README.md

Documentation: cppcolormap.readthedocs.org

Doxygen documentation: tdegeus.github.io/cppcolormap

cppcolormap

C++ and Python library specifying colormaps.

Contents

Disclaimer

This library is free to use under the GPLv3 license. Any additions are very much appreciated, in terms of suggested functionality, code, documentation, testimonials, word-of-mouth advertisement, etc. Bug reports or feature requests can be filed on GitHub. As always, the code comes with no guarantee. None of the developers can be held responsible for possible mistakes.

Download: .zip file | .tar.gz file.

(c - GPLv3) T.W.J. de Geus (Tom) | [email protected] | www.geus.me | github.com/tdegeus/cppcolormap

Contributors

• Wolf Vollprecht

Usage from C++

Getting cppcolormap

Using conda

conda install -c conda-forge cppcolormap

From source

# Download cppcolormap
git checkout https://github.com/tdegeus/cppcolormap.git
cd cppcolormap

# For CMake or pkg-config use
cmake .
make install

Usage

The principle interface is with these two functions:

#include <cppcolormap.h>

int main()
{
    std::cout << cppcolormap::colormap("Reds") << std::endl;
    std::cout << cppcolormap::colorcycle("tue") << std::endl;

    return 0;
}

Lists of colormaps and color-cycles can be found below.

The colormaps are stored as a matrix whereby each row contains the (R,G,B) colors. Each color value has a range [0..1]. The number of colors varies from map to map, but can be interpolated by specifying the number of colors you want:

#include <cppcolormap.h>

int main()
{
    std::cout << cppcolormap::colormap("Reds", 256) << std::endl;

    return 0;
}

Note that the colorcycles are not interpolatable. Consequently the functions do have a size option. Note also that the colormaps and colorcycles can also be called directly, e.g.

#include <cppcolormap.h>

int main()
{
    std::cout << cppcolormap::Reds() << std::endl;
    std::cout << cppcolormap::Reds(256) << std::endl;
    std::cout << cppcolormap::tue() << std::endl;

    return 0;
}

Find match

To find the closest match of each color of a colormap in another colormap you can use:

xt::xtensor<size_t,1> idx = cppcolormap::match(cmap1, cmap2);
xt::xtensor<size_t,1> idx = cppcolormap::match(cmap1, cmap2, cppcolormap::metric::euclidean);

The following metrics can be used:

• euclidean (default)
• fast_perceptual
• perceptual

Compiling

Using CMake

Using cppcolormap the CMakeLists.txt can be as follows

cmake_minimum_required(VERSION 3.1)
project(example)
find_package(cppcolormap REQUIRED)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE cppcolormap)

Note that the target cppcolormap includes the target xtensor (itself automatically enforcing the minimal C++14 standard), which is automatically searched using find_package(cppcolormap).

Compilation can then proceed using

• Unix:

  cmake .
  make
  

• Windows:

  cmake -G"NMake Makefiles" .
  nmake
  

Download example "CMakeLists.txt"

Using pkg-config

Presuming that the compiler is c++, compile using (Unix):

c++ `pkg-config --cflags cppcolormap` `pkg-config --cflags xtensor` -std=c++14 ...

By hand

Presuming that the compiler is c++, compile using (Unix):

c++ -I/path/to/cppcolormap/include -I/path/to/xtensor/include  -std=c++14 ...

Usage from Python

Getting cppcolormap

Using conda

conda install -c conda-forge python-cppcolormap

From source

# Download cppcolormap
git checkout https://github.com/tdegeus/cppcolormap.git
cd cppcolormap

# Compile and install
python -m pip install .

Note that you have to install the dependencies pybind11, xtensor, and pyxtensor first.

Usage

There are two principle functions, each returns a 2-d NumPy array:

import cppcolormap as cm

# number of colors in the colormap (optional, may be omitted)
N = 256

# specify the colormap as string
cols = cm.colormap("Reds", N)
cols = cm.colorcycle("tue")

# or call the functions directly
cols = cm.Reds(N)
cols = cm.tue()

(see lists of colormaps and color-cycles below).

Find match

To find the closest match of each color of a colormap in another colormap you can use:

idx = cm.match(cmap1, cmap2)
idx = cm.match(cmap1, cmap2, cm.metric.perceptual)

(See metrics above.)

Example

import matplotlib
import matplotlib.pyplot as plt
import numpy as np
import cppcolormap as cm

x, y = np.meshgrid(
    np.linspace(0, 1, 100),
    np.linspace(0, 1, 100))

d = np.sqrt(x ** 2.0 + y ** 2.0)

C = cm.Reds(256)
C = np.c_[C, np.ones(C.shape[0])]

cmap = matplotlib.colors.LinearSegmentedColormap.from_list('my_colormap', C)

fig, ax = plt.subplots()
cax = ax.imshow(d, cmap=cmap)
plt.show()

Available colormaps

ColorBrewer

Name	Inverse colormap
Accent	Accent_r
Dark2	Dark2_r
Paired	Paired_r
Spectral	Spectral_r
Pastel1	Pastel1_r
Pastel2	Pastel2_r
Set1	Set1_r
Set2	Set2_r
Set3	Set3_r
Blues	Blues_r
Greens	Greens_r
Greys	Greys_r
Oranges	Oranges_r
Purples	Purples_r
Reds	Reds_r
BuPu	BuPu_r
GnBu	GnBu_r
PuBu	PuBu_r
PuBuGn	PuBuGn_r
PuRd	PuRd_r
RdPu	RdPu_r
OrRd	OrRd_r
RdOrYl	RdOrYl_r
YlGn	YlGn_r
YlGnBu	YlGnBu_r
YlOrRd	YlOrRd_r
BrBG	BrBG_r
PuOr	PuOr_r
RdBu	RdBu_r
RdGy	RdGy_r
RdYlBu	RdYlBu_r
RdYlGn	RdYlGn_r
PiYG	PiYG_r
PRGn	PRGn_r

Copyright (c) 2002 Cynthia Brewer, Mark Harrower, and The Pennsylvania State University.

Licensed under the Apache License, Version 2.0

colorbrewer2.org

matplotlib

Name	Inverse colormap
spring	spring_r
summer	summer_r
autumn	autumn_r
winter	winter_r
bone	bone_r
cool	cool_r
hot	hot_r
copper	copper_r
hsv	hsv_r
nipy_spectral	nipy_spectral_r
terrain	terrain_r
seismic	seismic_r
afmhot	afmhot_r
magma	magma_r
inferno	inferno_r
plasma	plasma_r
viridis	viridis_r
jet	jet_r

Copyright (c) New matplotlib colormaps by Nathaniel J. Smith, Stefan van der Walt, and in the case of viridis) Eric Firing.

Licensed under the CC0 license / public domain dedication.

GitHub/BIDS

monocolor

Name	Inverse colormap	Source
White	-
Grey	-
Black	-
Red	-
Blue	-
tuedarkblue	-	[1]
tueblue	-	[1]
tuelightblue	-	[1]
tuewarmred	-	[1]
Apricot	-	[2]
Aquamarine	-	[2]
Bittersweet	-	[2]
Black	-	[2]
Blue	-	[2]
BlueGreen	-	[2]
BlueViolet	-	[2]
BrickRed	-	[2]
Brown	-	[2]
BurntOrange	-	[2]
CadetBlue	-	[2]
CarnationPink	-	[2]
Cerulean	-	[2]
CornflowerBlue	-	[2]
Cyan	-	[2]
Dandelion	-	[2]
DarkOrchid	-	[2]
Emerald	-	[2]
ForestGreen	-	[2]
Fuchsia	-	[2]
Goldenrod	-	[2]
Gray	-	[2]
Green	-	[2]
GreenYellow	-	[2]
JungleGreen	-	[2]
Lavender	-	[2]
LimeGreen	-	[2]
Magenta	-	[2]
Mahogany	-	[2]
Maroon	-	[2]
Melon	-	[2]
MidnightBlue	-	[2]
Mulberry	-	[2]
NavyBlue	-	[2]
OliveGreen	-	[2]
Orange	-	[2]
OrangeRed	-	[2]
Orchid	-	[2]
Peach	-	[2]
Periwinkle	-	[2]
PineGreen	-	[2]
Plum	-	[2]
ProcessBlue	-	[2]
Purple	-	[2]
RawSienna	-	[2]
Red	-	[2]
RedOrange	-	[2]
RedViolet	-	[2]
Rhodamine	-	[2]
RoyalBlue	-	[2]
RoyalPurple	-	[2]
RubineRed	-	[2]
Salmon	-	[2]
SeaGreen	-	[2]
Sepia	-	[2]
SkyBlue	-	[2]
SpringGreen	-	[2]
Tan	-	[2]
TealBlue	-	[2]
Thistle	-	[2]
Turquoise	-	[2]
Violet	-	[2]
VioletRed	-	[2]
White	-	[2]
WildStrawberry	-	[2]
Yellow	-	[2]
YellowGreen	-	[2]
YellowOrange	-	[2]

1. Eindhoven University of Technology
2. LaTeX xcolor (dvipsnames)

Available colorcycles

Xterm

Name	Inverse colormap
xterm	xterm_r

See this site

Eindhoven University of Technology

Name	Inverse colormap
tue	tue_r

Based on the corporate color scheme of the Eindhoven University of Technology.