This commit integrates icons in the resource system so that they
can be loaded (or reloaded, without restarting) in @2x mode, which
will be added in a future commit. png2c is no longer necessary.
png2c used to perform the following transformation:
if(r + g + b < 11) r = g = b = 11;
This is now achieved by switching the icons to RGBA mode and adding
alpha channel with the following imagemagick invocation, which is
equivalent to the transformation above:
for i in *.png; do
convert -fuzz 4% -channel rgba -matte \
-fill "rgba(255,255,255,0)" -opaque black \
$i $i
done
The Debian package solvespace now includes /usr/share/solvespace;
this should be split out into solvespace-data later.