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/*
* jccolor.c
*
* Copyright (C) 1991, 1992, Thomas G. Lane.
* 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 input colorspace conversion routines.
* These routines are invoked via the methods get_sample_rows
* and colorin_init/term.
*/
#include "jinclude.h"
static JSAMPARRAY pixel_row; /* Workspace for a pixel row in input format */
/**************** 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 + MAXJSAMPLE/2
* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + MAXJSAMPLE/2
* (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
*
* 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 MAXJSAMPLE/2 offsets and the rounding fudge-factor of 0.5 are included
* in the tables to save adding them separately in the inner loop.
*/
#ifdef SIXTEEN_BIT_SAMPLES
#define SCALEBITS 14 /* avoid overflow */
#else
#define SCALEBITS 16 /* speedier right-shift on some machines */
#endif
#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 register in the inner loops on many
* machines (more than can hold all eight addresses, anyway).
*/
static INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */
#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 colorspace conversion.
*/
METHODDEF void
rgb_ycc_init (compress_info_ptr cinfo)
{
INT32 i;
/* Allocate a workspace for the result of get_input_row. */
pixel_row = (*cinfo->emethods->alloc_small_sarray)
(cinfo->image_width, (long) cinfo->input_components);
/* Allocate and fill in the conversion tables. */
rgb_ycc_tab = (INT32 *) (*cinfo->emethods->alloc_small)
(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;
rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + ONE_HALF*(MAXJSAMPLE+1);
/* B=>Cb and R=>Cr tables are the same
rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + ONE_HALF*(MAXJSAMPLE+1);
*/
rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
}
}
/*
* Fetch some rows of pixels from get_input_row and convert to the
* JPEG colorspace.
*/
METHODDEF void
get_rgb_ycc_rows (compress_info_ptr cinfo,
int rows_to_read, JSAMPIMAGE image_data)
{
#ifdef SIXTEEN_BIT_SAMPLES
register UINT16 r, g, b;
#else
register int r, g, b;
#endif
register INT32 * ctab = rgb_ycc_tab;
register JSAMPROW inptr0, inptr1, inptr2;
register JSAMPROW outptr0, outptr1, outptr2;
register long col;
long width = cinfo->image_width;
int row;
for (row = 0; row < rows_to_read; row++) {
/* Read one row from the source file */
(*cinfo->methods->get_input_row) (cinfo, pixel_row);
/* Convert colorspace */
inptr0 = pixel_row[0];
inptr1 = pixel_row[1];
inptr2 = pixel_row[2];
outptr0 = image_data[0][row];
outptr1 = image_data[1][row];
outptr2 = image_data[2][row];
for (col = 0; col < width; col++) {
r = GETJSAMPLE(inptr0[col]);
g = GETJSAMPLE(inptr1[col]);
b = GETJSAMPLE(inptr2[col]);
/* 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 **************/
/*
* Fetch some rows of pixels from get_input_row and convert 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_init has been called (we only use the Y tables).
*/
METHODDEF void
get_rgb_gray_rows (compress_info_ptr cinfo,
int rows_to_read, JSAMPIMAGE image_data)
{
#ifdef SIXTEEN_BIT_SAMPLES
register UINT16 r, g, b;
#else
register int r, g, b;
#endif
register INT32 * ctab = rgb_ycc_tab;
register JSAMPROW inptr0, inptr1, inptr2;
register JSAMPROW outptr;
register long col;
long width = cinfo->image_width;
int row;
for (row = 0; row < rows_to_read; row++) {
/* Read one row from the source file */
(*cinfo->methods->get_input_row) (cinfo, pixel_row);
/* Convert colorspace */
inptr0 = pixel_row[0];
inptr1 = pixel_row[1];
inptr2 = pixel_row[2];
outptr = image_data[0][row];
for (col = 0; col < width; col++) {
r = GETJSAMPLE(inptr0[col]);
g = GETJSAMPLE(inptr1[col]);
b = GETJSAMPLE(inptr2[col]);
/* 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 */
outptr[col] = (JSAMPLE)
((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
>> SCALEBITS);
}
}
}
/*
* Initialize for colorspace conversion.
*/
METHODDEF void
colorin_init (compress_info_ptr cinfo)
{
/* Allocate a workspace for the result of get_input_row. */
pixel_row = (*cinfo->emethods->alloc_small_sarray)
(cinfo->image_width, (long) cinfo->input_components);
}
/*
* Fetch some rows of pixels from get_input_row and convert 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
get_grayscale_rows (compress_info_ptr cinfo,
int rows_to_read, JSAMPIMAGE image_data)
{
int row;
for (row = 0; row < rows_to_read; row++) {
/* Read one row from the source file */
(*cinfo->methods->get_input_row) (cinfo, pixel_row);
/* Convert colorspace (gamma mapping needed here) */
jcopy_sample_rows(pixel_row, 0, image_data[0], row,
1, cinfo->image_width);
}
}
/*
* Fetch some rows of pixels from get_input_row and convert to the
* JPEG colorspace.
* This version handles multi-component colorspaces without conversion.
*/
METHODDEF void
get_noconvert_rows (compress_info_ptr cinfo,
int rows_to_read, JSAMPIMAGE image_data)
{
int row, ci;
for (row = 0; row < rows_to_read; row++) {
/* Read one row from the source file */
(*cinfo->methods->get_input_row) (cinfo, pixel_row);
/* Convert colorspace (gamma mapping needed here) */
for (ci = 0; ci < cinfo->input_components; ci++) {
jcopy_sample_rows(pixel_row, ci, image_data[ci], row,
1, cinfo->image_width);
}
}
}
/*
* Finish up at the end of the file.
*/
METHODDEF void
colorin_term (compress_info_ptr cinfo)
{
/* no work (we let free_all release the workspace) */
}
/*
* The method selection routine for input colorspace conversion.
*/
GLOBAL void
jselccolor (compress_info_ptr cinfo)
{
/* Make sure input_components agrees with in_color_space */
switch (cinfo->in_color_space) {
case CS_GRAYSCALE:
if (cinfo->input_components != 1)
ERREXIT(cinfo->emethods, "Bogus input colorspace");
break;
case CS_RGB:
case CS_YCbCr:
case CS_YIQ:
if (cinfo->input_components != 3)
ERREXIT(cinfo->emethods, "Bogus input colorspace");
break;
case CS_CMYK:
if (cinfo->input_components != 4)
ERREXIT(cinfo->emethods, "Bogus input colorspace");
break;
default:
ERREXIT(cinfo->emethods, "Unsupported input colorspace");
break;
}
/* Standard init/term methods (may override below) */
cinfo->methods->colorin_init = colorin_init;
cinfo->methods->colorin_term = colorin_term;
/* Check num_components, set conversion method based on requested space */
switch (cinfo->jpeg_color_space) {
case CS_GRAYSCALE:
if (cinfo->num_components != 1)
ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
if (cinfo->in_color_space == CS_GRAYSCALE)
cinfo->methods->get_sample_rows = get_grayscale_rows;
else if (cinfo->in_color_space == CS_RGB) {
cinfo->methods->colorin_init = rgb_ycc_init;
cinfo->methods->get_sample_rows = get_rgb_gray_rows;
} else if (cinfo->in_color_space == CS_YCbCr)
cinfo->methods->get_sample_rows = get_grayscale_rows;
else
ERREXIT(cinfo->emethods, "Unsupported color conversion request");
break;
case CS_YCbCr:
if (cinfo->num_components != 3)
ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
if (cinfo->in_color_space == CS_RGB) {
cinfo->methods->colorin_init = rgb_ycc_init;
cinfo->methods->get_sample_rows = get_rgb_ycc_rows;
} else if (cinfo->in_color_space == CS_YCbCr)
cinfo->methods->get_sample_rows = get_noconvert_rows;
else
ERREXIT(cinfo->emethods, "Unsupported color conversion request");
break;
case CS_CMYK:
if (cinfo->num_components != 4)
ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
if (cinfo->in_color_space == CS_CMYK)
cinfo->methods->get_sample_rows = get_noconvert_rows;
else
ERREXIT(cinfo->emethods, "Unsupported color conversion request");
break;
default:
ERREXIT(cinfo->emethods, "Unsupported JPEG colorspace");
break;
}
}
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