如何将多个（大于4个）`CV :: Mat`图像`Size（M，N），CV_8UC1`加入一个RGBA图像中？

Question

So we have created many, (say 100 ) Mat::zeros(Size(100, 100), CV_8UC1); binary images (with values 0 or 255). We filled them with some data (that can overlay on different images). Now we want to join them into one savable RGBA image on which all data of each single Mat will be represented by unique RGB value and alpha == 0.5. How to do such thing with openCV 2?

Answer 1

Unfortunately openCV doesn't support alpha channel and I don't think any of it's file I/O libs support transparency on any of the formats that handle it (such as PNG)

"Only 8-bit (or 16-bit in the case of PNG, JPEG 2000 and TIFF) single-channel or 3-channel (with 'BGR' channel order) images can be saved using this function" http://opencv.willowgarage.com/documentation/cpp/reading_and_writing_images_and_video.html#cv-imwrite

You can create a 4 channel image format using CV_8UC4 and manipulate the alpha yourself but you won't be able to read/write it using imread/imwrite