DiffusionDither.java
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.image;
import java.awt.*;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.*;
import java.util.Random;
/**
* This {@code BufferedImageOp/RasterOp} implements basic
* Floyd-Steinberg error-diffusion algorithm for dithering.
* <p>
* The weights used are 7/16, 3/16, 5/16 and 1/16, distributed like this:
* <!-- - -
* | |x|7|
* - - - -
* |3|5|1|
* - - -->
* </p>
* <table border="1" cellpadding="4" cellspacing="0">
* <caption>Floyd-Steinberg error-diffusion weights</caption>
* <tr><td bgcolor="#000000"> </td><td class="TableHeadingColor"
* align="center">x</td><td>7/16</td></tr>
* <tr><td>3/16</td><td>5/16</td><td>1/16</td></tr>
* </table>
* <p>
* See <A href="http://www.awprofessional.com/bookstore/product.asp?isbn=0201848406&rl=1">Computer Graphics (Foley et al.)</a>
* for more information.
* </p>
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
*
* @version $Id: DiffusionDither.java#1 $
*/
public class DiffusionDither implements BufferedImageOp, RasterOp {
private static final int FS_SCALE = 1 << 8;
private static final Random RANDOM = new Random();
protected final IndexColorModel indexColorModel;
private boolean alternateScans = true;
/**
* Creates a {@code DiffusionDither}, using the given
* {@code IndexColorModel} for dithering into.
*
* @param pICM an IndexColorModel.
*/
public DiffusionDither(final IndexColorModel pICM) {
// Store color model
indexColorModel = pICM;
}
/**
* Creates a {@code DiffusionDither}, with no fixed
* {@code IndexColorModel}. The color model will be generated for each
* filtering, unless the destination image already has an
* {@code IndexColorModel}.
*/
public DiffusionDither() {
this(null);
}
/**
* Sets the scan mode. If the parameter is true, error distribution for
* every even line will be left-to-right, while odd lines will be
* right-to-left.
* The default is {@code true}.
*
* @param pUse {@code true} if scan mode should be alternating left/right
*/
public void setAlternateScans(boolean pUse) {
alternateScans = pUse;
}
/**
* Creates a compatible {@code BufferedImage} to dither into.
* Only {@code IndexColorModel} allowed.
*
* @return a compatible {@code BufferedImage}
*
* @throws ImageFilterException if {@code pDestCM} is not {@code null} or
* an instance of {@code IndexColorModel}.
*/
public final BufferedImage createCompatibleDestImage(BufferedImage pSource, ColorModel pDestCM) {
if (pDestCM == null) {
return new BufferedImage(pSource.getWidth(), pSource.getHeight(),
BufferedImage.TYPE_BYTE_INDEXED,
getICM(pSource));
}
else if (pDestCM instanceof IndexColorModel) {
return new BufferedImage(pSource.getWidth(), pSource.getHeight(),
BufferedImage.TYPE_BYTE_INDEXED,
(IndexColorModel) pDestCM);
}
else {
throw new ImageFilterException("Only IndexColorModel allowed.");
}
}
/**
* Creates a compatible {@code Raster} to dither into.
* Only {@code IndexColorModel} allowed.
*
* @param pSrc the source raster
*
* @return a {@code WritableRaster}
*/
public final WritableRaster createCompatibleDestRaster(Raster pSrc) {
return createCompatibleDestRaster(pSrc, getICM(pSrc));
}
/**
* Creates a compatible {@code Raster} to dither into.
*
* @param pSrc the source raster.
* @param pIndexColorModel the index color model used to create a {@code Raster}.
*
* @return a {@code WritableRaster}
*/
public final WritableRaster createCompatibleDestRaster(Raster pSrc, IndexColorModel pIndexColorModel) {
return pIndexColorModel.createCompatibleWritableRaster(pSrc.getWidth(), pSrc.getHeight());
}
/**
* Returns the bounding box of the filtered destination image. Since
* this is not a geometric operation, the bounding box does not
* change.
* @param pSrc the {@code BufferedImage} to be filtered
* @return the bounds of the filtered definition image.
*/
public final Rectangle2D getBounds2D(BufferedImage pSrc) {
return getBounds2D(pSrc.getRaster());
}
/**
* Returns the bounding box of the filtered destination Raster. Since
* this is not a geometric operation, the bounding box does not
* change.
* @param pSrc the {@code Raster} to be filtered
* @return the bounds of the filtered definition {@code Raster}.
*/
public final Rectangle2D getBounds2D(Raster pSrc) {
return pSrc.getBounds();
}
/**
* Returns the location of the destination point given a
* point in the source. If {@code dstPt} is not
* {@code null}, it will be used to hold the return value.
* Since this is not a geometric operation, the {@code srcPt}
* will equal the {@code dstPt}.
* @param pSrcPt a {@code Point2D} that represents a point
* in the source image
* @param pDstPt a {@code Point2D}that represents the location
* in the destination
* @return the {@code Point2D} in the destination that
* corresponds to the specified point in the source.
*/
public final Point2D getPoint2D(Point2D pSrcPt, Point2D pDstPt) {
// Create new Point, if needed
if (pDstPt == null) {
pDstPt = new Point2D.Float();
}
// Copy location
pDstPt.setLocation(pSrcPt.getX(), pSrcPt.getY());
// Return dest
return pDstPt;
}
/**
* Returns the rendering mHints for this op.
* @return the {@code RenderingHints} object associated
* with this op.
*/
public final RenderingHints getRenderingHints() {
return null;
}
/**
* Converts an int ARGB to int triplet.
*/
private static int[] toRGBArray(int pARGB, int[] pBuffer) {
pBuffer[0] = ((pARGB & 0x00ff0000) >> 16);
pBuffer[1] = ((pARGB & 0x0000ff00) >> 8);
pBuffer[2] = ((pARGB & 0x000000ff));
//pBuffer[3] = ((pARGB & 0xff000000) >> 24); // alpha
return pBuffer;
}
/**
* Converts a int triplet to int ARGB.
*/
private static int toIntARGB(int[] pRGB) {
return 0xff000000 // All opaque
| (pRGB[0] << 16)
| (pRGB[1] << 8)
| (pRGB[2]);
/*
| ((int) (pRGB[0] << 16) & 0x00ff0000)
| ((int) (pRGB[1] << 8) & 0x0000ff00)
| ((int) (pRGB[2] ) & 0x000000ff);
*/
}
/**
* Performs a single-input/single-output dither operation, applying basic
* Floyd-Steinberg error-diffusion to the image.
*
* @param pSource the source image
* @param pDest the destination image
*
* @return the destination image, or a new image, if {@code pDest} was
* {@code null}.
*/
public final BufferedImage filter(BufferedImage pSource, BufferedImage pDest) {
// Create destination image, if none provided
if (pDest == null) {
pDest = createCompatibleDestImage(pSource, getICM(pSource));
}
else if (!(pDest.getColorModel() instanceof IndexColorModel)) {
throw new ImageFilterException("Only IndexColorModel allowed.");
}
// Filter rasters
filter(pSource.getRaster(), pDest.getRaster(), (IndexColorModel) pDest.getColorModel());
return pDest;
}
/**
* Performs a single-input/single-output dither operation, applying basic
* Floyd-Steinberg error-diffusion to the image.
*
* @param pSource the source raster, assumed to be in sRGB
* @param pDest the destination raster, may be {@code null}
*
* @return the destination raster, or a new raster, if {@code pDest} was
* {@code null}.
*/
public final WritableRaster filter(final Raster pSource, WritableRaster pDest) {
return filter(pSource, pDest, getICM(pSource));
}
private IndexColorModel getICM(BufferedImage pSource) {
return (indexColorModel != null ? indexColorModel : IndexImage.getIndexColorModel(pSource, 256, IndexImage.TRANSPARENCY_BITMASK));
}
private IndexColorModel getICM(Raster pSource) {
return (indexColorModel != null ? indexColorModel : createIndexColorModel(pSource));
}
private IndexColorModel createIndexColorModel(Raster pSource) {
BufferedImage image = new BufferedImage(pSource.getWidth(), pSource.getHeight(),
BufferedImage.TYPE_INT_ARGB);
image.setData(pSource);
return IndexImage.getIndexColorModel(image, 256, IndexImage.TRANSPARENCY_BITMASK);
}
/**
* Performs a single-input/single-output dither operation, applying basic
* Floyd-Steinberg error-diffusion to the image.
*
* @param pSource the source raster, assumed to be in sRGB
* @param pDest the destination raster, may be {@code null}
* @param pColorModel the indexed color model to use
*
* @return the destination raster, or a new raster, if {@code pDest} was
* {@code null}.
*/
public final WritableRaster filter(final Raster pSource, WritableRaster pDest, IndexColorModel pColorModel) {
int width = pSource.getWidth();
int height = pSource.getHeight();
// Create destination raster if needed
if (pDest == null) {
pDest = createCompatibleDestRaster(pSource, pColorModel);
}
// Initialize Floyd-Steinberg error vectors.
// +2 to handle the previous pixel and next pixel case minimally
// When reference for column, add 1 to reference as this buffer is
// offset from actual column position by one to allow FS to not check
// left/right edge conditions
int[][] currErr = new int[width + 2][3];
int[][] nextErr = new int[width + 2][3];
// Random errors in [-1 .. 1] - for first row
for (int i = 0; i < width + 2; i++) {
// Note: This is broken for the strange cases where nextInt returns Integer.MIN_VALUE
currErr[i][0] = RANDOM.nextInt(FS_SCALE * 2) - FS_SCALE;
currErr[i][1] = RANDOM.nextInt(FS_SCALE * 2) - FS_SCALE;
currErr[i][2] = RANDOM.nextInt(FS_SCALE * 2) - FS_SCALE;
}
// Temp buffers
final int[] diff = new int[3]; // No alpha
final int[] inRGB = new int[4];
final int[] outRGB = new int[4];
Object pixel = null;
boolean forward = true;
// Loop through image data
for (int y = 0; y < height; y++) {
// Clear out next error rows for colour errors
for (int i = nextErr.length; --i >= 0;) {
nextErr[i][0] = 0;
nextErr[i][1] = 0;
nextErr[i][2] = 0;
}
// Set up start column and limit
int x;
int limit;
if (forward) {
x = 0;
limit = width;
}
else {
x = width - 1;
limit = -1;
}
// TODO: Use getPixels instead of getPixel for better performance?
// Loop over row
while (true) {
// Get RGB from original raster
// DON'T KNOW IF THIS WILL WORK FOR ALL TYPES.
pSource.getPixel(x, y, inRGB);
// Get error for this pixel & add error to rgb
for (int i = 0; i < 3; i++) {
// Make a 28.4 FP number, add Error (with fraction),
// rounding and truncate to int
inRGB[i] = ((inRGB[i] << 4) + currErr[x + 1][i] + 0x08) >> 4;
// Clamp
if (inRGB[i] > 255) {
inRGB[i] = 255;
}
else if (inRGB[i] < 0) {
inRGB[i] = 0;
}
}
// Get pixel value...
// It is VERY important that we are using a IndexColorModel that
// support reverse color lookup for speed.
pixel = pColorModel.getDataElements(toIntARGB(inRGB), pixel);
// ...set it...
pDest.setDataElements(x, y, pixel);
// ..and get back the closet match
pDest.getPixel(x, y, outRGB);
// Convert the value to default sRGB
// Should work for all transfertypes supported by IndexColorModel
toRGBArray(pColorModel.getRGB(outRGB[0]), outRGB);
// Find diff
diff[0] = inRGB[0] - outRGB[0];
diff[1] = inRGB[1] - outRGB[1];
diff[2] = inRGB[2] - outRGB[2];
// Apply F-S error diffusion
// Serpentine scan: left-right
if (forward) {
// Row 1 (y)
// Update error in this pixel (x + 1)
currErr[x + 2][0] += diff[0] * 7;
currErr[x + 2][1] += diff[1] * 7;
currErr[x + 2][2] += diff[2] * 7;
// Row 2 (y + 1)
// Update error in this pixel (x - 1)
nextErr[x][0] += diff[0] * 3;
nextErr[x][1] += diff[1] * 3;
nextErr[x][2] += diff[2] * 3;
// Update error in this pixel (x)
nextErr[x + 1][0] += diff[0] * 5;
nextErr[x + 1][1] += diff[1] * 5;
nextErr[x + 1][2] += diff[2] * 5;
// Update error in this pixel (x + 1)
// TODO: Consider calculating this using
// error term = error - sum(error terms 1, 2 and 3)
// See Computer Graphics (Foley et al.), p. 573
nextErr[x + 2][0] += diff[0]; // * 1;
nextErr[x + 2][1] += diff[1]; // * 1;
nextErr[x + 2][2] += diff[2]; // * 1;
// Next
x++;
// Done?
if (x >= limit) {
break;
}
}
else {
// Row 1 (y)
// Update error in this pixel (x - 1)
currErr[x][0] += diff[0] * 7;
currErr[x][1] += diff[1] * 7;
currErr[x][2] += diff[2] * 7;
// Row 2 (y + 1)
// Update error in this pixel (x + 1)
nextErr[x + 2][0] += diff[0] * 3;
nextErr[x + 2][1] += diff[1] * 3;
nextErr[x + 2][2] += diff[2] * 3;
// Update error in this pixel (x)
nextErr[x + 1][0] += diff[0] * 5;
nextErr[x + 1][1] += diff[1] * 5;
nextErr[x + 1][2] += diff[2] * 5;
// Update error in this pixel (x - 1)
// TODO: Consider calculating this using
// error term = error - sum(error terms 1, 2 and 3)
// See Computer Graphics (Foley et al.), p. 573
nextErr[x][0] += diff[0]; // * 1;
nextErr[x][1] += diff[1]; // * 1;
nextErr[x][2] += diff[2]; // * 1;
// Previous
x--;
// Done?
if (x <= limit) {
break;
}
}
}
// Make next error info current for next iteration
int[][] temperr;
temperr = currErr;
currErr = nextErr;
nextErr = temperr;
// Toggle direction
if (alternateScans) {
forward = !forward;
}
}
return pDest;
}
}