src/jpeg/jdsample.c

   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 JPEG_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 }