Optimize pnnquant2.js

[p01]

• Remove dead code
• Inline create_bin
• Remove unnecessary clamp
• Replace existsInPalette with built-in Array.indexOf
• Fork the "fill palette" loop to move the hasAlpha conditional outside of the hot path

[mattdesl]

Hey thanks!

I don't think indexOf will work as we are dealing with array equality:

[ [2, 255, 5] ].indexOf([ 2, 255, 5 ])
// -> -1

Second thing, I don't think "fill palette" is actually a hot code path (typically we are dealing with 256 colors or less) so I'm not sure it's worth optimizing at the expense of legibility/simplicity.

Did you manage to benchmark the others in Chrome? I think I tested inlining create_bin() and IIRC it performs about the same or better, but I could be mistaken.

[mattdesl]

I ended up cherry-picking a couple of these patches into the latest build, you could resolve conflicts and we could see if there's anything else here that could be optimized. I also didn't see much of a change in benchmarks when inlining the create_bin function.

[p01]

I need to verify the code, 'coz I use Github's UI to resolve the conflict :p