Performing Fast Fourier Transform on an Image

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C#

image-processing

I want to perform a Fast Fourier Transform on a fingerprint image of M x N pixels on small blocks of 32 x 32 pixels.
So do i need to resize the image to M x M (or) N x N (or) in any square size ?

If not..please help me how to traverse these blocks separately.

x=0;
y=0;
for (j = 0; j < Math.Ceiling((double)img.Height / 32); j++)
{
    for (i = 0; i < Math.Ceiling((double)(img.Width/ 32)); i++)
    {
        //transformation in each block of 32 x 32 pix
        a = i;
        b = j;
        for (q = b; q < y + 32;q++)
        {
            for (p = a; p < x + 32; p++)
            {
                //transformation
            }
        }
        x = x + 32;
        y = y + 32;
    }
}

Please help, anyone.

regards.