1/* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5/* 6 * jdsample.c 7 * 8 * Copyright (C) 1991-1996, Thomas G. Lane. 9 * This file is part of the Independent JPEG Group's software. 10 * For conditions of distribution and use, see the accompanying README file. 11 * 12 * This file contains upsampling routines. 13 * 14 * Upsampling input data is counted in "row groups". A row group 15 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size) 16 * sample rows of each component. Upsampling will normally produce 17 * max_v_samp_factor pixel rows from each row group (but this could vary 18 * if the upsampler is applying a scale factor of its own). 19 * 20 * An excellent reference for image resampling is 21 * Digital Image Warping, George Wolberg, 1990. 22 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7. 23 */ 24 25#define JPEG_INTERNALS 26#include "jinclude.h" 27#include "jpeglib.h" 28 29 30/* Pointer to routine to upsample a single component */ 31typedef JMETHOD(void, upsample1_ptr, 32 (j_decompress_ptr cinfo, jpeg_component_info * compptr, 33 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)); 34 35/* Private subobject */ 36 37typedef struct { 38 struct jpeg_upsampler pub; /* public fields */ 39 40 /* Color conversion buffer. When using separate upsampling and color 41 * conversion steps, this buffer holds one upsampled row group until it 42 * has been color converted and output. 43 * Note: we do not allocate any storage for component(s) which are full-size, 44 * ie do not need rescaling. The corresponding entry of color_buf[] is 45 * simply set to point to the input data array, thereby avoiding copying. 46 */ 47 JSAMPARRAY color_buf[MAX_COMPONENTS]; 48 49 /* Per-component upsampling method pointers */ 50 upsample1_ptr methods[MAX_COMPONENTS]; 51 52 int next_row_out; /* counts rows emitted from color_buf */ 53 JDIMENSION rows_to_go; /* counts rows remaining in image */ 54 55 /* Height of an input row group for each component. */ 56 int rowgroup_height[MAX_COMPONENTS]; 57 58 /* These arrays save pixel expansion factors so that int_expand need not 59 * recompute them each time. They are unused for other upsampling methods. 60 */ 61 UINT8 h_expand[MAX_COMPONENTS]; 62 UINT8 v_expand[MAX_COMPONENTS]; 63} my_upsampler; 64 65typedef my_upsampler * my_upsample_ptr; 66 67 68/* 69 * Initialize for an upsampling pass. 70 */ 71 72METHODDEF(void) 73start_pass_upsample (j_decompress_ptr cinfo) 74{ 75 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 76 77 /* Mark the conversion buffer empty */ 78 upsample->next_row_out = cinfo->max_v_samp_factor; 79 /* Initialize total-height counter for detecting bottom of image */ 80 upsample->rows_to_go = cinfo->output_height; 81} 82 83 84/* 85 * Control routine to do upsampling (and color conversion). 86 * 87 * In this version we upsample each component independently. 88 * We upsample one row group into the conversion buffer, then apply 89 * color conversion a row at a time. 90 */ 91 92METHODDEF(void) 93sep_upsample (j_decompress_ptr cinfo, 94 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 95 JDIMENSION in_row_groups_avail, 96 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 97 JDIMENSION out_rows_avail) 98{ 99 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 100 int ci; 101 jpeg_component_info * compptr; 102 JDIMENSION num_rows; 103 104 /* Fill the conversion buffer, if it's empty */ 105 if (upsample->next_row_out >= cinfo->max_v_samp_factor) { 106 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 107 ci++, compptr++) { 108 /* Invoke per-component upsample method. Notice we pass a POINTER 109 * to color_buf[ci], so that fullsize_upsample can change it. 110 */ 111 (*upsample->methods[ci]) (cinfo, compptr, 112 input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]), 113 upsample->color_buf + ci); 114 } 115 upsample->next_row_out = 0; 116 } 117 118 /* Color-convert and emit rows */ 119 120 /* How many we have in the buffer: */ 121 num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out); 122 /* Not more than the distance to the end of the image. Need this test 123 * in case the image height is not a multiple of max_v_samp_factor: 124 */ 125 if (num_rows > upsample->rows_to_go) 126 num_rows = upsample->rows_to_go; 127 /* And not more than what the client can accept: */ 128 out_rows_avail -= *out_row_ctr; 129 if (num_rows > out_rows_avail) 130 num_rows = out_rows_avail; 131 132 (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf, 133 (JDIMENSION) upsample->next_row_out, 134 output_buf + *out_row_ctr, 135 (int) num_rows); 136 137 /* Adjust counts */ 138 *out_row_ctr += num_rows; 139 upsample->rows_to_go -= num_rows; 140 upsample->next_row_out += num_rows; 141 /* When the buffer is emptied, declare this input row group consumed */ 142 if (upsample->next_row_out >= cinfo->max_v_samp_factor) 143 (*in_row_group_ctr)++; 144} 145 146 147/* 148 * These are the routines invoked by sep_upsample to upsample pixel values 149 * of a single component. One row group is processed per call. 150 */ 151 152 153/* 154 * For full-size components, we just make color_buf[ci] point at the 155 * input buffer, and thus avoid copying any data. Note that this is 156 * safe only because sep_upsample doesn't declare the input row group 157 * "consumed" until we are done color converting and emitting it. 158 */ 159 160METHODDEF(void) 161fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 162 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 163{ 164 *output_data_ptr = input_data; 165} 166 167 168/* 169 * This is a no-op version used for "uninteresting" components. 170 * These components will not be referenced by color conversion. 171 */ 172 173METHODDEF(void) 174noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 175 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 176{ 177 *output_data_ptr = NULL; /* safety check */ 178} 179 180 181/* 182 * This version handles any integral sampling ratios. 183 * This is not used for typical JPEG files, so it need not be fast. 184 * Nor, for that matter, is it particularly accurate: the algorithm is 185 * simple replication of the input pixel onto the corresponding output 186 * pixels. The hi-falutin sampling literature refers to this as a 187 * "box filter". A box filter tends to introduce visible artifacts, 188 * so if you are actually going to use 3:1 or 4:1 sampling ratios 189 * you would be well advised to improve this code. 190 */ 191 192METHODDEF(void) 193int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 194 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 195{ 196 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 197 JSAMPARRAY output_data = *output_data_ptr; 198 register JSAMPROW inptr, outptr; 199 register JSAMPLE invalue; 200 register int h; 201 JSAMPROW outend; 202 int h_expand, v_expand; 203 int inrow, outrow; 204 205 h_expand = upsample->h_expand[compptr->component_index]; 206 v_expand = upsample->v_expand[compptr->component_index]; 207 208 inrow = outrow = 0; 209 while (outrow < cinfo->max_v_samp_factor) { 210 /* Generate one output row with proper horizontal expansion */ 211 inptr = input_data[inrow]; 212 outptr = output_data[outrow]; 213 outend = outptr + cinfo->output_width; 214 while (outptr < outend) { 215 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 216 for (h = h_expand; h > 0; h--) { 217 *outptr++ = invalue; 218 } 219 } 220 /* Generate any additional output rows by duplicating the first one */ 221 if (v_expand > 1) { 222 jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 223 v_expand-1, cinfo->output_width); 224 } 225 inrow++; 226 outrow += v_expand; 227 } 228} 229 230 231/* 232 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical. 233 * It's still a box filter. 234 */ 235 236METHODDEF(void) 237h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 238 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 239{ 240 JSAMPARRAY output_data = *output_data_ptr; 241 register JSAMPROW inptr, outptr; 242 register JSAMPLE invalue; 243 JSAMPROW outend; 244 int inrow; 245 246 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) { 247 inptr = input_data[inrow]; 248 outptr = output_data[inrow]; 249 outend = outptr + cinfo->output_width; 250 while (outptr < outend) { 251 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 252 *outptr++ = invalue; 253 *outptr++ = invalue; 254 } 255 } 256} 257 258 259/* 260 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical. 261 * It's still a box filter. 262 */ 263 264METHODDEF(void) 265h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 266 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 267{ 268 JSAMPARRAY output_data = *output_data_ptr; 269 register JSAMPROW inptr, outptr; 270 register JSAMPLE invalue; 271 JSAMPROW outend; 272 int inrow, outrow; 273 274 inrow = outrow = 0; 275 while (outrow < cinfo->max_v_samp_factor) { 276 inptr = input_data[inrow]; 277 outptr = output_data[outrow]; 278 outend = outptr + cinfo->output_width; 279 while (outptr < outend) { 280 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 281 *outptr++ = invalue; 282 *outptr++ = invalue; 283 } 284 jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 285 1, cinfo->output_width); 286 inrow++; 287 outrow += 2; 288 } 289} 290 291 292/* 293 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical. 294 * 295 * The upsampling algorithm is linear interpolation between pixel centers, 296 * also known as a "triangle filter". This is a good compromise between 297 * speed and visual quality. The centers of the output pixels are 1/4 and 3/4 298 * of the way between input pixel centers. 299 * 300 * A note about the "bias" calculations: when rounding fractional values to 301 * integer, we do not want to always round 0.5 up to the next integer. 302 * If we did that, we'd introduce a noticeable bias towards larger values. 303 * Instead, this code is arranged so that 0.5 will be rounded up or down at 304 * alternate pixel locations (a simple ordered dither pattern). 305 */ 306 307METHODDEF(void) 308h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 309 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 310{ 311 JSAMPARRAY output_data = *output_data_ptr; 312 register JSAMPROW inptr, outptr; 313 register int invalue; 314 register JDIMENSION colctr; 315 int inrow; 316 317 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) { 318 inptr = input_data[inrow]; 319 outptr = output_data[inrow]; 320 /* Special case for first column */ 321 invalue = GETJSAMPLE(*inptr++); 322 *outptr++ = (JSAMPLE) invalue; 323 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2); 324 325 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) { 326 /* General case: 3/4 * nearer pixel + 1/4 * further pixel */ 327 invalue = GETJSAMPLE(*inptr++) * 3; 328 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2); 329 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2); 330 } 331 332 /* Special case for last column */ 333 invalue = GETJSAMPLE(*inptr); 334 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2); 335 *outptr++ = (JSAMPLE) invalue; 336 } 337} 338 339 340/* 341 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical. 342 * Again a triangle filter; see comments for h2v1 case, above. 343 * 344 * It is OK for us to reference the adjacent input rows because we demanded 345 * context from the main buffer controller (see initialization code). 346 */ 347 348METHODDEF(void) 349h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 350 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 351{ 352 JSAMPARRAY output_data = *output_data_ptr; 353 register JSAMPROW inptr0, inptr1, outptr; 354#if BITS_IN_JSAMPLE == 8 355 register int thiscolsum, lastcolsum, nextcolsum; 356#else 357 register INT32 thiscolsum, lastcolsum, nextcolsum; 358#endif 359 register JDIMENSION colctr; 360 int inrow, outrow, v; 361 362 inrow = outrow = 0; 363 while (outrow < cinfo->max_v_samp_factor) { 364 for (v = 0; v < 2; v++) { 365 /* inptr0 points to nearest input row, inptr1 points to next nearest */ 366 inptr0 = input_data[inrow]; 367 if (v == 0) /* next nearest is row above */ 368 inptr1 = input_data[inrow-1]; 369 else /* next nearest is row below */ 370 inptr1 = input_data[inrow+1]; 371 outptr = output_data[outrow++]; 372 373 /* Special case for first column */ 374 thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 375 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 376 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4); 377 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4); 378 lastcolsum = thiscolsum; thiscolsum = nextcolsum; 379 380 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) { 381 /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */ 382 /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */ 383 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 384 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4); 385 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4); 386 lastcolsum = thiscolsum; thiscolsum = nextcolsum; 387 } 388 389 /* Special case for last column */ 390 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4); 391 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4); 392 } 393 inrow++; 394 } 395} 396 397 398/* 399 * Module initialization routine for upsampling. 400 */ 401 402GLOBAL(void) 403jinit_upsampler (j_decompress_ptr cinfo) 404{ 405 my_upsample_ptr upsample; 406 int ci; 407 jpeg_component_info * compptr; 408 boolean need_buffer, do_fancy; 409 int h_in_group, v_in_group, h_out_group, v_out_group; 410 411 upsample = (my_upsample_ptr) 412 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 413 SIZEOF(my_upsampler)); 414 cinfo->upsample = (struct jpeg_upsampler *) upsample; 415 upsample->pub.start_pass = start_pass_upsample; 416 upsample->pub.upsample = sep_upsample; 417 upsample->pub.need_context_rows = FALSE; /* until we find out differently */ 418 419 if (cinfo->CCIR601_sampling) /* this isn't supported */ 420 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL); 421 422 /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1, 423 * so don't ask for it. 424 */ 425 do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1; 426 427 /* Verify we can handle the sampling factors, select per-component methods, 428 * and create storage as needed. 429 */ 430 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 431 ci++, compptr++) { 432 /* Compute size of an "input group" after IDCT scaling. This many samples 433 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels. 434 */ 435 h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) / 436 cinfo->min_DCT_scaled_size; 437 v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) / 438 cinfo->min_DCT_scaled_size; 439 h_out_group = cinfo->max_h_samp_factor; 440 v_out_group = cinfo->max_v_samp_factor; 441 upsample->rowgroup_height[ci] = v_in_group; /* save for use later */ 442 need_buffer = TRUE; 443 if (! compptr->component_needed) { 444 /* Don't bother to upsample an uninteresting component. */ 445 upsample->methods[ci] = noop_upsample; 446 need_buffer = FALSE; 447 } else if (h_in_group == h_out_group && v_in_group == v_out_group) { 448 /* Fullsize components can be processed without any work. */ 449 upsample->methods[ci] = fullsize_upsample; 450 need_buffer = FALSE; 451 } else if (h_in_group * 2 == h_out_group && 452 v_in_group == v_out_group) { 453 /* Special cases for 2h1v upsampling */ 454 if (do_fancy && compptr->downsampled_width > 2) 455 upsample->methods[ci] = h2v1_fancy_upsample; 456 else 457 upsample->methods[ci] = h2v1_upsample; 458 } else if (h_in_group * 2 == h_out_group && 459 v_in_group * 2 == v_out_group) { 460 /* Special cases for 2h2v upsampling */ 461 if (do_fancy && compptr->downsampled_width > 2) { 462 upsample->methods[ci] = h2v2_fancy_upsample; 463 upsample->pub.need_context_rows = TRUE; 464 } else 465 upsample->methods[ci] = h2v2_upsample; 466 } else if ((h_out_group % h_in_group) == 0 && 467 (v_out_group % v_in_group) == 0) { 468 /* Generic integral-factors upsampling method */ 469 upsample->methods[ci] = int_upsample; 470 upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group); 471 upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group); 472 } else 473 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL); 474 if (need_buffer) { 475 upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray) 476 ((j_common_ptr) cinfo, JPOOL_IMAGE, 477 (JDIMENSION) jround_up((long) cinfo->output_width, 478 (long) cinfo->max_h_samp_factor), 479 (JDIMENSION) cinfo->max_v_samp_factor); 480 } 481 } 482} 483