Iterate through 2D array and get average of its for neighboring cells

Question

What I am trying to do is iterate through the 2D array to find an average .

The values in the middle must be calculated as an average of 4 sides (Top,Bottom,Left,Right and recalculated) . I have to find the values of the four sides of the current index and replace the current index with that number. Any ideas would be appreciated.

final public class Matrix {
private final int M;             // number of rows
private final int N;             // number of columns
private final double[][] data;   // M-by-N array

// create M-by-N matrix of 0's
public Matrix(int M, int N) {
    this.M = M;
    this.N = N;
    data = new double[M][N];
}

// create matrix based on 2d array
public Matrix(double[][] data) {
    M = data.length;
    N = data[0].length;
    this.data = new double[M][N];
    for (int i = 0; i < M; i++)
        for (int j = 0; j < N; j++)
                this.data[i][j] = data[i][j];
}

// copy constructor
private Matrix(Matrix A) { this(A.data); }



// print matrix to standard output
public void show() {
    for (int i = 0; i < M; i++) {
        for (int j = 0; j < N; j++) 
            System.out.printf("%.1f ", data[i][j]);
        System.out.println();
    }
}



// test client
public static void main(String[] args) {
    double[][] d = { { 22.5,30,30,30,30,30,30,30,30,51 }, 
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 15,0,0,0,0,0,0,0,0,72 },
                     { 45,75,75,75,75,75,75,75,75,73.5 }

    };


    Matrix D = new Matrix(d);
    D.show(); 
    System.out.println();



}
}

Answer 1

What you're describing is just a really simplistic blur operation, basically a form of box blur . Any operation where you take an NxN submatrix for every pixel in an image and multiply it by another NxN matrix is called a kernel convolution . Rosetta Code has a good example in Java on this page .

If you can use AWT, the Java standard library already has ConvolveOp built in.