Update version to match ImageAlpha

[joeyhoer]

The version of posterizer provided in ImageAlpha is different from posterize as it exists in this repo. This becomes evident when running the following:

$ posterize -v 64 test.png test.png
MSE=20.288 (Q=43, 64 levels)
$ wc -c test.png
210715 test.png

$ /Applications/ImageAlpha.app/Contents/MacOS/posterizer -v 64 test.png test.png 
MSE=17.192 (Q=50, 64 levels)
$ wc -c test.png
137719 test.png

[kornelski]

It's the same source, but difference is from build config. You'll get the same result when you build it from ImageAlpha's Xcode project. It's probably difference between using Cocoa vs libpng for reading.

[joeyhoer]

Trying to build from ImageAlpha fails with an error:

Undefined symbols for architecture x86_64:
  "_optimizeForAverageFilter", referenced from:
      _main in posterize.o

Trying to build from the command line using USE_COCOA=1 make fails because pam.h isn't linked. After including the files from libimagequant, I get a second error: error: unknown type name 'LIQ_PRIVATE'.

Any thoughts on what's missing?

[kornelski]

I've added the missing file and set up posterizer as a submodule (git clone --recursive; or git submoodule init)

[kornelski]

It also requires ImageOptim to be checked out in sibling directory to ImageAlpha :)

[sergeevabc]

Front-page mentions switch -b, but Posterizer 1.6 says invalid option, why?