Hi guys, as the python manual described in the section Compositing\Color Nodes\Mix Nodes, black is 0 and white is 1. So multiplying a color with white will be making it out as the color.
However, if I make the image transparent, it does not work, where white (1) times blue should be blue. Does the system identify transparent also as white?
My guess is that you’re pulling the color from “Left_upper.png” and not the alpha. You have an Image and an Alpha output, but you’re only using the Image output, so the transparency (or alpha) is not being sent anywhere else. Any of those transparent pixels probably have a RGB value of (0,0,0), thus making them the same as the lines in the corner. You can see the difference, because you can see the alpha, but you’re not using the alpha, so there is no difference between (0,0,0,1) and (0,0,0,0)- your nodes see both as (0,0,0).