ConvolutionMatrix.java

package com.rec.photoeditor.graphics;

import android.graphics.Bitmap;
import android.graphics.Color;

public class ConvolutionMatrix
{
    public static final int SIZE = 3;

    public double[][] Matrix;
    public double Factor = 1;
    public double Offset = 1;

    public ConvolutionMatrix(int size) {
        Matrix = new double[size][size];
    }

    public void setAll(double value) {
        for (int x = 0; x < SIZE; ++x) {
            for (int y = 0; y < SIZE; ++y) {
                Matrix[x][y] = value;
            }
        }
    }

    public void applyConfig(double[][] config) {
    	for(int x = 0; x < SIZE; ++x) {
    		for(int y = 0; y < SIZE; ++y) {
    			Matrix[x][y] = config[x][y];
    		}
    	}
    }

    
    public static Bitmap computeConvolution(Bitmap src, ConvolutionMatrix matrix){
    	return computeConvolution3x3(src, matrix);
    }
    
    private static Bitmap computeConvolution3x3(Bitmap src, ConvolutionMatrix matrix) {
    	int width = src.getWidth();
    	int height = src.getHeight();
    	Bitmap result = Bitmap.createBitmap(width, height, src.getConfig());

    	int A, R, G, B;
    	int sumR, sumG, sumB;
    	int[][] pixels = new int[SIZE][SIZE];

    	for(int y = 0; y < height - 2; ++y) {
    		for(int x = 0; x < width - 2; ++x) {

    			for(int i = 0; i < SIZE; ++i) {
    				for(int j = 0; j < SIZE; ++j) {
    					pixels[i][j] = src.getPixel(x + i, y + j);
    				}
    			}

    			A = Color.alpha(pixels[1][1]);

    			sumR = sumG = sumB = 0;

    			for(int i = 0; i < SIZE; ++i) {
    				for(int j = 0; j < SIZE; ++j) {
    					sumR += (Color.red(pixels[i][j]) * matrix.Matrix[i][j]);
    					sumG += (Color.green(pixels[i][j]) * matrix.Matrix[i][j]);
    					sumB += (Color.blue(pixels[i][j]) * matrix.Matrix[i][j]);
    				}
    			}

    			R = (int)(sumR / matrix.Factor + matrix.Offset);
    			if(R < 0) { R = 0; }
    			else if(R > 255) { R = 255; }

    			G = (int)(sumG / matrix.Factor + matrix.Offset);
    			if(G < 0) { G = 0; }
    			else if(G > 255) { G = 255; }

    			B = (int)(sumB / matrix.Factor + matrix.Offset);
    			if(B < 0) { B = 0; }
    			else if(B > 255) { B = 255; }

    			result.setPixel(x + 1, y + 1, Color.argb(A, R, G, B));
    		}
    	}

    	return result;
    }
}