *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix); 175 } 176 inrow += v_expand; 177 } 178 } 179 180 181 /* 182 * Downsample pixel values of a single component. 183 * This version handles the special case of a full-size component, 184 * without smoothing. 185 */ 186 187 METHODDEF(void) 188 fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, 189 JSAMPARRAY input_data, JSAMPARRAY output_data) 190 { 191 /* Copy the data */ 192 jcopy_sample_rows(input_data, 0, output_data, 0, 193 cinfo->max_v_samp_factor, cinfo->image_width); 194 /* Edge-expand */ 195 expand_right_edge(output_data, cinfo->max_v_samp_factor, 196 cinfo->image_width, compptr->width_in_blocks * DCTSIZE); 197 } 198 199 200 /* 201 * Downsample pixel values of a single component. 202 * This version handles the common case of 2:1 horizontal and 1:1 vertical, 203 * without smoothing. 204 * 205 * A note about the "bias" calculations: when rounding fractional values to 206 * integer, we do not want to always round 0.5 up to the next integer. 207 * If we did that, we'd introduce a noticeable bias towards larger values. 208 * Instead, this code is arranged so that 0.5 will be rounded up or down at 209 * alternate pixel locations (a simple ordered dither pattern). 210 */ 211 212 METHODDEF(void) 213 h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, 214 JSAMPARRAY input_data, JSAMPARRAY output_data) 215 { 216 int outrow; 217 JDIMENSION outcol; 218 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; 219 register JSAMPROW inptr, outptr; 220 register int bias; 221 222 /* Expand input data enough to let all the output samples be generated 223 * by the standard loop. Special-casing padded output would be more 224 * efficient. 225 */ 226 expand_right_edge(input_data, cinfo->max_v_samp_factor, 227 cinfo->image_width, output_cols * 2); 228 229 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { 230 outptr = output_data[outrow]; 231 inptr = input_data[outrow]; 232 bias = 0; /* bias = 0,1,0,1,... for successive samples */ 233 for (outcol = 0; outcol < output_cols; outcol++) { 234 *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1]) 235 + bias) >> 1); 236 bias ^= 1; /* 0=>1, 1=>0 */ 237 inptr += 2; 238 } 239 } 240 } 241 242 243 /* 244 * Downsample pixel values of a single component. 245 * This version handles the standard case of 2:1 horizontal and 2:1 vertical, 246 * without smoothing. 247 */ 248 249 METHODDEF(void) 250 h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, 251 JSAMPARRAY input_data, JSAMPARRAY output_data) 252 { 253 int inrow, outrow; 254 JDIMENSION outcol; 255 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; 256 register JSAMPROW inptr0, inptr1, outptr; 257 register int bias; 258 259 /* Expand input data enough to let all the output samples be generated 260 * by the standard loop. Special-casing padded output would be more 261 * efficient. 262 */ 263 expand_right_edge(input_data, cinfo->max_v_samp_factor, 264 cinfo->image_width, output_cols * 2); 265 266 inrow = 0; 267 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { 268 outptr = output_data[outrow]; 269 inptr0 = input_data[inrow]; 270 inptr1 = input_data[inrow+1]; 271 bias = 1; /* bias = 1,2,1,2,... for successive samples */ 272 for (outcol = 0; outcol < output_cols; outcol++) { 273 *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + 274 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]) 275 + bias) >> 2); 276 bias ^= 3; /* 1=>2, 2=>1 */ 277 inptr0 += 2; inptr1 += 2; 278 } 279 inrow += 2; 280 } 281 } 282 283 284 #ifdef INPUT_SMOOTHING_SUPPORTED 285 286 /* 287 * Downsample pixel values of a single component. 288 * This version handles the standard case of 2:1 horizontal and 2:1 vertical, 289 * with smoothing. One row of context is required. 290 */ 291 292 METHODDEF(void) 293 h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr, 294 JSAMPARRAY input_data, JSAMPARRAY output_data) 295 { 296 int inrow, outrow; 297 JDIMENSION colctr; 298 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; 299 register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr; 300 INT32 membersum, neighsum, memberscale, neighscale; 301 302 /* Expand input data enough to let all the output samples be generated 303 * by the standard loop. Special-casing padded output would be more 304 * efficient. 305 */ 306 expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2, 307 cinfo->image_width, output_cols * 2); 308 309 /* We don't bother to form the individual "smoothed" input pixel values; 310 * we can directly compute the output which is the average of the four 311 * smoothed values. Each of the four member pixels contributes a fraction 312 * (1-8*SF) to its own smoothed image and a fraction SF to each of the three 313 * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final 314 * output. The four corner-adjacent neighbor pixels contribute a fraction 315 * SF to just one smoothed pixel, or SF/4 to the final output; while the 316 * eight edge-adjacent neighbors contribute SF to each of two smoothed 317 * pixels, or SF/2 overall. In order to use integer arithmetic, these 318 * factors are scaled by 2^16 = 65536. 319 * Also recall that SF = smoothing_factor / 1024. 320 */ 321 322 memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */ 323 neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */ 324 325 inrow = 0; 326 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { 327 outptr = output_data[outrow]; 328 inptr0 = input_data[inrow]; 329 inptr1 = input_data[inrow+1]; 330 above_ptr = input_data[inrow-1]; 331 below_ptr = input_data[inrow+2]; 332 333 /* Special case for first column: pretend column -1 is same as column 0 */ 334 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + 335 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]); 336 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) + 337 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) + 338 GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) + 339 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]); 340 neighsum += neighsum; 341 neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) + 342 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]); 343 membersum = membersum * memberscale + neighsum * neighscale; 344 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); 345 inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2; 346 347 for (colctr = output_cols - 2; colctr > 0; colctr--) { 348 /* sum of pixels directly mapped to this output element */ 349 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + 350 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]); 351 /* sum of edge-neighbor pixels */ 352 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) + 353 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) + 354 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) + 355 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]); 356 /* The edge-neighbors count twice as much as corner-neighbors */ 357 neighsum += neighsum; 358 /* Add in the corner-neighbors */ 359 neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) + 360 GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]); 361 /* form final output scaled up by 2^16 */ 362 membersum = membersum * memberscale + neighsum * neighscale; 363 /* round, descale and output it */ 364 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); 365 inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2; 366 } 367 368 /* Special case for last column */ 369 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) + 370 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]); 371 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) + 372 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) + 373 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) + 374 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]); 375 neighsum += neighsum; 376 neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) + 377 GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]); 378 membersum = membersum * memberscale + neighsum * neighscale; 379 *outptr = (JSAMPLE) ((membersum + 32768) >> 16); 380 381 inrow += 2; 382 } 383 } 384 385 386 /* 387 * Downsample pixel values of a single component. 388 * This version handles the special case of a full-size component, 389 * with smoothing. One row of context is required. 390 */ 391 392 METHODDEF(void) 393 fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr, 394 JSAMPARRAY input_data, JSAMPARRAY output_data) 395 { 396 int outrow; 397 JDIMENSION colctr; 398 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE; 399 register JSAMPROW inptr, above_ptr, below_ptr, outptr; 400 INT32 membersum, neighsum, memberscale, neighscale; 401 int colsum, lastcolsum, nextcolsum; 402 403 /* Expand input data enough to let all the output samples be generated 404 * by the standard loop. Special-casing padded output would be more 405 * efficient. 406 */ 407 expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2, 408 cinfo->image_width, output_cols); 409 410 /* Each of the eight neighbor pixels contributes a fraction SF to the 411 * smoothed pixel, while the main pixel contributes (1-8*SF). In order 412 * to use integer arithmetic, these factors are multiplied by 2^16 = 65536. 413 * Also recall that SF = smoothing_factor / 1024. 414 */ 415 416 memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */ 417 neighscale = cinfo->smoothing_factor * 64; /* scaled SF */ 418 419 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) { 420 outptr = output_data[outrow]; 421 inptr = input_data[outrow]; 422 above_ptr = input_data[outrow-1]; 423 below_ptr = input_data[outrow+1]; 424 425 /* Special case for first column */ 426 colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) + 427 GETJSAMPLE(*inptr); 428 membersum = GETJSAMPLE(*inptr++); 429 nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) + 430 GETJSAMPLE(*inptr); 431 neighsum = colsum + (colsum - membersum) + nextcolsum; 432 membersum = membersum * memberscale + neighsum * neighscale; 433 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); 434 lastcolsum = colsum; colsum = nextcolsum; 435 436 for (colctr = output_cols - 2; colctr > 0; colctr--) { 437 membersum = GETJSAMPLE(*inptr++); 438 above_ptr++; below_ptr++; 439 nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) + 440 GETJSAMPLE(*inptr); 441 neighsum = lastcolsum + (colsum - membersum) + nextcolsum; 442 membersum = membersum * memberscale + neighsum * neighscale; 443 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16); 444 lastcolsum = colsum; colsum = nextcolsum; 445 } 446 447 /* Special case for last column */ 448 membersum = GETJSAMPLE(*inptr); 449 neighsum = lastcolsum + (colsum - membersum) + colsum; 450 membersum = membersum * memberscale + neighsum * neighscale; 451 *outptr = (JSAMPLE) ((membersum + 32768) >> 16); 452 453 } 454 } 455 456 #endif /* INPUT_SMOOTHING_SUPPORTED */ 457 458 459 /* 460 * Module initialization routine for downsampling. 461 * Note that we must select a routine for each component. 462 */ 463 464 GLOBAL(void) 465 jinit_downsampler (j_compress_ptr cinfo) 466 { 467 my_downsample_ptr downsample; 468 int ci; 469 jpeg_component_info * compptr; 470 boolean smoothok = TRUE; 471 472 downsample = (my_downsample_ptr) 473 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 474 SIZEOF(my_downsampler)); 475 cinfo->downsample = (struct jpeg_downsampler *) downsample; 476 downsample->pub.start_pass = start_pass_downsample; 477 downsample->pub.downsample = sep_downsample; 478 downsample->pub.need_context_rows = FALSE; 479 480 if (cinfo->CCIR601_sampling) 481 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL); 482 483 /* Verify we can handle the sampling factors, and set up method pointers */ 484 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 485 ci++, compptr++) { 486 if (compptr->h_samp_factor == cinfo->max_h_samp_factor && 487 compptr->v_samp_factor == cinfo->max_v_samp_factor) { 488 #ifdef INPUT_SMOOTHING_SUPPORTED 489 if (cinfo->smoothing_factor) { 490 downsample->methods[ci] = fullsize_smooth_downsample; 491 downsample->pub.need_context_rows = TRUE; 492 } else 493 #endif 494 downsample->methods[ci] = fullsize_downsample; 495 } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor && 496 compptr->v_samp_factor == cinfo->max_v_samp_factor) { 497 smoothok = FALSE; 498 downsample->methods[ci] = h2v1_downsample; 499 } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor && 500 compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) { 501 #ifdef INPUT_SMOOTHING_SUPPORTED 502 if (cinfo->smoothing_factor) { 503 downsample->methods[ci] = h2v2_smooth_downsample; 504 downsample->pub.need_context_rows = TRUE; 505 } else 506 #endif 507 downsample->methods[ci] = h2v2_downsample; 508 } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 && 509 (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) { 510 smoothok = FALSE; 511 downsample->methods[ci] = int_downsample; 512 } else 513 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL); 514 } 515 516 #ifdef INPUT_SMOOTHING_SUPPORTED 517 if (cinfo->smoothing_factor && !smoothok) 518 TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL); 519 #endif 520 } 521 522 #endif //_FX_JPEG_TURBO_ 523
