怎样使用OpenCV_-dcmake_toolchain_file

1. 怎样编译 openCV

如果要使用opencv开发，必须下载源代码然后编译

https://linuxize.com/post/how-to-install-opencv-on-ubuntu-20-04/https://linuxize.com/post/how-to-install-opencv-on-ubuntu-20-04/

在opencv 目录下创建 build 文件夹然后执行cmake command

Set up the OpenCV build with CMake:

cmake -D CMAKE_BUILD_TYPE=RELEASE \    -D CMAKE_INSTALL_PREFIX=/usr/local \    -D INSTALL_C_EXAMPLES=ON \    -D INSTALL_PYTHON_EXAMPLES=ON \    -D OPENCV_GENERATE_PKGCONFIG=ON \    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_build/opencv_contrib/modules \    -D BUILD_EXAMPLES=ON ..

  -D 是变量的定义，控制了编译的模块等，上面的 .. 表示上级目录也指明了 cmake file在opencv 目录下的CMakeLists.txt，

执行cmake后输出log是：

--   OpenCV modules:
--     To be built:                 aruco barcode bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dnn_superres dpm face features2d flann freetype fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform java line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python2 python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
--     Disabled:                    world
--     Disabled by dependency:      -
--     Unavailable:                 alphamat cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv hdf julia matlab ovis sfm viz
--     Applications:                tests perf_tests examples apps
--     Documentation:               NO
--     Non-free algorithms:         NO

怎样控制编译的 modules:

1. cmake -D

如 BUILD_opencv_ml = OFF, 可以通过cmake的输入log: To be built:看是否有mk

cmake -D CMAKE_BUILD_TYPE=RELEASE \
      -D CMAKE_INSTALL_PREFIX=/usr/local/opencv4.4 \
      -D OPENCV_ENABLE_NONFREE=ON \
      -D OPENCV_EXTRA_MODULES_PATH=/home/zfb/opencv_contrib-4.4.0/modules \
      -D OPENCV_GENERATE_PKGCONFIG=YES \
      -D WITH_QT=ON \
      -D WITH_OPENGL=ON \
      -D WITH_CUDA=ON \
      -D BUILD_EXAMPLES=ON \
      -D INSTALL_PYTHON_EXAMPLES=ON \
      -D INSTALL_C_EXAMPLES=ON ..