focal
Image processing in C++20 with a zero-copy NumPy interface.
import focal
img = focal.imread("photo.jpg") # linear float32, (h, w, c)
img = focal.exposure(img, 0.5) # half a stop brighter
img = focal.gaussian_blur(img, 2.0)
focal.imwrite("out.png", img) # encodes back to sRGB
Design
Everything is a view. The core type is a non-owning {pointer, dtype, shape, strides} struct, so a crop, a single channel, and a NumPy array handed over
from Python are all the same type, and none of them copy. Strides are in bytes,
matching NumPy exactly, so wrapping an incoming array is copying six integers.
Nothing converts silently. Array arguments are declared .noconvert(), so
passing a float64 or non-contiguous array raises TypeError instead of quietly
costing a full-size copy. Converting is the caller's decision.
Filtering happens in linear light. imread decodes sRGB to linear float32
and imwrite encodes back. Blurring or resizing gamma-encoded values darkens
the result — on a synthetic test chart, a σ=3 blur done in gamma space came out
29% darker than the same blur done correctly, with individual pixels off by
74/255.
What's here
| I/O | imread, imwrite — PNG, JPEG, BMP, TGA via stb |
| Point ops | gamma, exposure, brightness_contrast, invert, clip, blend, apply_lut |
| Filtering | gaussian_blur (separable) |
| Sampling | sample — nearest and bilinear, border-aware |
| Color | srgb_to_linear, linear_to_srgb |
Border modes (clamp, reflect, reflect101, wrap, constant) are shared
by every spatial op and match scipy.ndimage's semantics.
Install
pip install focalpy
Building from source needs a C++20 compiler and CMake:
git clone https://github.com/edisons3608/focal
cd focal
pip install -e . --no-build-isolation
pytest
Status
Early. The API will change. Tests compare against scipy.ndimage and PIL
where an oracle exists.
License
MIT. Bundles stb (public domain).
1 maintainer
Metadata
1 maintainer
Release files for focalpy 0.0.1
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Source distribution (sdist)
| File | Size | Uploaded | Provenance | Actions |
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Built distributions (wheels)
| File | Actions Reset | |||
|---|---|---|---|---|
| focalpy-0.0.1-cp312-abi3-win_amd64.whl | CPython 3.12 | abi3 | Windows x86-64 | Details for focalpy-0.0.1-cp312-abi3-win_amd64.whl |
| focalpy-0.0.1-cp312-abi3-manylinux_2_27_x86_64.manylinux_2_28_x86_64.whl | CPython 3.12 | abi3 | Linux glibc 2.28+ x86-64, Linux glibc 2.27+ x86-64 | Details for focalpy-0.0.1-cp312-abi3-manylinux_2_27_x86_64.manylinux_2_28_x86_64.whl |
| focalpy-0.0.1-cp312-abi3-manylinux_2_27_aarch64.manylinux_2_28_aarch64.whl | CPython 3.12 | abi3 | Linux glibc 2.27+ ARM64, Linux glibc 2.28+ ARM64 | Details for focalpy-0.0.1-cp312-abi3-manylinux_2_27_aarch64.manylinux_2_28_aarch64.whl |
| focalpy-0.0.1-cp312-abi3-macosx_11_0_arm64.whl | CPython 3.12 | abi3 | macOS 11.0+ ARM64 | Details for focalpy-0.0.1-cp312-abi3-macosx_11_0_arm64.whl |
| focalpy-0.0.1-cp312-abi3-macosx_10_15_x86_64.whl | CPython 3.12 | abi3 | macOS 10.15+ x86-64 | Details for focalpy-0.0.1-cp312-abi3-macosx_10_15_x86_64.whl |
Total release size: 1.1 MB
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