Color Maps (#752)

* Color Maps

* Make color maps constexpr

[ci skip]

* Add newton fractal example

[ci skip]

* Remove some unused code.

* Make the color map base class generic in size

Fix naming convention
[ci skip]

* Begin documentation.

* Move helper functions from example into tools header

[ci skip]

* Update docs and remove non-ASCII characters from example

* Add image to docs

* Reduce size of virdis_newton_fractal from 1.31MB to 131KB

[ci skip]

* Add performance file

* Don't force linear complexity and fix CI failure for old clang versions

* Convert color_maps to free functions.

* Add missing header and remove constexpr test

* Convert tabs to spaces

[ci skip]

* Fix compile tests and make static constexpr uniform across data

* Add swatches to docs.

* Fix image links in docs

[ci skip]

Co-authored-by: Nick Thompson <nathompson7@protonmail.com>

reporting/performance/color_tables_performance.cpp

@@ -0,0 +1,30 @@
+//  (C) Copyright Matt Borland 2022.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <array>
+#include <random>
+#include <limits>
+#include <boost/math/tools/color_maps.hpp>
+#include <benchmark/benchmark.h>
+
+template <typename Real>
+void viridis_bm(benchmark::State& state)
+{
+    std::random_device rd;
+    std::mt19937_64 gen(rd());
+    std::uniform_real_distribution<Real> dist(0, 0.125);
+    Real x = dist(gen);
+    for (auto _ : state)
+    {
+        benchmark::DoNotOptimize(boost::math::tools::viridis(x));
+        x += std::numeric_limits<Real>::epsilon();
+    }
+}
+
+BENCHMARK_TEMPLATE(viridis_bm, float);
+BENCHMARK_TEMPLATE(viridis_bm, double);
+
+
+BENCHMARK_MAIN();