Optimized PNG looks a lot different

[reneruiz]

Running into a quirk where ImageOptim changes one of my PNGs during its optimization process. I don't fully understand why it's doing this.

I could ignore the specific file, but I actually do want it optimized. Just looking for some clues on what the problem is.

[toy]

You've attached resulting file? Could you please attach also the original png?
Try detecting the worker/utility causing problems by switching off png workers one by one.

[reneruiz]

Original:

When I disabled pngcrush, I got a clean looking version of the logo. So it looks like we found who to blame. lol

[toy]

What is the version of pngcrush you are using? Do you use custom settings for pngcrush?

[reneruiz]

This is what I'm using without any custom settings. I am however using imageoptim through Middleman. I opened an issue with that project but I was referenced here. plasticine/middleman-imageoptim#15

$ brew info pngcrush
pngcrush: stable 1.7.60
http://pmt.sourceforge.net/pngcrush/
/usr/local/Cellar/pngcrush/1.7.60 (3 files, 296K) *
  Built from source
From: https://github.com/Homebrew/homebrew/commits/master/Library/Formula/pngcrush.rb

[Arcovion]

FWIW I tried it via middleman and it works ok for me: 40.43% / 492B smaller
Running pngcrush 1.7.70 on windows with no options passed to middleman-imageoptim

[ewlarson]

We ran into this issue, too. Something about pngcrush 1.7.60 isn't right. Upgrading to 1.7.71 (latest release) solved it for us.

For Homebrew users, leave the brew alone for this one:

brew uninstall pngcrush
wget http://sourceforge.net/projects/pmt/files/pngcrush/1.7.71/pngcrush-1.7.71.tar.gz/download -O pngcrush-1.7.71.tar.gz
tar -xvzf pngcrush-1.7.71.tar.gz
cd pngcrush-1.7.71/
make
sudo mv pngcrush /usr/local/bin/

[toy]

@reneruiz @Arcovion @ewlarson Problem exists in version 1.7.60..1.7.65 of pngcrush. #38 will help with this, but it may be better to add some checking of used binaries when resolving them.

[toy]

@reneruiz @Arcovion @ewlarson I've added simple blacklisting of versions and I've already blacklisted misbehaving versions of pngcrush.