DitherFloydSteinberg.java

/*
  DitherFloydSteinberg.java

  (c) 2016 Edward Swartz

  All rights reserved. This program and the accompanying materials
  are made available under the terms of the Eclipse Public License v1.0
  which accompanies this distribution, and is available at
  http://www.eclipse.org/legal/epl-v10.html
 */
package v9t9.video.imageimport;

import java.awt.image.BufferedImage;

import org.ejs.gui.images.IPaletteColorMapper;
import org.ejs.gui.images.IPaletteMapper;

import v9t9.video.imageimport.ImageImportOptions.Dither;

/**
 * @author ejs
 *
 */
public class DitherFloydSteinberg implements IDither {

	private Dither ditherType;
	private boolean useColorMappedGreyScale;


	/**
	 * @param thePalette
	 * @param ditherType
	 */
	public DitherFloydSteinberg(boolean useColorMappedGreyScale, Dither ditherType) {
		this.useColorMappedGreyScale = useColorMappedGreyScale;
		this.ditherType = ditherType;
	}

	private final int clamp(int i) {
		return i < 0 ? 0 : i > 255 ? 255 : i;
	}

	// https://en.wikipedia.org/wiki/Floyd%E2%80%93Steinberg_dithering
	private void ditherFSPixel(BufferedImage img, IPaletteColorMapper mapColor,
			int x, int y) {
		
		int pixel = img.getRGB(x, y);

		int newC = mapColor.getClosestPaletteEntry(pixel);
		
		int newPixel = mapColor.getPalettePixel(newC);
		
		img.setRGB(x, y, newPixel | 0xff000000);
		
		int r_error;
		int g_error;
		int b_error;
		
		r_error = ((pixel >> 16) & 0xff) - ((newPixel >> 16) & 0xff);
		g_error = ((pixel >> 8) & 0xff) - ((newPixel >> 8) & 0xff);
		b_error = ((pixel >> 0) & 0xff) - ((newPixel >> 0) & 0xff);
		
		if (ditherType == Dither.FSR) {
			// reduce bleed by ignoring some error
			r_error = reduceBleed(r_error);
			g_error = reduceBleed(g_error);
			b_error = reduceBleed(b_error);
		}

		if (useColorMappedGreyScale) {
			int lum = (299 * r_error + 587 * g_error + 114 * b_error) / 1000;
			r_error = g_error = b_error = lum;
		}
		
		if ((r_error | g_error | b_error) != 0) {
			if (x + 1 < img.getWidth()) {
				// x+1, y
				ditherFSApplyError(img, x + 1, y,  
						7, r_error, g_error, b_error);
			}
			if (y + 1 < img.getHeight()) {
				if (x > 0) {
					ditherFSApplyError(img, x - 1, y + 1, 
							3, r_error, g_error, b_error);
				}
				ditherFSApplyError(img, x, y + 1, 
						5, r_error, g_error, b_error);
				if (x + 1 < img.getWidth()) {
					ditherFSApplyError(img, x + 1, y + 1, 
							1, r_error, g_error, b_error);
				}
			}
		}
	}
	
	/**
	 * @param b_error
	 * @return
	 */
	private int reduceBleed(int v) {
		if (v < 0)
			return -(-v / 3);
		else
			return v / 3;
	}
	
	private void ditherFSApplyError(BufferedImage img, int x, int y, int sixteenths, int r_error, int g_error, int b_error) {
		int pixel = img.getRGB(x, y);
		int r = clamp(((pixel >> 16) & 0xff) + (sixteenths * r_error / 16));
		int g = clamp(((pixel >> 8) & 0xff) + (sixteenths * g_error / 16));
		int b = clamp(((pixel >> 0) & 0xff) + (sixteenths * b_error / 16));
		img.setRGB(x, y, (r << 16) | (g << 8) | b | 0xff000000);
	
	}

	
	/* (non-Javadoc)
	 * @see v9t9.video.imageimport.IDither#run(java.awt.image.BufferedImage, org.ejs.gui.images.IPaletteMapper, org.ejs.gui.images.Histogram)
	 */
	@Override
	public void run(BufferedImage img, IPaletteMapper mapColor) {
		int h = img.getHeight();
		int w = img.getWidth();

		for (int y = 0; y < h; y++) {
			for (int x = 0; x < w; x++) {
				ditherFSPixel(img, mapColor, x, y);
			}
		}
		
	}

}