Cuda python opencv windows

Building OpenCV with CUDA using Visual Studio solution files from the command prompt (cmd)

The following steps will build opencv_worldxxx.dll which is suitable for use on the installed GPU and any other GPUs with the “same” compute capability. This is the best way to get started as it has the smallest build time, but it will limit your options if you want to build software which runs on a range of different GPUs. To fully understand the implications of this please read choosing a suitable CUDA compute capability.

1. Open windows command prompt, type cmd in the Windows search bar.

1. Paste the below⁵ into to the command prompt and press Enter.

   • All CUDA modules
   • cuDNN only
   • Without Python bindings
   • Without CUDA
   • Ninja

   set CMAKE_BUILD_PARALLEL_LEVEL=<N_THREADS>
   "C:\Program Files\CMake\bin\cmake.exe" -H"<PATH_TO_OPENCV_SOURCE>" -DOPENCV_EXTRA_MODULES_PATH="<PATH_TO_OPENCV_CONTRIB_MODULES>" -B"<PATH_TO_BUILD_DIR>" -G"Visual Studio 17 2022" -DINSTALL_TESTS=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DBUILD_opencv_world=ON -DENABLE_CUDA_FIRST_CLASS_LANGUAGE=ON -DWITH_CUDA=ON -DCUDA_GENERATION=Auto -DBUILD_opencv_python3=ON -DPYTHON3_INCLUDE_DIR=<PATH_TO_PYTHON_DIST>/include -DPYTHON3_LIBRARY=<PATH_TO_PYTHON_DIST>/libs/<PYTHON_Lib> -DPYTHON3_EXECUTABLE=<PATH_TO_PYTHON_DIST>/python.exe -DPYTHON3_NUMPY_INCLUDE_DIRS=<PATH_TO_PYTHON_DIST>/lib/site-packages/numpy/core/include -DPYTHON3_PACKAGES_PATH=<PATH_TO_PYTHON_DIST>/Lib/site-packages/

   If you just want to CUDA accelerate the DNN module and are not interested in building the rest of the CUDA modules this will significantly reduce compilation time and size of opencv_worldxxx.dll.

   set CMAKE_BUILD_PARALLEL_LEVEL=<N_THREADS>
   "C:\Program Files\CMake\bin\cmake.exe" -H"<PATH_TO_OPENCV_SOURCE>" -DOPENCV_EXTRA_MODULES_PATH="<PATH_TO_OPENCV_CONTRIB_MODULES>" -B"<PATH_TO_BUILD_DIR>" -G"Visual Studio 17 2022" -DINSTALL_TESTS=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DBUILD_opencv_world=ON -DENABLE_CUDA_FIRST_CLASS_LANGUAGE=ON -DWITH_CUDA=ON -DCUDA_GENERATION=Auto -DBUILD_opencv_cudaarithm=OFF -DBUILD_opencv_cudabgsegm=OFF -DBUILD_opencv_cudafeatures2d=OFF -DBUILD_opencv_cudafilters=OFF -DBUILD_opencv_cudaimgproc=OFF -DBUILD_opencv_cudalegacy=OFF -DBUILD_opencv_cudaobjdetect=OFF -DBUILD_opencv_cudaoptflow=OFF -DBUILD_opencv_cudastereo=OFF -DBUILD_opencv_cudawarping=OFF -DBUILD_opencv_cudacodec=OFF -DBUILD_opencv_python3=ON -DPYTHON3_INCLUDE_DIR=<PATH_TO_PYTHON_DIST>/include -DPYTHON3_LIBRARY=<PATH_TO_PYTHON_DIST>/libs/<PYTHON_Lib> -DPYTHON3_EXECUTABLE=<PATH_TO_PYTHON_DIST>/python.exe -DPYTHON3_NUMPY_INCLUDE_DIRS=<PATH_TO_PYTHON_DIST>/lib/site-packages/numpy/core/include -DPYTHON3_PACKAGES_PATH=<PATH_TO_PYTHON_DIST>/Lib/site-packages/

   set CMAKE_BUILD_PARALLEL_LEVEL=<N_THREADS>
   "C:\Program Files\CMake\bin\cmake.exe" -H"<PATH_TO_OPENCV_SOURCE>" -DOPENCV_EXTRA_MODULES_PATH="<PATH_TO_OPENCV_CONTRIB_MODULES>" -B"<PATH_TO_BUILD_DIR>" -G"Visual Studio 17 2022" -DINSTALL_TESTS=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DBUILD_opencv_world=ON -DENABLE_CUDA_FIRST_CLASS_LANGUAGE=ON -DWITH_CUDA=ON -DCUDA_GENERATION=Auto

   set CMAKE_BUILD_PARALLEL_LEVEL=<N_THREADS>
   "C:\Program Files\CMake\bin\cmake.exe" -H"<PATH_TO_OPENCV_SOURCE>" -DOPENCV_EXTRA_MODULES_PATH="<PATH_TO_OPENCV_CONTRIB_MODULES>" -B"<PATH_TO_BUILD_DIR>" -G"Visual Studio 17 2022" -DINSTALL_TESTS=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DBUILD_opencv_world=ON -DBUILD_opencv_python3=ON -DPYTHON3_INCLUDE_DIR=<PATH_TO_PYTHON_DIST>/include -DPYTHON3_LIBRARY=<PATH_TO_PYTHON_DIST>/libs/<PYTHON_Lib> -DPYTHON3_EXECUTABLE=<PATH_TO_PYTHON_DIST>/python.exe -DPYTHON3_NUMPY_INCLUDE_DIRS=<PATH_TO_PYTHON_DIST>/lib/site-packages/numpy/core/include -DPYTHON3_PACKAGES_PATH=<PATH_TO_PYTHON_DIST>/Lib/site-packages/

   For details see decreasing the build time with Ninja

   "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"
   "C:\Program Files\CMake\bin\cmake.exe" -H"<PATH_TO_OPENCV_SOURCE>" -DOPENCV_EXTRA_MODULES_PATH="<PATH_TO_OPENCV_CONTRIB_MODULES>" -B"<PATH_TO_BUILD_DIR>" -G"Ninja Multi-Config"" -DCMAKE_BUILD_TYPE=Release -DINSTALL_TESTS=ON -DINSTALL_C_EXAMPLES=ON -DBUILD_EXAMPLES=ON -DBUILD_opencv_world=ON -DENABLE_CUDA_FIRST_CLASS_LANGUAGE=ON -DWITH_CUDA=ON -DCUDA_GENERATION=Auto -DBUILD_opencv_python3=ON -DPYTHON3_INCLUDE_DIR=<PATH_TO_PYTHON_DIST>/include -DPYTHON3_LIBRARY=<PATH_TO_PYTHON_DIST>/libs/<PYTHON_Lib> -DPYTHON3_EXECUTABLE=<PATH_TO_PYTHON_DIST>/python.exe -DPYTHON3_NUMPY_INCLUDE_DIRS=<PATH_TO_PYTHON_DIST>/lib/site-packages/numpy/core/include -DPYTHON3_PACKAGES_PATH=<PATH_TO_PYTHON_DIST>/Lib/site-packages/

   Following the configuration step the build is started with

   "C:\Program Files\CMake\bin\cmake.exe" --build PATH_TO_BUILD_DIR --target install --config Release

   where

   1. <N_THREADS> should be set to the number of cores/logical processors on your CPU,
   2. <PATH_TO_OPENCV_SOURCE> is the root of the OpenCV files you downloaded or cloned (the directory containing 3rdparty, apps, build, etc.),
   3. <PATH_TO_OPENCV_CONTRIB_MODULES>⁶ is the path to the modules directory inside the opencv-contrib repository (the directory containing cudaarithm, cudabgsegm, etc.),
   4. <PATH_TO_BUILD_DIR> is the path to the directory where the build files should go,
   5. <PATH_TO_PYTHON_DIST>⁷ is the directory where miniforge was installed and,
   6. <PYTHON_LIB> is the concatination of “python” with the major and minor version of your python install and “.lib”, e.g. for Python 3.10.6 <PYTHON_LIB>==python310.lib. You can confirm this by looking in your <PATH_TO_PYTHON_DIST>/libs directory.

   When passing paths to CMake on the command line make sure not to terminate them using \ as this is a special character and will cause the following arguments to be ignored. e.g. PATH_TO_OPENCV_SOURCE can be D:\opencv or D:\opencv/ but not D:\opencv\.

   This will generate the build files for OpenCV with python bindings with CUDA acceleration including all the corresponding tests and examples for verifcation. Additionally if the Nvidia Video Codec SDK or cuDNN are installed the corresponding modules will automatically be included.

   Expand the tips below for an example of the CMake output if the configuration step is successful and how to check that output to make sure the Python bindings will be being built.

   Example of CMake Configuration Output

   --
   -- General configuration for OpenCV 4.10.0-dev =====================================
   --   Version control:               4.9.0-571-g2629688d11
   --
   --   Extra modules:
   --     Location (extra):            D:/repos/opencv/contrib/modules
   --     Version control (extra):     4.9.0-84-gb236c71c
   --
   --   Platform:
   --     Timestamp:                   2024-06-11T08:50:41Z
   --     Host:                        Windows 10.0.22631 AMD64
   --     CMake:                       3.29.5
   --     CMake generator:             Ninja Multi-Config
   --     CMake build tool:            D:/bin/ninja/ninja.exe
   --     MSVC:                        1940
   --     Configuration:               Debug Release
   --
   --   CPU/HW features:
   --     Baseline:                    SSE SSE2 SSE3
   --       requested:                 SSE3
   --     Dispatched code generation:  SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
   --       requested:                 SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
   --       SSE4_1 (18 files):         + SSSE3 SSE4_1
   --       SSE4_2 (2 files):          + SSSE3 SSE4_1 POPCNT SSE4_2
   --       FP16 (1 files):            + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
   --       AVX (9 files):             + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
   --       AVX2 (38 files):           + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
   --       AVX512_SKX (8 files):      + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX
   --
   --   C/C++:
   --     Built as dynamic libs?:      YES
   --     C++ standard:                11
   --     C++ Compiler:                C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.40.33807/bin/Hostx64/x64/cl.exe  (ver 19.40.33811.0)
   --     C++ flags (Release):         /DWIN32 /D_WINDOWS /W4 /GR  /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi  /fp:precise /FS     /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /wd4819  /O2 /Ob2 /DNDEBUG  /Zi
   --     C++ flags (Debug):           /DWIN32 /D_WINDOWS /W4 /GR  /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi  /fp:precise /FS     /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /wd4819  /Zi /Ob0 /Od /RTC1
   --     C Compiler:                  C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.40.33807/bin/Hostx64/x64/cl.exe
   --     C flags (Release):           /DWIN32 /D_WINDOWS /W3  /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi  /fp:precise /FS       /O2 /Ob2 /DNDEBUG  /Zi
   --     C flags (Debug):             /DWIN32 /D_WINDOWS /W3  /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi  /fp:precise /FS     /Zi /Ob0 /Od /RTC1
   --     Linker flags (Release):      /machine:x64  /INCREMENTAL:NO  /debug
   --     Linker flags (Debug):        /machine:x64  /debug /INCREMENTAL
   --     ccache:                      NO
   --     Precompiled headers:         NO
   --     Extra dependencies:          C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/cudart_static.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppial.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppc.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppitc.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppig.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppist.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppidei.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/cublas.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/cublasLt.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/cufft.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppif.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppim.lib C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5/lib/x64/nppicc.lib
   --     3rdparty dependencies:
   --
   --   OpenCV modules:
   --     To be built:                 aruco bgsegm bioinspired calib3d ccalib core cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape signal stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab wechat_qrcode world xfeatures2d ximgproc xobjdetect xphoto
   --     Disabled:                    -
   --     Disabled by dependency:      -
   --     Unavailable:                 alphamat cannops cvv freetype hdf java julia matlab ovis python2 python2 sfm viz
   --     Applications:                tests perf_tests examples apps
   --     Documentation:               doxygen
   --     Non-free algorithms:         NO
   --
   --   Windows RT support:            NO
   --
   --   GUI:
   --     Win32 UI:                    YES
   --     VTK support:                 NO
   --
   --   Media I/O:
   --     ZLib:                        build (ver 1.3.1)
   --     JPEG:                        build-libjpeg-turbo (ver 3.0.3-70)
   --       SIMD Support Request:      YES
   --       SIMD Support:              NO
   --     WEBP:                        build (ver encoder: 0x020f)
   --     PNG:                         build (ver 1.6.43)
   --       SIMD Support Request:      YES
   --       SIMD Support:              YES (Intel SSE)
   --     TIFF:                        build (ver 42 - 4.6.0)
   --     JPEG 2000:                   build (ver 2.5.0)
   --     OpenEXR:                     build (ver 2.3.0)
   --     HDR:                         YES
   --     SUNRASTER:                   YES
   --     PXM:                         YES
   --     PFM:                         YES
   --
   --   Video I/O:
   --     DC1394:                      NO
   --     FFMPEG:                      YES (prebuilt binaries)
   --       avcodec:                   YES (58.134.100)
   --       avformat:                  YES (58.76.100)
   --       avutil:                    YES (56.70.100)
   --       swscale:                   YES (5.9.100)
   --       avresample:                YES (4.0.0)
   --     GStreamer:                   NO
   --     DirectShow:                  YES
   --     Media Foundation:            YES
   --       DXVA:                      YES
   --
   --   Parallel framework:            Concurrency
   --
   --   Trace:                         YES (with Intel ITT)
   --
   --   Other third-party libraries:
   --     Intel IPP:                   2021.11.0 [2021.11.0]
   --            at:                   D:/build/opencv/4_10/3rdparty/ippicv/ippicv_win/icv
   --     Intel IPP IW:                sources (2021.11.0)
   --               at:                D:/build/opencv/4_10/3rdparty/ippicv/ippicv_win/iw
   --     Lapack:                      NO
   --     Eigen:                       NO
   --     Custom HAL:                  NO
   --     Protobuf:                    build (3.19.1)
   --     Flatbuffers:                 builtin/3rdparty (23.5.9)
   --
   --   NVIDIA CUDA:                   YES (ver 12.5.40, CUFFT CUBLAS NVCUVID NVCUVENC)
   --     NVIDIA GPU arch:             50 52 60 61 70 75 80 86 89 90
   --     NVIDIA PTX archs:            90
   --
   --   cuDNN:                         YES (ver 9.2.0)
   --
   --   OpenCL:                        YES (NVD3D11)
   --     Include path:                D:/repos/opencv/opencv/3rdparty/include/opencl/1.2
   --     Link libraries:              Dynamic load
   --
   --   Python 3:
   --     Interpreter:                 C:/Users/b/miniforge3/envs/py37_mini/python.exe (ver 3.7.12)
   --     Libraries:                   C:/Users/b/miniforge3/envs/py37_mini/libs/python37.lib (ver 3.7.12)
   --     Limited API:                 NO
   --     numpy:                       C:/Users/b/miniforge3/envs/py37_mini/Lib/site-packages/numpy/core/include (ver 1.21.6)
   --     install path:                C:/Users/b/miniforge3/envs/py37_mini/Lib/site-packages/cv2/python-3.7
   --
   --   Python (for build):            C:/Users/b/miniforge3/envs/py37_mini/python.exe
   --
   --   Java:
   --     ant:                         NO
   --     Java:                        NO
   --     JNI:                         NO
   --     Java wrappers:               NO
   --     Java tests:                  NO
   --
   --   Install to:                    D:/build/opencv/4_10/install
   -- -----------------------------------------------------------------
   --
   -- Configuring done (63.3s)
   -- Generating done (21.4s)
   -- Build files have been written to: D:/build/opencv/4_10

   Verify configuration includes Python bindings before building

   If you are building the python bindings look for python3 in the To be built: section of your CMake configuration output and if its not present look for any python related errors in the output preceeding it. e.g.

   --   OpenCV modules:
   --     To be built:                 aruco bgsegm bioinspired calib3d ccalib core cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev datasets dnn dnn_objdetect dpm face features2d flann fuzzy hfs highgui img_hash imgcodecs imgproc line_descriptor ml objdetect optflow phase_unwrapping photo plot python2 python3 quality reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab world xfeatures2d ximgproc xobjdetect xphoto

2. The OpenCV.sln solution file should now be in your PATH_TO_BUILD_DIR directory. To build OpenCV you have two options depending on you preference you can:

   1. Build directly from the command line by simply entering the following (swaping Release for Debug to build a release version)

      "C:\Program Files\CMake\bin\cmake.exe" --build PATH_TO_BUILD_DIR --target install --config Debug

   2. Build through Visual Studio GUI by opening up the OpenCV.sln in Visual Studio, selecting your Configuration, clicking on Solution Explorer, expanding CMakeTargets, right clicking on INSTALL and clicking Build.

   Either approach will both build the library, install the Python bindings and copy the necessary redistributable parts to the install directory (PATH_TO_BUILD_DIR/build/install). All that is required now to run any programs compiled against these libs is to add the directory containing opencv_worldxxx.dll to you user path environmental variable.

If everything was successful, congratulations, you now have OpenCV built with CUDA. To quickly verify that the CUDA modules are working and check if there is any performance benefit on your specific hardware see verifying OpenCV is CUDA accelerated.

Decreasing the build time with Ninja

The build time for OpenCV can be reduced by more than 2x (from 2 hours to 30 mins to under an hour on an i7-8700) by utilizing the Ninja build system instead of directly generating Visual Studio solution files.

Ninja is installed by default if the Desktop development with C++ workload is selected when installing Visual Studio, therefore building with Ninja only requires two extra configuration steps:

1. Configuring Visual Studio Development tools by entering the following into the command prompt before entering the CMake command (changing Community to either Professional or Enterprise if necessary)

   "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"

2. Telling CMake to use Ninja instead of Visual Studio, i.e. replacing -G»Visual Studio 17 2022″ with -G»Ninja Multi-Config».

Once the build files have been generated the build can be kicked off in the same way as before. i.e.

"C:\Program Files\CMake\bin\cmake.exe" --build PATH_TO_BUILD_DIR --target install --config Release

for an example fo the full command line for building a Release version of OpenCV with the Ninja build system go to the Ninja tab.

Generate Python bindings for a Debug Build

Python bindings cannot by default be generated for a Debug configuration, that is unless you have specificaly built or downloaded a debug version of Python. That said you can make a Debug build if you first modify the contents of PATH_TO_PYTHON_DIST/include/pyconfig.h, changing

pragma comment(lib,"pythonxx_d.lib")

to

pragma comment(lib,"pythonxx.lib")

and

to

Then simply follow the instructions above for building with CMake.

Troubleshooting Python Bindings Installation issues

If you are unable to import cv2 without errors then check below to see if there is a solution to the error you recieve.

1. ModuleNotFoundError: No module named 'cv2'

   The installation of the Python bindings has failed, check

   1. the build was successful,
   2. -DPYTHON3_PACKAGES_PATH=PATH_TO_PYTHON_DIST/Lib/site-packages/ was set correctly, and
   3. if you are still seeing the above error try manually installing opencv Python bindings.

1. ImportError: ERROR: recursion is detected during loading of "cv2" binary extensions. Check OpenCV installation.

   The main two reasons for this are:

   1. You have another installation of OpenCV, either manually installed or through the package manager (pip/mamba etc.). This can easily be fixed by first uninstalling any opencv-python, opencv-contrib-python distributions from your package manager and then deleting the cv2 directory (PATH_TO_PYTHON_DIST/Lib/site-packages/cv2/) or bindings file (PATH_TO_PYTHON_DIST/Lib/site-packages/cv2.cpxx-win_amd64.pyd) if they exist.

   2. You have built a Debug configuration. Currently (https://github.com/opencv/opencv/issues/23568) when building this configuration the cv2.cpxx-win_amd64.pyd shared library is not copied into site-packages-x.x
      directory on installation. This can easily be resolved by creating the python-x.x directory and copying the shared library accross so you have PATH_TO_PYTHON_DIST/Lib/site-packages/cv2/python-x.x/cv2.cpxx-win_amd64.pyd, where xx is the PYTHON_VERSION.

2. ImportError: DLL load failed: The specified module could not be found.

   The directory of one or more of the required DLL’s has not been added with os.add_dll_directory(). Whilst the automatic installation of the bindings should have added all the directories containing the dependant DLL’s to config.py it’s possible that one has been missed or you are using a less common configuration. In these cases you will have to

   1. first track down which DLL’s are missing (see this guide for assistance) and then
   2. permanantly add the directory containing them to your installation by modifying the contents of PATH_TO_PYTHON_DIST/Lib/site-packages/cv2/config.py.

   e.g. If you built OpenCV against CUDA 12.1 and your own version of the FFMpeg libraries (-DOPENCV_FFMPEG_USE_FIND_PACKAGE=ON) instead of using the provided opencv_videoio_ffmpegxxx_64.dll plugin, the contents of config.py should look like

   import os
   
   BINARIES_PATHS = [
       os.path.join('D:/build/opencv/install', 'x64/vc17/bin'),
       os.path.join(os.getenv('CUDA_PATH', 'C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.5'), 'bin')
       os.path.join(`D:/ffmpeg/bin`)
   ] + BINARIES_PATHS

3. ImportError: DLL load failed while importing cv2: A dynamic link library (DLL) initialization routine failed.

   The most common cause of this is out of date Visual C++ Redistributable libraries. These can be loaded from your windows system or your python installation depending on your configuration. The easiest thing to do is update both by

   1. downloading and installing the latest version of the Visual C++ Redistributable from Microsoft, and
   2. checking your python package manager (pip/mamba/conda/… list) for the vc or vc14_runtime packages and updating them to the latest version (e.g. pip install vc --upgrade or mamba/conda upgrade vc) and try importing OpenCV again.

Manually installing OpenCV Python bindings

If you have downloaded the pre-built binaries or are having issues with the automatic installation then you can manually install the python bindings following the steps below:

1. Remove any pre-existing OpenCV installations.

2. Copy PATH_TO_BUILD_DIR/lib/python3/cv2.cpxx-win_amd64.pyd to PATH_TO_PYTHON_DIST/Lib/site-packages/cv2.cpxx-win_amd64.pyd

3. Determine the paths to the directories containing any dependant shared libraries (see here for assistance).

4. Adding the locations from (3) by calling os.add_dll_directory() for each one before importing the OpenCV python module. e.g. If you have followed the guide exactly this will be the directories containing the OpenCV and Nvidia shared libaries, which you would add as

   import os
   os.add_dll_directory('C:\\Program Files\\NVIDIA GPU Computing Toolkit\\CUDA\\vxx.x\\bin')
   os.add_dll_directory('PATH_TO_BUILD_DIR/bin')

   before calling

CMake command line options to control cubin/PTX content of the OpenCV shared library

Given (1)-(3) above, the command line options that you want to pass to CMake when building OpenCV will depend on your specific requirements. I have given some examples below for various scenarios given a main GPU with compute capability 6.1 and CUDA toolkit 12:

• Firstly stick with the defaults (-DCUDA_GENERATION=Auto) if your programs will always be run on your main GPU. It should take around an hour to build, depending on your CPU and the resulting shared library should not be larger than 200 MB.
• If you want maximum coverage then use Nvidia’s recommended settings for future compatibility. That is compile for all supported major and minor real architectures, and the highest major virtual architecture by passing -DCUDA_ARCH_BIN=50,52,60,61,70,75,80,86,89,90 and -DCUDA_ARCH_PTX=90 to CMake.
• If you are going to deploy your application, but only to newer GPU’s pass -DCUDA_ARCH_BIN=61,70,80,86,89,90 and -DCUDA_ARCH_PTX=90 to CMake for maximum performance and future compatibility. This is advisable because you may not have any control over the size of the JIT cache on the target machine, therefore including cubin’s for all compute-capabilities you want to support, is the only way be sure to prevent JIT compilation delay on every invocation of your application.
• If size is really an issue but you don’t know which GPU’s you want to run your application on then to ensure that your program will run on all current and future supported GPU’s pass -DCUDA_ARCH_BIN=61 and -DCUDA_ARCH_PTX=30 to CMake for maximum coverage.