jdsample.c (16381B)
1 /* 2 * jdsample.c 3 * 4 * Copyright (C) 1991-1996, 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 upsampling routines. 9 * 10 * Upsampling input data is counted in "row groups". A row group 11 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size) 12 * sample rows of each component. Upsampling will normally produce 13 * max_v_samp_factor pixel rows from each row group (but this could vary 14 * if the upsampler is applying a scale factor of its own). 15 * 16 * An excellent reference for image resampling is 17 * Digital Image Warping, George Wolberg, 1990. 18 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7. 19 */ 20 21 #define JPEG_INTERNALS 22 #include "jinclude.h" 23 #include "jpeglib.h" 24 25 26 /* Pointer to routine to upsample a single component */ 27 typedef JMETHOD(void, upsample1_ptr, 28 (j_decompress_ptr cinfo, jpeg_component_info * compptr, 29 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)); 30 31 /* Private subobject */ 32 33 typedef struct { 34 struct jpeg_upsampler pub; /* public fields */ 35 36 /* Color conversion buffer. When using separate upsampling and color 37 * conversion steps, this buffer holds one upsampled row group until it 38 * has been color converted and output. 39 * Note: we do not allocate any storage for component(s) which are full-size, 40 * ie do not need rescaling. The corresponding entry of color_buf[] is 41 * simply set to point to the input data array, thereby avoiding copying. 42 */ 43 JSAMPARRAY color_buf[MAX_COMPONENTS]; 44 45 /* Per-component upsampling method pointers */ 46 upsample1_ptr methods[MAX_COMPONENTS]; 47 48 int next_row_out; /* counts rows emitted from color_buf */ 49 JDIMENSION rows_to_go; /* counts rows remaining in image */ 50 51 /* Height of an input row group for each component. */ 52 int rowgroup_height[MAX_COMPONENTS]; 53 54 /* These arrays save pixel expansion factors so that int_expand need not 55 * recompute them each time. They are unused for other upsampling methods. 56 */ 57 UINT8 h_expand[MAX_COMPONENTS]; 58 UINT8 v_expand[MAX_COMPONENTS]; 59 } my_upsampler; 60 61 typedef my_upsampler * my_upsample_ptr; 62 63 64 /* 65 * Initialize for an upsampling pass. 66 */ 67 68 METHODDEF(void) 69 start_pass_upsample (j_decompress_ptr cinfo) 70 { 71 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 72 73 /* Mark the conversion buffer empty */ 74 upsample->next_row_out = cinfo->max_v_samp_factor; 75 /* Initialize total-height counter for detecting bottom of image */ 76 upsample->rows_to_go = cinfo->output_height; 77 } 78 79 80 /* 81 * Control routine to do upsampling (and color conversion). 82 * 83 * In this version we upsample each component independently. 84 * We upsample one row group into the conversion buffer, then apply 85 * color conversion a row at a time. 86 */ 87 88 METHODDEF(void) 89 sep_upsample (j_decompress_ptr cinfo, 90 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 91 JDIMENSION in_row_groups_avail, 92 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 93 JDIMENSION out_rows_avail) 94 { 95 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 96 int ci; 97 jpeg_component_info * compptr; 98 JDIMENSION num_rows; 99 100 /* Fill the conversion buffer, if it's empty */ 101 if (upsample->next_row_out >= cinfo->max_v_samp_factor) { 102 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 103 ci++, compptr++) { 104 /* Invoke per-component upsample method. Notice we pass a POINTER 105 * to color_buf[ci], so that fullsize_upsample can change it. 106 */ 107 (*upsample->methods[ci]) (cinfo, compptr, 108 input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]), 109 upsample->color_buf + ci); 110 } 111 upsample->next_row_out = 0; 112 } 113 114 /* Color-convert and emit rows */ 115 116 /* How many we have in the buffer: */ 117 num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out); 118 /* Not more than the distance to the end of the image. Need this test 119 * in case the image height is not a multiple of max_v_samp_factor: 120 */ 121 if (num_rows > upsample->rows_to_go) 122 num_rows = upsample->rows_to_go; 123 /* And not more than what the client can accept: */ 124 out_rows_avail -= *out_row_ctr; 125 if (num_rows > out_rows_avail) 126 num_rows = out_rows_avail; 127 128 (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf, 129 (JDIMENSION) upsample->next_row_out, 130 output_buf + *out_row_ctr, 131 (int) num_rows); 132 133 /* Adjust counts */ 134 *out_row_ctr += num_rows; 135 upsample->rows_to_go -= num_rows; 136 upsample->next_row_out += num_rows; 137 /* When the buffer is emptied, declare this input row group consumed */ 138 if (upsample->next_row_out >= cinfo->max_v_samp_factor) 139 (*in_row_group_ctr)++; 140 } 141 142 143 /* 144 * These are the routines invoked by sep_upsample to upsample pixel values 145 * of a single component. One row group is processed per call. 146 */ 147 148 149 /* 150 * For full-size components, we just make color_buf[ci] point at the 151 * input buffer, and thus avoid copying any data. Note that this is 152 * safe only because sep_upsample doesn't declare the input row group 153 * "consumed" until we are done color converting and emitting it. 154 */ 155 156 METHODDEF(void) 157 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 158 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 159 { 160 *output_data_ptr = input_data; 161 } 162 163 164 /* 165 * This is a no-op version used for "uninteresting" components. 166 * These components will not be referenced by color conversion. 167 */ 168 169 METHODDEF(void) 170 noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 171 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 172 { 173 *output_data_ptr = NULL; /* safety check */ 174 } 175 176 177 /* 178 * This version handles any integral sampling ratios. 179 * This is not used for typical JPEG files, so it need not be fast. 180 * Nor, for that matter, is it particularly accurate: the algorithm is 181 * simple replication of the input pixel onto the corresponding output 182 * pixels. The hi-falutin sampling literature refers to this as a 183 * "box filter". A box filter tends to introduce visible artifacts, 184 * so if you are actually going to use 3:1 or 4:1 sampling ratios 185 * you would be well advised to improve this code. 186 */ 187 188 METHODDEF(void) 189 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 190 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 191 { 192 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 193 JSAMPARRAY output_data = *output_data_ptr; 194 register JSAMPROW inptr, outptr; 195 register JSAMPLE invalue; 196 register int h; 197 JSAMPROW outend; 198 int h_expand, v_expand; 199 int inrow, outrow; 200 201 h_expand = upsample->h_expand[compptr->component_index]; 202 v_expand = upsample->v_expand[compptr->component_index]; 203 204 inrow = outrow = 0; 205 while (outrow < cinfo->max_v_samp_factor) { 206 /* Generate one output row with proper horizontal expansion */ 207 inptr = input_data[inrow]; 208 outptr = output_data[outrow]; 209 outend = outptr + cinfo->output_width; 210 while (outptr < outend) { 211 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 212 for (h = h_expand; h > 0; h--) { 213 *outptr++ = invalue; 214 } 215 } 216 /* Generate any additional output rows by duplicating the first one */ 217 if (v_expand > 1) { 218 jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 219 v_expand-1, cinfo->output_width); 220 } 221 inrow++; 222 outrow += v_expand; 223 } 224 } 225 226 227 /* 228 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical. 229 * It's still a box filter. 230 */ 231 232 METHODDEF(void) 233 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 234 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 235 { 236 JSAMPARRAY output_data = *output_data_ptr; 237 register JSAMPROW inptr, outptr; 238 register JSAMPLE invalue; 239 JSAMPROW outend; 240 int inrow; 241 242 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) { 243 inptr = input_data[inrow]; 244 outptr = output_data[inrow]; 245 outend = outptr + cinfo->output_width; 246 while (outptr < outend) { 247 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 248 *outptr++ = invalue; 249 *outptr++ = invalue; 250 } 251 } 252 } 253 254 255 /* 256 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical. 257 * It's still a box filter. 258 */ 259 260 METHODDEF(void) 261 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 262 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 263 { 264 JSAMPARRAY output_data = *output_data_ptr; 265 register JSAMPROW inptr, outptr; 266 register JSAMPLE invalue; 267 JSAMPROW outend; 268 int inrow, outrow; 269 270 inrow = outrow = 0; 271 while (outrow < cinfo->max_v_samp_factor) { 272 inptr = input_data[inrow]; 273 outptr = output_data[outrow]; 274 outend = outptr + cinfo->output_width; 275 while (outptr < outend) { 276 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 277 *outptr++ = invalue; 278 *outptr++ = invalue; 279 } 280 jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 281 1, cinfo->output_width); 282 inrow++; 283 outrow += 2; 284 } 285 } 286 287 288 /* 289 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical. 290 * 291 * The upsampling algorithm is linear interpolation between pixel centers, 292 * also known as a "triangle filter". This is a good compromise between 293 * speed and visual quality. The centers of the output pixels are 1/4 and 3/4 294 * of the way between input pixel centers. 295 * 296 * A note about the "bias" calculations: when rounding fractional values to 297 * integer, we do not want to always round 0.5 up to the next integer. 298 * If we did that, we'd introduce a noticeable bias towards larger values. 299 * Instead, this code is arranged so that 0.5 will be rounded up or down at 300 * alternate pixel locations (a simple ordered dither pattern). 301 */ 302 303 METHODDEF(void) 304 h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 305 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 306 { 307 JSAMPARRAY output_data = *output_data_ptr; 308 register JSAMPROW inptr, outptr; 309 register int invalue; 310 register JDIMENSION colctr; 311 int inrow; 312 313 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) { 314 inptr = input_data[inrow]; 315 outptr = output_data[inrow]; 316 /* Special case for first column */ 317 invalue = GETJSAMPLE(*inptr++); 318 *outptr++ = (JSAMPLE) invalue; 319 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2); 320 321 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) { 322 /* General case: 3/4 * nearer pixel + 1/4 * further pixel */ 323 invalue = GETJSAMPLE(*inptr++) * 3; 324 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2); 325 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2); 326 } 327 328 /* Special case for last column */ 329 invalue = GETJSAMPLE(*inptr); 330 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2); 331 *outptr++ = (JSAMPLE) invalue; 332 } 333 } 334 335 336 /* 337 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical. 338 * Again a triangle filter; see comments for h2v1 case, above. 339 * 340 * It is OK for us to reference the adjacent input rows because we demanded 341 * context from the main buffer controller (see initialization code). 342 */ 343 344 METHODDEF(void) 345 h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 346 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 347 { 348 JSAMPARRAY output_data = *output_data_ptr; 349 register JSAMPROW inptr0, inptr1, outptr; 350 #if BITS_IN_JSAMPLE == 8 351 register int thiscolsum, lastcolsum, nextcolsum; 352 #else 353 register INT32 thiscolsum, lastcolsum, nextcolsum; 354 #endif 355 register JDIMENSION colctr; 356 int inrow, outrow, v; 357 358 inrow = outrow = 0; 359 while (outrow < cinfo->max_v_samp_factor) { 360 for (v = 0; v < 2; v++) { 361 /* inptr0 points to nearest input row, inptr1 points to next nearest */ 362 inptr0 = input_data[inrow]; 363 if (v == 0) /* next nearest is row above */ 364 inptr1 = input_data[inrow-1]; 365 else /* next nearest is row below */ 366 inptr1 = input_data[inrow+1]; 367 outptr = output_data[outrow++]; 368 369 /* Special case for first column */ 370 thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 371 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 372 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4); 373 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4); 374 lastcolsum = thiscolsum; thiscolsum = nextcolsum; 375 376 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) { 377 /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */ 378 /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */ 379 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 380 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4); 381 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4); 382 lastcolsum = thiscolsum; thiscolsum = nextcolsum; 383 } 384 385 /* Special case for last column */ 386 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4); 387 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4); 388 } 389 inrow++; 390 } 391 } 392 393 394 /* 395 * Module initialization routine for upsampling. 396 */ 397 398 GLOBAL(void) 399 jinit_upsampler (j_decompress_ptr cinfo) 400 { 401 my_upsample_ptr upsample; 402 int ci; 403 jpeg_component_info * compptr; 404 boolean need_buffer, do_fancy; 405 int h_in_group, v_in_group, h_out_group, v_out_group; 406 407 upsample = (my_upsample_ptr) 408 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 409 SIZEOF(my_upsampler)); 410 cinfo->upsample = (struct jpeg_upsampler *) upsample; 411 upsample->pub.start_pass = start_pass_upsample; 412 upsample->pub.upsample = sep_upsample; 413 upsample->pub.need_context_rows = FALSE; /* until we find out differently */ 414 415 if (cinfo->CCIR601_sampling) /* this isn't supported */ 416 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL); 417 418 /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1, 419 * so don't ask for it. 420 */ 421 do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1; 422 423 /* Verify we can handle the sampling factors, select per-component methods, 424 * and create storage as needed. 425 */ 426 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 427 ci++, compptr++) { 428 /* Compute size of an "input group" after IDCT scaling. This many samples 429 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels. 430 */ 431 h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) / 432 cinfo->min_DCT_scaled_size; 433 v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) / 434 cinfo->min_DCT_scaled_size; 435 h_out_group = cinfo->max_h_samp_factor; 436 v_out_group = cinfo->max_v_samp_factor; 437 upsample->rowgroup_height[ci] = v_in_group; /* save for use later */ 438 need_buffer = TRUE; 439 if (! compptr->component_needed) { 440 /* Don't bother to upsample an uninteresting component. */ 441 upsample->methods[ci] = noop_upsample; 442 need_buffer = FALSE; 443 } else if (h_in_group == h_out_group && v_in_group == v_out_group) { 444 /* Fullsize components can be processed without any work. */ 445 upsample->methods[ci] = fullsize_upsample; 446 need_buffer = FALSE; 447 } else if (h_in_group * 2 == h_out_group && 448 v_in_group == v_out_group) { 449 /* Special cases for 2h1v upsampling */ 450 if (do_fancy && compptr->downsampled_width > 2) 451 upsample->methods[ci] = h2v1_fancy_upsample; 452 else 453 upsample->methods[ci] = h2v1_upsample; 454 } else if (h_in_group * 2 == h_out_group && 455 v_in_group * 2 == v_out_group) { 456 /* Special cases for 2h2v upsampling */ 457 if (do_fancy && compptr->downsampled_width > 2) { 458 upsample->methods[ci] = h2v2_fancy_upsample; 459 upsample->pub.need_context_rows = TRUE; 460 } else 461 upsample->methods[ci] = h2v2_upsample; 462 } else if ((h_out_group % h_in_group) == 0 && 463 (v_out_group % v_in_group) == 0) { 464 /* Generic integral-factors upsampling method */ 465 upsample->methods[ci] = int_upsample; 466 upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group); 467 upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group); 468 } else 469 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL); 470 if (need_buffer) { 471 upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray) 472 ((j_common_ptr) cinfo, JPOOL_IMAGE, 473 (JDIMENSION) jround_up((long) cinfo->output_width, 474 (long) cinfo->max_h_samp_factor), 475 (JDIMENSION) cinfo->max_v_samp_factor); 476 } 477 } 478 }