Hello!

Right now I am programming a little game with a friend and there's a little problem with the transparency of images.
At the moment we've got a background and a protagonist, both as an image on our drawing panel.
Now the protagonist is a 20x15 pixel image and the unused pixel spots are still white.
Well these unused pixels in this image are visible on the background of course so there's always a rectangular white frame around our character.
Of course I could use PNGs which already got the transparency but GIFs for example are quite smaller.

In other pixelart games I saw a (mostly) very extreme color as a background in the spritesand somehow this was not be seen in the later background. So somehow the programm recognized this color and replaced it with the color of the real background beneath it.
Maybe that would be a nice approach but I really cannot figure it out myself

Thanks already for help  :)