RGBComposite.java

/*
Copyright 2006 Jerry Huxtable

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package com.jhlabs.composite;

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

public abstract class RGBComposite implements Composite {

	protected float extraAlpha;

	public RGBComposite() {
		this( 1.0f );
	}

	public RGBComposite( float alpha ) {
		if ( alpha < 0.0f || alpha > 1.0f ) {
                    throw new IllegalArgumentException("RGBComposite: alpha must be between 0 and 1");
                }
		this.extraAlpha = alpha;
	}

	public float getAlpha() {
		return extraAlpha;
	}

        @Override
	public int hashCode() {
		return Float.floatToIntBits(extraAlpha);
	}

        @Override
	public boolean equals(Object o) {
		if (!(o instanceof RGBComposite)) {
                    return false;
                }
		RGBComposite c = (RGBComposite)o;

		return extraAlpha == c.extraAlpha;
	}

    public abstract static class RGBCompositeContext implements CompositeContext {

        // Multiply two numbers in the range 0..255 such that 255*255=255
        static int multiply255(int a, int b) {
            int t = a * b + 0x80;
            return ((t >> 8) + t) >> 8;
        }

        static int clamp(int a) {
            return a < 0 ? 0 : a > 255 ? 255 : a;
        }

        private final float alpha;
        private final ColorModel srcColorModel;
        private final ColorModel dstColorModel;

        public RGBCompositeContext( float alpha, ColorModel srcColorModel, ColorModel dstColorModel ) {
            this.alpha = alpha;
            this.srcColorModel = srcColorModel;
            this.dstColorModel = dstColorModel;
        }

        @Override
        public void dispose() {
        }
        public abstract void composeRGB( int[] src, int[] dst, float alpha);
        
        @Override
        public void compose( Raster src, Raster dstIn, WritableRaster dstOut) {
            float alpha = this.alpha;

            int[] srcPix = null;
            int[] dstPix = null;

            int x = dstOut.getMinX();
            int w = dstOut.getWidth();
            int y0 = dstOut.getMinY();
            int y1 = y0 + dstOut.getHeight();

            for ( int y = y0; y < y1; y++ ) {
                srcPix = src.getPixels( x, y, w, 1, srcPix );
                dstPix = dstIn.getPixels( x, y, w, 1, dstPix );
                composeRGB( srcPix, dstPix, alpha );
                dstOut.setPixels( x, y, w, 1, dstPix );
            }
        }
	

    }
}