cppolfarve

Øl farve ("beer color") renders SRM and EBC beer color values as sRGB colors, following the spectral model described by A. J. de Lange, "Color," in Brewing Materials and Processes, Elsevier, 2016, pp. 199-249.

Given a color value and an optical path length (the width of the glass the beer is viewed through), the sample's spectral transmittance is derived from its absorption coefficient at 430 nm via the Beer-Lambert law, integrated against the CIE 1931 color matching functions of the 2 degree standard colorimetric observer under illuminant D65, and the resulting XYZ tristimulus values are transformed to sRGB.

Installation

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
cmake --install build --prefix /usr/local

The library requires C++17 or newer and has no runtime dependencies. Static and shared builds are both supported, through BUILD_SHARED_LIBS.

Usage

Consume it with:

find_package(olfarve 1.0 REQUIRED)
target_link_libraries(my_app PRIVATE olfarve::olfarve)

or vendor the sources and add_subdirectory() them, which contributes nothing but the library.

#include <olfarve/olfarve.hpp>

olfarve::srm_to_srgb(10.0).to_hex();
olfarve::ebc_to_srgb(20.0).to_hex();

// The default path length is 5 cm, the width of a typical sample glass
olfarve::srm_to_srgb(10.0, 1.0).to_hex();

// Results are srgb_color aggregates of gamma encoded components in [0, 1]
const olfarve::srgb_color color = olfarve::srm_to_srgb(10.0);
const auto [red, green, blue] = color;
const olfarve::rgb8 quantized = color.to_rgb8();

// Or start from an absorbance measured at 430 nm
olfarve::absorption_to_srgb(0.7874);

Development

cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug \
  -DCMAKE_COMPILE_WARNING_AS_ERROR=ON -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
cmake --build build
ctest --test-dir build
clang-tidy -p build src/color.cpp tests/*.cpp

Naming and layout follow the Boost conventions, encoded in .clang-format; what the code does follows the C++ Core Guidelines, enforced by .clang-tidy.