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/*
 * Gray8Statistics.java
 *
 * Created on November 11, 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 .
 *
 */

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.MathPlus;

/**
 * Gray8Statistics is used to measure the mean and variance of a gray
 * image.
 * 
 * 
 * @author webb
 */
public class Gray8Statistics {
    private int nMean; // mean image value, times 256
    private int nVariance; // image variance, times 256
    
    /**
     * Creates a new instance of Gray8Statistics
     */
    public Gray8Statistics() {
    }
    
    /** Estimate the mean and variance of an input gray image.
     *
     * @param image the input image.
     * @throws com.github.ojil.core.Error if the input image is not gray.
     */
    public void push(Image image) throws com.github.ojil.core.Error
    {
        if (!(image instanceof Gray8Image)) {
            throw new Error(
                			Error.PACKAGE.ALGORITHM,
                			ErrorCodes.IMAGE_NOT_GRAY8IMAGE,
                			image.toString(),
                			null,
                			null);
        }
        Gray8Image gray = (Gray8Image) image;
        int nSum = 0, nSumSq = 0;
        Byte[] data = gray.getData();
        for (int i=0; i