1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387
|
/*
* jcdctmgr.c
*
* Copyright (C) 1994-1996, Thomas G. Lane.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains the forward-DCT management logic.
* This code selects a particular DCT implementation to be used,
* and it performs related housekeeping chores including coefficient
* quantization.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h" /* Private declarations for DCT subsystem */
/* Private subobject for this module */
typedef struct {
struct jpeg_forward_dct pub; /* public fields */
/* Pointer to the DCT routine actually in use */
forward_DCT_method_ptr do_dct;
/* The actual post-DCT divisors --- not identical to the quant table
* entries, because of scaling (especially for an unnormalized DCT).
* Each table is given in normal array order.
*/
DCTELEM * divisors[NUM_QUANT_TBLS];
#ifdef DCT_FLOAT_SUPPORTED
/* Same as above for the floating-point case. */
float_DCT_method_ptr do_float_dct;
FAST_FLOAT * float_divisors[NUM_QUANT_TBLS];
#endif
} my_fdct_controller;
typedef my_fdct_controller * my_fdct_ptr;
/*
* Initialize for a processing pass.
* Verify that all referenced Q-tables are present, and set up
* the divisor table for each one.
* In the current implementation, DCT of all components is done during
* the first pass, even if only some components will be output in the
* first scan. Hence all components should be examined here.
*/
METHODDEF(void)
start_pass_fdctmgr (j_compress_ptr cinfo)
{
my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
int ci, qtblno, i;
jpeg_component_info *compptr;
JQUANT_TBL * qtbl;
DCTELEM * dtbl;
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
qtblno = compptr->quant_tbl_no;
/* Make sure specified quantization table is present */
if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
cinfo->quant_tbl_ptrs[qtblno] == NULL)
ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
qtbl = cinfo->quant_tbl_ptrs[qtblno];
/* Compute divisors for this quant table */
/* We may do this more than once for same table, but it's not a big deal */
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
/* For LL&M IDCT method, divisors are equal to raw quantization
* coefficients multiplied by 8 (to counteract scaling).
*/
if (fdct->divisors[qtblno] == NULL) {
fdct->divisors[qtblno] = (DCTELEM *)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
DCTSIZE2 * SIZEOF(DCTELEM));
}
dtbl = fdct->divisors[qtblno];
for (i = 0; i < DCTSIZE2; i++) {
dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3;
}
break;
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
{
/* For AA&N IDCT method, divisors are equal to quantization
* coefficients scaled by scalefactor[row]*scalefactor[col], where
* scalefactor[0] = 1
* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
* We apply a further scale factor of 8.
*/
#define CONST_BITS 14
static const INT16 aanscales[DCTSIZE2] = {
/* precomputed values scaled up by 14 bits */
16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
};
SHIFT_TEMPS
if (fdct->divisors[qtblno] == NULL) {
fdct->divisors[qtblno] = (DCTELEM *)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
DCTSIZE2 * SIZEOF(DCTELEM));
}
dtbl = fdct->divisors[qtblno];
for (i = 0; i < DCTSIZE2; i++) {
dtbl[i] = (DCTELEM)
DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
(INT32) aanscales[i]),
CONST_BITS-3);
}
}
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
{
/* For float AA&N IDCT method, divisors are equal to quantization
* coefficients scaled by scalefactor[row]*scalefactor[col], where
* scalefactor[0] = 1
* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
* We apply a further scale factor of 8.
* What's actually stored is 1/divisor so that the inner loop can
* use a multiplication rather than a division.
*/
FAST_FLOAT * fdtbl;
int row, col;
static const double aanscalefactor[DCTSIZE] = {
1.0, 1.387039845, 1.306562965, 1.175875602,
1.0, 0.785694958, 0.541196100, 0.275899379
};
if (fdct->float_divisors[qtblno] == NULL) {
fdct->float_divisors[qtblno] = (FAST_FLOAT *)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
DCTSIZE2 * SIZEOF(FAST_FLOAT));
}
fdtbl = fdct->float_divisors[qtblno];
i = 0;
for (row = 0; row < DCTSIZE; row++) {
for (col = 0; col < DCTSIZE; col++) {
fdtbl[i] = (FAST_FLOAT)
(1.0 / (((double) qtbl->quantval[i] *
aanscalefactor[row] * aanscalefactor[col] * 8.0)));
i++;
}
}
}
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
}
}
/*
* Perform forward DCT on one or more blocks of a component.
*
* The input samples are taken from the sample_data[] array starting at
* position start_row/start_col, and moving to the right for any additional
* blocks. The quantized coefficients are returned in coef_blocks[].
*/
METHODDEF(void)
forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr,
JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
JDIMENSION start_row, JDIMENSION start_col,
JDIMENSION num_blocks)
/* This version is used for integer DCT implementations. */
{
/* This routine is heavily used, so it's worth coding it tightly. */
my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
forward_DCT_method_ptr do_dct = fdct->do_dct;
DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
DCTELEM workspace[DCTSIZE2]; /* work area for FDCT subroutine */
JDIMENSION bi;
sample_data += start_row; /* fold in the vertical offset once */
for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
/* Load data into workspace, applying unsigned->signed conversion */
{ register DCTELEM *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
#else
{ register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--) {
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
}
}
#endif
}
}
/* Perform the DCT */
(*do_dct) (workspace);
/* Quantize/descale the coefficients, and store into coef_blocks[] */
{ register DCTELEM temp, qval;
register int i;
register JCOEFPTR output_ptr = coef_blocks[bi];
for (i = 0; i < DCTSIZE2; i++) {
qval = divisors[i];
temp = workspace[i];
/* Divide the coefficient value by qval, ensuring proper rounding.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
*
* In most files, at least half of the output values will be zero
* (at default quantization settings, more like three-quarters...)
* so we should ensure that this case is fast. On many machines,
* a comparison is enough cheaper than a divide to make a special test
* a win. Since both inputs will be nonnegative, we need only test
* for a < b to discover whether a/b is 0.
* If your machine's division is fast enough, define FAST_DIVIDE.
*/
#ifdef FAST_DIVIDE
#define DIVIDE_BY(a,b) a /= b
#else
#define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0
#endif
if (temp < 0) {
temp = -temp;
temp += qval>>1; /* for rounding */
DIVIDE_BY(temp, qval);
temp = -temp;
} else {
temp += qval>>1; /* for rounding */
DIVIDE_BY(temp, qval);
}
output_ptr[i] = (JCOEF) temp;
}
}
}
}
#ifdef DCT_FLOAT_SUPPORTED
METHODDEF(void)
forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr,
JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
JDIMENSION start_row, JDIMENSION start_col,
JDIMENSION num_blocks)
/* This version is used for floating-point DCT implementations. */
{
/* This routine is heavily used, so it's worth coding it tightly. */
my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
float_DCT_method_ptr do_dct = fdct->do_float_dct;
FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */
JDIMENSION bi;
sample_data += start_row; /* fold in the vertical offset once */
for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
/* Load data into workspace, applying unsigned->signed conversion */
{ register FAST_FLOAT *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
#else
{ register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--) {
*workspaceptr++ = (FAST_FLOAT)
(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
}
}
#endif
}
}
/* Perform the DCT */
(*do_dct) (workspace);
/* Quantize/descale the coefficients, and store into coef_blocks[] */
{ register FAST_FLOAT temp;
register int i;
register JCOEFPTR output_ptr = coef_blocks[bi];
for (i = 0; i < DCTSIZE2; i++) {
/* Apply the quantization and scaling factor */
temp = workspace[i] * divisors[i];
/* Round to nearest integer.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
* The maximum coefficient size is +-16K (for 12-bit data), so this
* code should work for either 16-bit or 32-bit ints.
*/
output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384);
}
}
}
}
#endif /* DCT_FLOAT_SUPPORTED */
/*
* Initialize FDCT manager.
*/
GLOBAL(void)
jinit_forward_dct (j_compress_ptr cinfo)
{
my_fdct_ptr fdct;
int i;
fdct = (my_fdct_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
SIZEOF(my_fdct_controller));
cinfo->fdct = (struct jpeg_forward_dct *) fdct;
fdct->pub.start_pass = start_pass_fdctmgr;
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
fdct->pub.forward_DCT = forward_DCT;
fdct->do_dct = jpeg_fdct_islow;
break;
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
fdct->pub.forward_DCT = forward_DCT;
fdct->do_dct = jpeg_fdct_ifast;
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
fdct->pub.forward_DCT = forward_DCT_float;
fdct->do_float_dct = jpeg_fdct_float;
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
/* Mark divisor tables unallocated */
for (i = 0; i < NUM_QUANT_TBLS; i++) {
fdct->divisors[i] = NULL;
#ifdef DCT_FLOAT_SUPPORTED
fdct->float_divisors[i] = NULL;
#endif
}
}
|