This is spr2png, a small python script to convert legacy .spr files (a
homegrown and impractical format) into standard PNG format. Note that the file
name is irrelevant for Thunder&Lightning, so many of the former .spr files are
now really PNG files.

In versions of Thunder&Lightning after Fri, Jun 29 2007, there has been a
change in the semantic of PNG files. They will now be read to memory so that
their origin (the zeroth color and texture coordinates (0,0) ) is the
bottom-left corner of the image. Formerly, it was the top-right corner. This
happened to comply with OpenGL comventions. For remaining partly
backwards-compatible, the .spr loading was left as is.

This may result in (bottom-top-) flipped textures appearing in the game. Please
fix this by modifying the game, not the PNGs!

