Zopfli worker

[kaspergrubbe]

This is initial idea of a Zopfli worker, but after working with it I am not sure it fits into the idea of image_optim.

Zopfli creates a .gz version of the png file, which seems to be incompatible with png openers (Which makes sense).

I took some ideas from https://github.com/mathiasbynens/grunt-zopfli/blob/master/tasks/zopfli.js

brew install zopfli
zopli -i15 image.png # this creates image.png.gz

zopli -c -i15 image.png > image.png # this creates image.png but it is gzipped

Do you have any idea how to approach this?

This references issue #17

[toy]

You need to use zopflipng instead of zopfli. Also please add zopfli installation to .travis.yml.

[kaspergrubbe]

I see, zopflipng is not part of the 1.0.0 release, and seems to be in current master, but not in a version yet.

Perhaps we should wait until Google releases a new version? We could try to ask the developers.

[toy]

Sure we can ask developer, but I think it is ok to use zopflipng even if there is no version with it.

[toy]

And there is no package zopfli, you need to compile it from source

[nelsonjchen]

Imageoptim uses advpng for its zopfli.

advancecomp v1.18 by Andrea Mazzoleni
Usage: advpng [options] [FILES...]

Modes:
  -l, --list            List the content of the files
  -z, --recompress      Recompress the specified files
Options:
  -0, --shrink-store    Don't compress
  -1, --shrink-fast     Compress fast (zlib)
  -2, --shrink-normal   Compress normal (7z)
  -3, --shrink-extra    Compress extra (7z)
  -4, --shrink-insane   Compress extreme (zopfli)
  -i N, --iter=N        Compress iterations
  -f, --force           Force the new file also if it's bigger
  -q, --quiet           Don't print on the console
  -h, --help            Help of the program
  -V, --version         Version of the program

I was just about to rebase and polish up the commits for the fixed version of this branch along with the necessary Travis-CI fixes and stuff before I do a pull request with a fixed version of this but then I decided to take a look at ImageOptim was doing. 😔

Then I looked at the default for the advpng worker. Guess what? -4 is the default.

[nelsonjchen]

Wait, nevermind. I have no idea where I got that idea where ImageOptim was using advpng for zopfli. They actually use a fork.

https://github.com/pornel/zopfli

[kaspergrubbe]

How nice that advpng uses zopfli, that is pretty nice. I guess that makes this PR not needed, I was also tired of waiting on zopflipng.

[toy]

@nelsonjchen @kaspergrubbe I've already noticed that advpng uses zopfli, I was just thinking that image_optim should probably check version of advpng to warn if it is an outdated version without zopfli support, otherwise creating zopfli worker is redundant.