We introduce the PyMatting package for Python which implements various methods to solve the alpha matting problem.
Given an input image and a hand-drawn trimap (top row), alpha matting estimates the alpha channel of a foreground object which can then be composed onto a different background (bottom row).
- Alpha matting implementations for:
- Foreground estimation implementations for:
- Fast multithreaded KNN search
- Preconditioners to accelerate the convergence rate of conjugate gradient descent:
- The incomplete thresholded Cholesky decomposition (Incomplete is part of the name. The implementation is quite complete.)
- The V-Cycle Geometric Multigrid preconditioner
- Readable code leveraging NumPy, SciPy and Numba
Additional requirements for GPU support
- cupy-cuda90>=6.5.0 or similar
Requirements to run the tests
Installation with PyPI
pip3 install pymatting
Installation from Source
git clone https://github.com/pymatting/pymatting cd pymatting pip3 install .
from pymatting import cutout cutout( # input image path "data/lemur/lemur.png", # input trimap path "data/lemur/lemur_trimap.png", # output cutout path "lemur_cutout.png")
All implemented methods rely on trimaps which roughly classify the image into foreground, background and unknown reagions.
Trimaps are expected to be
numpy.ndarrays of type
np.float64 having the same shape as the input image with only one color-channel.
Trimap values of 0.0 denote pixels which are 100% background.
Similarly, trimap values of 1.0 denote pixels which are 100% foreground.
All other values indicate unknown pixels which will be estimated by the algorithm.
Run the tests from the main directory:
python3 tests/download_images.py pip3 install -r requirements_tests.txt pytest
Currently 89% of the code is covered by tests.
pip3 install --upgrade pymatting python3 -c "import pymatting"
The last line is necessary to rebuild the ahead-of-time compiled module. Without it, the module will be rebuilt on first import, but the old module will already be loaded at that point, which might cause compatibility issues. Simply re-running the code should usually fix it.
Bug Reports, Questions and Pull-Requests
Please, see our community guidelines.
- Thomas Germer
- Tobias Uelwer
- Stefan Conrad
- Stefan Harmeling
See also the list of contributors who participated in this project.