@u4/opencv-build

A simple script to auto build recent OpenCV + contrib version via npm. This script is used to auto build opencv4nodejs.

Main changes from the original project

• OpenCV is explicitly built with opencv-build-npm and accepting parameters see opencv-build-npm --help
• OpenCV build can now be configured with new OpenCVBuilder({autoBuildOpencvVersion: "4.10.0", autoBuildBuildCuda: true, autoBuildWithoutContrib: false }).install()
• Each OPENCV_VERSION will be build in his own directory.
• Each AUTOBUILD_FLAGS will be build in his own directory. (induce massive time gain during development)
• All build can now be build outside node_modules using OPENCV_BUILD_ROOT environement variable.
• New MSBuild.exe localisation, also works with VS 2019, 2022+
• Script output is now colorized.
• Add some useful log.
• Big code refactor.
• Enforce typing.
• Add comments and documentations.

Each OpenCV build will take around 2Gb on your drive, so I recommend you to define the OPENCV_BUILD_ROOT environment variable to avoid duplicate builds and avoid node_modules auto flushes.

Install

npm install opencv-build

usage

opencv-build-npm usage:
   --version <value>    OpenCV version                           (OPENCV4NODEJS_AUTOBUILD_OPENCV_VERSION env variable)
   --flags <value>      OpenCV cMake Build flags                 (OPENCV4NODEJS_AUTOBUILD_FLAGS env variable)
   --root <value>       OpenCV-build root directory (deprecated) (INIT_CWD env variable)
   --buildRoot <value>  OpenCV build directory                   (OPENCV_BUILD_ROOT env variable)
   --cuda               Enable cuda in OpenCV build              (OPENCV4NODEJS_BUILD_CUDA env variable)
   --cudaArch <value>   Specify the cuda arch will drastically reduce build time, see https://en.wikipedia.org/wiki/CUDA,
                        ex if you have a RTX 3080 use --cudaArch=8.6, if you have also a RTX 2080 --cudaArch=7.5,8.6
                                                                 (OPENCV4NODEJS_BUILD_CUDA_ARCH env variable)
   --nocontrib          Do not compile Contrib modules           (OPENCV4NODEJS_AUTOBUILD_WITHOUT_CONTRIB env variable)
   --nobuild            Disable OpenCV auto build                (OPENCV4NODEJS_DISABLE_AUTOBUILD env variable)
   --incDir <value>     OpenCV include directory                 (OPENCV_INCLUDE_DIR env variable)
   --libDir <value>     OpenCV library directory                 (OPENCV_LIB_DIR env variable)
   --binDir <value>     OpenCV bin directory                     (OPENCV_BIN_DIR env variable)
   --keepsources        Keep sources OpenCV source after build
   --dry-run            Display command line use to build library
   --git-cache          Reduce Bandwidth usage, by keeping a local git source in the buildRoot (OPENCV_GIT_CACHE env variable)
   --json               Output build configuration in JSON format (N-API support)

Requirements

• cmake

Windows

for nodejs <= 12

npm install --global windows-build-tools

OpenCVBuildEnv options

It's possible to specify build environment variables by passing argument to the builder script

node lib/main.js --version 4.5.5 --buildRoot ~/openCV

with flags, do not forget the quotes "

node lib/main.js --version 4.5.5 --buildRoot ~/openCV --flags "-DOPENCV_GENERATE_PKGCONFIG=ON -DOPENCV_PC_FILE_NAME=opencv.pc"

Using the bin alias

opencv-build-npm --version 4.5.5

Or by inserting them into the package.json where the dependency is declared an object like:

{
  "opencv4nodejs": {
    "autoBuildFlags": "-DOPENCV_GENERATE_PKGCONFIG=ON -DOPENCV_PC_FILE_NAME=opencv.pc",
    "autoBuildOpencvVersion": "4.6.0"
  }
}

By using environment variables.

export OPENCV4NODEJS_AUTOBUILD_FLAGS="-DOPENCV_GENERATE_PKGCONFIG=ON -DOPENCV_PC_FILE_NAME=opencv.pc"
export OPENCV4NODEJS_AUTOBUILD_OPENCV_VERSION="4.10.0"
export OPENCV_BUILD_ROOT="~/openCV"

node build/main.js

prebuild

The prebuild is a smart version selector, to avoid futher re-compilation, accepted values are:

• "latestBuild" use the last built version
• "latestVersion" use the highest version number built
• "oldestBuild" use the olderst built version
• "oldestVersion" use the lowest version number built

the prebuild option intends to be used at runtime, so you do not have to keep track of the version you want to use.

• this parameter can only be provided in OpenCVBuildEnv constructor options.
• prebuild is ignored if OPENCV4NODEJS_DISABLE_AUTOBUILD env variable is set, or disableAutoBuild is set in package.json

autoBuildOpencvVersion

Choose the openCV version you want to build, default is 4.10.0,

This option value can be provide using:

• The --version in build script
• The autoBuildOpencvVersion options field provided to OpenCVBuildEnv constructor options.
• The autoBuildOpencvVersion field in the current package.json opencv4nodejs object.
• The OPENCV4NODEJS_AUTOBUILD_OPENCV_VERSION environment variable.

The buildRoot is the most important parameter, it defines the directory used to build openCV, Default value is the npm-opencv-build directory. You generally want to use this value to persist your build files out of your node_modules directory, and by doing some sharing openCV built between your project.

This option value can be provide using:

• The --buildRoot in build script
• The buildRoot options field provided to OpenCVBuildEnv constructor options.
• The OPENCV_BUILD_ROOT environment variable.

The git-cache reduces git clone data transfer, git data will be cached in your buildRoot, so you will only download all git files once.

This option value can be provide using:

• The --git-cache in build script
• The git-cache options field provided to OpenCVBuildEnv constructor options.
• The OPENCV_GIT_CACHE environment variable.

autoBuildBuildCuda

Set any value to enable, the following cMake flag will be added:

• DWITH_CUDA=ON
• DBUILD_opencv_cudacodec=OFF // video codec (NVCUVID) is deprecated in cuda 10, so don't add it
• DCUDA_FAST_MATH=ON // optional
• DWITH_CUBLAS=ON // optional

This option value can be enable using:

• The --cuda in build script
• The autoBuildBuildCuda options field provided to OpenCVBuildEnv constructor options.
• The autoBuildBuildCuda field in the current package.json opencv4nodejs object.
• The OPENCV4NODEJS_BUILD_CUDA environment variable.

autoBuildFlags

Append option to CMake flags.

This option value can be enable using:

• The --flags in build script
• The autoBuildFlags options field provided to OpenCVBuildEnv constructor options.
• The autoBuildFlags field in the current package.json opencv4nodejs object.
• The OPENCV4NODEJS_AUTOBUILD_FLAGS environment variable.

autoBuildWithoutContrib

Set any value to enable, this option will skip openCV Contribs.

This option value can be enable using:

• The --nocontrib in build script
• The autoBuildWithoutContrib options field provided to OpenCVBuildEnv constructor options.
• The autoBuildWithoutContrib field in the current package.json opencv4nodejs object.
• The OPENCV4NODEJS_AUTOBUILD_WITHOUT_CONTRIB environment variable.

disableAutoBuild

Set any value to disable compilation from sources.

This option value can be enable using:

• The --nobuild in build script
• The disableAutoBuild options field provided to OpenCVBuildEnv constructor options.
• The disableAutoBuild field in the current package.json opencv4nodejs object.
• The OPENCV4NODEJS_DISABLE_AUTOBUILD environment variable.

Generally you should prefer using the environment variables OPENCV4NODEJS_DISABLE_AUTOBUILD

opencvIncludeDir

Overwrite the OPENCV_INCLUDE_DIR environment variables

opencvLibDir

Overwrite the OPENCV_LIB_DIR environment variables

opencvBinDir

Overwrite the OPENCV_BIN_DIR environment variables

N-API Support (--json)

The --json flag allows you to output the entire build configuration in a machine-readable JSON format. This is particularly useful for N-API based projects that need to programmatically access OpenCV's include paths, library directories, and linked modules.

When using --json, the script will NOT perform an installation/build but will instead output the OpenCVBuildInfo object:

opencv-build-npm --json

Example output:

{
  "opencvVersion": "4.10.0",
  "buildWithCuda": false,
  "isWithoutContrib": false,
  "isAutoBuildDisabled": false,
  "buildRoot": "/path/to/build",
  "modules": [
    { "opencvModule": "core", "libPath": "..." },
    ...
  ],
  "libs": [
    "/path/to/lib/libopencv_core.so",
    ...
  ]
}

build test

opencv-build-npm --flags="-DBUILD_LIST=core,imgproc,imgcodecs,videoio,highgui,video,calib3d,features2d,objdetect,dnn,ml,flann,photo,stitching,gapi" --version=3.4.15 --nocontrib

opencv-build-npm --version=4.10.0 --nocontrib