Doxygen Source Code Documentation
jidctint.c File Reference
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"
Go to the source code of this file.
Defines | |
#define | JPEG_INTERNALS |
#define | CONST_BITS 13 |
#define | PASS1_BITS 2 |
#define | FIX_0_298631336 ((INT32) 2446) |
#define | FIX_0_390180644 ((INT32) 3196) |
#define | FIX_0_541196100 ((INT32) 4433) |
#define | FIX_0_765366865 ((INT32) 6270) |
#define | FIX_0_899976223 ((INT32) 7373) |
#define | FIX_1_175875602 ((INT32) 9633) |
#define | FIX_1_501321110 ((INT32) 12299) |
#define | FIX_1_847759065 ((INT32) 15137) |
#define | FIX_1_961570560 ((INT32) 16069) |
#define | FIX_2_053119869 ((INT32) 16819) |
#define | FIX_2_562915447 ((INT32) 20995) |
#define | FIX_3_072711026 ((INT32) 25172) |
#define | MULTIPLY(var, const) MULTIPLY16C16(var,const) |
#define | DEQUANTIZE(coef, quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval)) |
Functions | |
jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col) |
Define Documentation
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Definition at line 78 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 140 of file jidctint.c. |
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Definition at line 93 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 94 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 95 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 96 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 97 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 98 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 99 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 100 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 101 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 102 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 103 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 104 of file jidctint.c. Referenced by jpeg_idct_islow(). |
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Definition at line 28 of file jidctint.c. |
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Definition at line 129 of file jidctint.c. |
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Definition at line 79 of file jidctint.c. Referenced by jpeg_idct_islow(). |
Function Documentation
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Definition at line 148 of file jidctint.c. References coef_block, compptr, CONST_BITS, jpeg_component_info::dct_table, DEQUANTIZE, DESCALE, FIX_0_298631336, FIX_0_390180644, FIX_0_541196100, FIX_0_765366865, FIX_0_899976223, FIX_1_175875602, FIX_1_501321110, FIX_1_847759065, FIX_1_961570560, FIX_2_053119869, FIX_2_562915447, FIX_3_072711026, IDCT_range_limit, INT32, ISLOW_MULT_TYPE, JCOEFPTR, JDIMENSION, JSAMPARRAY, JSAMPLE, JSAMPROW, MULTIPLY, output_col, PASS1_BITS, RANGE_MASK, and z1. Referenced by start_pass().
00151 { 00152 INT32 tmp0, tmp1, tmp2, tmp3; 00153 INT32 tmp10, tmp11, tmp12, tmp13; 00154 INT32 z1, z2, z3, z4, z5; 00155 JCOEFPTR inptr; 00156 ISLOW_MULT_TYPE * quantptr; 00157 int * wsptr; 00158 JSAMPROW outptr; 00159 JSAMPLE *range_limit = IDCT_range_limit(cinfo); 00160 int ctr; 00161 int workspace[DCTSIZE2]; /* buffers data between passes */ 00162 SHIFT_TEMPS 00163 00164 /* Pass 1: process columns from input, store into work array. */ 00165 /* Note results are scaled up by sqrt(8) compared to a true IDCT; */ 00166 /* furthermore, we scale the results by 2**PASS1_BITS. */ 00167 00168 inptr = coef_block; 00169 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; 00170 wsptr = workspace; 00171 for (ctr = DCTSIZE; ctr > 0; ctr--) { 00172 /* Due to quantization, we will usually find that many of the input 00173 * coefficients are zero, especially the AC terms. We can exploit this 00174 * by short-circuiting the IDCT calculation for any column in which all 00175 * the AC terms are zero. In that case each output is equal to the 00176 * DC coefficient (with scale factor as needed). 00177 * With typical images and quantization tables, half or more of the 00178 * column DCT calculations can be simplified this way. 00179 */ 00180 00181 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && 00182 inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 && 00183 inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 && 00184 inptr[DCTSIZE*7] == 0) { 00185 /* AC terms all zero */ 00186 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS; 00187 00188 wsptr[DCTSIZE*0] = dcval; 00189 wsptr[DCTSIZE*1] = dcval; 00190 wsptr[DCTSIZE*2] = dcval; 00191 wsptr[DCTSIZE*3] = dcval; 00192 wsptr[DCTSIZE*4] = dcval; 00193 wsptr[DCTSIZE*5] = dcval; 00194 wsptr[DCTSIZE*6] = dcval; 00195 wsptr[DCTSIZE*7] = dcval; 00196 00197 inptr++; /* advance pointers to next column */ 00198 quantptr++; 00199 wsptr++; 00200 continue; 00201 } 00202 00203 /* Even part: reverse the even part of the forward DCT. */ 00204 /* The rotator is sqrt(2)*c(-6). */ 00205 00206 z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); 00207 z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); 00208 00209 z1 = MULTIPLY(z2 + z3, FIX_0_541196100); 00210 tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065); 00211 tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865); 00212 00213 z2 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); 00214 z3 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]); 00215 00216 tmp0 = (z2 + z3) << CONST_BITS; 00217 tmp1 = (z2 - z3) << CONST_BITS; 00218 00219 tmp10 = tmp0 + tmp3; 00220 tmp13 = tmp0 - tmp3; 00221 tmp11 = tmp1 + tmp2; 00222 tmp12 = tmp1 - tmp2; 00223 00224 /* Odd part per figure 8; the matrix is unitary and hence its 00225 * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively. 00226 */ 00227 00228 tmp0 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); 00229 tmp1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); 00230 tmp2 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); 00231 tmp3 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); 00232 00233 z1 = tmp0 + tmp3; 00234 z2 = tmp1 + tmp2; 00235 z3 = tmp0 + tmp2; 00236 z4 = tmp1 + tmp3; 00237 z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */ 00238 00239 tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */ 00240 tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */ 00241 tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */ 00242 tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */ 00243 z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */ 00244 z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */ 00245 z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */ 00246 z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */ 00247 00248 z3 += z5; 00249 z4 += z5; 00250 00251 tmp0 += z1 + z3; 00252 tmp1 += z2 + z4; 00253 tmp2 += z2 + z3; 00254 tmp3 += z1 + z4; 00255 00256 /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */ 00257 00258 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS); 00259 wsptr[DCTSIZE*7] = (int) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS); 00260 wsptr[DCTSIZE*1] = (int) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS); 00261 wsptr[DCTSIZE*6] = (int) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS); 00262 wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS); 00263 wsptr[DCTSIZE*5] = (int) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS); 00264 wsptr[DCTSIZE*3] = (int) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS); 00265 wsptr[DCTSIZE*4] = (int) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS); 00266 00267 inptr++; /* advance pointers to next column */ 00268 quantptr++; 00269 wsptr++; 00270 } 00271 00272 /* Pass 2: process rows from work array, store into output array. */ 00273 /* Note that we must descale the results by a factor of 8 == 2**3, */ 00274 /* and also undo the PASS1_BITS scaling. */ 00275 00276 wsptr = workspace; 00277 for (ctr = 0; ctr < DCTSIZE; ctr++) { 00278 outptr = output_buf[ctr] + output_col; 00279 /* Rows of zeroes can be exploited in the same way as we did with columns. 00280 * However, the column calculation has created many nonzero AC terms, so 00281 * the simplification applies less often (typically 5% to 10% of the time). 00282 * On machines with very fast multiplication, it's possible that the 00283 * test takes more time than it's worth. In that case this section 00284 * may be commented out. 00285 */ 00286 00287 #ifndef NO_ZERO_ROW_TEST 00288 if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 && 00289 wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { 00290 /* AC terms all zero */ 00291 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) 00292 & RANGE_MASK]; 00293 00294 outptr[0] = dcval; 00295 outptr[1] = dcval; 00296 outptr[2] = dcval; 00297 outptr[3] = dcval; 00298 outptr[4] = dcval; 00299 outptr[5] = dcval; 00300 outptr[6] = dcval; 00301 outptr[7] = dcval; 00302 00303 wsptr += DCTSIZE; /* advance pointer to next row */ 00304 continue; 00305 } 00306 #endif 00307 00308 /* Even part: reverse the even part of the forward DCT. */ 00309 /* The rotator is sqrt(2)*c(-6). */ 00310 00311 z2 = (INT32) wsptr[2]; 00312 z3 = (INT32) wsptr[6]; 00313 00314 z1 = MULTIPLY(z2 + z3, FIX_0_541196100); 00315 tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065); 00316 tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865); 00317 00318 tmp0 = ((INT32) wsptr[0] + (INT32) wsptr[4]) << CONST_BITS; 00319 tmp1 = ((INT32) wsptr[0] - (INT32) wsptr[4]) << CONST_BITS; 00320 00321 tmp10 = tmp0 + tmp3; 00322 tmp13 = tmp0 - tmp3; 00323 tmp11 = tmp1 + tmp2; 00324 tmp12 = tmp1 - tmp2; 00325 00326 /* Odd part per figure 8; the matrix is unitary and hence its 00327 * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively. 00328 */ 00329 00330 tmp0 = (INT32) wsptr[7]; 00331 tmp1 = (INT32) wsptr[5]; 00332 tmp2 = (INT32) wsptr[3]; 00333 tmp3 = (INT32) wsptr[1]; 00334 00335 z1 = tmp0 + tmp3; 00336 z2 = tmp1 + tmp2; 00337 z3 = tmp0 + tmp2; 00338 z4 = tmp1 + tmp3; 00339 z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */ 00340 00341 tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */ 00342 tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */ 00343 tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */ 00344 tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */ 00345 z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */ 00346 z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */ 00347 z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */ 00348 z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */ 00349 00350 z3 += z5; 00351 z4 += z5; 00352 00353 tmp0 += z1 + z3; 00354 tmp1 += z2 + z4; 00355 tmp2 += z2 + z3; 00356 tmp3 += z1 + z4; 00357 00358 /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */ 00359 00360 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp3, 00361 CONST_BITS+PASS1_BITS+3) 00362 & RANGE_MASK]; 00363 outptr[7] = range_limit[(int) DESCALE(tmp10 - tmp3, 00364 CONST_BITS+PASS1_BITS+3) 00365 & RANGE_MASK]; 00366 outptr[1] = range_limit[(int) DESCALE(tmp11 + tmp2, 00367 CONST_BITS+PASS1_BITS+3) 00368 & RANGE_MASK]; 00369 outptr[6] = range_limit[(int) DESCALE(tmp11 - tmp2, 00370 CONST_BITS+PASS1_BITS+3) 00371 & RANGE_MASK]; 00372 outptr[2] = range_limit[(int) DESCALE(tmp12 + tmp1, 00373 CONST_BITS+PASS1_BITS+3) 00374 & RANGE_MASK]; 00375 outptr[5] = range_limit[(int) DESCALE(tmp12 - tmp1, 00376 CONST_BITS+PASS1_BITS+3) 00377 & RANGE_MASK]; 00378 outptr[3] = range_limit[(int) DESCALE(tmp13 + tmp0, 00379 CONST_BITS+PASS1_BITS+3) 00380 & RANGE_MASK]; 00381 outptr[4] = range_limit[(int) DESCALE(tmp13 - tmp0, 00382 CONST_BITS+PASS1_BITS+3) 00383 & RANGE_MASK]; 00384 00385 wsptr += DCTSIZE; /* advance pointer to next row */ 00386 } 00387 } |