* jidctfst.c
*
* Copyright (C) 1994-1998, Thomas G. Lane.
+ * Modified 2015 by Guido Vollbeding.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
#endif
-/* Like DESCALE, but applies to a DCTELEM and produces an int.
- * We assume that int right shift is unsigned if INT32 right shift is.
- */
-
-#ifdef RIGHT_SHIFT_IS_UNSIGNED
-#define ISHIFT_TEMPS DCTELEM ishift_temp;
-#if BITS_IN_JSAMPLE == 8
-#define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */
-#else
-#define DCTELEMBITS 32 /* DCTELEM must be 32 bits */
-#endif
-#define IRIGHT_SHIFT(x,shft) \
- ((ishift_temp = (x)) < 0 ? \
- (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \
- (ishift_temp >> (shft)))
-#else
-#define ISHIFT_TEMPS
-#define IRIGHT_SHIFT(x,shft) ((x) >> (shft))
-#endif
-
-#ifdef USE_ACCURATE_ROUNDING
-#define IDESCALE(x,n) ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n))
-#else
-#define IDESCALE(x,n) ((int) IRIGHT_SHIFT(x, n))
-#endif
-
-
/*
* Perform dequantization and inverse DCT on one block of coefficients.
+ *
+ * cK represents cos(K*pi/16).
*/
GLOBAL(void)
int ctr;
int workspace[DCTSIZE2]; /* buffers data between passes */
SHIFT_TEMPS /* for DESCALE */
- ISHIFT_TEMPS /* for IDESCALE */
+ ISHIFT_TEMPS /* for IRIGHT_SHIFT */
/* Pass 1: process columns from input, store into work array. */
tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
- tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
- tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
+ tmp10 = z5 - MULTIPLY(z12, FIX_1_082392200); /* 2*(c2-c6) */
+ tmp12 = z5 - MULTIPLY(z10, FIX_2_613125930); /* 2*(c2+c6) */
tmp6 = tmp12 - tmp7; /* phase 2 */
tmp5 = tmp11 - tmp6;
- tmp4 = tmp10 + tmp5;
+ tmp4 = tmp10 - tmp5;
wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7);
wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7);
wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6);
wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5);
wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5);
- wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4);
- wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4);
+ wsptr[DCTSIZE*3] = (int) (tmp3 + tmp4);
+ wsptr[DCTSIZE*4] = (int) (tmp3 - tmp4);
inptr++; /* advance pointers to next column */
quantptr++;
wsptr++;
}
- /* Pass 2: process rows from work array, store into output array. */
- /* Note that we must descale the results by a factor of 8 == 2**3, */
- /* and also undo the PASS1_BITS scaling. */
+ /* Pass 2: process rows from work array, store into output array.
+ * Note that we must descale the results by a factor of 8 == 2**3,
+ * and also undo the PASS1_BITS scaling.
+ */
wsptr = workspace;
for (ctr = 0; ctr < DCTSIZE; ctr++) {
outptr = output_buf[ctr] + output_col;
+
+ /* Add range center and fudge factor for final descale and range-limit. */
+ z5 = (DCTELEM) wsptr[0] +
+ ((((DCTELEM) RANGE_CENTER) << (PASS1_BITS+3)) +
+ (1 << (PASS1_BITS+2)));
+
/* Rows of zeroes can be exploited in the same way as we did with columns.
* However, the column calculation has created many nonzero AC terms, so
* the simplification applies less often (typically 5% to 10% of the time).
if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
/* AC terms all zero */
- JSAMPLE dcval = range_limit[IDESCALE(wsptr[0], PASS1_BITS+3)
+ JSAMPLE dcval = range_limit[(int) IRIGHT_SHIFT(z5, PASS1_BITS+3)
& RANGE_MASK];
outptr[0] = dcval;
/* Even part */
- tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]);
- tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]);
+ tmp10 = z5 + (DCTELEM) wsptr[4];
+ tmp11 = z5 - (DCTELEM) wsptr[4];
- tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]);
- tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562)
- - tmp13;
+ tmp13 = (DCTELEM) wsptr[2] + (DCTELEM) wsptr[6];
+ tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6],
+ FIX_1_414213562) - tmp13; /* 2*c4 */
tmp0 = tmp10 + tmp13;
tmp3 = tmp10 - tmp13;
tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
- tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
- tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
+ tmp10 = z5 - MULTIPLY(z12, FIX_1_082392200); /* 2*(c2-c6) */
+ tmp12 = z5 - MULTIPLY(z10, FIX_2_613125930); /* 2*(c2+c6) */
tmp6 = tmp12 - tmp7; /* phase 2 */
tmp5 = tmp11 - tmp6;
- tmp4 = tmp10 + tmp5;
+ tmp4 = tmp10 - tmp5;
/* Final output stage: scale down by a factor of 8 and range-limit */
- outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3)
+ outptr[0] = range_limit[(int) IRIGHT_SHIFT(tmp0 + tmp7, PASS1_BITS+3)
& RANGE_MASK];
- outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3)
+ outptr[7] = range_limit[(int) IRIGHT_SHIFT(tmp0 - tmp7, PASS1_BITS+3)
& RANGE_MASK];
- outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3)
+ outptr[1] = range_limit[(int) IRIGHT_SHIFT(tmp1 + tmp6, PASS1_BITS+3)
& RANGE_MASK];
- outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3)
+ outptr[6] = range_limit[(int) IRIGHT_SHIFT(tmp1 - tmp6, PASS1_BITS+3)
& RANGE_MASK];
- outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3)
+ outptr[2] = range_limit[(int) IRIGHT_SHIFT(tmp2 + tmp5, PASS1_BITS+3)
& RANGE_MASK];
- outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3)
+ outptr[5] = range_limit[(int) IRIGHT_SHIFT(tmp2 - tmp5, PASS1_BITS+3)
& RANGE_MASK];
- outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3)
+ outptr[3] = range_limit[(int) IRIGHT_SHIFT(tmp3 + tmp4, PASS1_BITS+3)
& RANGE_MASK];
- outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3)
+ outptr[4] = range_limit[(int) IRIGHT_SHIFT(tmp3 - tmp4, PASS1_BITS+3)
& RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
projects / reactos.git / blobdiff