add compute_histogram python bindings (#64)

* rename kornia-py

* include python bindings

.github/workflows/python_release.yml

@@ -23,7 +23,7 @@ jobs:
           target: ${{ matrix.target }}
           manylinux: auto
           command: build
-          args: --release --out dist -i python${{ matrix.python-version }} -m py-kornia/Cargo.toml --sdist
+          args: --release --out dist -i python${{ matrix.python-version }} -m kornia-py/Cargo.toml --sdist
       - name: Upload wheels
         uses: actions/upload-artifact@v2
         with:
@@ -53,7 +53,7 @@ jobs:
         with:
           command: build
           maturin-version: latest
-          args: --release --target ${{ matrix.target }}-apple-darwin --out dist -i python${{ matrix.python-version }} -m py-kornia/Cargo.toml --sdist
+          args: --release --target ${{ matrix.target }}-apple-darwin --out dist -i python${{ matrix.python-version }} -m kornia-py/Cargo.toml --sdist
       - name: Upload wheels
         uses: actions/upload-artifact@v2
         with:
@@ -82,7 +82,7 @@ jobs:
         with:
           command: build
           maturin-version: latest
-          args: --release --out dist -i python${{ matrix.python-version }} -m py-kornia/Cargo.toml --sdist
+          args: --release --out dist -i python${{ matrix.python-version }} -m kornia-py/Cargo.toml --sdist
       - name: Upload wheels
         uses: actions/upload-artifact@v2
         with:

.github/workflows/python_test.yml

@@ -4,14 +4,14 @@ on:
   pull_request:
     paths:
       - Cargo.lock
-      - py-kornia/**
+      - kornia-py/**
       - .github/workflows/test-python.yml
   push:
     branches:
       - main
     paths:
       - Cargo.lock
-      - py-kornia/**
+      - kornia-py/**
       - .github/workflows/test-python.yml
 
 concurrency:
@@ -51,11 +51,11 @@ jobs:
         with:
           command: build
           maturin-version: latest
-          args: --target x86_64-apple-darwin --out dist -m py-kornia/Cargo.toml
+          args: --target x86_64-apple-darwin --out dist -m kornia-py/Cargo.toml
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip |
           python -m pip install dist/*.whl |
           python -m pip install pytest torch numpy
       - name: Build and test
-        run: pytest py-kornia/tests
+        run: pytest kornia-py/tests

Makefile

@@ -17,23 +17,23 @@ endif
 .PHONY: requirements
 requirements: .venv  ## Install/refresh Python project requirements
 	$(VENV_BIN)/python -m pip install --upgrade pip
-	$(VENV_BIN)/python -m pip install -r py-kornia/requirements-dev.txt
+	$(VENV_BIN)/python -m pip install -r kornia-py/requirements-dev.txt
 
 .PHONY: build-python
 build-python: .venv  ## Compile and install Python for development
 	@unset CONDA_PREFIX && source $(VENV_BIN)/activate \
-	&& maturin develop -m py-kornia/Cargo.toml \
+	&& maturin develop -m kornia-py/Cargo.toml \
 
 .PHONY: build-python-release
 build-python-release: .venv  ## Compile and install a faster Python binary with full optimizations
 	@unset CONDA_PREFIX && source $(VENV_BIN)/activate \
-	&& maturin develop -m py-kornia/Cargo.toml --release \
+	&& maturin develop -m kornia-py/Cargo.toml --release \
 
 .PHONY: test-python
 test-python: .venv  ## Run Python tests
 	@unset CONDA_PREFIX && source $(VENV_BIN)/activate \
-	&& maturin develop -m py-kornia/Cargo.toml \
-	&& $(VENV_BIN)/pytest py-kornia/tests
+	&& maturin develop -m kornia-py/Cargo.toml \
+	&& $(VENV_BIN)/pytest kornia-py/tests
 
 .PHONY: clippy
 clippy:  ## Run clippy with all features
@@ -53,7 +53,7 @@ clean:  ## Clean up caches and build artifacts
 	@rm -rf target/
 	@rm -f Cargo.lock
 	@cargo clean
-	@$(MAKE) -s -C py-kornia/ $@
+	@$(MAKE) -s -C kornia-py/ $@
 
 .PHONY: help
 help:  ## Display this help screen

kornia-py/benchmark/bench_histogram.py

@@ -0,0 +1,42 @@
+import timeit
+
+import cv2
+import kornia_rs as K
+import numpy as np
+
+image_path = "tests/data/dog.jpeg"
+N = 5000  # number of iterations
+
+img = K.read_image_jpeg(image_path)[..., :1]
+
+
+# 0.04 ms :)
+def hist_opencv(image: np.ndarray) -> np.ndarray:
+    return cv2.calcHist([image], [0], None, [256], [0, 256])
+
+
+# 0.17 ms :(
+def hist_kornia(image: np.ndarray) -> np.ndarray:
+    return K.compute_histogram(image, num_bins=256)
+
+
+tests = [
+    {
+        "name": "OpenCV",
+        "stmt": "hist_opencv(image)",
+        "setup": "from __main__ import hist_opencv",
+        "globals": {"image": img},
+    },
+    {
+        "name": "Kornia",
+        "stmt": "hist_kornia(image)",
+        "setup": "from __main__ import hist_kornia",
+        "globals": {"image": img},
+    },
+]
+
+for test in tests:
+    timer = timeit.Timer(
+        stmt=test["stmt"], setup=test["setup"], globals=test["globals"]
+    )
+    print(f"{test['name']}: {timer.timeit(N)/ N * 1e3:.2f} ms")

kornia-py/src/histogram.rs

@@ -0,0 +1,28 @@
+use pyo3::prelude::*;
+
+use crate::image::{FromPyImage, PyImage};
+use kornia_rs::image::Image;
+
+/// Compute the pixel-wise histogram of an image.
+/// --
+///
+/// This function computes the histogram of an image with a given number of bins.
+///
+/// # Arguments
+///
+/// * `image` - The input image to compute the histogram with shape (H, W, 1) and dtype uint8.
+/// * `num_bins` - The number of bins to use for the histogram.
+///
+/// # Returns
+///
+/// A vector of size `num_bins` containing the histogram.
+#[pyfunction]
+pub fn compute_histogram(image: PyImage, num_bins: usize) -> PyResult<Vec<usize>> {
+    let image = Image::from_pyimage(image)
+        .map_err(|e| PyErr::new::<pyo3::exceptions::PyException, _>(format!("{}", e)))?;
+
+    let histogram = kornia_rs::histogram::compute_histogram(&image, num_bins)
+        .map_err(|e| PyErr::new::<pyo3::exceptions::PyException, _>(format!("{}", e)))?;
+
+    Ok(histogram)
+}

py-kornia/src/lib.rs → kornia-py/src/lib.rs

@@ -1,3 +1,4 @@
+mod histogram;
 mod image;
 mod io;
 mod resize;
@@ -24,6 +25,7 @@ pub fn kornia_rs(_py: Python, m: &PyModule) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(write_image_jpeg, m)?)?;
     m.add_function(wrap_pyfunction!(read_image_any, m)?)?;
     m.add_function(wrap_pyfunction!(resize::resize, m)?)?;
+    m.add_function(wrap_pyfunction!(histogram::compute_histogram, m)?)?;
     m.add_class::<PyImageSize>()?;
     m.add_class::<PyImageDecoder>()?;
     m.add_class::<PyImageEncoder>()?;

kornia-py/tests/test_histogram.py

@@ -0,0 +1,18 @@
+from __future__ import annotations
+import kornia_rs as K
+
+import numpy as np
+
+
+def test_histogram():
+    # load an image with libjpeg-turbo
+    img = np.array([0, 2, 4, 128, 130, 132, 254, 255, 255], dtype=np.uint8).reshape(
+        3, 3, 1
+    )
+
+    img_histogram: list[int] = K.compute_histogram(img, num_bins=3)
+
+    assert len(img_histogram) == 3
+    assert img_histogram[0] == 3
+    assert img_histogram[1] == 3
+    assert img_histogram[2] == 3

src/histogram.rs

@@ -2,7 +2,7 @@ use anyhow::Result;
 
 use crate::image::Image;
 
-/// Compute the histogram of an image.
+/// Compute the pixel intensity histogram of an image.
 ///
 /// NOTE: this is limited to 8-bit 1-channel images.
 ///