jfdctflt.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "mrpt_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.
                */

           GLOBAL(void) jpeg_fdct_float(FAST_FLOAT* data)
{
        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;
        int ctr;

        /* Pass 1: process rows. */

        dataptr = data;
        for (ctr = DCTSIZE - 1; ctr >= 0; ctr--)
        {
                tmp0 = dataptr[0] + dataptr[7];
                tmp7 = dataptr[0] - dataptr[7];
                tmp1 = dataptr[1] + dataptr[6];
                tmp6 = dataptr[1] - dataptr[6];
                tmp2 = dataptr[2] + dataptr[5];
                tmp5 = dataptr[2] - dataptr[5];
                tmp3 = dataptr[3] + dataptr[4];
                tmp4 = dataptr[3] - dataptr[4];

                /* Even part */

                tmp10 = tmp0 + tmp3; /* phase 2 */
                tmp13 = tmp0 - tmp3;
                tmp11 = tmp1 + tmp2;
                tmp12 = tmp1 - tmp2;

                dataptr[0] = tmp10 + tmp11; /* 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 */