Yeah, I know, there is supposed to be a tutorial for this:
The problem is that newer versions of Paint.net does not seems (at least for me) to include the bit depth in the save-as dialog.
Newest version would be: 3.5.10.
The link in that post, and others, works, except that inside the zip file for 3.5.x you will find 3.5.10 whatever the x value.
I search others programs, but did not found an open-source software with this ability yet.
Or I may be just dumb, as usual.
[Edit1]Hum… At first I thought Gimp was not doing this, but I just found:
Menu Image/Mode/Indexed Colors
Now I am mot sure if using an optimized palette is a good idea.
I wanted this to try the level generator.
Now, I jsut need to have Gimp for Windows rather than for Linux.
The problem is that 73 Mb is not what I was thinking when I wrote ‘small program’.[/Edit1]