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/*
* jdcolor.c
*
* Copyright (C) 1991, 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 output colorspace conversion routines.
* These routines are invoked via the methods color_convert
* and colorout_init/term.
*/
#include "jinclude.h"
/*
* Initialize for colorspace conversion.
*/
METHODDEF void
colorout_init (decompress_info_ptr cinfo)
{
/* no work needed */
}
/*
* Convert some rows of samples to the output colorspace.
* This version handles YCbCr -> RGB conversion.
* 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.
*/
METHODDEF void
ycc_rgb_convert (decompress_info_ptr cinfo, int num_rows,
JSAMPIMAGE input_data, JSAMPIMAGE output_data)
{
register INT32 y, u, v, x;
register JSAMPROW inptr0, inptr1, inptr2;
register JSAMPROW outptr0, outptr1, outptr2;
register long col;
register long width = cinfo->image_width;
register int row;
for (row = 0; row < num_rows; row++) {
inptr0 = input_data[0][row];
inptr1 = input_data[1][row];
inptr2 = input_data[2][row];
outptr0 = output_data[0][row];
outptr1 = output_data[1][row];
outptr2 = output_data[2][row];
for (col = width; col > 0; col--) {
y = GETJSAMPLE(*inptr0++);
u = (int) GETJSAMPLE(*inptr1++) - CENTERJSAMPLE;
v = (int) GETJSAMPLE(*inptr2++) - CENTERJSAMPLE;
/* Note: if the inputs were computed directly from RGB values,
* range-limiting would be unnecessary here; but due to possible
* noise in the DCT/IDCT phase, we do need to apply range limits.
*/
y *= 1024; /* in case compiler can't spot common subexpression */
x = y + 1436*v + 512; /* red */
if (x < 0) x = 0;
if (x > ((INT32) MAXJSAMPLE*1024)) x = (INT32) MAXJSAMPLE*1024;
*outptr0++ = x >> 10;
x = y - 352*u - 731*v + 512; /* green */
if (x < 0) x = 0;
if (x > ((INT32) MAXJSAMPLE*1024)) x = (INT32) MAXJSAMPLE*1024;
*outptr1++ = x >> 10;
x = y + 1815*u + 512; /* blue */
if (x < 0) x = 0;
if (x > ((INT32) MAXJSAMPLE*1024)) x = (INT32) MAXJSAMPLE*1024;
*outptr2++ = x >> 10;
}
}
}
/*
* Color conversion for no colorspace change: just copy the data.
*/
METHODDEF void
null_convert (decompress_info_ptr cinfo, int num_rows,
JSAMPIMAGE input_data, JSAMPIMAGE output_data)
{
short ci;
for (ci = 0; ci < cinfo->num_components; ci++) {
jcopy_sample_rows(input_data[ci], 0, output_data[ci], 0,
num_rows, cinfo->image_width);
}
}
/*
* Color conversion for grayscale: just copy the data.
* This also works for YCbCr/YIQ -> grayscale conversion, in which
* we just copy the Y (luminance) component and ignore chrominance.
*/
METHODDEF void
grayscale_convert (decompress_info_ptr cinfo, int num_rows,
JSAMPIMAGE input_data, JSAMPIMAGE output_data)
{
jcopy_sample_rows(input_data[0], 0, output_data[0], 0,
num_rows, cinfo->image_width);
}
/*
* Finish up at the end of the file.
*/
METHODDEF void
colorout_term (decompress_info_ptr cinfo)
{
/* no work needed */
}
/*
* The method selection routine for output colorspace conversion.
*/
GLOBAL void
jseldcolor (decompress_info_ptr cinfo)
{
/* Make sure num_components agrees with jpeg_color_space */
switch (cinfo->jpeg_color_space) {
case CS_GRAYSCALE:
if (cinfo->num_components != 1)
ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
break;
case CS_RGB:
case CS_YIQ:
case CS_YCbCr:
if (cinfo->num_components != 3)
ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
break;
case CS_CMYK:
if (cinfo->num_components != 4)
ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
break;
default:
ERREXIT(cinfo->emethods, "Unsupported JPEG colorspace");
break;
}
/* Set color_out_comps and conversion method based on requested space */
switch (cinfo->out_color_space) {
case CS_GRAYSCALE:
cinfo->color_out_comps = 1;
if (cinfo->jpeg_color_space == CS_GRAYSCALE ||
cinfo->jpeg_color_space == CS_YCbCr ||
cinfo->jpeg_color_space == CS_YIQ)
cinfo->methods->color_convert = grayscale_convert;
else
ERREXIT(cinfo->emethods, "Unsupported color conversion request");
break;
case CS_RGB:
cinfo->color_out_comps = 3;
if (cinfo->jpeg_color_space == CS_YCbCr)
cinfo->methods->color_convert = ycc_rgb_convert;
else if (cinfo->jpeg_color_space == CS_RGB)
cinfo->methods->color_convert = null_convert;
else
ERREXIT(cinfo->emethods, "Unsupported color conversion request");
break;
case CS_CMYK:
cinfo->color_out_comps = 4;
if (cinfo->jpeg_color_space == CS_CMYK)
cinfo->methods->color_convert = null_convert;
else
ERREXIT(cinfo->emethods, "Unsupported color conversion request");
break;
default:
ERREXIT(cinfo->emethods, "Unsupported output colorspace");
break;
}
if (cinfo->quantize_colors)
cinfo->final_out_comps = 1; /* single colormapped output component */
else
cinfo->final_out_comps = cinfo->color_out_comps;
cinfo->methods->colorout_init = colorout_init;
cinfo->methods->colorout_term = colorout_term;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.