Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the develop branch, built from commit eb47817f5a.
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Color Maps

Synopsis
#include <boost/math/tools/color_maps.hpp>

namespace boost::math::tools {

template<typename Real>
std::array<Real, 3> viridis(Real x);

template<typename Real>
std::array<Real, 3> plasma(Real x);

template<typename Real>
std::array<Real, 3> black_body(Real x);

template<typename Real>
std::array<Real, 3> inferno(Real x);

template<typename Real>
std::array<Real, 3> smooth_cool_warm(Real x);

template<typename Real>
std::array<Real, 3> kindlmann(Real x);

template<typename Real>
std::array<Real, 3> extended_kindlmann(Real x);

template<typename Real>
std::array<uint8_t, 4> to_8bit_rgba(std::array<Real, 3> const & color);

} // namespaces
Description

Abstractly, a color map is any function which maps [0, 1] -> [0, 1]^3. As stated, this definition is too broad to be useful, so in Boost, we restrict our attention to the subset of color maps which are useful for the understanding of scientific data. Much research has demonstrated that color maps differ wildly in their usefulness for interpreting quantitative data; see here for details. In addition, different color maps are useful in different contexts. For example, the smooth_cool_warm color map is useful for examining surfaces embedded in 3-space which have scalar fields defined on them, whereas the inferno color map is better for understanding 2D data.

Despite the fact that a color map, per our definition, has a domain of [0, 1], we nonetheless do not throw an exception if the value provided falls outside this range. This is for two reasons: First, visualizations are themselves amazing debuggers, and if we threw an exception the calculation would not complete and visual debugging would be inaccessible. Second, often small changes in floating point rounding cause the value provided to be only slightly below zero, or just slightly above 1. Hence, we make a call to std::clamp before interpolating into the color table.

For an example of how to use these facilites please refer to example/color_maps_example.cpp and example/color_maps_sf_example.cpp Note: To compile the examples directly you will need to have lodepng. An example of the viridis color map using the newton fractal is shown below:

An example from example/color_maps_example.cpp plots 1F1 on a logarithmic scale:

Swatches of each are listed below:

References

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