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/*
Copyright 2006 Jerry Huxtable
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package com.jhlabs.image;
import java.awt.*;
import java.awt.image.*;
/**
* A filter which uses Floyd-Steinberg error diffusion dithering to halftone an image.
*/
public class DiffusionFilter extends WholeImageFilter {
protected final static int[] diffusionMatrix = {
0, 0, 0,
0, 0, 7,
3, 5, 1,
};
private int[] matrix;
private int sum = 3+5+7+1;
private boolean serpentine = true;
private boolean colorDither = true;
public int levels = 6;
/**
* Construct a DiffusionFilter
*/
public DiffusionFilter() {
setMatrix(diffusionMatrix);
}
/**
* Set whether to use a serpentine pattern for return or not. This can reduce 'avalanche' artifacts in the output.
* @param serpentine true to use serpentine pattern
*/
public void setSerpentine(boolean serpentine) {
this.serpentine = serpentine;
}
/**
* Return the serpentine setting
* @return the current setting
*/
public boolean getSerpentine() {
return serpentine;
}
public void setColorDither(boolean colorDither) {
this.colorDither = colorDither;
}
public boolean getColorDither() {
return colorDither;
}
public void setMatrix(int[] matrix) {
this.matrix = matrix;
sum = 0;
for (int i = 0; i < matrix.length; i++)
sum += matrix[i];
}
public int[] getMatrix() {
return matrix;
}
public void setLevels(int levels) {
this.levels = levels;
}
public int getLevels() {
return levels;
}
protected int[] filterPixels( int width, int height, int[] inPixels, Rectangle transformedSpace ) {
int[] outPixels = new int[width * height];
int index = 0;
int[] map = new int[levels];
for (int i = 0; i < levels; i++) {
int v = 255 * i / (levels-1);
map[i] = v;
}
int[] div = new int[256];
for (int i = 0; i < 256; i++)
div[i] = levels*i / 256;
for (int y = 0; y < height; y++) {
boolean reverse = serpentine && (y & 1) == 1;
int direction;
if (reverse) {
index = y*width+width-1;
direction = -1;
} else {
index = y*width;
direction = 1;
}
for (int x = 0; x < width; x++) {
int rgb1 = inPixels[index];
int r1 = (rgb1 >> 16) & 0xff;
int g1 = (rgb1 >> 8) & 0xff;
int b1 = rgb1 & 0xff;
if (!colorDither)
r1 = g1 = b1 = (r1+g1+b1) / 3;
int r2 = map[div[r1]];
int g2 = map[div[g1]];
int b2 = map[div[b1]];
outPixels[index] = 0xff000000 | (r2 << 16) | (g2 << 8) | b2;
int er = r1-r2;
int eg = g1-g2;
int eb = b1-b2;
for (int i = -1; i <= 1; i++) {
int iy = i+y;
if (0 <= iy && iy < height) {
for (int j = -1; j <= 1; j++) {
int jx = j+x;
if (0 <= jx && jx < width) {
int w;
if (reverse)
w = matrix[(i+1)*3-j+1];
else
w = matrix[(i+1)*3+j+1];
if (w != 0) {
int k = reverse ? index - j : index + j;
rgb1 = inPixels[k];
r1 = (rgb1 >> 16) & 0xff;
g1 = (rgb1 >> 8) & 0xff;
b1 = rgb1 & 0xff;
r1 += er * w/sum;
g1 += eg * w/sum;
b1 += eb * w/sum;
inPixels[k] = (PixelUtils.clamp(r1) << 16) | (PixelUtils.clamp(g1) << 8) | PixelUtils.clamp(b1);
}
}
}
}
}
index += direction;
}
}
return outPixels;
}
public String toString() {
return "Colors/Diffusion Dither...";
}
}
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