Comment # 5 on bug 78009 from Benjamin Bellec

I don't think this is a Mesa bug.
I already noted this problem with ETQW back to July 2012 (maybe even earlier)
and found a workaround. You can convert the picture to PNG thanks to
ImageMagick, just run :
$ convert -alpha off shot00016.tga shot00016.png

With my RV770, I just tested mesa-10.3-rc2, mesa-9.2.5 and mesa-9.1.7. All of
them gives bad TGA screenshots.