/*
* Copyright (c) 2010, grossmann
* All rights reserved.
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package org.jowidgets.spi.impl.swt.common.image.util;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.PaletteData;
import org.eclipse.swt.graphics.RGB;
public final class AntiAliasingFilter {
private AntiAliasingFilter() {};
/**
* Filters an image as preliminary for an scale function. If an image must be scaled to an lower resolution,
* it must be low pass filtered to respect the nyquist theorem. After it was scaled, it can be
* scaled (resampled) with an lower resolution (frequency).
*
* Remark: This algorithm is only used in case of RWT. To simplify matters this implementation filters
* in the 'position space' an not in the 'frequency space'.
* Feel free to implement this method with help of convolution and FFT and send me the patch.
* With respect to the performance, the maximal possible gauss matrix is 25x25. For scaled factors bigger
* than 1/25 aliasing could still occur.
*
* @param originalData The image data than should be resized.
* @param resultWidth the width of the image after scaling
* @param resultHeight the height of the image after scaling
* @return The image data of the low pass filtered image, if the new image is smaller than the original, otherwise
* the original
*/
public static ImageData filter(final ImageData originalData, final int resultWidth, final int resultHeight) {
final Double[][] filter = getFilter(originalData.width, originalData.height, resultWidth, resultHeight);
if (filter != null) {
final ImageData result = (ImageData) originalData.clone();
final HighResolutionPixel[][] highResDataSource = createHighResolutionData(result);
final HighResolutionPixel[][] highResDataDest = new HighResolutionPixel[originalData.width][originalData.height];
final int filterLength = filter.length;
final int offset = (filter.length - 1) / 2;
for (int x = 0; x < result.width; x++) {
for (int y = 0; y < result.height; y++) {
HighResolutionPixel pixel = new HighResolutionPixel();
for (int filterX = 0; filterX < filterLength; filterX++) {
for (int filterY = 0; filterY < filterLength; filterY++) {
int xPos = x + filterX - offset;
int yPos = y + filterY - offset;
//mirror the picture if filter mask is beyond image
if (xPos < 0) {
xPos = x + (filterLength - filterX) - offset;
}
if (xPos >= result.width) {
xPos = x + (filterX - filterLength) - offset;
}
if (yPos < 0) {
yPos = y + (filterLength - filterY) - offset;
}
if (yPos >= result.height) {
yPos = y + (filterY - filterLength) - offset;
}
pixel = pixel.add(highResDataSource[xPos][yPos].multiply(filter[filterX][filterY]));
}
}
highResDataDest[x][y] = pixel;
}
}
setLowResolutionData(result, highResDataDest);
return result;
}
return originalData;
}
private static Double[][] getFilter(
final int originalWidth,
final int originalHeight,
final int resultWidth,
final int resultHeight) {
final double scaleFacX = ((double) originalWidth) / resultWidth;
final double scaleFacY = ((double) originalHeight) / resultHeight;
final double scaleFac = Math.max(scaleFacX, scaleFacY);
if (scaleFac > 1) {
return GaussMatrix.getGaussMatrix((int) Math.min(Math.round(scaleFac) + 2, GaussMatrix.MAX_DEPTH));
}
return null;
}
private static HighResolutionPixel[][] createHighResolutionData(final ImageData imageData) {
final HighResolutionPixel[][] result = new HighResolutionPixel[imageData.width][imageData.height];
for (int x = 0; x < imageData.width; x++) {
for (int y = 0; y < imageData.height; y++) {
result[x][y] = new HighResolutionPixel(imageData.getPixel(x, y), imageData.palette);
}
}
return result;
}
private static void setLowResolutionData(final ImageData imageData, final HighResolutionPixel[][] highResolutionData) {
for (int x = 0; x < imageData.height; x++) {
for (int y = 0; y < imageData.width; y++) {
imageData.setPixel(
x,
y,
highResolutionData[x][y].getLowResolutionPixel(imageData.getPixel(x, y), imageData.palette));
}
}
}
}
class HighResolutionPixel {
private final double red;
private final double green;
private final double blue;
HighResolutionPixel(final int originalPixel, final PaletteData paletteData) {
this.red = paletteData.getRGB(originalPixel).red;
this.green = paletteData.getRGB(originalPixel).green;
this.blue = paletteData.getRGB(originalPixel).blue;
}
HighResolutionPixel() {
this(0.0, 0.0, 0.0);
}
HighResolutionPixel(final double red, final double green, final double blue) {
this.red = red;
this.green = green;
this.blue = blue;
}
public HighResolutionPixel add(final HighResolutionPixel highResolutionPixel) {
final double newRed = red + highResolutionPixel.red;
final double newGreen = green + highResolutionPixel.green;
final double newBlue = blue + highResolutionPixel.blue;
return new HighResolutionPixel(newRed, newGreen, newBlue);
}
public HighResolutionPixel multiply(final Double factor) {
return new HighResolutionPixel(red * factor, green * factor, blue * factor);
}
public HighResolutionPixel divide(final int divisor) {
return new HighResolutionPixel(red / divisor, green / divisor, blue / divisor);
}
public int getLowResolutionPixel(final int originalPixel, final PaletteData paletteData) {
final int result = paletteData.getPixel(new RGB((int) red, (int) green, (int) blue));
final int mask = 0xFFFFFFFF & ~paletteData.redMask & ~paletteData.greenMask & ~paletteData.blueMask;
final int clearedOriginal = originalPixel & mask;
final int modifiedOriginal = clearedOriginal | result;
return modifiedOriginal;
}
}