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/*
 * Gray8Sub.java
 *
 * 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.Error;
import com.github.ojil.core.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.Ladder;

/**
 * Subtracts one gray image from another. To be used as a join operation in a 
 * Ladder operation.
 * @author webb
 */
public class Gray8Sub implements Ladder.Join {
    
    /** Creates a new instance of Gray8Sub */
    public Gray8Sub() {
    }
    
    /**
     * Subtracts one gray image from another. Result is clamped between 
     * Byte.MIN_VALUE and Byte.MAX_VALUE.
     * @param imageFirst the first image (and output)
     * @param imageSecond the second image
     * @return the difference of the two byte images, replacing the first
     * @throws com.github.ojil.core.Error if either image is not a gray 8-bit
     * image, or they are of different sizes.
     */
    public Image doJoin(Image imageFirst, Image imageSecond)
        throws com.github.ojil.core.Error
    {
        if (!(imageFirst instanceof Gray8Image)) {
            throw new Error(
            				Error.PACKAGE.ALGORITHM,
            				ErrorCodes.IMAGE_NOT_GRAY8IMAGE,
            				imageFirst.toString(),
            				null,
            				null);
        }
        if (!(imageSecond instanceof Gray8Image)) {
            throw new Error(
            				Error.PACKAGE.ALGORITHM,
            				ErrorCodes.IMAGE_NOT_GRAY8IMAGE,
            				imageSecond.toString(),
            				null,
            				null);
        }
        if (imageFirst.getWidth() != imageSecond.getWidth() ||
        	imageSecond.getHeight() != imageSecond.getHeight()) {
        	throw new Error(
        				Error.PACKAGE.ALGORITHM,
        				ErrorCodes.IMAGE_SIZES_DIFFER,
        				imageFirst.toString(),
        				imageSecond.toString(),
        				null);
        
        }
        Gray8Image gray1 = (Gray8Image) imageFirst;
        Gray8Image gray2 = (Gray8Image) imageSecond;
        Byte[] data1 = gray1.getData();
        Byte[] data2 = gray2.getData();
        for (int i=0; i