cetcolors is a collection of perceptually uniform colormaps for use with Python plotting programs like bokeh, matplotlib, holoviews, and datashader.
Most colormaps provided for use in Python programs are highly perceptually nonuniform, which means that small changes in data values result in large changes in the perceptual appearance of the corresponding colors, or vice versa. For instance, the matplotlib "hot" and "jet" colormaps have long stretches where the apparent colors change imperceptively, such as the yellow region in "hot" and the cyan/green region in "jet":
When colormaps are used for visualizing scientific datasets, these perceptual nonlinearities can make interpretation of this data very difficult, because false boundaries appear in the data, and genuine boundaries and changes can be obscured.
To combat these issues, Peter Kovesi at the Center for Exploration Targeting created a set of colormaps that are sampled uniformly in a perceptual color space, using methods he describes in a paper on arXiv. For instance, the perceptually uniform versions of the above colormaps are called "fire" and "rainbow" in this package:
Peter provides versions of 50 colormaps for a variety of different plotting programs, and this package provides those colormaps ready to use from within Python programs. The colormaps are all illustrated in an example notebook that describes the different types available and allows you to test how perceptually uniform they are on your particular display device.
cetcolors is available on most platforms using the conda package manager,
from the bokeh channel:
conda install -c bokeh cetcolors
or by using pip:
pip install cetcolors
Alternatively, you can manually install from the repository if you wish to be able to modify the code over time:
git clone https://github.com/bokeh/cetcolors.git
cd cetcolors
python setup.py develop
You see more perceptually uniform colormaps and learn more about them in Peter Kovesi's 2015 arXiv paper, and at the matplotlib site, the cmocean site, and a 1996 paper from IBM.