jidctred.cpp

Go to the documentation of this file.

/* +------------------------------------------------------------------------+
   |                     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 IDCT_SCALING_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

/* Scaling is the same as in jidctint.c. */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS 13
#define PASS1_BITS 2
#else
#define CONST_BITS 13
#define PASS1_BITS 1 /* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 13
#define FIX_0_211164243 ((INT32)1730) /* FIX(0.211164243) */
#define FIX_0_509795579 ((INT32)4176) /* FIX(0.509795579) */
#define FIX_0_601344887 ((INT32)4926) /* FIX(0.601344887) */
#define FIX_0_720959822 ((INT32)5906) /* FIX(0.720959822) */
#define FIX_0_765366865 ((INT32)6270) /* FIX(0.765366865) */
#define FIX_0_850430095 ((INT32)6967) /* FIX(0.850430095) */
#define FIX_0_899976223 ((INT32)7373) /* FIX(0.899976223) */
#define FIX_1_061594337 ((INT32)8697) /* FIX(1.061594337) */
#define FIX_1_272758580 ((INT32)10426) /* FIX(1.272758580) */
#define FIX_1_451774981 ((INT32)11893) /* FIX(1.451774981) */
#define FIX_1_847759065 ((INT32)15137) /* FIX(1.847759065) */
#define FIX_2_172734803 ((INT32)17799) /* FIX(2.172734803) */
#define FIX_2_562915447 ((INT32)20995) /* FIX(2.562915447) */
#define FIX_3_624509785 ((INT32)29692) /* FIX(3.624509785) */
#else
#define FIX_0_211164243 FIX(0.211164243)
#define FIX_0_509795579 FIX(0.509795579)
#define FIX_0_601344887 FIX(0.601344887)
#define FIX_0_720959822 FIX(0.720959822)
#define FIX_0_765366865 FIX(0.765366865)
#define FIX_0_850430095 FIX(0.850430095)
#define FIX_0_899976223 FIX(0.899976223)
#define FIX_1_061594337 FIX(1.061594337)
#define FIX_1_272758580 FIX(1.272758580)
#define FIX_1_451774981 FIX(1.451774981)
#define FIX_1_847759065 FIX(1.847759065)
#define FIX_2_172734803 FIX(2.172734803)
#define FIX_2_562915447 FIX(2.562915447)
#define FIX_3_624509785 FIX(3.624509785)
#endif

/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */

#if BITS_IN_JSAMPLE == 8
#define MULTIPLY(var, const) MULTIPLY16C16(var, const)
#else
#define MULTIPLY(var, const) ((var) * (const))
#endif

/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */

#define DEQUANTIZE(coef, quantval) (((ISLOW_MULT_TYPE)(coef)) * (quantval))

           /*
                * Perform dequantization and inverse DCT on one block of coefficients,
                * producing a reduced-size 4x4 output block.
                */

           GLOBAL(void) jpeg_idct_4x4(
                   j_decompress_ptr cinfo, jpeg_component_info* compptr,
                   JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
{
        INT32 tmp0, tmp2, tmp10, tmp12;
        INT32 z1, z2, z3, z4;
        JCOEFPTR inptr;
        ISLOW_MULT_TYPE* quantptr;
        int* wsptr;
        JSAMPROW outptr;
        JSAMPLE* range_limit = IDCT_range_limit(cinfo);
        int ctr;
        int workspace[DCTSIZE * 4]; /* buffers data between passes */
        SHIFT_TEMPS

        /* Pass 1: process columns from input, store into work array. */

        inptr = coef_block;
        quantptr = (ISLOW_MULT_TYPE*)compptr->dct_table;
        wsptr = workspace;
        for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--)
        {
                /* Don't bother to process column 4, because second pass won't use it */
                if (ctr == DCTSIZE - 4) continue;
                if (inptr[DCTSIZE * 1] == 0 && inptr[DCTSIZE * 2] == 0 &&
                        inptr[DCTSIZE * 3] == 0 && inptr[DCTSIZE * 5] == 0 &&
                        inptr[DCTSIZE * 6] == 0 && inptr[DCTSIZE * 7] == 0)
                {
                        /* AC terms all zero; we need not examine term 4 for 4x4 output */
                        int dcval = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0])
                                                << PASS1_BITS;

                        wsptr[DCTSIZE * 0] = dcval;
                        wsptr[DCTSIZE * 1] = dcval;
                        wsptr[DCTSIZE * 2] = dcval;
                        wsptr[DCTSIZE * 3] = dcval;

                        continue;
                }

                /* Even part */

                tmp0 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
                tmp0 <<= (CONST_BITS + 1);

                z2 = DEQUANTIZE(inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2]);
                z3 = DEQUANTIZE(inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6]);

                tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, -FIX_0_765366865);

                tmp10 = tmp0 + tmp2;
                tmp12 = tmp0 - tmp2;

                /* Odd part */

                z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
                z2 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
                z3 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
                z4 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);

                tmp0 = MULTIPLY(z1, -FIX_0_211164243) /* sqrt(2) * (c3-c1) */
                           + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
                           + MULTIPLY(z3, -FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
                           + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

                tmp2 = MULTIPLY(z1, -FIX_0_509795579) /* sqrt(2) * (c7-c5) */
                           + MULTIPLY(z2, -FIX_0_601344887) /* sqrt(2) * (c5-c1) */
                           + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
                           + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

                /* Final output stage */

                wsptr[DCTSIZE * 0] =
                        (int)DESCALE(tmp10 + tmp2, CONST_BITS - PASS1_BITS + 1);
                wsptr[DCTSIZE * 3] =
                        (int)DESCALE(tmp10 - tmp2, CONST_BITS - PASS1_BITS + 1);
                wsptr[DCTSIZE * 1] =
                        (int)DESCALE(tmp12 + tmp0, CONST_BITS - PASS1_BITS + 1);
                wsptr[DCTSIZE * 2] =
                        (int)DESCALE(tmp12 - tmp0, CONST_BITS - PASS1_BITS + 1);
        }

        /* Pass 2: process 4 rows from work array, store into output array. */

        wsptr = workspace;
        for (ctr = 0; ctr < 4; ctr++)
        {
                outptr = output_buf[ctr] + output_col;
/* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
                if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[5] == 0 &&
                        wsptr[6] == 0 && wsptr[7] == 0)
                {
                        /* AC terms all zero */
                        JSAMPLE dcval =
                                range_limit[(int)DESCALE((INT32)wsptr[0], PASS1_BITS + 3) &
                                                        RANGE_MASK];

                        outptr[0] = dcval;
                        outptr[1] = dcval;
                        outptr[2] = dcval;
                        outptr[3] = dcval;

                        wsptr += DCTSIZE; /* advance pointer to next row */
                        continue;
                }
#endif

                /* Even part */

                tmp0 = ((INT32)wsptr[0]) << (CONST_BITS + 1);

                tmp2 = MULTIPLY((INT32)wsptr[2], FIX_1_847759065) +
                           MULTIPLY((INT32)wsptr[6], -FIX_0_765366865);

                tmp10 = tmp0 + tmp2;
                tmp12 = tmp0 - tmp2;

                /* Odd part */

                z1 = (INT32)wsptr[7];
                z2 = (INT32)wsptr[5];
                z3 = (INT32)wsptr[3];
                z4 = (INT32)wsptr[1];

                tmp0 = MULTIPLY(z1, -FIX_0_211164243) /* sqrt(2) * (c3-c1) */
                           + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
                           + MULTIPLY(z3, -FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
                           + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

                tmp2 = MULTIPLY(z1, -FIX_0_509795579) /* sqrt(2) * (c7-c5) */
                           + MULTIPLY(z2, -FIX_0_601344887) /* sqrt(2) * (c5-c1) */
                           + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
                           + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

                /* Final output stage */

                outptr[0] =
                        range_limit[(int)DESCALE(
                                                        tmp10 + tmp2, CONST_BITS + PASS1_BITS + 3 + 1) &
                                                RANGE_MASK];
                outptr[3] =
                        range_limit[(int)DESCALE(
                                                        tmp10 - tmp2, CONST_BITS + PASS1_BITS + 3 + 1) &
                                                RANGE_MASK];
                outptr[1] =
                        range_limit[(int)DESCALE(
                                                        tmp12 + tmp0, CONST_BITS + PASS1_BITS + 3 + 1) &
                                                RANGE_MASK];
                outptr[2] =
                        range_limit[(int)DESCALE(
                                                        tmp12 - tmp0, CONST_BITS + PASS1_BITS + 3 + 1) &
                                                RANGE_MASK];

                wsptr += DCTSIZE; /* advance pointer to next row */
        }
}

/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 2x2 output block.
 */

GLOBAL(void)
jpeg_idct_2x2(
        j_decompress_ptr cinfo, jpeg_component_info* compptr, JCOEFPTR coef_block,
        JSAMPARRAY output_buf, JDIMENSION output_col)
{
        INT32 tmp0, tmp10, z1;
        JCOEFPTR inptr;
        ISLOW_MULT_TYPE* quantptr;
        int* wsptr;
        JSAMPROW outptr;
        JSAMPLE* range_limit = IDCT_range_limit(cinfo);
        int ctr;
        int workspace[DCTSIZE * 2]; /* buffers data between passes */
        SHIFT_TEMPS

        /* Pass 1: process columns from input, store into work array. */

        inptr = coef_block;
        quantptr = (ISLOW_MULT_TYPE*)compptr->dct_table;
        wsptr = workspace;
        for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--)
        {
                /* Don't bother to process columns 2,4,6 */
                if (ctr == DCTSIZE - 2 || ctr == DCTSIZE - 4 || ctr == DCTSIZE - 6)
                        continue;
                if (inptr[DCTSIZE * 1] == 0 && inptr[DCTSIZE * 3] == 0 &&
                        inptr[DCTSIZE * 5] == 0 && inptr[DCTSIZE * 7] == 0)
                {
                        /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output
                         */
                        int dcval = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0])
                                                << PASS1_BITS;

                        wsptr[DCTSIZE * 0] = dcval;
                        wsptr[DCTSIZE * 1] = dcval;

                        continue;
                }

                /* Even part */

                z1 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
                tmp10 = z1 << (CONST_BITS + 2);

                /* Odd part */

                z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
                tmp0 = MULTIPLY(z1, -FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
                z1 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
                tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
                z1 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
                tmp0 += MULTIPLY(z1, -FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
                z1 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);
                tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

                /* Final output stage */

                wsptr[DCTSIZE * 0] =
                        (int)DESCALE(tmp10 + tmp0, CONST_BITS - PASS1_BITS + 2);
                wsptr[DCTSIZE * 1] =
                        (int)DESCALE(tmp10 - tmp0, CONST_BITS - PASS1_BITS + 2);
        }

        /* Pass 2: process 2 rows from work array, store into output array. */

        wsptr = workspace;
        for (ctr = 0; ctr < 2; ctr++)
        {
                outptr = output_buf[ctr] + output_col;
/* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
                if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0)
                {
                        /* AC terms all zero */
                        JSAMPLE dcval =
                                range_limit[(int)DESCALE((INT32)wsptr[0], PASS1_BITS + 3) &
                                                        RANGE_MASK];

                        outptr[0] = dcval;
                        outptr[1] = dcval;

                        wsptr += DCTSIZE; /* advance pointer to next row */
                        continue;
                }
#endif

                /* Even part */

                tmp10 = ((INT32)wsptr[0]) << (CONST_BITS + 2);

                /* Odd part */

                tmp0 =
                        MULTIPLY(
                                (INT32)wsptr[7], -FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
                        +
                        MULTIPLY(
                                (INT32)wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
                        + MULTIPLY(
                                  (INT32)wsptr[3],
                                  -FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
                        +
                        MULTIPLY(
                                (INT32)wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

                /* Final output stage */

                outptr[0] =
                        range_limit[(int)DESCALE(
                                                        tmp10 + tmp0, CONST_BITS + PASS1_BITS + 3 + 2) &
                                                RANGE_MASK];
                outptr[1] =
                        range_limit[(int)DESCALE(
                                                        tmp10 - tmp0, CONST_BITS + PASS1_BITS + 3 + 2) &
                                                RANGE_MASK];

                wsptr += DCTSIZE; /* advance pointer to next row */
        }
}

/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 1x1 output block.
 */

GLOBAL(void)
jpeg_idct_1x1(
        j_decompress_ptr cinfo, jpeg_component_info* compptr, JCOEFPTR coef_block,
        JSAMPARRAY output_buf, JDIMENSION output_col)
{
        int dcval;
        ISLOW_MULT_TYPE* quantptr;
        JSAMPLE* range_limit = IDCT_range_limit(cinfo);
        SHIFT_TEMPS

        /* We hardly need an inverse DCT routine for this: just take the
         * average pixel value, which is one-eighth of the DC coefficient.
         */
        quantptr = (ISLOW_MULT_TYPE*)compptr->dct_table;
        dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
        dcval = (int)DESCALE((INT32)dcval, 3);

        output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}

#endif /* IDCT_SCALING_SUPPORTED */