与 matplotlib.imshow() 相比，似乎 matplotlib.imsave() 会使图像变亮。例如，看下面的代码。
import imageio
import matplotlib.pyplot as plt
image = imageio.imread('image.jpg')
plt.imshow(image)
plt.imsave('image_new.jpg',image )
image_new = imageio.imread('image_new.jpg')
plt.imshow(image_new)
保存的图像“image_new.jpg”（右）比“image.jpg”（左）略亮
图片来源： https ://c1.staticflickr.com/9/8191/8424182610_e23dcc6b4d_b.jpg
