swingx-master/swingx-graphics/src/main/java/org/jdesktop/swingx/image/StackBlurFilter.java
/*
 * $Id$
 *
 * Dual-licensed under LGPL (Sun and Romain Guy) and BSD (Romain Guy).
 *
 * Copyright 2006 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 *
 * Copyright (c) 2006 Romain Guy <romain.guy@mac.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.jdesktop.swingx.image;

import java.awt.image.BufferedImage;

import org.jdesktop.swingx.util.GraphicsUtilities;

/**
 * <p>A stack blur filter can be used to create an approximation of a
 * Gaussian blur. The approximation is controlled by the number of times the
 * {@link org.jdesktop.swingx.image.FastBlurFilter} is applied onto the source
 * picture. The default number of iterations, 3, provides a decent compromise
 * between speed and rendering quality.</p>
 * <p>The force of the blur can be controlled with a radius and the
 * default radius is 3. Since the blur clamps values on the edges of the
 * source picture, you might need to provide a picture with empty borders
 * to avoid artifacts at the edges. The performance of this filter are
 * independent from the radius.</p>
 *
 * @author Romain Guy <romain.guy@mac.com>
*/
public class StackBlurFilter extends AbstractFilter {
    private final int radius;
    private final int iterations;

    /**
     * <p>Creates a new blur filter with a default radius of 3 and 3 iterations.</p>
     */
    public StackBlurFilter() {
        this(3, 3);
    }

    /**
     * <p>Creates a new blur filter with the specified radius and 3 iterations.
     * If the radius is lower than 1, a radius of 1 will be used automatically.</p>
     *
     * @param radius the radius, in pixels, of the blur
     */
    public StackBlurFilter(int radius) {
        this(radius, 3);
    }

    /**
     * <p>Creates a new blur filter with the specified radius. If the radius
     * is lower than 1, a radius of 1 will be used automatically. The number
     * of iterations controls the approximation to a Gaussian blur. If the
     * number of iterations is lower than 1, one iteration will be used
     * automatically.</p>
     *
     * @param radius the radius, in pixels, of the blur
     * @param iterations the number of iterations to approximate a Gaussian blur
     */
    public StackBlurFilter(int radius, int iterations) {
        if (radius < 1) {
            radius = 1;
        }
        if (iterations < 1) {
            iterations = 1;
        }

        this.radius = radius;
        this.iterations = iterations;
    }

    /**
     * <p>Returns the effective radius of the stack blur. If the radius of the
     * blur is 1 and the stack iterations count is 3, then the effective blur
     * radius is 1 * 3 = 3.</p>
     * @return the number of iterations times the blur radius
     */
    public int getEffectiveRadius() {
        return getIterations() * getRadius();
    }

    /**
     * <p>Returns the radius used by this filter, in pixels.</p>
     *
     * @return the radius of the blur
     */
    public int getRadius() {
        return radius;
    }

    /**
     * <p>Returns the number of iterations used to approximate a Gaussian
     * blur.</p>
     *
     * @return the number of iterations used by this blur
     */
    public int getIterations() {
        return iterations;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public BufferedImage filter(BufferedImage src, BufferedImage dst) {
        int width = src.getWidth();
        int height = src.getHeight();

        if (dst == null) {
            dst = createCompatibleDestImage(src, null);
        }

        int[] srcPixels = new int[width * height];
        int[] dstPixels = new int[width * height];

        GraphicsUtilities.getPixels(src, 0, 0, width, height, srcPixels);
        for (int i = 0; i < iterations; i++) {
            // horizontal pass
            FastBlurFilter.blur(srcPixels, dstPixels, width, height, radius);
            // vertical pass
            FastBlurFilter.blur(dstPixels, srcPixels, height, width, radius);
        }
        // the result is now stored in srcPixels due to the 2nd pass
        GraphicsUtilities.setPixels(dst, 0, 0, width, height, srcPixels);

        return dst;
    }
}
