nitrofurano on 2009/09/04 10:14:

For having a spritesheet with transparent background i used imagemagick and a simple text editor:

1- in the terminal, convert the bmp (or whatever) to xpm (xpm is a very useful format) - like 'convert picture01.bmp picture 01.xpm'
2- open the xpm in a text editor (such as gedit, kate, etc.)
3- since you must know which colour is what you want to replace to transparent, like #FF00FF, just replace '#FF00FF' to 'none'
4- save the file
5- in the terminal, convert the result xpm into png - like 'convert picture01.xpm picture01.png

And that's it, the spritesheet is ready - please note this changes only one indexed colour, which doesn't provide alpha values, like having soft contourns or whatever - .xpm on transparencies are like .gif: or 100% or 0% - if you're working with few colours, like only indexed colours, not having more than 256, and don't mind about harsh contourn edges on sprites, this may be a good suggestion...

Anyway, it's surprising the power a .xpm file can provide to you: it's a picture file, and you can be completelly independent of a picture editor for that, since you can edit it on any text editor.