distortion_transforms.py 文件源码

def _butterworth_filter(rows, cols, thresh, order):
    # X and Y matrices with ranges normalised to +/- 0.5
    array1 = np.ones(rows)
    array2 = np.ones(cols)
    array3 = np.arange(1,rows+1)
    array4 = np.arange(1,cols+1)

    x = np.outer(array1, array4)
    y = np.outer(array3, array2)

    x = x - float(cols/2) - 1
    y = y - float(rows/2) - 1

    x = x / cols
    y = y / rows

    radius = np.sqrt(np.square(x) + np.square(y))

    matrix1 = radius/thresh
    matrix2 = np.power(matrix1, 2*order)
    f = np.reciprocal(1 + matrix2)

    return f