This Fortran library is independent of any graphical toolkit: its main functionality is to convert a real value to RGB values that you can use with any drawing toolkit. It offers various methods and options to manage colormaps. It includes:
- the 222 colormaps of the Scientific colour maps collection v8.0.1 by Fabio Crameri. See Fabio Crameri's poster "Scientific Colour Maps" for more information and my No Bijection! text about the mysteries and wonders of colors,
- the "magma", "inferno","plasma", "viridis" matplotlib colormaps,
- the Dave Green's cubehelix colormap,
- a few basic colormaps: "black_body", "fire", "rainbow", "inv_rainbow", "zebra".
Assuming your graphical library has a setpixelgb()
-like function and you know your z
values will be for example in the [0, 2] range, you can write something like:
use forcolormap, only: Colormap, wp
...
type(Colormap) :: cmap
integer :: red, green, blue
real(wp) :: z, x, y
...
! Let's use the glasgow colormap:
call cmap%set("glasgow", 0.0_wp, 2.0_wp)
...
z = f(x,y)
call cmap%compute_RGB(z, red, green, blue)
call setpixelrgb(x, y, red, green, blue)
The library is using the precision wp=>real64
defined in the module iso_fortran_env
. And depending on the integers expected by your graphical library, you may need to convert the kinds of red, green, blue variables by writing for example int(red, kind=int16)
if you need 16 bit integers.
This guideline can help you choose the right kind of colormap. And you can visually choose the available colormaps in the colormaps_list/ForColormap.pdf manual or on this page (under development): https://github.com/gha3mi/forcolormap/tree/dev
You need, whatever your operating system:
- a modern Fortran compiler, for example GFortran or the Intel ifort/ifx compilers. See the Fortran-lang.org compilers page for other compilers.
- The Fortran Package Manager fpm or CMake (>=3.24) & pkg-config for building the project.
- For writing PPM files, the library ForImage is used as a fpm or CMake dependency (automatically downloaded).
If you have a GitHub account, just clone the repository. Then launch the demo example, which is creating PPM files with colormaps and colorbars for all the available colormaps:
$ git clone [email protected]:vmagnin/forcolormap.git
$ cd forcolormap
$ fpm run --example demo
To use ForColormap within your own fpm
project, add the following lines to your fpm.toml
manifest file:
[dependencies]
forcolormap = {git = "https://github.com/vmagnin/forcolormap.git" }
You can also build the project with CMake:
$ git clone [email protected]:vmagnin/forcolormap.git
$ cd forcolormap
$ mkdir build && cd build
$ cmake ..
$ make
$ sudo make install
By default, ForColormap is built as a static library by CMake. You can compile your program with the -static
option:
$ gfortran -static my_program.f90 $(pkg-config --cflags --libs forcolormap forimage)
Note that ForColormap is depending on ForImage, and for linking you must respect that order.
There is a CMake option to obtain a shared library:
$ cmake -D BUILD_SHARED_LIBS=true ..
You can compile your program like this:
$ gfortran my_program.f90 $(pkg-config --cflags --libs forcolormap)
If you encounter linking problems, you should verify the content of your PKG_CONFIG_PATH
and `` environment variables. For example, in Ubuntu or FreeBSD the .pc
files will be installed in `/usr/local/lib/pkgconfig/` and the libraries in `/usr/local/lib/`.
$ export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig/
You can build the examples with:
$ cmake -D BUILD_FORCOLORMAP_EXAMPLES=true ..
$ make
$ cd example
The automatic tests can be run with:
$ cmake -D BUILD_TESTING=true ..
$ make
$ ctest
From the build
directory:
$ sudo make uninstall_forcolormap
Note that its dependency ForImage will also be uninstalled! You will have to reinstall it if needed.
You can also choose and remove files listed in build/install_manifest.txt
one by one.
See CMake basics for more information.
In the example
directory, you will find these commented demos:
demo.f90
creates demo PPM files for each built-in colormap, plus a PPM file with the corresponding colorbars. It also demonstrates how to create your own colormap defined in an array and how to download a colormap from a.txt
file.demo_reverse.f90
demonstrates the usage of thereverse=.true.
option to reverse the direction of a colormap.colormaps_list.f90
generates thecolormaps_list/COLORMAPS_LIST_*.md
files.example1.f90
demonstrates how ForImage can be used to import/export PPM files.create.f90
demonstrates creating a custom colormap using methods likecreate_lagrange()
andcreate_bezier()
.extract.f90
demonstrates how to create a specific colormap by extracting a specified number of colors of a colormap.info.f90
demonstrates how to obtain information about a colormap using theColormaps_info
class.modify.f90
demonstrates how you can modify a colormap with methods likeshift()
, in concrete cases.
They can be launched with the command fpm run --example name_of_the_example
(without the .f90
extension).
In the gtk-fortran-extra repository, you will also find a physical model demonstrating the use of ForColormap. It creates a movie with Turing patterns, displayed with various colormaps:
https://www.youtube.com/watch?v=cVHLCVVvZ4U
This project is under MIT license. The logo files are under license CC BY-SA 4.0.
As any work, a colormap should be cited:
- For Scientific colour maps, please cite these two items:
- Crameri, F. (2018a), Scientific colour maps. Zenodo. https://doi.org/10.5281/zenodo.1243862
- Crameri, Fabio, Grace E. Shephard, and Philip J. Heron. “The Misuse of Colour in Science Communication.” Nature Communications 11, no. 1 (October 28, 2020): 5444. https://doi.org/10.1038/s41467-020-19160-7.
- For the matplotlib colormaps, you can cite this webpage https://bids.github.io/colormap/
- For the cubehelix colormap, please cite:
- Green, D. A. “A Colour Scheme for the Display of Astronomical Intensity Images.” arXiv, August 30, 2011. https://arxiv.org/abs/1108.5083.
- Nuñez, Jamie R., Christopher R. Anderton, and Ryan S. Renslow. “Optimizing Colormaps with Consideration for Color Vision Deficiency to Enable Accurate Interpretation of Scientific Data.” Edited by Jesús Malo. PLOS ONE 13, no. 7, August 1, 2018, e0199239. https://doi.org/10.1371/journal.pone.0199239.
- Rogowitz, Bernice E, and Lloyd A Treinish. “Why Should Engineers and Scientists Be Worried About Color?”
- Thyng, Kristen, Chad Greene, Robert Hetland, Heather Zimmerle, and Steven DiMarco. “True Colors of Oceanography: Guidelines for Effective and Accurate Colormap Selection.” Oceanography 29, no. 3, September 1, 2016, pp. 9–13. https://doi.org/10.5670/oceanog.2016.66.
- Valeur, Bernard. La couleur dans tous ses éclats. Bibliothèque scientifique. Paris: Belin-"Pour la science", 2011, ISBN 9782701158761.
- Valeur, Bernard. Lumière et luminescence - Ces phénomènes lumineux qui nous entourent. Bibliothèque scientifique. Paris: Belin-"Pour la science", 2005, ISBN 9782701136035.
- https://en.wikipedia.org/wiki/Color_gradient
- https://en.wikipedia.org/wiki/Heat_map
- Ken Hughes, "Default colormaps: Are Parula and Viridis really an improvement over Jet?", posted on October 1, 2019.
- "In Search of a Perfect Colormap", https://inversed.ru/Blog_2.htm
- The Data Visualisation Guide section about colours
- Cubehelix (Dave Green, public domain): https://people.phy.cam.ac.uk/dag9/CUBEHELIX/
- Scientific colour maps (Fabio Crameri, MIT license):
- https://www.fabiocrameri.ch/colourmaps/
- https://s-ink.org/colour-map-guideline
- https://s-ink.org/scientific-colour-maps
- Seminar talk by Fabio Crameri about the scientific use of colour in science communication for the University of Oslo GeoHyd seminar: https://www.youtube.com/watch?v=iDPzWARbFrs
- Matplotlib colormaps (CC0 license / public domain):
- Stéfan van der Walt and Nathaniel Smith: https://bids.github.io/colormap/
- Python version: https://github.com/BIDS/colormap/blob/master/colormaps.py
- Nathaniel Smith and Stéfan van der Walt, A Better Default Colormap for Matplotlib, SciPy 2015: https://www.youtube.com/watch?v=xAoljeRJ3lU
- Black Body colormap (CC0 license / public domain) by Kenneth Moreland: "Color Map Advice for Scientific Visualization".
- Colors for data scientists. Generate and refine palettes of optimally distinct colors.