Moderators - Reputation: 8570
Posted 28 October 2012 - 09:25 PM
My suggestion is that you avoid using JPG for sprites, though. Typically, a sprite is going to have transparent areas, and JPG doesn't support alpha channel. Also, JPG compression is lossy, so you can lose detail. I'd suggest going with PNG, TGA or some other format that supports loss-less compression and a alpha channel.
Members - Reputation: 364
Posted 29 October 2012 - 01:24 PM
Since you have antialised edges on the paddle, simply filling the selection is likely to either produce white lines along the edge or significantly shrink your sprite. The white-edges-case can be seen on the left two examples of the attached image.
Luckily, GIMP comes with a great (preinstalled) plugin called "Colour to Alpha". This will not completely replace the old color, but work gradually, depending on how much of the old color is to be found in each pixel. Here's how to use it:
1. Use the fuzzy select to select the white background.
2. Go to "Select->Grow->1px->OK" to make sure you get all the edges
3. Go to "Colours->Colour to Alpha...->From white->OK"
The result is a transparent background with antialised edges, so that the sprite will blend nicely atop any color as can be seen in the two examples on the right.
Edited by Tobl, 29 October 2012 - 01:26 PM.