/*
 * Gray8VertAvg.java
 *
 * Created on September 9, 2006, 2:17 PM
 *
 * 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.Gray8Image;

/**
 * Forms the one-dimensional vector that is the vertical average
 * of the input gray image. Not a pipeline stage. The class may not
 * be instantiated; all members are static.
 *
 * @author webb
 */
public class Gray8VertAvg {
    
    /** Creates a new instance of Gray8VertAvg. May not be used. */
    private Gray8VertAvg() {
    }
    
    /** Form the one-dimensional byte vector that is the vertical
     * average of the input gray image. 
     *
     * @param image the input image.
     * @return a byte vector of length equal to the image width.
     * element i of this vector is the average of column i in the
     * image.
     */
    public static byte[] push(Gray8Image image) {
        int[] sum = new int[image.getWidth()];
        byte[] data = image.getData();
        for (int i=0; i<image.getHeight(); i++) {
            for (int j=0; j<image.getWidth(); j++) {
                sum[j] += data[i*image.getWidth() + j];
            }
        }
        byte[] result = new byte[image.getWidth()];
        for (int i=0; i<image.getWidth(); i++) {
            result[i] = (byte) (sum[i] / image.getHeight());
        }
        return result;
    }
}