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/*
* Copyright (c) 1992 The Regents of the University of California.
* All rights reserved.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose, without fee, and without written agreement is
* hereby granted, provided that the above copyright notice and the following
* two paragraphs appear in all copies of this software.
*
* IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
* OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
* CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/
/* This file contains C code to implement an ordered dither. */
#include <config.h>
#include "video.h"
#include "proto.h"
#include "dither.h"
#define DITH_SIZE 16
/* Structures used to implement hybrid ordered dither/floyd-steinberg
dither algorithm.
*/
static unsigned char *l_darrays[DITH_SIZE];
static unsigned char cr_fsarray[256][4];
static unsigned char cb_fsarray[256][4];
/*
*--------------------------------------------------------------
*
* InitHybridDither--
*
* Structures intialized for hybrid dithering. Ordered dither
* patterns set for luminance channel, f-s errors precomputed
* for chrominance channels.
*
* Results:
* None.
*
* Side effects:
* None.
*
*--------------------------------------------------------------
*/
void
InitHybridDither()
{
int i, j, k, err_range, threshval;
unsigned char *lmark;
for (i=0; i<DITH_SIZE; i++) {
lmark = l_darrays[i] = (unsigned char *) malloc(256);
for (j=0; j<lum_values[0]; j++) {
*lmark++ = 0;
}
for (j=0; j<(LUM_RANGE-1); j++) {
err_range = lum_values[j+1] - lum_values[j];
threshval = ((i * err_range) / DITH_SIZE)+lum_values[j];
for (k=lum_values[j]; k<lum_values[j+1]; k++) {
if (k > threshval) *lmark++ = ((j+1) * (CR_RANGE * CB_RANGE));
else *lmark++ = (j * (CR_RANGE * CB_RANGE));
}
}
for (j=lum_values[LUM_RANGE-1]; j<256; j++) {
*lmark++ = (LUM_RANGE-1)*(CR_RANGE * CB_RANGE);
}
}
{
int cr1, cr2, cr3, cr4, err1, err2;
int cb1, cb2, cb3, cb4, val, nval;
for (i=0; i<256; i++) {
val = i;
cr1 = (val * CR_RANGE) / 256;
err1 = (val - cr_values[cr1])/2;
err2 = (val - cr_values[cr1]) - err1;
nval = val+err1;
if (nval > 255) nval = 255;
else if (nval < 0) nval = 0;
cr2 = (nval * CR_RANGE) / 256;
err1 = (nval - cr_values[cr2])/2;
nval = val+err2;
if (nval > 255) nval = 255;
else if (nval < 0) nval = 0;
cr3 = (nval * CR_RANGE) / 256;
err2 = (nval - cr_values[cr3])/2;
nval = val+err1+err2;
if (nval > 255) nval = 255;
else if (nval < 0) nval = 0;
cr4 = (nval * CR_RANGE) / 256;
cr_fsarray[i][0] = cr1*CB_RANGE;
cr_fsarray[i][1] = cr2*CB_RANGE;
cr_fsarray[i][2] = cr3*CB_RANGE;
cr_fsarray[i][3] = cr4*CB_RANGE;
}
for (i=0; i<256; i++) {
val = i;
cb1 = (val * CB_RANGE) / 256;
err1 = (val - cb_values[cb1])/2;
err2 = (val - cb_values[cb1]) - err1;
nval = val+err1;
if (nval > 255) nval = 255;
else if (nval < 0) nval = 0;
cb2 = (nval * CB_RANGE) / 256;
err1 = (nval - cb_values[cb2])/2;
nval = val+err2;
if (nval > 255) nval = 255;
else if (nval < 0) nval = 0;
cb3 = (nval * CB_RANGE) / 256;
err2 = (nval - cb_values[cb3])/2;
nval = val+err1+err2;
if (nval > 255) nval = 255;
else if (nval < 0) nval = 0;
cb4 = (nval * CB_RANGE) / 256;
cb_fsarray[i][0] = cb1;
cb_fsarray[i][1] = cb2;
cb_fsarray[i][2] = cb3;
cb_fsarray[i][3] = cb4;
}
}
}
/*
*--------------------------------------------------------------
*
* HybridDitherImage --
*
* Dithers an image using an ordered dither.
* Assumptions made:
* 1) The color space is allocated y:cr:cb = 8:4:4
* 2) The spatial resolution of y:cr:cb is 4:1:1
* The luminance channel is dithered based on the standard
* ordered dither pattern for a 4x4 area. The Chrominance
* channels are dithered based on precomputed f-s errors.
* Two errors are propogated per pixel. Errors are NOT propogated
* beyond a 2x2 pixel area.
*
* Results:
* None.
*
* Side effects:
* None.
*
*--------------------------------------------------------------
*/
void
HybridDitherImage (lum, cr, cb, out, h, w)
unsigned char *lum;
unsigned char *cr;
unsigned char *cb;
unsigned char *out;
int w, h;
{
unsigned char *l, *r, *b, *o1, *o2;
unsigned char *l2;
int i, j;
l = lum;
l2 = lum+w;
r = cr;
b = cb;
o1 = out;
o2 = out+w;
for (i=0; i<h; i+=4) {
for (j=0; j<w; j+=4) {
*o1++ = pixel[(l_darrays[0][*l++] | cr_fsarray[*r][0] | cb_fsarray[*b][0])];
*o1++ = pixel[(l_darrays[8][*l++] | cr_fsarray[*r][1] | cb_fsarray[*b][1])];
*o2++ = pixel[(l_darrays[12][*l2++] | cr_fsarray[*r][2] | cb_fsarray[*b][2])];
*o2++ = pixel[(l_darrays[4][*l2++] | cr_fsarray[*r++][3] | cb_fsarray[*b++][3])];
*o1++ = pixel[(l_darrays[2][*l++] | cr_fsarray[*r][0] | cb_fsarray[*b][0])];
*o1++ = pixel[(l_darrays[10][*l++] | cr_fsarray[*r][1] | cb_fsarray[*b][1])];
*o2++ = pixel[(l_darrays[14][*l2++] | cr_fsarray[*r][2] | cb_fsarray[*b][2])];
*o2++ = pixel[(l_darrays[6][*l2++] | cr_fsarray[*r++][3] | cb_fsarray[*b++][3])];
}
l += w; l2 += w;
o1 += w; o2 += w;
for (j=0; j<w; j+=4) {
*o1++ = pixel[(l_darrays[3][*l++] | cr_fsarray[*r][1] | cb_fsarray[*b][1])];
*o1++ = pixel[(l_darrays[11][*l++] | cr_fsarray[*r][0] | cb_fsarray[*b][0])];
*o2++ = pixel[(l_darrays[15][*l2++] | cr_fsarray[*r][3] | cb_fsarray[*b][3])];
*o2++ = pixel[(l_darrays[7][*l2++] | cr_fsarray[*r++][2] | cb_fsarray[*b++][2])];
*o1++ = pixel[(l_darrays[1][*l++] | cr_fsarray[*r][1] | cb_fsarray[*b][1])];
*o1++ = pixel[(l_darrays[9][*l++] | cr_fsarray[*r][0] | cb_fsarray[*b][0])];
*o2++ = pixel[(l_darrays[13][*l2++] | cr_fsarray[*r][3] | cb_fsarray[*b][3])];
*o2++ = pixel[(l_darrays[5][*l2++] | cr_fsarray[*r++][2] | cb_fsarray[*b++][2])];
}
l += w; l2 += w;
o1 += w; o2 += w;
}
}
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