jdsample.cpp (18363B)
1 /* 2 * jdsample.c 3 * 4 * Copyright (C) 1991-1994, 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 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 71 72 /* Mark the conversion buffer empty */ 73 upsample->next_row_out = cinfo->max_v_samp_factor; 74 /* Initialize total-height counter for detecting bottom of image */ 75 upsample->rows_to_go = cinfo->output_height; 76 } 77 78 79 /* 80 * Control routine to do upsampling (and color conversion). 81 * 82 * In this version we upsample each component independently. 83 * We upsample one row group into the conversion buffer, then apply 84 * color conversion a row at a time. 85 */ 86 87 METHODDEF void 88 sep_upsample( j_decompress_ptr cinfo, 89 JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr, 90 JDIMENSION in_row_groups_avail, 91 JSAMPARRAY output_buf, JDIMENSION * out_row_ctr, 92 JDIMENSION out_rows_avail ) { 93 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 94 int ci; 95 jpeg_component_info * compptr; 96 JDIMENSION num_rows; 97 98 /* Fill the conversion buffer, if it's empty */ 99 if ( upsample->next_row_out >= cinfo->max_v_samp_factor ) { 100 for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 101 ci++, compptr++ ) { 102 /* Invoke per-component upsample method. Notice we pass a POINTER 103 * to color_buf[ci], so that fullsize_upsample can change it. 104 */ 105 ( *upsample->methods[ci] )( cinfo, compptr, 106 input_buf[ci] + ( *in_row_group_ctr * upsample->rowgroup_height[ci] ), 107 upsample->color_buf + ci ); 108 } 109 upsample->next_row_out = 0; 110 } 111 112 /* Color-convert and emit rows */ 113 114 /* How many we have in the buffer: */ 115 num_rows = (JDIMENSION) ( cinfo->max_v_samp_factor - upsample->next_row_out ); 116 /* Not more than the distance to the end of the image. Need this test 117 * in case the image height is not a multiple of max_v_samp_factor: 118 */ 119 if ( num_rows > upsample->rows_to_go ) { 120 num_rows = upsample->rows_to_go; 121 } 122 /* And not more than what the client can accept: */ 123 out_rows_avail -= *out_row_ctr; 124 if ( num_rows > out_rows_avail ) { 125 num_rows = out_rows_avail; 126 } 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 /* 145 * These are the routines invoked by sep_upsample to upsample pixel values 146 * of a single component. One row group is processed per call. 147 */ 148 149 150 /* 151 * For full-size components, we just make color_buf[ci] point at the 152 * input buffer, and thus avoid copying any data. Note that this is 153 * safe only because sep_upsample doesn't declare the input row group 154 * "consumed" until we are done color converting and emitting it. 155 */ 156 157 METHODDEF void 158 fullsize_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr, 159 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) { 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 *output_data_ptr = NULL;/* safety check */ 173 } 174 175 176 /* 177 * This version handles any integral sampling ratios. 178 * This is not used for typical JPEG files, so it need not be fast. 179 * Nor, for that matter, is it particularly accurate: the algorithm is 180 * simple replication of the input pixel onto the corresponding output 181 * pixels. The hi-falutin sampling literature refers to this as a 182 * "box filter". A box filter tends to introduce visible artifacts, 183 * so if you are actually going to use 3:1 or 4:1 sampling ratios 184 * you would be well advised to improve this code. 185 */ 186 187 METHODDEF void 188 int_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr, 189 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) { 190 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 191 JSAMPARRAY output_data = *output_data_ptr; 192 register JSAMPROW inptr, outptr; 193 register JSAMPLE invalue; 194 register int h; 195 JSAMPROW outend; 196 int h_expand, v_expand; 197 int inrow, outrow; 198 199 h_expand = upsample->h_expand[compptr->component_index]; 200 v_expand = upsample->v_expand[compptr->component_index]; 201 202 inrow = outrow = 0; 203 while ( outrow < cinfo->max_v_samp_factor ) { 204 /* Generate one output row with proper horizontal expansion */ 205 inptr = input_data[inrow]; 206 outptr = output_data[outrow]; 207 outend = outptr + cinfo->output_width; 208 while ( outptr < outend ) { 209 invalue = *inptr++;/* don't need GETJSAMPLE() here */ 210 for ( h = h_expand; h > 0; h-- ) { 211 *outptr++ = invalue; 212 } 213 } 214 /* Generate any additional output rows by duplicating the first one */ 215 if ( v_expand > 1 ) { 216 jcopy_sample_rows( output_data, outrow, output_data, outrow + 1, 217 v_expand - 1, cinfo->output_width ); 218 } 219 inrow++; 220 outrow += v_expand; 221 } 222 } 223 224 225 /* 226 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical. 227 * It's still a box filter. 228 */ 229 230 METHODDEF void 231 h2v1_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr, 232 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) { 233 JSAMPARRAY output_data = *output_data_ptr; 234 register JSAMPROW inptr, outptr; 235 register JSAMPLE invalue; 236 JSAMPROW outend; 237 int inrow; 238 239 for ( inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++ ) { 240 inptr = input_data[inrow]; 241 outptr = output_data[inrow]; 242 outend = outptr + cinfo->output_width; 243 while ( outptr < outend ) { 244 invalue = *inptr++;/* don't need GETJSAMPLE() here */ 245 *outptr++ = invalue; 246 *outptr++ = invalue; 247 } 248 } 249 } 250 251 252 /* 253 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical. 254 * It's still a box filter. 255 */ 256 257 METHODDEF void 258 h2v2_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr, 259 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) { 260 JSAMPARRAY output_data = *output_data_ptr; 261 register JSAMPROW inptr, outptr; 262 register JSAMPLE invalue; 263 JSAMPROW outend; 264 int inrow, outrow; 265 266 inrow = outrow = 0; 267 while ( outrow < cinfo->max_v_samp_factor ) { 268 inptr = input_data[inrow]; 269 outptr = output_data[outrow]; 270 outend = outptr + cinfo->output_width; 271 while ( outptr < outend ) { 272 invalue = *inptr++;/* don't need GETJSAMPLE() here */ 273 *outptr++ = invalue; 274 *outptr++ = invalue; 275 } 276 jcopy_sample_rows( output_data, outrow, output_data, outrow + 1, 277 1, cinfo->output_width ); 278 inrow++; 279 outrow += 2; 280 } 281 } 282 283 284 /* 285 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical. 286 * 287 * The upsampling algorithm is linear interpolation between pixel centers, 288 * also known as a "triangle filter". This is a good compromise between 289 * speed and visual quality. The centers of the output pixels are 1/4 and 3/4 290 * of the way between input pixel centers. 291 * 292 * A note about the "bias" calculations: when rounding fractional values to 293 * integer, we do not want to always round 0.5 up to the next integer. 294 * If we did that, we'd introduce a noticeable bias towards larger values. 295 * Instead, this code is arranged so that 0.5 will be rounded up or down at 296 * alternate pixel locations (a simple ordered dither pattern). 297 */ 298 299 METHODDEF void 300 h2v1_fancy_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr, 301 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) { 302 JSAMPARRAY output_data = *output_data_ptr; 303 register JSAMPROW inptr, outptr; 304 register int invalue; 305 register JDIMENSION colctr; 306 int inrow; 307 308 for ( inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++ ) { 309 inptr = input_data[inrow]; 310 outptr = output_data[inrow]; 311 /* Special case for first column */ 312 invalue = GETJSAMPLE( *inptr++ ); 313 *outptr++ = (JSAMPLE) invalue; 314 *outptr++ = (JSAMPLE) ( ( invalue * 3 + GETJSAMPLE( *inptr ) + 2 ) >> 2 ); 315 316 for ( colctr = compptr->downsampled_width - 2; colctr > 0; colctr-- ) { 317 /* General case: 3/4 * nearer pixel + 1/4 * further pixel */ 318 invalue = GETJSAMPLE( *inptr++ ) * 3; 319 *outptr++ = (JSAMPLE) ( ( invalue + GETJSAMPLE( inptr[-2] ) + 1 ) >> 2 ); 320 *outptr++ = (JSAMPLE) ( ( invalue + GETJSAMPLE( *inptr ) + 2 ) >> 2 ); 321 } 322 323 /* Special case for last column */ 324 invalue = GETJSAMPLE( *inptr ); 325 *outptr++ = (JSAMPLE) ( ( invalue * 3 + GETJSAMPLE( inptr[-1] ) + 1 ) >> 2 ); 326 *outptr++ = (JSAMPLE) invalue; 327 } 328 } 329 330 331 /* 332 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical. 333 * Again a triangle filter; see comments for h2v1 case, above. 334 * 335 * It is OK for us to reference the adjacent input rows because we demanded 336 * context from the main buffer controller (see initialization code). 337 */ 338 339 METHODDEF void 340 h2v2_fancy_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr, 341 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) { 342 JSAMPARRAY output_data = *output_data_ptr; 343 register JSAMPROW inptr0, inptr1, outptr; 344 #if BITS_IN_JSAMPLE == 8 345 register int thiscolsum, lastcolsum, nextcolsum; 346 #else 347 register INT32 thiscolsum, lastcolsum, nextcolsum; 348 #endif 349 register JDIMENSION colctr; 350 int inrow, outrow, v; 351 352 inrow = outrow = 0; 353 while ( outrow < cinfo->max_v_samp_factor ) { 354 for ( v = 0; v < 2; v++ ) { 355 /* inptr0 points to nearest input row, inptr1 points to next nearest */ 356 inptr0 = input_data[inrow]; 357 if ( v == 0 ) {/* next nearest is row above */ 358 inptr1 = input_data[inrow - 1]; 359 } else {/* next nearest is row below */ 360 inptr1 = input_data[inrow + 1]; 361 } 362 outptr = output_data[outrow++]; 363 364 /* Special case for first column */ 365 thiscolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ ); 366 nextcolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ ); 367 *outptr++ = (JSAMPLE) ( ( thiscolsum * 4 + 8 ) >> 4 ); 368 *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + nextcolsum + 7 ) >> 4 ); 369 lastcolsum = thiscolsum; 370 thiscolsum = nextcolsum; 371 372 for ( colctr = compptr->downsampled_width - 2; colctr > 0; colctr-- ) { 373 /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */ 374 /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */ 375 nextcolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ ); 376 *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + lastcolsum + 8 ) >> 4 ); 377 *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + nextcolsum + 7 ) >> 4 ); 378 lastcolsum = thiscolsum; 379 thiscolsum = nextcolsum; 380 } 381 382 /* Special case for last column */ 383 *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + lastcolsum + 8 ) >> 4 ); 384 *outptr++ = (JSAMPLE) ( ( thiscolsum * 4 + 7 ) >> 4 ); 385 } 386 inrow++; 387 } 388 } 389 390 391 /* 392 * Module initialization routine for upsampling. 393 */ 394 395 GLOBAL void 396 jinit_upsampler( j_decompress_ptr cinfo ) { 397 my_upsample_ptr upsample; 398 int ci; 399 jpeg_component_info * compptr; 400 boolean need_buffer, do_fancy; 401 int h_in_group, v_in_group, h_out_group, v_out_group; 402 403 upsample = (my_upsample_ptr) 404 ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE, 405 SIZEOF( my_upsampler ) ); 406 cinfo->upsample = (struct jpeg_upsampler *) upsample; 407 upsample->pub.start_pass = start_pass_upsample; 408 upsample->pub.upsample = sep_upsample; 409 upsample->pub.need_context_rows = FALSE;/* until we find out differently */ 410 411 if ( cinfo->CCIR601_sampling ) {/* this isn't supported */ 412 ERREXIT( cinfo, JERR_CCIR601_NOTIMPL ); 413 } 414 415 /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1, 416 * so don't ask for it. 417 */ 418 do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1; 419 420 /* Verify we can handle the sampling factors, select per-component methods, 421 * and create storage as needed. 422 */ 423 for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 424 ci++, compptr++ ) { 425 /* Compute size of an "input group" after IDCT scaling. This many samples 426 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels. 427 */ 428 h_in_group = ( compptr->h_samp_factor * compptr->DCT_scaled_size ) / 429 cinfo->min_DCT_scaled_size; 430 v_in_group = ( compptr->v_samp_factor * compptr->DCT_scaled_size ) / 431 cinfo->min_DCT_scaled_size; 432 h_out_group = cinfo->max_h_samp_factor; 433 v_out_group = cinfo->max_v_samp_factor; 434 upsample->rowgroup_height[ci] = v_in_group;/* save for use later */ 435 need_buffer = TRUE; 436 if ( !compptr->component_needed ) { 437 /* Don't bother to upsample an uninteresting component. */ 438 upsample->methods[ci] = noop_upsample; 439 need_buffer = FALSE; 440 } else if ( h_in_group == h_out_group && v_in_group == v_out_group ) { 441 /* Fullsize components can be processed without any work. */ 442 upsample->methods[ci] = fullsize_upsample; 443 need_buffer = FALSE; 444 } else if ( h_in_group * 2 == h_out_group && 445 v_in_group == v_out_group ) { 446 /* Special cases for 2h1v upsampling */ 447 if ( ( do_fancy ) && ( compptr->downsampled_width > 2 ) ) { 448 upsample->methods[ci] = h2v1_fancy_upsample; 449 } else { 450 upsample->methods[ci] = h2v1_upsample; 451 } 452 } else if ( h_in_group * 2 == h_out_group && 453 v_in_group * 2 == v_out_group ) { 454 /* Special cases for 2h2v upsampling */ 455 if ( ( do_fancy ) && ( compptr->downsampled_width > 2 ) ) { 456 upsample->methods[ci] = h2v2_fancy_upsample; 457 upsample->pub.need_context_rows = TRUE; 458 } else { 459 upsample->methods[ci] = h2v2_upsample; 460 } 461 } else if ( ( h_out_group % h_in_group ) == 0 && 462 ( v_out_group % v_in_group ) == 0 ) { 463 /* Generic integral-factors upsampling method */ 464 upsample->methods[ci] = int_upsample; 465 upsample->h_expand[ci] = (UINT8) ( h_out_group / h_in_group ); 466 upsample->v_expand[ci] = (UINT8) ( v_out_group / v_in_group ); 467 } else { 468 ERREXIT( cinfo, JERR_FRACT_SAMPLE_NOTIMPL ); 469 } 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 }