Rotating an image with respect to its center

Question

I am trying rotate a matrix, an image more specifically, by a alpha degree. I am using a rotation matrix in order find rotate it but if the matrix is not square then the rotation fails and gives an corrupt output.

let's see we have a mxn matrix

    for i to m
        for j to n
            new_i = i*cos(alpha) - j*sin(alpha)
            new_j = i*sin(alpha) + j*cos(alpha)
            write the value of sourceimage[i][j] to a new image[new_i][new_j]

What am i missing here?

Answer 1

The problem has nothing to do with the shape of the matrix. You are accessing illegal indexes.