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Daltonize simulates the three types of dichromatic color blindness for images and matplotlib figures. Generalizing and omitting a lot of details these types are:

  • Deuteranopia: green weakness
  • Protanopia: red weakness
  • Tritanopia: blue weakness (extremely rare)

Daltonize can also adjust the color palette of an input image or matplotlib figure such that a color blind person can perceive the full information content. It can be used as a command line tool to convert pixel images but also as a Python module. If used as the latter, it provides an API to simulate and correct for color blindness in matplotlib figures.

This allows to create color blind friendly vector graphics suitable for publication.

Color vision deficiencies are in fact very complex and can differ in intensity from person to person. The algorithms used in here and in many other comparable software packages are based on often simplifying assumptions. Nicolas Burrus discussed these simplification and reviews daltonize and other software packages in a blog post.


pip install daltonize


As a command line tool:

$ -h
usage: [-h] [-s | -d] [-t {d,p,t}] [-g {2.4}] input_image output_image

positional arguments:

optional arguments:
  -h, --help            show this help message and exit
  -s, --simulate        create simulated image
  -d, --daltonize       adjust image color palette for color blindness
  -t {d,p,t}, --type {d,p,t}
                        type of color blindness (deuteranopia, protanopia,
                        tritanopia), default is deuteranopia (most common)
  -g --gamma {2.4}      exponent of the sRGB gamma correction. The default 
                        2.4 corresponds to an effective exponent of 2.2

As a Python module:

In [1]: from daltonize import daltonize

[ Create a figure ]

In [10]: sim_fig = daltonize.simulate_mpl(fig, copy=True)

In [11]: daltonized_fig = daltonize.daltonize_mpl(fig, copy=True)


Based on the work and original matlab code by Onur Fidaner, Poliang Lin, Nevran Ozguven. This can be found in 'doc/'.

Based on original Python code by Oliver Siemoneit.

Further information on color blindness and daltonization is available at many web resources, including

Color blind friendly color maps can be found at All of these are included in the python matplotlib and seaborn plotting libraries.

Example Images for Color Blindness

The directory 'example_images/' contains three example Ishihara plates to test for red-green deficiency. This table describes what people with normal, red/green deficient color vision, and total color blindness see on these plates:

Plate Normal r/g deficiency total color blindness
3 29 70 x
7 74 21 x
8 6 x x

You can verify the r/g deficiency column by running with the -s/--simulate option and -t/--type d or p on these images.




daltonize -s -t=d example_images/Ishihara_Plate_3.jpg example_images/Ishihara_Plate_3-Deuteranopia.jpg



daltonize -s -t=p example_images/Ishihara_Plate_3.jpg example_images/Ishihara_Plate_3-Protanopia.jpg



This code is released und the GNU GPL version 2. See COPYING for details.