本文用 Python 实现 PS 滤镜中的 USM 锐化效果，具体的算法原理和效果可以参考之前的博客：

http://blog.csdn.net/matrix_space/article/details/51169960

import matplotlib.pyplot as plt

from skimage import io

from skimage.filters import gaussian

file_name='D:/Visual Effects/PS Algorithm/4.jpg';

img=io.imread(file_name)

img = img * 1.0

gauss_out = gaussian(img, sigma=5, multichannel=True)

# alpha 0 - 5

alpha = 1.5

img_out = (img - gauss_out) * alpha + img

img_out = img_out/255.0

# 饱和处理

mask_1 = img_out  < 0

mask_2 = img_out  > 1

img_out = img_out * (1-mask_1)

img_out = img_out * (1-mask_2) + mask_2

plt.figure()

plt.imshow(img/255.0)

plt.axis('off')

plt.figure(2)

plt.imshow(img_out)

plt.axis('off')

plt.show()