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());
float alpha = composite.getAlpha();
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) & 0xFF;
srcPixel[3] = (pixel >> 24) & 0xFF;
pixel = dstPixels[x];
dstPixel[0] = (pixel >> 16) & 0xFF;
dstPixel[1] = (pixel >> 8) & 0xFF;
dstPixel[2] = (pixel) & 0xFF;
dstPixel[3] = (pixel >> 24) & 0xFF;
int[] result = blender.blend(srcPixel, dstPixel);
// mixes the result with the opacity
dstPixels[x] =
((int) (dstPixel[3] + (result[3] - dstPixel[3]) * alpha) & 0xFF) << 24
| ((int) (dstPixel[0] + (result[0] - dstPixel[0]) * alpha) & 0xFF) << 16
| ((int) (dstPixel[1] + (result[1] - dstPixel[1]) * alpha) & 0xFF) << 8
| (int) (dstPixel[2] + (result[2] - dstPixel[2]) * alpha) & 0xFF;
}
dstOut.setDataElements(0, y, width, 1, dstPixels);
}
}
private BlendingContext(BlendComposite composite) {
this.composite = composite;
this.blender = Blender.getBlenderFor(composite);
}