本文用 Python 实现 PS 滤镜中的素描特效，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/38687427

from skimage import img_as_float

import matplotlib.pyplot as plt

from skimage import io

from skimage.filters._gaussian import gaussian

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

img=io.imread(file_name)

img = img_as_float(img)

I_out = (img[:, :, 0] + img[:, :, 1] + img[:, :, 2]) / 3.0

I_invert = 1.0 - I_out

I_gauss = gaussian(I_invert, sigma=5)

delta = 0.0001

I_dodge = (I_out + delta) / (1 + delta - I_gauss)

th = 0.95

mask = I_dodge > th

max_val = I_dodge.max()

I_dodge = I_dodge * (1-mask) + (th + I_dodge / max_val * (1 - th)) * mask

img_out = I_dodge.copy()

plt.figure(1)

plt.imshow(img)

plt.axis('off')

plt.figure(2)

plt.imshow(img_out, plt.cm.gray)

plt.axis('off')

plt.show()