color-channel

There are various ways of reading an image file in java such as BufferedImage and ImageIcon to name a few. I want to know what is the difference between these cases? Are they context dependent that in a particular case only one of them can be used? What would be the best way of reading a image selected by JFileChooser by the user and separating the color channels of an image? Alexis Dufrenoy A good way is to use the different ImageIO.read methods, which return BufferedImage objects. Image is an abstract class, so I think the real question is which subclass is more efficient for your program.

It's possible to access the alpha channel of a given bitmap with extractAlpha() , but I haven't been able to find any way to actually set the alpha channel of a bitmap. How can multiple greyscale images be recombined as channels into a Bitmap with Android? It is quite possible to re-combine separate channels back into an ARGB image. You just need the grayscale channel images and an image with the alpha channel you want - note that this is not an opaque grayscale image, but an image with the alpha you want. You then draw each channel with a Paint using the appropriate PorterDuffXfermode onto a

How to set given channel of a cv::Mat to a given value efficiently without changing other channels? For example, I want to set its fourth channel (alpha channel) value to 120 (i.e. half transparent), something like: cv::Mat mat; // with type CV_BGRA ... mat.getChannel(3) = Scalar(120); // <- this is what I want to do P.S.: My current solution is first split the mat into multiple channels and set the alpha channel, and then merge them back. P.S.2: I know that I can do this quickly if I also want to change other channels as well by: mat.setTo(Scalar(54, 154, 65, 120)); Update with generalized