// Catalano Imaging Library
// The Catalano Framework
//
// Copyright © Diego Catalano, 2012-2016
// diego.catalano at live.com
//
//
//    This library 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 2.1 of the License, or (at your option) any later version.
//
//    This library 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 GNU Lesser General Public
//    License along with this library; if not, write to the Free Software
//    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
//

package Catalano.Imaging.Filters;

import Catalano.Imaging.FastBitmap;
import Catalano.Imaging.IApplyInPlace;
import Catalano.Imaging.Tools.ImageStatistics;

/**
 * Image Normalization.
 * 
 * References: http://www.ccis2k.org/iajit/PDF/vol.4,no.4/12-Qader.pdf
 * @author Diego Catalano
 */
public class ImageNormalization implements IApplyInPlace{
    
    private float mean = 160;
    private float variance = 150;

    /**
     * Get Mean.
     * @return Mean.
     */
    public float getMean() {
        return mean;
    }

    /**
     * Set Mean.
     * @param mean Mean.
     */
    public void setMean(float mean) {
        this.mean = Math.max(0, Math.min(255, mean));
    }

    /**
     * Get Variance.
     * @return Variance.
     */
    public float getVariance() {
        return variance;
    }

    /**
     * Set Variance.
     * @param variance Variance.
     */
    public void setVariance(float variance) {
        this.variance = Math.max(0, Math.min(255, variance));
    }

    /**
     * Initialize a new instance of the ImageNormalization class.
     */
    public ImageNormalization() {}

    /**
     * Initialize a new instance of the ImageNormalization class.
     * @param mean Desired mean.
     * @param variance Desired variance.
     */
    public ImageNormalization(float mean, float variance) {
        setMean(mean);
        setVariance(variance);
    }

    @Override
    public void applyInPlace(FastBitmap fastBitmap) {
        
        if (fastBitmap.isGrayscale()){
            
            float globalMean = ImageStatistics.Mean(fastBitmap);
            float globalVariance = ImageStatistics.Variance(fastBitmap, globalMean);
            
            int size = fastBitmap.getSize();
            for (int i = 0; i < size; i++) {
                int g = fastBitmap.getGray(i);
                float common = (float)Math.sqrt((variance * (float)Math.pow(g - globalMean, 2)) / globalVariance);
                int n = 0;
                if (g > globalMean){
                    n = (int)(mean + common);
                }
                else{
                    n = (int)(mean - common);
                }

                n = n > 255 ? 255 : n;
                n = n < 0 ? 0 : n;

                fastBitmap.setGray(i, n);
            }
        }
        else{
            throw new IllegalArgumentException("ImageNormalization only works with grayscale images.");
        }
    }
}