+++ /dev/null
-/*
- * jfdctflt.c
- *
- * Copyright (C) 1994-1996, Thomas G. Lane.
- * Modified 2003-2015 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.
- *
- * This file contains a floating-point implementation of the
- * forward DCT (Discrete Cosine Transform).
- *
- * This implementation should be more accurate than either of the integer
- * DCT implementations. However, it may not give the same results on all
- * machines because of differences in roundoff behavior. Speed will depend
- * on the hardware's floating point capacity.
- *
- * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
- * on each column. Direct algorithms are also available, but they are
- * much more complex and seem not to be any faster when reduced to code.
- *
- * This implementation is based on Arai, Agui, and Nakajima's algorithm for
- * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in
- * Japanese, but the algorithm is described in the Pennebaker & Mitchell
- * JPEG textbook (see REFERENCES section in file README). The following code
- * is based directly on figure 4-8 in P&M.
- * While an 8-point DCT cannot be done in less than 11 multiplies, it is
- * possible to arrange the computation so that many of the multiplies are
- * simple scalings of the final outputs. These multiplies can then be
- * folded into the multiplications or divisions by the JPEG quantization
- * table entries. The AA&N method leaves only 5 multiplies and 29 adds
- * to be done in the DCT itself.
- * The primary disadvantage of this method is that with a fixed-point
- * implementation, accuracy is lost due to imprecise representation of the
- * scaled quantization values. However, that problem does not arise if
- * we use floating point arithmetic.
- */
-
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "jpeglib.h"
-#include "jdct.h" /* Private declarations for DCT subsystem */
-
-#ifdef DCT_FLOAT_SUPPORTED
-
-
-/*
- * This module is specialized to the case DCTSIZE = 8.
- */
-
-#if DCTSIZE != 8
- Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
-#endif
-
-
-/*
- * Perform the forward DCT on one block of samples.
- *
- * cK represents cos(K*pi/16).
- */
-
-GLOBAL(void)
-jpeg_fdct_float (FAST_FLOAT * data, JSAMPARRAY sample_data, JDIMENSION start_col)
-{
- FAST_FLOAT tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
- FAST_FLOAT tmp10, tmp11, tmp12, tmp13;
- FAST_FLOAT z1, z2, z3, z4, z5, z11, z13;
- FAST_FLOAT *dataptr;
- JSAMPROW elemptr;
- int ctr;
-
- /* Pass 1: process rows. */
-
- dataptr = data;
- for (ctr = 0; ctr < DCTSIZE; ctr++) {
- elemptr = sample_data[ctr] + start_col;
-
- /* Load data into workspace */
- tmp0 = (FAST_FLOAT) (GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]));
- tmp7 = (FAST_FLOAT) (GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]));
- tmp1 = (FAST_FLOAT) (GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]));
- tmp6 = (FAST_FLOAT) (GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]));
- tmp2 = (FAST_FLOAT) (GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]));
- tmp5 = (FAST_FLOAT) (GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]));
- tmp3 = (FAST_FLOAT) (GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]));
- tmp4 = (FAST_FLOAT) (GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]));
-
- /* Even part */
-
- tmp10 = tmp0 + tmp3; /* phase 2 */
- tmp13 = tmp0 - tmp3;
- tmp11 = tmp1 + tmp2;
- tmp12 = tmp1 - tmp2;
-
- /* Apply unsigned->signed conversion. */
- dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
- dataptr[4] = tmp10 - tmp11;
-
- z1 = (tmp12 + tmp13) * ((FAST_FLOAT) 0.707106781); /* c4 */
- dataptr[2] = tmp13 + z1; /* phase 5 */
- dataptr[6] = tmp13 - z1;
-
- /* Odd part */
-
- tmp10 = tmp4 + tmp5; /* phase 2 */
- tmp11 = tmp5 + tmp6;
- tmp12 = tmp6 + tmp7;
-
- /* The rotator is modified from fig 4-8 to avoid extra negations. */
- z5 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
- z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
- z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
- z3 = tmp11 * ((FAST_FLOAT) 0.707106781); /* c4 */
-
- z11 = tmp7 + z3; /* phase 5 */
- z13 = tmp7 - z3;
-
- dataptr[5] = z13 + z2; /* phase 6 */
- dataptr[3] = z13 - z2;
- dataptr[1] = z11 + z4;
- dataptr[7] = z11 - z4;
-
- dataptr += DCTSIZE; /* advance pointer to next row */
- }
-
- /* Pass 2: process columns. */
-
- dataptr = data;
- for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
- tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
- tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
- tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
- tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
- tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
- tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
- tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
- tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
-
- /* Even part */
-
- tmp10 = tmp0 + tmp3; /* phase 2 */
- tmp13 = tmp0 - tmp3;
- tmp11 = tmp1 + tmp2;
- tmp12 = tmp1 - tmp2;
-
- dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */
- dataptr[DCTSIZE*4] = tmp10 - tmp11;
-
- z1 = (tmp12 + tmp13) * ((FAST_FLOAT) 0.707106781); /* c4 */
- dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */
- dataptr[DCTSIZE*6] = tmp13 - z1;
-
- /* Odd part */
-
- tmp10 = tmp4 + tmp5; /* phase 2 */
- tmp11 = tmp5 + tmp6;
- tmp12 = tmp6 + tmp7;
-
- /* The rotator is modified from fig 4-8 to avoid extra negations. */
- z5 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
- z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
- z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
- z3 = tmp11 * ((FAST_FLOAT) 0.707106781); /* c4 */
-
- z11 = tmp7 + z3; /* phase 5 */
- z13 = tmp7 - z3;
-
- dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */
- dataptr[DCTSIZE*3] = z13 - z2;
- dataptr[DCTSIZE*1] = z11 + z4;
- dataptr[DCTSIZE*7] = z11 - z4;
-
- dataptr++; /* advance pointer to next column */
- }
-}
-
-#endif /* DCT_FLOAT_SUPPORTED */
projects / reactos.git / blobdiff