I would like to know what are the transparency buttons (select transparent color, remove color from transparency and add color to transparency) for?
When they are used and for what purpose? Please give me the scenarios when they are used.
PS: the buttons can be found in Image Preview dialogue box and in the Optimize panel
With a GIF, the "select transparent color" sets the color (the one color of the 256) that will be transparent.
I've never used the other buttons, but I expect you can add or remove colors in the design (selected from the full color range) from being mapped to the transparent color in the 256-color palette.