zorro_util.py 文件源码

def lanczosSubPixKernel( subPixShift, kernelShape=3, lobes=None  ):
    """
    Generate a kernel suitable for ni.convolve to subpixally shift an image.
    """
    kernelShape = np.array( [kernelShape], dtype='int' )
    if kernelShape.ndim == 1: # make it 2-D
        kernelShape = np.array( [kernelShape[0], kernelShape[0]], dtype='int' )

    if lobes is None:
        lobes = (kernelShape[0]+1)/2

    x_range = np.arange(-kernelShape[1]/2,kernelShape[1]/2)+1.0-subPixShift[1]
    x_range = ( 2.0 / kernelShape[1] ) * x_range 
    y_range = np.arange(-kernelShape[1]/2,kernelShape[0]/2)+1.0-subPixShift[0]
    y_range = ( 2.0 /kernelShape[0] ) * y_range
    [xmesh,ymesh] = np.meshgrid( x_range, y_range )


    lanczos_filt = np.sinc(xmesh * lobes) * np.sinc(xmesh) * np.sinc(ymesh * lobes) * np.sinc(ymesh)

    lanczos_filt = lanczos_filt / np.sum(lanczos_filt) # Normalize filter output
    return lanczos_filt