jccolor.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"

/* Private subobject */

typedef struct
{
        struct jpeg_color_converter pub; /* public fields */

        /* Private state for RGB->YCC conversion */
        INT32* rgb_ycc_tab; /* => table for RGB to YCbCr conversion */
} my_color_converter;

typedef my_color_converter* my_cconvert_ptr;

/**************** RGB -> YCbCr conversion: most common case **************/

/*
 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
 * The conversion equations to be implemented are therefore
 *      Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
 *      Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE
 *      Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
 * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
 * were not represented exactly.  Now we sacrifice exact representation of
 * maximum red and maximum blue in order to get exact grayscales.
 *
 * To avoid floating-point arithmetic, we represent the fractional constants
 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
 * the products by 2^16, with appropriate rounding, to get the correct answer.
 *
 * For even more speed, we avoid doing any multiplications in the inner loop
 * by precalculating the constants times R,G,B for all possible values.
 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
 * for 12-bit samples it is still acceptable.  It's not very reasonable for
 * 16-bit samples, but if you want lossless storage you shouldn't be changing
 * colorspace anyway.
 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
 * in the tables to save adding them separately in the inner loop.
 */

#define SCALEBITS 16 /* speediest right-shift on some machines */
#define CBCR_OFFSET ((INT32)CENTERJSAMPLE << SCALEBITS)
#define ONE_HALF ((INT32)1 << (SCALEBITS - 1))
#define FIX(x) ((INT32)((x) * (1L << SCALEBITS) + 0.5))

/* We allocate one big table and divide it up into eight parts, instead of
 * doing eight alloc_small requests.  This lets us use a single table base
 * address, which can be held in a in the inner loops on many
 * machines (more than can hold all eight addresses, anyway).
 */

#define R_Y_OFF 0 /* offset to R => Y section */
#define G_Y_OFF (1 * (MAXJSAMPLE + 1)) /* offset to G => Y section */
#define B_Y_OFF (2 * (MAXJSAMPLE + 1)) /* etc. */
#define R_CB_OFF (3 * (MAXJSAMPLE + 1))
#define G_CB_OFF (4 * (MAXJSAMPLE + 1))
#define B_CB_OFF (5 * (MAXJSAMPLE + 1))
#define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */
#define G_CR_OFF (6 * (MAXJSAMPLE + 1))
#define B_CR_OFF (7 * (MAXJSAMPLE + 1))
#define TABLE_SIZE (8 * (MAXJSAMPLE + 1))

/*
 * Initialize for RGB->YCC colorspace conversion.
 */

METHODDEF(void)
rgb_ycc_start(j_compress_ptr cinfo)
{
        my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;
        INT32* rgb_ycc_tab;
        INT32 i;

        /* Allocate and fill in the conversion tables. */
        cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32*)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, (TABLE_SIZE * SIZEOF(INT32)));

        for (i = 0; i <= MAXJSAMPLE; i++)
        {
                rgb_ycc_tab[i + R_Y_OFF] = FIX(0.29900) * i;
                rgb_ycc_tab[i + G_Y_OFF] = FIX(0.58700) * i;
                rgb_ycc_tab[i + B_Y_OFF] = FIX(0.11400) * i + ONE_HALF;
                rgb_ycc_tab[i + R_CB_OFF] = (-FIX(0.16874)) * i;
                rgb_ycc_tab[i + G_CB_OFF] = (-FIX(0.33126)) * i;
                /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
                 * This ensures that the maximum output will round to MAXJSAMPLE
                 * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
                 */
                rgb_ycc_tab[i + B_CB_OFF] =
                        FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF - 1;
                /*  B=>Cb and R=>Cr tables are the same
                        rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET +
                   ONE_HALF-1;
                */
                rgb_ycc_tab[i + G_CR_OFF] = (-FIX(0.41869)) * i;
                rgb_ycc_tab[i + B_CR_OFF] = (-FIX(0.08131)) * i;
        }
}

/*
 * Convert some rows of samples to the JPEG colorspace.
 *
 * Note that we change from the application's interleaved-pixel format
 * to our internal noninterleaved, one-plane-per-component format.
 * The input buffer is therefore three times as wide as the output buffer.
 *
 * A starting row offset is provided only for the output buffer.  The caller
 * can easily adjust the passed input_buf value to accommodate any row
 * offset required on that side.
 */

METHODDEF(void)
rgb_ycc_convert(
        j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
        JDIMENSION output_row, int num_rows)
{
        my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;
        int r, g, b;
        INT32* ctab = cconvert->rgb_ycc_tab;
        JSAMPROW inptr;
        JSAMPROW outptr0, outptr1, outptr2;
        JDIMENSION col;
        JDIMENSION num_cols = cinfo->image_width;

        while (--num_rows >= 0)
        {
                inptr = *input_buf++;
                outptr0 = output_buf[0][output_row];
                outptr1 = output_buf[1][output_row];
                outptr2 = output_buf[2][output_row];
                output_row++;
                for (col = 0; col < num_cols; col++)
                {
                        r = GETJSAMPLE(inptr[RGB_RED]);
                        g = GETJSAMPLE(inptr[RGB_GREEN]);
                        b = GETJSAMPLE(inptr[RGB_BLUE]);
                        inptr += RGB_PIXELSIZE;
                        /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
                         * must be too; we do not need an explicit range-limiting operation.
                         * Hence the value being shifted is never negative, and we don't
                         * need the general RIGHT_SHIFT macro.
                         */
                        /* Y */
                        outptr0[col] = (JSAMPLE)(
                                (ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF]) >>
                                SCALEBITS);
                        /* Cb */
                        outptr1[col] = (JSAMPLE)(
                                (ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] +
                                 ctab[b + B_CB_OFF]) >>
                                SCALEBITS);
                        /* Cr */
                        outptr2[col] = (JSAMPLE)(
                                (ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] +
                                 ctab[b + B_CR_OFF]) >>
                                SCALEBITS);
                }
        }
}

/**************** Cases other than RGB -> YCbCr **************/

/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles RGB->grayscale conversion, which is the same
 * as the RGB->Y portion of RGB->YCbCr.
 * We assume rgb_ycc_start has been called (we only use the Y tables).
 */

METHODDEF(void)
rgb_gray_convert(
        j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
        JDIMENSION output_row, int num_rows)
{
        my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;
        int r, g, b;
        INT32* ctab = cconvert->rgb_ycc_tab;
        JSAMPROW inptr;
        JSAMPROW outptr;
        JDIMENSION col;
        JDIMENSION num_cols = cinfo->image_width;

        while (--num_rows >= 0)
        {
                inptr = *input_buf++;
                outptr = output_buf[0][output_row];
                output_row++;
                for (col = 0; col < num_cols; col++)
                {
                        r = GETJSAMPLE(inptr[RGB_RED]);
                        g = GETJSAMPLE(inptr[RGB_GREEN]);
                        b = GETJSAMPLE(inptr[RGB_BLUE]);
                        inptr += RGB_PIXELSIZE;
                        /* Y */
                        outptr[col] = (JSAMPLE)(
                                (ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF]) >>
                                SCALEBITS);
                }
        }
}

/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles Adobe-style CMYK->YCCK conversion,
 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 * conversion as above, while passing K (black) unchanged.
 * We assume rgb_ycc_start has been called.
 */

METHODDEF(void)
cmyk_ycck_convert(
        j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
        JDIMENSION output_row, int num_rows)
{
        my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;
        int r, g, b;
        INT32* ctab = cconvert->rgb_ycc_tab;
        JSAMPROW inptr;
        JSAMPROW outptr0, outptr1, outptr2, outptr3;
        JDIMENSION col;
        JDIMENSION num_cols = cinfo->image_width;

        while (--num_rows >= 0)
        {
                inptr = *input_buf++;
                outptr0 = output_buf[0][output_row];
                outptr1 = output_buf[1][output_row];
                outptr2 = output_buf[2][output_row];
                outptr3 = output_buf[3][output_row];
                output_row++;
                for (col = 0; col < num_cols; col++)
                {
                        r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
                        g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
                        b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
                        /* K passes through as-is */
                        outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */
                        inptr += 4;
                        /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
                         * must be too; we do not need an explicit range-limiting operation.
                         * Hence the value being shifted is never negative, and we don't
                         * need the general RIGHT_SHIFT macro.
                         */
                        /* Y */
                        outptr0[col] = (JSAMPLE)(
                                (ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF]) >>
                                SCALEBITS);
                        /* Cb */
                        outptr1[col] = (JSAMPLE)(
                                (ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] +
                                 ctab[b + B_CB_OFF]) >>
                                SCALEBITS);
                        /* Cr */
                        outptr2[col] = (JSAMPLE)(
                                (ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] +
                                 ctab[b + B_CR_OFF]) >>
                                SCALEBITS);
                }
        }
}

/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles grayscale output with no conversion.
 * The source can be either plain grayscale or YCbCr (since Y == gray).
 */

METHODDEF(void)
grayscale_convert(
        j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
        JDIMENSION output_row, int num_rows)
{
        JSAMPROW inptr;
        JSAMPROW outptr;
        JDIMENSION col;
        JDIMENSION num_cols = cinfo->image_width;
        int instride = cinfo->input_components;

        while (--num_rows >= 0)
        {
                inptr = *input_buf++;
                outptr = output_buf[0][output_row];
                output_row++;
                for (col = 0; col < num_cols; col++)
                {
                        outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */
                        inptr += instride;
                }
        }
}

/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles multi-component colorspaces without conversion.
 * We assume input_components == num_components.
 */

METHODDEF(void)
null_convert(
        j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
        JDIMENSION output_row, int num_rows)
{
        JSAMPROW inptr;
        JSAMPROW outptr;
        JDIMENSION col;
        int ci;
        int nc = cinfo->num_components;
        JDIMENSION num_cols = cinfo->image_width;

        while (--num_rows >= 0)
        {
                /* It seems fastest to make a separate pass for each component. */
                for (ci = 0; ci < nc; ci++)
                {
                        inptr = *input_buf;
                        outptr = output_buf[ci][output_row];
                        for (col = 0; col < num_cols; col++)
                        {
                                outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
                                inptr += nc;
                        }
                }
                input_buf++;
                output_row++;
        }
}

/*
 * Empty method for start_pass.
 */

METHODDEF(void)
null_method(j_compress_ptr) { /* no work needed */}
/*
 * Module initialization routine for input colorspace conversion.
 */

GLOBAL(void)
jinit_color_converter(j_compress_ptr cinfo)
{
        my_cconvert_ptr cconvert;

        cconvert = (my_cconvert_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(my_color_converter));
        cinfo->cconvert = (struct jpeg_color_converter*)cconvert;
        /* set start_pass to null method until we find out differently */
        cconvert->pub.start_pass = null_method;

        /* Make sure input_components agrees with in_color_space */
        switch (cinfo->in_color_space)
        {
                case JCS_GRAYSCALE:
                        if (cinfo->input_components != 1)
                                ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
                        break;

                case JCS_RGB:
#if RGB_PIXELSIZE != 3
                        if (cinfo->input_components != RGB_PIXELSIZE)
                                ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
                        break;
#endif /* else share code with YCbCr */

                case JCS_YCbCr:
                        if (cinfo->input_components != 3)
                                ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
                        break;

                case JCS_CMYK:
                case JCS_YCCK:
                        if (cinfo->input_components != 4)
                                ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
                        break;

                default: /* JCS_UNKNOWN can be anything */
                        if (cinfo->input_components < 1)
                                ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
                        break;
        }

        /* Check num_components, set conversion method based on requested space */
        switch (cinfo->jpeg_color_space)
        {
                case JCS_GRAYSCALE:
                        if (cinfo->num_components != 1)
                                ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
                        if (cinfo->in_color_space == JCS_GRAYSCALE)
                                cconvert->pub.color_convert = grayscale_convert;
                        else if (cinfo->in_color_space == JCS_RGB)
                        {
                                cconvert->pub.start_pass = rgb_ycc_start;
                                cconvert->pub.color_convert = rgb_gray_convert;
                        }
                        else if (cinfo->in_color_space == JCS_YCbCr)
                                cconvert->pub.color_convert = grayscale_convert;
                        else
                                ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
                        break;

                case JCS_RGB:
                        if (cinfo->num_components != 3)
                                ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
                        if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
                                cconvert->pub.color_convert = null_convert;
                        else
                                ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
                        break;

                case JCS_YCbCr:
                        if (cinfo->num_components != 3)
                                ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
                        if (cinfo->in_color_space == JCS_RGB)
                        {
                                cconvert->pub.start_pass = rgb_ycc_start;
                                cconvert->pub.color_convert = rgb_ycc_convert;
                        }
                        else if (cinfo->in_color_space == JCS_YCbCr)
                                cconvert->pub.color_convert = null_convert;
                        else
                                ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
                        break;

                case JCS_CMYK:
                        if (cinfo->num_components != 4)
                                ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
                        if (cinfo->in_color_space == JCS_CMYK)
                                cconvert->pub.color_convert = null_convert;
                        else
                                ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
                        break;

                case JCS_YCCK:
                        if (cinfo->num_components != 4)
                                ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
                        if (cinfo->in_color_space == JCS_CMYK)
                        {
                                cconvert->pub.start_pass = rgb_ycc_start;
                                cconvert->pub.color_convert = cmyk_ycck_convert;
                        }
                        else if (cinfo->in_color_space == JCS_YCCK)
                                cconvert->pub.color_convert = null_convert;
                        else
                                ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
                        break;

                default: /* allow null conversion of JCS_UNKNOWN */
                        if (cinfo->jpeg_color_space != cinfo->in_color_space ||
                                cinfo->num_components != cinfo->input_components)
                                ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
                        cconvert->pub.color_convert = null_convert;
                        break;
        }
}