Color quantization: Difference between revisions
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=={{header|Java}}==
A simple median cut algorithm.
</syntaxhighlight>
import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import javax.imageio.ImageIO;
public final class ColorQuantization {
public static void main(String[] aArgs) throws IOException {
BufferedImage original = ImageIO.read( new File("quantum_frog.png") );
final int width = original.getWidth();
final int height = original.getHeight();
int[] originalPixels = original.getRGB(0, 0, width, height, null, 0, width);
List<Item> bucket = new ArrayList<Item>();
for ( int i = 0; i < originalPixels.length; i++ ) {
bucket.add( new Item(new Color(originalPixels[i]), i) );
}
int[] resultPixels = new int[originalPixels.length];
medianCut(bucket, 4, resultPixels);
BufferedImage result = new BufferedImage(width, height, original.getType());
result.setRGB(0, 0, width, height, resultPixels, 0, width);
ImageIO.write(result, "png", new File("Quantum_frog16Java.png"));
System.out.println("The 16 colors used in Red, Green, Blue format are:");
for ( Color color : colorsUsed ) {
System.out.println("(" + color.getRed() + ", " + color.getGreen() + ", " + color.getBlue() + ")");
}
}
private static void medianCut(List<Item> aBucket, int aDepth, int[] aResultPixels) {
if ( aDepth == 0 ) {
quantize(aBucket, aResultPixels);
return;
}
int[] minimumValue = new int[] { 256, 256, 256 };
int[] maximumValue = new int[] { 0, 0, 0 };
for ( Item item : aBucket ) {
for ( Channel channel : Channel.values() ) {
int value = item.getPrimary(channel);
if ( value < minimumValue[channel.index] ) {
minimumValue[channel.index] = value;
}
if ( value > maximumValue[channel.index] ) {
maximumValue[channel.index] = value;
}
}
}
int[] valueRange = new int[] { maximumValue[Channel.RED.index] - minimumValue[Channel.RED.index],
maximumValue[Channel.GREEN.index] - minimumValue[Channel.GREEN.index],
maximumValue[Channel.BLUE.index] - minimumValue[Channel.BLUE.index] };
Channel selectedChannel = ( valueRange[Channel.RED.index] >= valueRange[Channel.GREEN.index] )
? ( valueRange[Channel.RED.index] >= valueRange[Channel.BLUE.index] ) ? Channel.RED : Channel.BLUE
: ( valueRange[Channel.GREEN.index] >= valueRange[Channel.BLUE.index] ) ? Channel.GREEN : Channel.BLUE;
Collections.sort(aBucket, switch(selectedChannel) {
case RED -> redComparator;
case GREEN -> greenComparator;
case BLUE -> blueComparator; });
final int medianIndex = aBucket.size() / 2;
medianCut(new ArrayList<Item>(aBucket.subList(0, medianIndex)), aDepth - 1, aResultPixels);
medianCut(new ArrayList<Item>(aBucket.subList(medianIndex, aBucket.size())), aDepth - 1, aResultPixels);
}
private static void quantize(List<Item> aBucket, int[] aResultPixels) {
int[] means = new int[Channel.values().length];
for ( Item item : aBucket ) {
for ( Channel channel : Channel.values() ) {
means[channel.index] += item.getPrimary(channel);
}
}
for ( Channel channel : Channel.values() ) {
means[channel.index] /= aBucket.size();
}
Color color = new Color(means[Channel.RED.index], means[Channel.GREEN.index], means[Channel.BLUE.index]);
colorsUsed.add(color);
for ( Item item : aBucket ) {
aResultPixels[item.aIndex] = color.getRGB();
}
}
private enum Channel {
RED(0), GREEN(1), BLUE(2);
private Channel(int aIndex) {
index = aIndex;
}
private final int index;
}
private record Item(Color aColor, Integer aIndex) {
public int getPrimary(Channel aChannel) {
return switch(aChannel) {
case RED -> aColor.getRed();
case GREEN -> aColor.getGreen();
case BLUE -> aColor.getBlue();
};
}
}
private static Comparator<Item> redComparator =
(one, two) -> Integer.compare(one.aColor.getRed(), two.aColor.getRed());
private static Comparator<Item> greenComparator =
(one, two) -> Integer.compare(one.aColor.getGreen(), two.aColor.getGreen());
private static Comparator<Item> blueComparator =
(one, two) -> Integer.compare(one.aColor.getBlue(), two.aColor.getBlue());
private static List<Color> colorsUsed = new ArrayList<Color>();
}
</syntaxhighlight>
{{ out }}
[[Media:Quantum_frog16Java.png]]
<pre>
The 16 colors used in Red, Green, Blue format are:
(8, 36, 0)
(7, 54, 0)
(22, 66, 0)
(51, 99, 3)
(53, 129, 1)
(64, 140, 2)
(67, 142, 5)
(71, 144, 11)
(79, 143, 11)
(99, 139, 14)
(88, 156, 18)
(129, 171, 23)
(127, 165, 53)
(166, 205, 65)
(165, 189, 123)
(205, 226, 159)
</pre>
=={{header|Julia}}==
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