The Independent JPEG Group's JPEG software v9b
This commit is contained in:
Guido Vollbeding
DRC
89
jidctfst.c
89
jidctfst.c
@@ -2,6 +2,7 @@
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* jidctfst.c
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*
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* Copyright (C) 1994-1998, Thomas G. Lane.
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* Modified 2015 by Guido Vollbeding.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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@@ -133,35 +134,10 @@
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#endif
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/* Like DESCALE, but applies to a DCTELEM and produces an int.
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* We assume that int right shift is unsigned if INT32 right shift is.
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*/
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#ifdef RIGHT_SHIFT_IS_UNSIGNED
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#define ISHIFT_TEMPS DCTELEM ishift_temp;
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#if BITS_IN_JSAMPLE == 8
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#define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */
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#else
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#define DCTELEMBITS 32 /* DCTELEM must be 32 bits */
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#endif
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#define IRIGHT_SHIFT(x,shft) \
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((ishift_temp = (x)) < 0 ? \
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(ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \
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(ishift_temp >> (shft)))
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#else
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#define ISHIFT_TEMPS
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#define IRIGHT_SHIFT(x,shft) ((x) >> (shft))
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#endif
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#ifdef USE_ACCURATE_ROUNDING
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#define IDESCALE(x,n) ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n))
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#else
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#define IDESCALE(x,n) ((int) IRIGHT_SHIFT(x, n))
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#endif
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/*
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* Perform dequantization and inverse DCT on one block of coefficients.
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*
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* cK represents cos(K*pi/16).
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*/
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GLOBAL(void)
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@@ -180,7 +156,7 @@ jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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int ctr;
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int workspace[DCTSIZE2]; /* buffers data between passes */
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SHIFT_TEMPS /* for DESCALE */
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ISHIFT_TEMPS /* for IDESCALE */
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ISHIFT_TEMPS /* for IRIGHT_SHIFT */
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/* Pass 1: process columns from input, store into work array. */
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@@ -253,12 +229,12 @@ jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
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z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
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tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
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tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
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tmp10 = z5 - MULTIPLY(z12, FIX_1_082392200); /* 2*(c2-c6) */
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tmp12 = z5 - MULTIPLY(z10, FIX_2_613125930); /* 2*(c2+c6) */
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tmp6 = tmp12 - tmp7; /* phase 2 */
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tmp5 = tmp11 - tmp6;
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tmp4 = tmp10 + tmp5;
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tmp4 = tmp10 - tmp5;
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wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7);
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wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7);
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@@ -266,21 +242,28 @@ jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6);
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wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5);
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wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5);
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wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4);
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wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4);
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wsptr[DCTSIZE*3] = (int) (tmp3 + tmp4);
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wsptr[DCTSIZE*4] = (int) (tmp3 - tmp4);
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inptr++; /* advance pointers to next column */
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quantptr++;
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wsptr++;
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}
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/* Pass 2: process rows from work array, store into output array. */
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/* Note that we must descale the results by a factor of 8 == 2**3, */
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/* and also undo the PASS1_BITS scaling. */
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/* Pass 2: process rows from work array, store into output array.
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* Note that we must descale the results by a factor of 8 == 2**3,
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* and also undo the PASS1_BITS scaling.
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*/
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wsptr = workspace;
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for (ctr = 0; ctr < DCTSIZE; ctr++) {
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outptr = output_buf[ctr] + output_col;
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/* Add range center and fudge factor for final descale and range-limit. */
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z5 = (DCTELEM) wsptr[0] +
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((((DCTELEM) RANGE_CENTER) << (PASS1_BITS+3)) +
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(1 << (PASS1_BITS+2)));
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/* Rows of zeroes can be exploited in the same way as we did with columns.
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* However, the column calculation has created many nonzero AC terms, so
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* the simplification applies less often (typically 5% to 10% of the time).
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@@ -293,7 +276,7 @@ jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
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wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
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/* AC terms all zero */
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JSAMPLE dcval = range_limit[IDESCALE(wsptr[0], PASS1_BITS+3)
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JSAMPLE dcval = range_limit[(int) IRIGHT_SHIFT(z5, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[0] = dcval;
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@@ -312,12 +295,12 @@ jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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/* Even part */
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tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]);
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tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]);
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tmp10 = z5 + (DCTELEM) wsptr[4];
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tmp11 = z5 - (DCTELEM) wsptr[4];
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tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]);
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tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562)
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- tmp13;
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tmp13 = (DCTELEM) wsptr[2] + (DCTELEM) wsptr[6];
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tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6],
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FIX_1_414213562) - tmp13; /* 2*c4 */
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tmp0 = tmp10 + tmp13;
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tmp3 = tmp10 - tmp13;
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@@ -335,30 +318,30 @@ jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
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z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
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tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
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tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
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tmp10 = z5 - MULTIPLY(z12, FIX_1_082392200); /* 2*(c2-c6) */
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tmp12 = z5 - MULTIPLY(z10, FIX_2_613125930); /* 2*(c2+c6) */
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tmp6 = tmp12 - tmp7; /* phase 2 */
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tmp5 = tmp11 - tmp6;
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tmp4 = tmp10 + tmp5;
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tmp4 = tmp10 - tmp5;
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/* Final output stage: scale down by a factor of 8 and range-limit */
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outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3)
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outptr[0] = range_limit[(int) IRIGHT_SHIFT(tmp0 + tmp7, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3)
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outptr[7] = range_limit[(int) IRIGHT_SHIFT(tmp0 - tmp7, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3)
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outptr[1] = range_limit[(int) IRIGHT_SHIFT(tmp1 + tmp6, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3)
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outptr[6] = range_limit[(int) IRIGHT_SHIFT(tmp1 - tmp6, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3)
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outptr[2] = range_limit[(int) IRIGHT_SHIFT(tmp2 + tmp5, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3)
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outptr[5] = range_limit[(int) IRIGHT_SHIFT(tmp2 - tmp5, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3)
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outptr[3] = range_limit[(int) IRIGHT_SHIFT(tmp3 + tmp4, PASS1_BITS+3)
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& RANGE_MASK];
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outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3)
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outptr[4] = range_limit[(int) IRIGHT_SHIFT(tmp3 - tmp4, PASS1_BITS+3)
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& RANGE_MASK];
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wsptr += DCTSIZE; /* advance pointer to next row */
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