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/*
 * Gray8LinComb.java
 *   Forms the linear combination of two gray images
 *
 * Created on September 9, 2006, 10:25 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 *
 * Copyright 2007 by Jon A. Webb
 *     This program is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU Lesser General Public License as published by
 *    the Free Software Foundation, either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Lesser General Public License for more details.
 *
 *    You should have received a copy of the Lesser GNU General Public License
 *    along with this program.  If not, see .
 *
 */

package com.github.ojil.algorithm;

import com.github.ojil.core.ErrorCodes;
import com.github.ojil.core.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.ImageError;
import com.github.ojil.core.Ladder;

/**
 * Computes linear combination of two Gray8Images. Result is (a*first image +
 * b*second image) / c. The signed image values are shifted so the minimum value
 * is 0 and the result is then shifted back to the signed range.

 * Intended to be used as a combination stage in a ladder operation.
 * 
 * @author webb
 */
public class Gray8LinComb implements Ladder.Join {
    private final int nA;
    private final int nB;
    private final int nC;
    
    /**
     * Creates a new instance of Gray8LinComb
     * 
     * @param a
     *            Multiplier for first image.
     * @param b
     *            Multiplier for second image.
     * @param c
     *            Divisor for linear combination.
     * @throws ImageError
     *             if the divisor (c) is 0.
     */
    public Gray8LinComb(final int a, final int b, final int c) throws ImageError {
        if (c == 0) {
            throw new ImageError(ImageError.PACKAGE.CORE, ErrorCodes.MATH_DIVISION_ZERO, null, null, null);
        }
        nA = a;
        nB = b;
        nC = c;
    }
    
    /**
     * Computes the linear combination of the two images, forming a*the first
     * image + b *the second image, all divided by c.
     * 
     * @param imageFirst
     *            the first image (and output)
     * @param imageSecond
     *            the second image
     * @return the linear combination of the two byte images, replacing the
     *         first.
     * @throws ImageError
     *             if either image is not a gray 8-bit image, or they are of
     *             different sizes.
     */
    @Override
    public Image doJoin(final Image imageFirst, final Image imageSecond) throws ImageError {
        if (!(imageFirst instanceof Gray8Image)) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_NOT_GRAY8IMAGE, imageFirst.toString(), null, null);
        }
        if (!(imageSecond instanceof Gray8Image)) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_NOT_GRAY8IMAGE, imageSecond.toString(), null, null);
        }
        if ((imageFirst.getWidth() != imageSecond.getWidth()) || (imageSecond.getHeight() != imageSecond.getHeight())) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_SIZES_DIFFER, imageFirst.toString(), imageSecond.toString(), null);
        }
        final Gray8Image gray1 = (Gray8Image) imageFirst;
        final Gray8Image gray2 = (Gray8Image) imageSecond;
        final Byte[] data1 = gray1.getData();
        final Byte[] data2 = gray2.getData();
        for (int i = 0; i < data1.length; i++) {
            final int nD1 = data1[i] - Byte.MIN_VALUE;
            final int nD2 = data2[i] - Byte.MIN_VALUE;
            data1[i] = (byte) Math.min(Byte.MAX_VALUE, Math.max(Byte.MIN_VALUE, (((nD1 * nA) + (nD2 * nB)) / nC) + Byte.MIN_VALUE));
        }
        return gray1;
    }
    
}