如何在Python OpenCV中读取TIFF图像的Alpha通道？

问题描述

我想使用Python OpenCV从tiff图像中读取alpha通道。我正在使用带有OpenCV 2.4.5-3模块的Enthought Canopy。

I want to read the alpha channel from a tiff image using Python OpenCV. I am using Enthought Canopy with OpenCV 2.4.5-3 module.

我遵循了OpenCV网站的教程，使用的是cv2.imread，但似乎不起作用。

I followed the OpenCV website's tutorial using cv2.imread, but it doesn't seem to work.

我现在拥有的是：

import cv2
image = cv2.imread('image.tif', -1)

然后我用了： print（image.shape），它仍显示（8192，8192，3）。但是我用Matlab读取相同的图像，我可以看到该图像的尺寸为（8192，8192，4）。

Then I used: print (image.shape), it still shows the (8192, 8192, 3). But I used Matlab to read the same image, I can see the dimension of this image is (8192, 8192, 4).

我不确定应该怎么做才能读取此图像的Alpha通道。

I am not sure what should I do to read the alpha channel of this image.

谢谢！！
Nan

Thanks in advance!!Nan

推荐答案

这是一个老问题，但以防万一有人偶然发现它：if img.tiff是4通道TIFF，则

This is an old question, but just in case someone else stumbles on it: if img.tiff is a 4-channel TIFF, then

import cv2
img = cv2.imread('img.tiff', cv2.IMREAD_UNCHANGED)
print img.shape

产量（212,296， 4 ）。

yields (212,296,4) as expected.

如果您随后使用

channels = cv2.split(img)

您可以引用alpha层（ channel [3] ）-例如，作为遮罩。

you can reference the alpha layer (channels[3]) - for instance, as a mask.

这个想法来自巧妙地使用假层和合并可以恢复单个RGB图层的实际颜色。

The idea for this was taken from How do I use Gimp / OpenCV Color to separate images into coloured RGB layers? which cleverly uses a fake layer and merge to enable recovery of the individual RGB layers in their actual colours.

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