Pillow and JPEG2000: decoder jpeg2k not available

Question

I\'m trying to set up Flask-IIIF to work with jp2-files, or JPEG2000. Right out of the box I get an error from the Pillow library: IOError: decoder jpeg2k

Answer 1

for linux

sudo yum install -y libjpeg-devel
sudo pip uninstall pillow
sudo pip install pillow

for windows

# download
import imageio
imageio.plugins.freeimage.download()

# install
pip uninstall pillow
pip install pillow

Answer 2

Pillow needs the OpenJPEG library to decode JPEG2000 files. libjpeg only deals with regular JPEGs.

See the note in the Pillow docs at the end of this section: http://pillow.readthedocs.io/en/latest/handbook/image-file-formats.html#jpeg-2000

Answer 3

Windows users: After you installed OpenJPEG and added its bin folder to PATH, you need to re-build the pillow library. Using Conda I didn't find a solution to do that so I ended up using the windows installer from PyPi as suggested in this answer here. The installer found my Anaconda installation and it seems it simply overwrote the pillow library there.