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/*
* jccolor.c
*
* Copyright (C) 1991-1996, Thomas G. Lane.
* Modified 2011-2013 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 input colorspace conversion routines.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "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 Recommendation ITU-R BT.601-7 (03/2011),
* previously known as Recommendation CCIR 601-1, except that Cb and Cr
* are normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
* sRGB (standard RGB color space) is defined per IEC 61966-2-1:1999.
* sYCC (standard luma-chroma-chroma color space with extended gamut)
* is defined per IEC 61966-2-1:1999 Amendment A1:2003 Annex F.
* bg-sRGB and bg-sYCC (big gamut standard color spaces)
* are defined per IEC 61966-2-1:1999 Amendment A1:2003 Annex G.
* Note that the derived conversion coefficients given in some of these
* documents are imprecise. The general conversion equations are
* Y = Kr * R + (1 - Kr - Kb) * G + Kb * B
* Cb = 0.5 * (B - Y) / (1 - Kb)
* Cr = 0.5 * (R - Y) / (1 - Kr)
* With Kr = 0.299 and Kb = 0.114 (derived according to SMPTE RP 177-1993
* from the 1953 FCC NTSC primaries and CIE Illuminant C),
* the conversion equations to be implemented are therefore
* Y = 0.299 * R + 0.587 * G + 0.114 * B
* Cb = -0.168735892 * R - 0.331264108 * G + 0.5 * B + CENTERJSAMPLE
* Cr = 0.5 * R - 0.418687589 * G - 0.081312411 * B + CENTERJSAMPLE
* 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 9-bit to 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 register 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(0.299) * i;
rgb_ycc_tab[i+G_Y_OFF] = FIX(0.587) * i;
rgb_ycc_tab[i+B_Y_OFF] = FIX(0.114) * i + ONE_HALF;
rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.168735892)) * i;
rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.331264108)) * 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(0.5) * i + CBCR_OFFSET + ONE_HALF-1;
/* B=>Cb and R=>Cr tables are the same
rgb_ycc_tab[i+R_CR_OFF] = FIX(0.5) * i + CBCR_OFFSET + ONE_HALF-1;
*/
rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.418687589)) * i;
rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.081312411)) * 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;
register INT32 * ctab = cconvert->rgb_ycc_tab;
register int r, g, b;
register JSAMPROW inptr;
register JSAMPROW outptr0, outptr1, outptr2;
register 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]);
/* 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);
inptr += RGB_PIXELSIZE;
}
}
}
/**************** 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;
register INT32 * ctab = cconvert->rgb_ycc_tab;
register int r, g, b;
register JSAMPROW inptr;
register JSAMPROW outptr;
register JDIMENSION col;
JDIMENSION num_cols = cinfo->image_width;
while (--num_rows >= 0) {
inptr = *input_buf++;
outptr = output_buf[0][output_row++];
for (col = 0; col < num_cols; col++) {
r = GETJSAMPLE(inptr[RGB_RED]);
g = GETJSAMPLE(inptr[RGB_GREEN]);
b = GETJSAMPLE(inptr[RGB_BLUE]);
/* Y */
outptr[col] = (JSAMPLE)
((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
>> SCALEBITS);
inptr += RGB_PIXELSIZE;
}
}
}
/*
* 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;
register INT32 * ctab = cconvert->rgb_ycc_tab;
register int r, g, b;
register JSAMPROW inptr;
register JSAMPROW outptr0, outptr1, outptr2, outptr3;
register 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 */
/* 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);
inptr += 4;
}
}
}
/*
* Convert some rows of samples to the JPEG colorspace.
* [R,G,B] to [R-G,G,B-G] conversion with modulo calculation
* (forward reversible color transform).
* This can be seen as an adaption of the general RGB->YCbCr
* conversion equation with Kr = Kb = 0, while replacing the
* normalization by modulo calculation.
*/
METHODDEF(void)
rgb_rgb1_convert (j_compress_ptr cinfo,
JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
JDIMENSION output_row, int num_rows)
{
register int r, g, b;
register JSAMPROW inptr;
register JSAMPROW outptr0, outptr1, outptr2;
register 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]);
/* Assume that MAXJSAMPLE+1 is a power of 2, so that the MOD
* (modulo) operator is equivalent to the bitmask operator AND.
*/
outptr0[col] = (JSAMPLE) ((r - g + CENTERJSAMPLE) & MAXJSAMPLE);
outptr1[col] = (JSAMPLE) g;
outptr2[col] = (JSAMPLE) ((b - g + CENTERJSAMPLE) & MAXJSAMPLE);
inptr += RGB_PIXELSIZE;
}
}
}
/*
* 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 YCC (since Y == gray).
*/
METHODDEF(void)
grayscale_convert (j_compress_ptr cinfo,
JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
JDIMENSION output_row, int num_rows)
{
int instride = cinfo->input_components;
register JSAMPROW inptr;
register JSAMPROW outptr;
register JDIMENSION col;
JDIMENSION num_cols = cinfo->image_width;
while (--num_rows >= 0) {
inptr = *input_buf++;
outptr = output_buf[0][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.
* No colorspace conversion, but change from interleaved
* to separate-planes representation.
*/
METHODDEF(void)
rgb_convert (j_compress_ptr cinfo,
JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
JDIMENSION output_row, int num_rows)
{
register JSAMPROW inptr;
register JSAMPROW outptr0, outptr1, outptr2;
register 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++) {
/* We can dispense with GETJSAMPLE() here */
outptr0[col] = inptr[RGB_RED];
outptr1[col] = inptr[RGB_GREEN];
outptr2[col] = inptr[RGB_BLUE];
inptr += RGB_PIXELSIZE;
}
}
}
/*
* 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)
{
int ci;
register int nc = cinfo->num_components;
register JSAMPROW inptr;
register JSAMPROW outptr;
register JDIMENSION col;
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[0] + ci;
outptr = output_buf[ci][output_row];
for (col = 0; col < num_cols; col++) {
*outptr++ = *inptr; /* don't need GETJSAMPLE() here */
inptr += nc;
}
}
input_buf++;
output_row++;
}
}
/*
* Empty method for start_pass.
*/
METHODDEF(void)
null_method (j_compress_ptr cinfo)
{
/* 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 = &cconvert->pub;
/* 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:
case JCS_BG_RGB:
if (cinfo->input_components != RGB_PIXELSIZE)
ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
break;
case JCS_YCbCr:
case JCS_BG_YCC:
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;
}
/* Support color transform only for RGB colorspaces */
if (cinfo->color_transform &&
cinfo->jpeg_color_space != JCS_RGB &&
cinfo->jpeg_color_space != JCS_BG_RGB)
ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
/* 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);
switch (cinfo->in_color_space) {
case JCS_GRAYSCALE:
case JCS_YCbCr:
case JCS_BG_YCC:
cconvert->pub.color_convert = grayscale_convert;
break;
case JCS_RGB:
cconvert->pub.start_pass = rgb_ycc_start;
cconvert->pub.color_convert = rgb_gray_convert;
break;
default:
ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
}
break;
case JCS_RGB:
case JCS_BG_RGB:
if (cinfo->num_components != 3)
ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
if (cinfo->in_color_space == cinfo->jpeg_color_space) {
switch (cinfo->color_transform) {
case JCT_NONE:
cconvert->pub.color_convert = rgb_convert;
break;
case JCT_SUBTRACT_GREEN:
cconvert->pub.color_convert = rgb_rgb1_convert;
break;
default:
ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
}
} else
ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
break;
case JCS_YCbCr:
if (cinfo->num_components != 3)
ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
switch (cinfo->in_color_space) {
case JCS_RGB:
cconvert->pub.start_pass = rgb_ycc_start;
cconvert->pub.color_convert = rgb_ycc_convert;
break;
case JCS_YCbCr:
cconvert->pub.color_convert = null_convert;
break;
default:
ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
}
break;
case JCS_BG_YCC:
if (cinfo->num_components != 3)
ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
switch (cinfo->in_color_space) {
case JCS_RGB:
/* For conversion from normal RGB input to BG_YCC representation,
* the Cb/Cr values are first computed as usual, and then
* quantized further after DCT processing by a factor of
* 2 in reference to the nominal quantization factor.
*/
/* need quantization scale by factor of 2 after DCT */
cinfo->comp_info[1].component_needed = TRUE;
cinfo->comp_info[2].component_needed = TRUE;
/* compute normal YCC first */
cconvert->pub.start_pass = rgb_ycc_start;
cconvert->pub.color_convert = rgb_ycc_convert;
break;
case JCS_YCbCr:
/* need quantization scale by factor of 2 after DCT */
cinfo->comp_info[1].component_needed = TRUE;
cinfo->comp_info[2].component_needed = TRUE;
/*FALLTHROUGH*/
case JCS_BG_YCC:
/* Pass through for BG_YCC input */
cconvert->pub.color_convert = null_convert;
break;
default:
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);
switch (cinfo->in_color_space) {
case JCS_CMYK:
cconvert->pub.start_pass = rgb_ycc_start;
cconvert->pub.color_convert = cmyk_ycck_convert;
break;
case JCS_YCCK:
cconvert->pub.color_convert = null_convert;
break;
default:
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;
}
}
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