function interpolate

Returns the interpolated value of a given position (x,y). If x and y are integers the value at that position is returned without any interpolation.

result = interpolate(A, x, y [, kernel_size])

A:   A 2D-image.
x:   An real number.
x:   An real number.
kernel_size:   Any integer number, default is 4. Remember that points near the image border can't be interpolated (border-size is half the kernel-size)