/**
* Copyright (c) 2005 Hin-Tak Leung. All rights reserved.
*
**/
/*
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
**/
/*
* jccolor.c
*
* Copyright (C) 1991-1996, 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.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jpeg_jcs.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 register in the inner loops on many
* machines (more than can hold all eight addresses, anyway).
*/
#define JR_HALF_OFF 0 /* offset to R => half section */
#define JR_MINUSHALF_OFF (1*(MAXJSAMPLE+1)) /* offset to G => -half section */
#define JR_TABLE_SIZE (2*(MAXJSAMPLE+1))
/*
* Initialize for RGB->JETREADY colorspace conversion.
*/
METHODDEF(void)
rgb_jr_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,
(JR_TABLE_SIZE * SIZEOF(INT32)));
for (i = 0; i <= MAXJSAMPLE; i++) {
rgb_ycc_tab[i+JR_HALF_OFF] = FIX(0.50000) * i + ONE_HALF;
rgb_ycc_tab[i+JR_MINUSHALF_OFF] = (-FIX(0.50000)) * i + CBCR_OFFSET - 1;
}
}
/*
* 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_jr_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 int r, g, b;
register INT32 * ctab = cconvert->rgb_ycc_tab;
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]);
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+JR_HALF_OFF])
>> SCALEBITS);
/* Cb */
outptr1[col] = (JSAMPLE)
((ctab[r+JR_HALF_OFF] + ctab[g+JR_MINUSHALF_OFF])
>> SCALEBITS);
/* Cr */
outptr2[col] = (JSAMPLE)
((ctab[r+JR_HALF_OFF] + ctab[b+JR_MINUSHALF_OFF])
>> SCALEBITS);
}
}
}
METHODDEF(void)
gray_jr_convert (j_compress_ptr cinfo,
JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
JDIMENSION output_row, int num_rows)
{
register int y;
register JSAMPROW inptr;
register JSAMPROW outptr;
register 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++) {
y = GETJSAMPLE(inptr[0]);
inptr += instride;
/* 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) (MAXJSAMPLE - y);
}
}
}
/**************** Cases other than RGB -> YCbCr **************/
/*
* 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)
{
register JSAMPROW inptr;
register JSAMPROW outptr;
register JDIMENSION col;
register 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 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 = (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_JETREADY:
cconvert->pub.start_pass = rgb_jr_start;
if (cinfo->input_components == 1)
{
cconvert->pub.color_convert = gray_jr_convert;
} else
cconvert->pub.color_convert = rgb_jr_convert;
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;
}
}