Gray8QmSum.java

/*
 * Gray8QmSum.java
 *
 * Created on August 27, 2006, 9:02 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 <http://www.gnu.org/licenses/>.
 *
 */

package jjil.algorithm;
import jjil.core.Error;
import jjil.core.Gray32Image;
import jjil.core.Gray8Image;
import jjil.core.Image;
import jjil.core.PipelineStage;
/**
 * Gray8QmSum forms the cumulative sum of an image.
 * <blockquote> Output(i,j) = ∑<sub>k ≤ i, l ≤ j</sub> Input(k,l). </blockquote>
 *  Output is a 32-bit gray image.
 *  Input is an 8-bit gray image.<p>
 * Note that since the output is 32 bits the input image cannot have more than
 * 2<sup>24</sup> pixels without risking overflow. For example, an image larger than
 * 4096 × 4096 (=2<sup>12</sup> × 2<sup>12</sup>) might overflow.
 * @author webb
 */
public class Gray8QmSum extends PipelineStage {
    
    /**
     * Creates a new instance of Gray8QmSum
     */
    public Gray8QmSum() {
    }
    
    /** Forms the cumulative sum of an image.
     *  Output(i,j) = ∑<sub>k ≤ i, l ≤ j</sub> Input(k,l)).
     *  Output is 32-bit gray image.
     *  Input is 8-bit gray image.
     *
     * @param image the input image.
     * @throws jjil.core.Error if the input is not a Gray8Image
     */
    public void push(Image image) throws jjil.core.Error {
        if (!(image instanceof Gray8Image)) {
            throw new Error(
            				Error.PACKAGE.ALGORITHM,
            				ErrorCodes.IMAGE_NOT_GRAY8IMAGE,
            				image.toString(),
            				null,
            				null);
        }
        Gray8Image gray = (Gray8Image) image;
        Gray32Image gray32 = new Gray32Image(image.getWidth(), image.getHeight());
        byte[] grayData = gray.getData();
        int[] gray32Data = gray32.getData();
        // First row
        int nSum = 0;
        for (int j=0; j<gray.getWidth(); j++) {
            /* Convert from signed byte value to unsigned byte for storage
             * in the 32-bit image.
             */
            int grayUnsigned = (grayData[j]) - Byte.MIN_VALUE;
            /* Assign 32-bit output */
            nSum += grayUnsigned;
            gray32Data[j] = nSum;
        }
        // Other rows
        for (int i=1; i<gray.getHeight(); i++) {
            nSum = 0;
            for (int j=0; j<gray.getWidth(); j++) {
                /* Convert from signed byte value to unsigned byte for storage
                 * in the 32-bit image.
                 */
                int grayUnsigned = 
                        (grayData[i*gray.getWidth()+j]) - Byte.MIN_VALUE;
                nSum += grayUnsigned;
                gray32Data[i*gray.getWidth()+j] = 
                        gray32Data[(i-1)*gray.getWidth()+j] +
                        nSum;
            }
        }
        super.setOutput(gray32);
    }
}