src/jpeg/jcdctmgr.c

   1 /*
   2  * jcdctmgr.c
   3  *
   4  * Copyright (C) 1994-1996, 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 the forward-DCT management logic.
   9  * This code selects a particular DCT implementation to be used,
  10  * and it performs related housekeeping chores including coefficient
  11  * quantization.
  12  */
  13
  14 #define JPEG_INTERNALS
  15 #include "jinclude.h"
  16 #include "jpeglib.h"
  17 #include "jdct.h"               /* Private declarations for DCT subsystem */
  18
  19
  20 /* Private subobject for this module */
  21
  22 typedef struct {
  23   struct jpeg_forward_dct pub;  /* public fields */
  24
  25   /* Pointer to the DCT routine actually in use */
  26   forward_DCT_method_ptr do_dct;
  27
  28   /* The actual post-DCT divisors --- not identical to the quant table
  29    * entries, because of scaling (especially for an unnormalized DCT).
  30    * Each table is given in normal array order.
  31    */
  32   DCTELEM * divisors[NUM_QUANT_TBLS];
  33
  34 #ifdef DCT_FLOAT_SUPPORTED
  35   /* Same as above for the floating-point case. */
  36   float_DCT_method_ptr do_float_dct;
  37   FAST_FLOAT * float_divisors[NUM_QUANT_TBLS];
  38 #endif
  39 } my_fdct_controller;
  40
  41 typedef my_fdct_controller * my_fdct_ptr;
  42
  43
  44 /*
  45  * Initialize for a processing pass.
  46  * Verify that all referenced Q-tables are present, and set up
  47  * the divisor table for each one.
  48  * In the current implementation, DCT of all components is done during
  49  * the first pass, even if only some components will be output in the
  50  * first scan.  Hence all components should be examined here.
  51  */
  52
  53 METHODDEF(void)
  54 start_pass_fdctmgr (j_compress_ptr cinfo)
  55 {
  56   my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
  57   int ci, qtblno, i;
  58   jpeg_component_info *compptr;
  59   JQUANT_TBL * qtbl;
  60   DCTELEM * dtbl;
  61
  62   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
  63        ci++, compptr++) {
  64     qtblno = compptr->quant_tbl_no;
  65     /* Make sure specified quantization table is present */
  66     if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
  67         cinfo->quant_tbl_ptrs[qtblno] == NULL)
  68       ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
  69     qtbl = cinfo->quant_tbl_ptrs[qtblno];
  70     /* Compute divisors for this quant table */
  71     /* We may do this more than once for same table, but it's not a big deal */
  72     switch (cinfo->dct_method) {
  73 #ifdef DCT_ISLOW_SUPPORTED
  74     case JDCT_ISLOW:
  75       /* For LL&M IDCT method, divisors are equal to raw quantization
  76        * coefficients multiplied by 8 (to counteract scaling).
  77        */
  78       if (fdct->divisors[qtblno] == NULL) {
  79         fdct->divisors[qtblno] = (DCTELEM *)
  80           (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  81                                       DCTSIZE2 * SIZEOF(DCTELEM));
  82       }
  83       dtbl = fdct->divisors[qtblno];
  84       for (i = 0; i < DCTSIZE2; i++) {
  85         dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3;
  86       }
  87       break;
  88 #endif
  89 #ifdef DCT_IFAST_SUPPORTED
  90     case JDCT_IFAST:
  91       {
  92         /* For AA&N IDCT method, divisors are equal to quantization
  93          * coefficients scaled by scalefactor[row]*scalefactor[col], where
  94          *   scalefactor[0] = 1
  95          *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
  96          * We apply a further scale factor of 8.
  97          */
  98 #define CONST_BITS 14
  99         static const INT16 aanscales[DCTSIZE2] = {
 100           /* precomputed values scaled up by 14 bits */
 101           16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
 102           22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
 103           21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
 104           19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
 105           16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
 106           12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
 107            8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
 108            4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
 109         };
 110         SHIFT_TEMPS
 111
 112         if (fdct->divisors[qtblno] == NULL) {
 113           fdct->divisors[qtblno] = (DCTELEM *)
 114             (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 115                                         DCTSIZE2 * SIZEOF(DCTELEM));
 116         }
 117         dtbl = fdct->divisors[qtblno];
 118         for (i = 0; i < DCTSIZE2; i++) {
 119           dtbl[i] = (DCTELEM)
 120             DESCALE(MULTIPLY16V16((JPEG_INT32) qtbl->quantval[i],
 121                                   (JPEG_INT32) aanscales[i]),
 122                     CONST_BITS-3);
 123         }
 124       }
 125       break;
 126 #endif
 127 #ifdef DCT_FLOAT_SUPPORTED
 128     case JDCT_FLOAT:
 129       {
 130         /* For float AA&N IDCT method, divisors are equal to quantization
 131          * coefficients scaled by scalefactor[row]*scalefactor[col], where
 132          *   scalefactor[0] = 1
 133          *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
 134          * We apply a further scale factor of 8.
 135          * What's actually stored is 1/divisor so that the inner loop can
 136          * use a multiplication rather than a division.
 137          */
 138         FAST_FLOAT * fdtbl;
 139         int row, col;
 140         static const double aanscalefactor[DCTSIZE] = {
 141           1.0, 1.387039845, 1.306562965, 1.175875602,
 142           1.0, 0.785694958, 0.541196100, 0.275899379
 143         };
 144
 145         if (fdct->float_divisors[qtblno] == NULL) {
 146           fdct->float_divisors[qtblno] = (FAST_FLOAT *)
 147             (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 148                                         DCTSIZE2 * SIZEOF(FAST_FLOAT));
 149         }
 150         fdtbl = fdct->float_divisors[qtblno];
 151         i = 0;
 152         for (row = 0; row < DCTSIZE; row++) {
 153           for (col = 0; col < DCTSIZE; col++) {
 154             fdtbl[i] = (FAST_FLOAT)
 155               (1.0 / (((double) qtbl->quantval[i] *
 156                        aanscalefactor[row] * aanscalefactor[col] * 8.0)));
 157             i++;
 158           }
 159         }
 160       }
 161       break;
 162 #endif
 163     default:
 164       ERREXIT(cinfo, JERR_NOT_COMPILED);
 165       break;
 166     }
 167   }
 168 }
 169
 170
 171 /*
 172  * Perform forward DCT on one or more blocks of a component.
 173  *
 174  * The input samples are taken from the sample_data[] array starting at
 175  * position start_row/start_col, and moving to the right for any additional
 176  * blocks. The quantized coefficients are returned in coef_blocks[].
 177  */
 178
 179 METHODDEF(void)
 180 forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr,
 181              JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
 182              JDIMENSION start_row, JDIMENSION start_col,
 183              JDIMENSION num_blocks)
 184 /* This version is used for integer DCT implementations. */
 185 {
 186   /* This routine is heavily used, so it's worth coding it tightly. */
 187   my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
 188   forward_DCT_method_ptr do_dct = fdct->do_dct;
 189   DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
 190   DCTELEM workspace[DCTSIZE2];  /* work area for FDCT subroutine */
 191   JDIMENSION bi;
 192
 193   sample_data += start_row;     /* fold in the vertical offset once */
 194
 195   for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
 196     /* Load data into workspace, applying unsigned->signed conversion */
 197     { register DCTELEM *workspaceptr;
 198       register JSAMPROW elemptr;
 199       register int elemr;
 200
 201       workspaceptr = workspace;
 202       for (elemr = 0; elemr < DCTSIZE; elemr++) {
 203         elemptr = sample_data[elemr] + start_col;
 204 #if DCTSIZE == 8                /* unroll the inner loop */
 205         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 206         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 207         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 208         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 209         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 210         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 211         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 212         *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 213 #else
 214         { register int elemc;
 215           for (elemc = DCTSIZE; elemc > 0; elemc--) {
 216             *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 217           }
 218         }
 219 #endif
 220       }
 221     }
 222
 223     /* Perform the DCT */
 224     (*do_dct) (workspace);
 225
 226     /* Quantize/descale the coefficients, and store into coef_blocks[] */
 227     { register DCTELEM temp, qval;
 228       register int i;
 229       register JCOEFPTR output_ptr = coef_blocks[bi];
 230
 231       for (i = 0; i < DCTSIZE2; i++) {
 232         qval = divisors[i];
 233         temp = workspace[i];
 234         /* Divide the coefficient value by qval, ensuring proper rounding.
 235          * Since C does not specify the direction of rounding for negative
 236          * quotients, we have to force the dividend positive for portability.
 237          *
 238          * In most files, at least half of the output values will be zero
 239          * (at default quantization settings, more like three-quarters...)
 240          * so we should ensure that this case is fast.  On many machines,
 241          * a comparison is enough cheaper than a divide to make a special test
 242          * a win.  Since both inputs will be nonnegative, we need only test
 243          * for a < b to discover whether a/b is 0.
 244          * If your machine's division is fast enough, define FAST_DIVIDE.
 245          */
 246 #ifdef FAST_DIVIDE
 247 #define DIVIDE_BY(a,b)  a /= b
 248 #else
 249 #define DIVIDE_BY(a,b)  if (a >= b) a /= b; else a = 0
 250 #endif
 251         if (temp < 0) {
 252           temp = -temp;
 253           temp += qval>>1;      /* for rounding */
 254           DIVIDE_BY(temp, qval);
 255           temp = -temp;
 256         } else {
 257           temp += qval>>1;      /* for rounding */
 258           DIVIDE_BY(temp, qval);
 259         }
 260         output_ptr[i] = (JCOEF) temp;
 261       }
 262     }
 263   }
 264 }
 265
 266
 267 #ifdef DCT_FLOAT_SUPPORTED
 268
 269 METHODDEF(void)
 270 forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr,
 271                    JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
 272                    JDIMENSION start_row, JDIMENSION start_col,
 273                    JDIMENSION num_blocks)
 274 /* This version is used for floating-point DCT implementations. */
 275 {
 276   /* This routine is heavily used, so it's worth coding it tightly. */
 277   my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
 278   float_DCT_method_ptr do_dct = fdct->do_float_dct;
 279   FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
 280   FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */
 281   JDIMENSION bi;
 282
 283   sample_data += start_row;     /* fold in the vertical offset once */
 284
 285   for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
 286     /* Load data into workspace, applying unsigned->signed conversion */
 287     { register FAST_FLOAT *workspaceptr;
 288       register JSAMPROW elemptr;
 289       register int elemr;
 290
 291       workspaceptr = workspace;
 292       for (elemr = 0; elemr < DCTSIZE; elemr++) {
 293         elemptr = sample_data[elemr] + start_col;
 294 #if DCTSIZE == 8                /* unroll the inner loop */
 295         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 296         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 297         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 298         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 299         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 300         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 301         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 302         *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 303 #else
 304         { register int elemc;
 305           for (elemc = DCTSIZE; elemc > 0; elemc--) {
 306             *workspaceptr++ = (FAST_FLOAT)
 307               (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 308           }
 309         }
 310 #endif
 311       }
 312     }
 313
 314     /* Perform the DCT */
 315     (*do_dct) (workspace);
 316
 317     /* Quantize/descale the coefficients, and store into coef_blocks[] */
 318     { register FAST_FLOAT temp;
 319       register int i;
 320       register JCOEFPTR output_ptr = coef_blocks[bi];
 321
 322       for (i = 0; i < DCTSIZE2; i++) {
 323         /* Apply the quantization and scaling factor */
 324         temp = workspace[i] * divisors[i];
 325         /* Round to nearest integer.
 326          * Since C does not specify the direction of rounding for negative
 327          * quotients, we have to force the dividend positive for portability.
 328          * The maximum coefficient size is +-16K (for 12-bit data), so this
 329          * code should work for either 16-bit or 32-bit ints.
 330          */
 331         output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384);
 332       }
 333     }
 334   }
 335 }
 336
 337 #endif /* DCT_FLOAT_SUPPORTED */
 338
 339
 340 /*
 341  * Initialize FDCT manager.
 342  */
 343
 344 GLOBAL(void)
 345 jinit_forward_dct (j_compress_ptr cinfo)
 346 {
 347   my_fdct_ptr fdct;
 348   int i;
 349
 350   fdct = (my_fdct_ptr)
 351     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 352                                 SIZEOF(my_fdct_controller));
 353   cinfo->fdct = (struct jpeg_forward_dct *) fdct;
 354   fdct->pub.start_pass = start_pass_fdctmgr;
 355
 356   switch (cinfo->dct_method) {
 357 #ifdef DCT_ISLOW_SUPPORTED
 358   case JDCT_ISLOW:
 359     fdct->pub.forward_DCT = forward_DCT;
 360     fdct->do_dct = jpeg_fdct_islow;
 361     break;
 362 #endif
 363 #ifdef DCT_IFAST_SUPPORTED
 364   case JDCT_IFAST:
 365     fdct->pub.forward_DCT = forward_DCT;
 366     fdct->do_dct = jpeg_fdct_ifast;
 367     break;
 368 #endif
 369 #ifdef DCT_FLOAT_SUPPORTED
 370   case JDCT_FLOAT:
 371     fdct->pub.forward_DCT = forward_DCT_float;
 372     fdct->do_float_dct = jpeg_fdct_float;
 373     break;
 374 #endif
 375   default:
 376     ERREXIT(cinfo, JERR_NOT_COMPILED);
 377     break;
 378   }
 379
 380   /* Mark divisor tables unallocated */
 381   for (i = 0; i < NUM_QUANT_TBLS; i++) {
 382     fdct->divisors[i] = NULL;
 383 #ifdef DCT_FLOAT_SUPPORTED
 384     fdct->float_divisors[i] = NULL;
 385 #endif
 386   }
 387 }