/*

 * Copyright (c) 2008, Harald Kuhr

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *     * Redistributions of source code must retain the above copyright

 *       notice, this list of conditions and the following disclaimer.

 *     * 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.

 *     * Neither the name "TwelveMonkeys" nor the

 *       names of its contributors may be used to endorse or promote products

 *       derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "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 COPYRIGHT OWNER OR

 * CONTRIBUTORS 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 com.twelvemonkeys.image;



import java.awt.image.RGBImageFilter;





/**

 * Adjusts the contrast and brightness of an image.

 * <p/>

 * For brightness, the valid range is {@code -2.0,..,0.0,..,2.0}.

 * A value of {@code 0.0} means no change.

 * Negative values will make the pixels darker.

 * Maximum negative value ({@code -2}) will make all filtered pixels black.

 * Positive values will make the pixels brighter.

 * Maximum positive value ({@code 2}) will make all filtered pixels white.

 * <p/>

 * For contrast, the valid range is {@code -1.0,..,0.0,..,1.0}.

 * A value of {@code 0.0} means no change.

 * Negative values will reduce contrast.

 * Maximum negative value ({@code -1}) will make all filtered pixels grey

 * (no contrast).

 * Positive values will increase contrast.

 * Maximum positive value ({@code 1}) will make all filtered pixels primary

 * colors (either black, white, cyan, magenta, yellow, red, blue or green).

 *

 * @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>

 * @author last modified by $Author: haku $

 *

 * @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/image/BrightnessContrastFilter.java#1 $

 *

 * @todo consider doing something similar to http://archives.java.sun.com/cgi-bin/wa?A2=ind0302&L=jai-interest&F=&S=&P=15947

 */



public class BrightnessContrastFilter extends RGBImageFilter {



    // This filter can filter IndexColorModel, as it is does not depend on

    // the pixels' location

    {

        canFilterIndexColorModel = true;

    }



    // Use a precalculated lookup table for performace

    private final int[] LUT;



    /**

     * Creates a BrightnessContrastFilter with default values

     * ({@code brightness=0.3, contrast=0.3}).

     * <p/>

     * This will slightly increase both brightness and contrast.

     */

    public BrightnessContrastFilter() {

        this(0.3f, 0.3f);

    }



    /**

     * Creates a BrightnessContrastFilter with the given values for brightness

     * and contrast.

     * <p/>

     * For brightness, the valid range is {@code -2.0,..,0.0,..,2.0}.

     * A value of {@code 0.0} means no change.

     * Negative values will make the pixels darker.

     * Maximum negative value ({@code -2}) will make all filtered pixels black.

     * Positive values will make the pixels brighter.

     * Maximum positive value ({@code 2}) will make all filtered pixels white.

     * <p/>

     * For contrast, the valid range is {@code -1.0,..,0.0,..,1.0}.

     * A value of {@code 0.0} means no change.

     * Negative values will reduce contrast.

     * Maximum negative value ({@code -1}) will make all filtered pixels grey

     * (no contrast).

     * Positive values will increase contrast.

     * Maximum positive value ({@code 1}) will make all filtered pixels primary

     * colors (either black, white, cyan, magenta, yellow, red, blue or green).

     *

     * @param pBrightness adjust the brightness of the image, in the range

     * {@code -2.0,..,0.0,..,2.0}.

     * @param pContrast adjust the contrast of the image, in the range

     * {@code -1.0,..,0.0,..,1.0}.

     */

    public BrightnessContrastFilter(float pBrightness, float pContrast) {

        LUT = createLUT(pBrightness, pContrast);

    }



    private static int[] createLUT(float pBrightness, float pContrast) {

        int[] lut = new int[256];



        // Hmmm.. This approximates Photoshop values.. Not good though..

        double contrast = pContrast > 0 ? Math.pow(pContrast, 7.0) * 127.0 : pContrast;



        // Convert range [-1,..,0,..,1] -> [0,..,1,..,2]

        double brightness = pBrightness + 1.0;



        for (int i = 0; i < 256; i++) {

            lut[i] = clamp((int) (127.5 * brightness + (i - 127) * (contrast + 1.0)));

        }



        // Special case, to ensure only primary colors for max contrast

        if (pContrast == 1f) {

            lut[127] = lut[126];

        }



        return lut;

    }



    private static int clamp(int i) {

        if (i < 0) {

            return 0;

        }

        if (i > 255) {

            return 255;

        }

        return i;

    }



    /**

     * Filters one pixel, adjusting brightness and contrast according to this

     * filter.

     *

     * @param pX x

     * @param pY y

     * @param pARGB pixel value in default color space

     *

     * @return the filtered pixel value in the default color space

     */



    public int filterRGB(int pX, int pY, int pARGB) {

        // Get color components

        int r = pARGB >> 16 & 0xFF;

        int g = pARGB >> 8 & 0xFF;

        int b = pARGB & 0xFF;



        // Scale to new contrast

        r = LUT[r];

        g = LUT[g];

        b = LUT[b];



        // Return ARGB pixel, leave transparency as is

        return (pARGB & 0xFF000000) | (r << 16) | (g << 8) | b;

    }

}