[build] Test building CUDA-enabled OpenCV (#225)

Author: Breakthrough

.github/workflows/build-windows-cuda.yml

@@ -0,0 +1,100 @@
+# GitHub Actions Workflow: Build opencv-python with CUDA support on Windows
+#
+# This workflow compiles opencv-python from source with CUDA enabled on a
+# GitHub-hosted Windows runner. The resulting Python wheel is then uploaded
+# as a build artifact.
+#
+# This is a complex and long-running process. It is configured to run only
+# on manual trigger (workflow_dispatch).
+
+name: Build OpenCV (Windows, CUDA)
+
+on:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: windows-latest
+
+    defaults:
+      run:
+        shell: pwsh
+
+    steps:
+      - name: 📥 Checkout code
+        uses: actions/checkout@v4
+
+      - name: 🏗️ Install Build Dependencies
+        run: |
+          echo "Installing CMake and Ninja for building..."
+          choco install -y cmake ninja
+
+      - name: 🐍 Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: 📦 Install Python Build Requirements
+        run: |
+          python -m pip install --upgrade pip
+          pip install numpy wheel
+
+      - name: 🔧 Install NVIDIA CUDA Toolkit
+        run: |
+          echo "Downloading CUDA Toolkit..."
+          $cuda_installer_url = "https://developer.download.nvidia.com/compute/cuda/12.1.1/network_installers/cuda_12.1.1_windows_network.exe"
+          # Use the runner's temp directory, which is guaranteed to exist.
+          $installer_path = Join-Path $env:RUNNER_TEMP "cuda_installer.exe"
+          curl -L -o $installer_path $cuda_installer_url
+          
+          echo "Installing CUDA Toolkit silently..."
+          # Use Start-Process for robust execution in PowerShell.
+          # The arguments must be passed as a single string.
+          $arguments = "-s nvcc_12.1 cudart_12.1"
+          Start-Process -FilePath $installer_path -ArgumentList $arguments -Wait -NoNewWindow
+          
+          echo "Adding CUDA to PATH..."
+          $cuda_path = "C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v12.1"
+          echo "CUDA_PATH=$cuda_path" | Out-File -FilePath $env:GITHUB_ENV -Append
+          echo "$cuda_path\bin" | Out-File -FilePath $env:GITHUB_PATH -Append
+          echo "$cuda_path\lib\x64" | Out-File -FilePath $env:GITHUB_PATH -Append
+        shell: pwsh
+
+      - name: Clone opencv-python repository
+        run: |
+          git clone --depth 1 --recursive https://github.com/opencv/opencv-python.git
+
+      - name: 🛠️ Build opencv-python with CUDA
+        run: |
+          cd opencv-python
+
+          # Set environment variables to configure the build.
+          # This is the core of the customization.
+          # - WITH_CUDA=ON: Enables CUDA support.
+          # - CUDA_ARCH_BIN: Specifies the CUDA architectures to build for.
+          # - CUDA_ARCH_PTX: Specifies the virtual architecture for forward compatibility.
+          # - BUILD_TESTS=OFF: Speeds up the build by not compiling tests.
+          # Use single quotes to avoid PowerShell parsing issues with nested quotes.
+          $env:CMAKE_ARGS = '-D CMAKE_BUILD_TYPE=RELEASE -D WITH_CUDA=ON -D CUDA_ARCH_BIN="6.0;6.1;7.0;7.5" -D CUDA_ARCH_PTX=7.5 -D OPENCV_ENABLE_NONFREE=ON -D BUILD_TESTS=OFF -D BUILD_PERF_TESTS=OFF -D BUILD_EXAMPLES=OFF'
+
+          # Set this to force a build from source instead of downloading a pre-built wheel.
+          $env:PIP_NO_BINARY = ":all:"
+
+          # Run the build process. This will compile OpenCV and create a wheel.
+          # The output wheel will be placed in the 'wheelhouse' directory.
+          pip wheel . --wheel-dir ../wheelhouse
+
+      - name: 🧪 Verify Build
+        run: |
+          # Install the wheel we just built
+          pip install ../wheelhouse/opencv_python*.whl
+
+          # Print OpenCV build information. We expect to see the "CUDA" section.
+          echo "Verifying OpenCV build..."
+          python -c "import cv2; print(cv2.getBuildInformation())"
+
+      - name: 📤 Upload Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: opencv-python-cuda-wheel
+          path: wheelhouse/