Single-file, public domain implementation of color blindness / color vision deficiency (CVD) simulation in C.

There are no dependencies, just include the C header and source file in your project and call:

void dl_simulate_cvd (enum DLDeficiency deficiency, 
                      float severity,
                      unsigned char *srgba_image, 
                      size_t width, 
                      size_t height, 
                      size_t bytesPerRow);

Two algorithms are implemented:

• Computerized simulation of color appearance for dichromats by Brettel, H. and Viénot, F. and Mollon, J. D. (1997). This is the most accurate approach, but it's slightly more expensive, so it's only chosen by default for tritanopia.

• Digital video colourmaps for checking the legibility of displays by dichromats by Viénot, F. and Brettel, H. and Mollon, J. D. (1999). Their followup paper is a bit faster for protanopia and tritanopia and has a similar accuracy, so it's used by default for these deficiencies.

This implementation is meant to be an easy-to-read reference that can be easily copy/pasted/adapted/optimized in other languages or contexts.

It is unit-tested against DaltonLens-Python, which is itself unit tested against external references. The precomputed matrices / values are also generated from a notebook in DaltonLens-Python, so you can easily change the LMS model by running it with different parameters.

For a discussion about which CVD simulation algorithms are the most accurate see our Review of Open Source Color Blindness Simulations.

For more information about the math of the chosen algorithms see our article Understanding CVD Simulation.

This library is part of the DaltonLens project.

A port as SVG filter is available in the svg subfolder. It includes an implementation of Brettel et al., which is non-trivial. Live demo.