red
and blue
只是您图像的视图。当你这样做时img[:,:,0] = red
这改变了img
但是也blue
这只是一个视图(基本上只是对子数组的引用img[:,:,0]
)不是副本,因此您会丢失原始的蓝色通道值。基本上,您认为是临时副本的内容实际上并非如此。添加.copy()
它会起作用的。
img = np.arange(27).reshape((3,3,3))
red = img[:,:,2].copy()
blue = img[:,:,0].copy()
img[:,:,0] = red
img[:,:,2] = blue
print("with copy:\n", img)
img = np.arange(27).reshape((3,3,3))
red = img[:,:,2]
blue = img[:,:,0]
img[:,:,0] = red
img[:,:,2] = blue
print("without copy:\n",img)
results:
带副本:
[[[ 2 1 0]
[ 5 4 3]
[ 8 7 6]]
[[11 10 9]
[14 13 12]
[17 16 15]]
[[20 19 18]
[23 22 21]
[26 25 24]]]
没有副本:
[[[ 2 1 2]
[ 5 4 5]
[ 8 7 8]]
[[11 10 11]
[14 13 14]
[17 16 17]]
[[20 19 20]
[23 22 23]
[26 25 26]]]
注意:您实际上只需要 1 个通道的 1 个临时副本。
或者你也可以简单地做img[:,:,::-1]
这将再次创建一个视图,但交换通道,img
将保持不变,除非您重新分配它:
img = np.arange(27).reshape((3,3,3))
print(img[:,:,::-1])
print(img)
img = img[:,:,::-1]
print(img)
results:
[[[ 2 1 0]
[ 5 4 3]
[ 8 7 6]]
[[11 10 9]
[14 13 12]
[17 16 15]]
[[20 19 18]
[23 22 21]
[26 25 24]]]
[[[ 0 1 2]
[ 3 4 5]
[ 6 7 8]]
[[ 9 10 11]
[12 13 14]
[15 16 17]]
[[18 19 20]
[21 22 23]
[24 25 26]]]
[[[ 2 1 0]
[ 5 4 3]
[ 8 7 6]]
[[11 10 9]
[14 13 12]
[17 16 15]]
[[20 19 18]
[23 22 21]
[26 25 24]]]