MultiplyComposite.java

package sample4_fancy;

import java.awt.Composite;
import java.awt.CompositeContext;
import java.awt.RenderingHints;
import java.awt.image.ColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;

/**
 * Multiplies two images
 * @author Martin Steiger
 */
public class MultiplyComposite implements Composite
{
	/**
	 * The default implementation
	 */
	public static final MultiplyComposite Default = new MultiplyComposite();

	private MultiplyComposite()
	{
		// empty
	}
	
	@Override
	public CompositeContext createContext(ColorModel srcColorModel, ColorModel dstColorModel, RenderingHints hints)
	{
		return new CompositeContext()
		{
			@Override
			public void compose(Raster src, Raster dstIn, WritableRaster dstOut)
			{
				if (src.getSampleModel().getDataType() != DataBuffer.TYPE_INT
						|| dstIn.getSampleModel().getDataType() != DataBuffer.TYPE_INT
						|| dstOut.getSampleModel().getDataType() != DataBuffer.TYPE_INT)
				{
					throw new IllegalStateException("Source and destination must store pixels as INT.");
				}
	
				int width = Math.min(src.getWidth(), dstIn.getWidth());
				int height = Math.min(src.getHeight(), dstIn.getHeight());
	
				int[] srcPixel = new int[4];
				int[] dstPixel = new int[4];
				int[] srcPixels = new int[width];
				int[] dstPixels = new int[width];
	
				for (int y = 0; y < height; y++)
				{
					src.getDataElements(0, y, width, 1, srcPixels);
					dstIn.getDataElements(0, y, width, 1, dstPixels);
				
					for (int x = 0; x < width; x++)
					{
						// pixels are stored as INT_ARGB
						// our arrays are [R, G, B, A]
						int pixel = srcPixels[x];
						srcPixel[0] = (pixel >> 16) & 0xFF;
						srcPixel[1] = (pixel >>  8) & 0xFF;
						srcPixel[2] = (pixel >>  0) & 0xFF;
						srcPixel[3] = (pixel >> 24) & 0xFF;
	
						pixel = dstPixels[x];
						dstPixel[0] = (pixel >> 16) & 0xFF;
						dstPixel[1] = (pixel >>  8) & 0xFF;
						dstPixel[2] = (pixel >>  0) & 0xFF;
						dstPixel[3] = (pixel >> 24) & 0xFF;
	
						int[] result = new int[] 
						{ 
							(srcPixel[0] * dstPixel[0]) >> 8, 
							(srcPixel[1] * dstPixel[1]) >> 8, 
							(srcPixel[2] * dstPixel[2]) >> 8,
							(srcPixel[3] * dstPixel[3]) >> 8 
						};
	
						// mixes the result with the opacity
						dstPixels[x] = 
								  (result[3] ) << 24
								| (result[0] ) << 16
								| (result[1] ) << 8
								| (result[2] );
					}
					dstOut.setDataElements(0, y, width, 1, dstPixels);
				}
			}
	
			@Override
			public void dispose()
			{
				// empty
			}
		};
	}
}