qualpal

Spec sheet

What it does

Qualpal generates qualitative color palettes whose colors are selected for perceptual distinctiveness.Read 14 Oct 2026 · jolars.github.io

Purpose

Qualpal is a C++ library for generating qualitative color palettes with maximum perceptual distinctiveness, especially for data visualization.Read 4 Oct 2026 · jolars.github.io

Platforms

Prebuilt binaries are available for Linux, macOS, and Windows.Read 4 Oct 2026 · github.com

License

The source repository states that Qualpal is available under the MIT License.Read 4 Oct 2026 · github.com

Maker

Johan Larsson is listed as the author and maintainer of Qualpal.Read 14 Oct 2026 · jolars.co

Algorithm

The algorithm uses deterministic farthest-point sampling to improve the minimum pairwise color distance.Read 14 Oct 2026 · theoj.org

Background color

You can specify a background color so generated colors are selected to remain distinct from it.Read 4 Oct 2026 · jolars.github.io

Background optimization

Palette generation can include a background color so selected colors remain distinct from it.Read 14 Oct 2026 · theoj.org

Builder API

The C++ interface uses a builder-style API for configuring palette generation.Read 14 Oct 2026 · jolars.github.io

C++ library

The core product is a C++ library for palette generation.Read 14 Oct 2026 · github.com

CLI

Qualpal includes a command-line interface for generating and analyzing palettes.Read 14 Oct 2026 · github.com

Color accessibility

Palettes can be adapted using color vision deficiency simulation.Read 14 Oct 2026 · jolars.github.io

Color space

The official site describes perceptually uniform color selection in DIN99d color space.Read 14 Oct 2026 · jolars.github.io

Dependencies

The JOSS paper describes the C++ library as lightweight and having no external dependencies.Read 14 Oct 2026 · theoj.org

Distance metrics

The project supports CIEDE2000, DIN99d and CIE76 color-difference metrics.Read 14 Oct 2026 · theoj.org

Input formats

The C++ project accepts RGB values, hexadecimal colors, HSL ranges and built-in palettes.Read 14 Oct 2026 · github.com

Large color spaces

The project advertises fast algorithms for large color spaces.Read 14 Oct 2026 · jolars.github.io

Limit

Qualpal does not consider aesthetic factors such as color harmony or complementary colors when choosing colors.Read 4 Oct 2026 · jolars.github.io

Limit: build setup

The PyPI description says installing the Python package from source requires a C++ compiler.Read 14 Oct 2026 · pypi.org

Limit: maturity

PyPI classifies the Python distribution as development status 4, Beta.Read 14 Oct 2026 · pypi.org

Limit: R parity

The repository warns that qualpalr can lag behind the latest C++ library features.Read 14 Oct 2026 · github.com

Limit: web functionality

The official repository says the web app has slightly less functionality than the library and R package.Read 14 Oct 2026 · github.com

Maker role

Larsson's CV lists him as a Thiele Postdoctoral Researcher in the Department of Mathematical Sciences at Copenhagen University since 2024.Read 14 Oct 2026 · jolars.co

Palette extension

The library can extend an existing palette while keeping specified colors fixed.Read 4 Oct 2026 · jolars.github.io

Palette inputs

It accepts RGB colors, HSL or LCHab color spaces, and predefined palettes as inputs.Read 4 Oct 2026 · jolars.github.io

Praise: accessibility

The independent JOSS paper highlights support for the full dichromacy spectrum and multiple color-vision-deficiency types.Read 14 Oct 2026 · theoj.org

Praise: flexibility

The independent paper emphasizes flexible generation from HSL, LCHab and fixed RGB inputs.Read 14 Oct 2026 · theoj.org

Publication

The JOSS paper was published October 16, 2025.Read 14 Oct 2026 · theoj.org

Python features

The Python package provides CVD optimization, perceptual-distance analysis, CSS and JSON export, matplotlib visualization and Jupyter HTML display.Read 14 Oct 2026 · pypi.org

Python integration

The project README lists a Python package called qualpal.Read 4 Oct 2026 · github.com

Python licence

The PyPI package metadata identifies the Python implementation as MIT licensed.Read 14 Oct 2026 · pypi.org

Python package

The project is also distributed as the Python package qualpal on PyPI.Read 14 Oct 2026 · pypi.org

Python platforms

PyPI classifies the package for macOS, Windows, POSIX/Linux and Unix systems.Read 14 Oct 2026 · pypi.org

Python release

PyPI lists qualpal 1.1.0 as released January 9, 2026.Read 14 Oct 2026 · pypi.org

Python requirement

The Python package requires Python 3.9 or newer.Read 14 Oct 2026 · pypi.org

R API

qualpalr documents functions for palette generation, palette retrieval, color conversion, analysis, plotting and printing.Read 14 Oct 2026 · jolars.github.io

R dependencies

The R package imports graphics, stats, utils and Rcpp, links to Rcpp, and lists additional suggested packages.Read 14 Oct 2026 · web-r.org

R documentation

CRAN provides a reference manual and two vignettes, including an introduction and an alternatives comparison.Read 14 Oct 2026 · mirror.ibcp.fr

R integration

The project provides an R package called qualpalr for generating palettes in R workflows.Read 4 Oct 2026 · jolars.github.io

R licence

The CRAN R package is licensed under GPL-3.Read 14 Oct 2026 · mirror.ibcp.fr

R package

The library is distributed for R as qualpalr.Read 14 Oct 2026 · jolars.github.io

R requirements

qualpalr requires R 4.0 or newer, C++17 and compilation.Read 14 Oct 2026 · mirror.ibcp.fr

R version

CRAN metadata lists qualpalr version 2.0.0, published January 29, 2026.Read 14 Oct 2026 · mirror.ibcp.fr

Release quality

The R project's Windows CRAN check reports qualpalr 2.0.0 installed successfully under R 4.6.1 and Windows Server 2022.Read 14 Oct 2026 · r-project.org

Requirements

Building from source requires CMake 3.15 or later and a C++17-compatible compiler; OpenMP is optional for parallelization.Read 4 Oct 2026 · github.com

Web app

A browser application is available at qualpal.cc.Read 14 Oct 2026 · jolars.github.io

Where Specifiction places it

• Color Palette Generators#20 of 347.4