function ret = getBkgOffsetFromCorners(img, x_fraction, y_fraction) % image must be a 2D numerical array [dim1, dim2] = size(img); s1 = img(1:round(dim1 * y_fraction), 1:round(dim2 * x_fraction)); s2 = img(1:round(dim1 * y_fraction), round(dim2 - dim2 * x_fraction):dim2); s3 = img(round(dim1 - dim1 * y_fraction):dim1, 1:round(dim2 * x_fraction)); s4 = img(round(dim1 - dim1 * y_fraction):dim1, round(dim2 - dim2 * x_fraction):dim2); ret = mean([mean(s1(:)), mean(s2(:)), mean(s3(:)), mean(s4(:))]); end