pylcms2

Simplified Python binding of LittleCMS2 library.

Installation

Wheel files for 64-bit Windows and Python 3.13 are available from PyPI. Use pip to install the package:

pip install pylcms2

The package can be uninstalled using the corresponding command:

python -m pip uninstall -y pylcms2

Getting started

Little CMS functionality is implemented by two classes: Profile and Transform.

Profiles

A Profile object can be created using one of the built-in profiles, by reading a profile file (using the filename argument) or from data stored in memory as Python bytes object (buffer argument).

Built-in profiles include sRGB, Lab and XYZ provided by the Little CMS library and additional RGB profiles: Adobe RGB (1998), Apple RGB, Best RGB, Beta RGB, Bruce RGB, CIE RGB, ColorMatch RGB, Don RGB 4, ECI RGB v2, Ekta Space PS5, NTSC RGB, PAL/SECAM RGB, ProPhoto RGB, SMPTE-C RGB, and Wide Gamut RGB.

import pylcms2

x = pylcms2.Profile("sRGB")
p = pylcms2.Profile("ProPhoto RGB")
y = pylcms2.Profile(filename="CMYK.icm")

with open("CMYK.icm", "rb") as f:
    z = pylcms2.Profile(buffer=f.read)

Transforms

Transforms between profiles are implemented by the respective class. To create an instance of Transform call its constructor and provide six arguments: (1) source profile, (2) source data type string, (3) destination profile, (4) destination data type string, (5) rendering intent string (optional, defaults to "PERCEPTUAL"), and (6) flags (optional, the default value is "NONE").

lab_profile = pylcms2.create_profile("Lab")
rgb_profile = pylcms2.create_profile("sRGB")
transform = pylcms2.Transform(lab_profile, "Lab_DBL",
                              rgb_profile, "RGB_16",
                              "PERCEPTUAL",
                              "NONE")

Supported format strings can be listed as follows:

pylcms2.DATA_TYPES.keys()

Rendering intents could be one of the following: 'PERCEPTUAL', 'RELATIVE_COLORIMETRIC', 'SATURATION', and 'ABSOLUTE_COLORIMETRIC' (see pylcms2.INTENT dictionary).

Likewise, supported transform flags are available as keys of the pylcms2.FLAG dictionary. Several flags can be combined by including them in the flags argument string separating them by commas, semicolons, spaces or the pipe symbol |, for example

flags = "GAMUTCHECK,SOFTPROOFING,PRESERVEBLACK"

The transform is calculated using the Transform.apply method, for example:

neutral_grey = transform.apply([50.0, 0.0, 0.0])

The method takes a Numpy array (or an object convertible to NumPy array) and returns a transformed array of appropriate shape. The data type of the input array must correspond to the input data type specified during transform creation. When lists and other array-compatible objects are used the data types will be converted, when possible. For instance in the example above the input data could be provided as [50, 0, 0] (list containing integers):

neutral_grey = transform.apply([50, 0, 0])

Proofing transform

Little CMS proofing transforms can be created by supplying two extra parameters to the Transform class constructor:

proof = pylcms2.Transform(lab_profile, "Lab_DBL",
                          rgb_profile, "RGB_16",
                          proofing_profile=printer_profile,
                          proofing_intent="PRESERVE_K_ONLY_PERCEPTUAL",
                          intent="PERCEPTUAL",
                          flags="SOFTPROOFING")

The proofing_profile argument defines the profile of the device to be emulated and the proofing_intent is one of the following: PRESERVE_K_ONLY_PERCEPTUAL, PRESERVE_K_ONLY_RELATIVE_COLORIMETRIC, PRESERVE_K_ONLY_SATURATION, PRESERVE_K_PLANE_PERCEPTUAL, PRESERVE_K_PLANE_RELATIVE_COLORIMETRIC and PRESERVE_K_PLANE_SATURATION. The SOFTPROFING flag should be set to enable soft proofing.

Building form source

To build pylcms2 for your own platform, clone the repository with its submodules:

git clone --recurse-submodules git@github.com:RomanKosobrodov/python-lcms2.git

Check that the build package is installed:

python -m pip install build --upgrade

navigate to the root directory of the repository (the one containing the pyproject.toml file) and run:

python -m build --wheel

If everything goes smoothly you will have a wheel file for you platform generated in the dist directory. It can be installed by pip as follows:

python -m pip install --upgrade dist/pylcms2*.whl

Building the package on Windows might involve minor modifications to include and library paths. An attempt was made to automate the process (see setup.py) though there is no guarantee that the code works on your version of Windows.

Issues, bugs and feedback

You are likely to hit a few bugs and issues while using pylcms2. Please report them through GitHub Issues.