optisorl 0.1.0

Backend plugin for sorl-thumbnail that optimizes thumbnails

Copyright Peter Bengtsson, [e-mail], 2015

License: BSD

About optisorl

sorl-thumbnail is a great Django library that takes your stored images and automatically convert them into desired sized thumbnails and store them with nice names in the MEDIA_ROOT. The problem is that the engines that do the resizing often doesn’t do an amazing job of optimizing them. Usually optimizing an image means carefully deleting things the human eye can’t notice anyway. This becomes incredibly relevant when the thumbnail you create is so small in resolution that the user really stands very little chance to notice.

This package, is a pluggable backend to sorl-thumbnail that attempts to do a good job of optimizing the generated thumbnail just right after it has been written to disk.

Optimizing PNGs

optisorl uses a binary called pngquant which is a command line tool that do lossy compression of PNG images and supports alpha transparency. pngquant is BSD licensed. It’s easy to install on most systems. For example brew install pngquant or apt-get install pngquant.

What happens is that when optisorl notices that a thumbnail was created it (and stored in MEDIA_ROOT) it then takes that file and executes pngquant something like this:

pngquant -o /path/file.tmp.png --skip-if-larger -- /path/file.png

Note the --skip-if-larger which means that if the thumbnail is really really small already the resulting optimization might not be any better and it thus omits doing an optimization.

If you want to override the location of the executable pngquant you can set this setting for example:

# in settings.py or equivalent

PNGQUANT_LOCATION = '/opt/special/bin/pngquant2.0'

Limitations

Help is most welcome. At the moment…

• Does not support S3 storage

• Unable to NOT optimize images

• Not possible to override certain pngquant parameters

• Only able to optimize .png thumbnails