Switch to a different PNG loader?

[hpjansson]

The STB PNG decoder is very fast, quite a bit faster than LodePNG (approx 2x according to benchmarks I've seen). It's also widely used, so should receive plenty of testing. And the license is very permissive/PD.

Does it support everything LodePNG does, though? We'd have to investigate.

[hpjansson]

libspng looks like another interesting candidate. According to its own documentation it's both faster, more secure (fuzzing regime and test cases) and more versatile (progressive loading etc) than the alternatives.