colormaps

Introduction

Transform data into rgba data using discrete lookup tables or color gradients.

Usage

Create a discrete colormap with the same two colors:

>>> import colormaps
>>> colormap = colormaps.DiscreteColormap(
...     data=[(0, (255, 0, 0, 255)),
...           (1, (0, 0, 255, 127))],
...     masked=(255, 0, 0, 255),
...     invalid=(0, 255, 0, 255),
... )

Create a gradient colormap from red to semi-transparent blue:

>>> import colormaps
>>> colormap = colormaps.GradientColormap(
...     data=[(0, (255, 0,   0, 255)),
...           (1, (  0, 0, 255, 127))],
...     size=2048,
...     masked=(0, 0, 255, 255),
... )

Where size is the amount of entries in the prepared look-up table.

Calculate the value at some positions:

>>> colormap([0, 0.5, 1])
array([[255,   0,   0, 255],
       [127,   0, 127, 190],
       [  0,   0, 255, 127]], dtype=uint8)

Register the colormap for use in other places:

>>> colormap.register('my_gradient')
>>> colormaps.get('my_gradient')
<GradientColormap: size 2048, limits 0 - 1, log False, interp False>

Use a collection of predefined colors using a manager:

>>> manager = colormaps.Manager()
>>> manager.get('jet')
<GradientColormap: size 256, limits 0.0 - 1.0, log False, interp False>

>>> sorted(manager.registered.keys())[:3]
['Accent', 'Accent_r', 'Blues']

Or use your own collection:

>>> manager = colormaps.Manager('path/to/my/colormap/collection')

The path should point to a folder with json-files ('my-colormap.json') containing the kwargs for colormaps.create() like this:

{
  "type": "GradientColormap",
  "data": [
      [0.000, [  0,   0,   0, 255]],
      [0.700, [255, 255, 255, 0]],
      [1.000, [255, 255, 255, 255]]
  ]
}

Development installation

For development, you can use a docker-compose setup:

$ docker-compose build --build-arg uid=`id -u` --build-arg gid=`id -g` lib
$ docker-compose up --no-start
$ docker-compose start
$ docker-compose exec lib bash

Create a virtualenv:

(docker)$ virtualenv .venv  # note that Dockerfile prepends .venv/bin to $PATH

Install stuff and run the tests:

(docker)$ pip install -r requirements.txt
(docker)$ pip install -e .[test]
(docker)$ pytest

Update packages:

(docker)$ rm -rf .venv
(docker)$ virtualenv .venv
(docker)$ pip install -e .
(docker)$ pip freeze | grep -v colormaps > requirements.txt