|Subject:||paste()/rubthrough() should adapt the source image data to the target|
Currently pasting a 3 channel image onto a 1 channel image writes the red channel as the grey channel. This is broken. Currently pasting a 1 channel image onto a 3 channel image writes junk into the green and blue channels. Currently pasting a 4 channel image onto a 3 channel image does something, whether that something is useful or not is hard to say. Currently pasting a 3 channel image onto a 4 channel image writes junk as the alpha channel. There are similar issues with rubthrough.