media/thumbnailer: Better quality for 1-bit / 8-bit color palette images

[superdump]

Pillow will use nearest neighbour as the resampling algorithm if the
source image is either 1-bit or a color palette using 8 bits. If we
convert to RGB before scaling, we'll probably get a better result.

Note: I haven't actually tested this but setting up a synapse just to do so is more effort than I'm willing at this particular moment.

[ara4n]

lgtm, but please do test it first. setting up a synapse on OSX is absolutely trivial and very worthwhile - in your git checkout, just:

# deps, if needed
sudo easy_install pip
sudo pip install virtualenv
brew install pkg-config libffi

virtualenv -p python2.7 env
source env/bin/activate
pip install --upgrade pip
pip install --upgrade setuptools
python synapse/python_dependencies.py | xargs pip install
pip install lxml mock

# gen the config
python -m synapse.app.homeserver \
    --server-name my.domain.name \
    --config-path homeserver.yaml \
    --generate-config \
    --report-stats=yes

# start the synapse
./synctl start

i'd be surprised if copy-pasting that didn't give you a working homeserver on port 8008 ready to test against.

[NegativeMjark]

LGTM, but it might be nice to test uploading a 1-bit image with a unit test or a sytest. (I'm happy to take you at your word wrt image quality, but it would be nice to have some way to check it doesn't crash)

[APwhitehat]

I tried uploading 1-bit & 8-bit image via riot-web and synapse showed no errors.
I used this and this .

Tell me if more rigorous test is required.

[richvdh]

I don't know why we never merged this