zopfliPNG

[aitte]

Would you be able to include the world's best PNG compressor in the export features? It usually produces files 60-80% of the Affinity PNG size and is available as a C library. The compression is the best in the world, and the only feature they lack is extra-advanced palette optimization (it does optimize, but could be even smarter, it is on their todo list), but even without that they're still smaller than all other PNG compressors.

License is apache 2.0 = free for commercial use if you attribute them in the about-box.

Project was made by Google employees.

If you include it then please preserve control over the various tuning/algorithm parameters (you'll see what I mean if you try their command line version), because that is how to achieve the best compression.

[aitte]

To show the results for some graphics, here are some compression numbers. The "Input size" is the size that was created by Affinity Designer, and the "Result size" is the zopflipng result.

 

+ $ ./zopflipng --filters=01234me -m ~/Downloads/backgrounds.png ~/Downloads/backgroundzop.png 

Optimizing /Users/Aitte/Downloads/backgrounds.png

Filter strategy zero: 152892 bytes

Filter strategy one: 109296 bytes

Filter strategy two: 115480 bytes

Filter strategy three: 113140 bytes

Filter strategy four: 107029 bytes

Filter strategy minimum sum: 105744 bytes

Filter strategy entropy: 105074 bytes

Result is smaller

Input size: 130432 (127K)

Result size: 105074 (102K). Percentage of original: 80.558%

 

+ $ ./zopflipng --filters=01234me -m ~/Downloads/test.png ~/Downloads/z.png

Optimizing /Users/Aitte/Downloads/test.png

Filter strategy zero: 108460 bytes

Filter strategy one: 97149 bytes

Filter strategy two: 100206 bytes

Filter strategy three: 101311 bytes

Filter strategy four: 98841 bytes

Filter strategy minimum sum: 98427 bytes

Filter strategy entropy: 97128 bytes

Result is smaller

Input size: 124845 (121K)

Result size: 97128 (94K). Percentage of original: 77.799%

 

 

Also, you will notice I ran with all filters (01234me), but they recommend "0me" because usually one of those three is gonna be the winner. So a good default profile is "0me". And the extra "-m" flag I specified just makes it do more iterations to try to make the file even smaller, but usually that's not needed.

[anon1]

Sounds very promising!

[Andy Somerfield]

Sorry I didn't get to this sooner - if it does what it says it does, and the licences are as quoted, I will certainly look into it..

 

Thanks,

 

Andy.

[aitte]

Hi Andy! Yep I just verified that the license is Apache 2.0 even for the PNG part:

https://github.com/google/zopfli/blob/master/src/zopflipng/zopflipng_lib.h

 

Good luck and have fun investigating this. It would certainly remove the advantage photoshop has in the "export for web" filesize department.

 

If it makes it into Affinity, I suggest something like an export checkbox saying "Optimize Filesize (Slow)" which runs the "0me" algorithms with the default iteration count (usually, but not always, finds the smallest filesize and does it reasonably fast). And an "advanced" button to enable other algorithms or increase iteration count.

 

And... Since zopfli is somewhat slow, it may be worth showing a progress window which shows the algorithms it's trying and what sizes it finds, while the user waits (i.e exactly what the command line tool above outputs). Maybe as some nice "size" bars to get the user excited about getting efficient files for the web. That feedback also helps a lot; i.e next time you wanna export the same resource you may know that the "e (entropy)" algorithm was the correct one for that particular image, and can uncheck the rest to save time. Maybe the GUI could even help do that automatically.

 

Well, there are lots of considerations so I'll let you have fun exploring the tool and checking it out now :)