wrap opencv c++ for python

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how opencv do ?

opencv_hdrs: 头文件集合

set(opencv_hdrs
    "${OPENCV_MODULE_opencv_core_LOCATION}/include/opencv2/core/core.hpp"
    "${OPENCV_MODULE_opencv_flann_LOCATION}/include/opencv2/flann/miniflann.hpp"
    "${OPENCV_MODULE_opencv_imgproc_LOCATION}/include/opencv2/imgproc/imgproc.hpp"
    "${OPENCV_MODULE_opencv_video_LOCATION}/include/opencv2/video/background_segm.hpp"
    "${OPENCV_MODULE_opencv_video_LOCATION}/include/opencv2/video/tracking.hpp"
    "${OPENCV_MODULE_opencv_photo_LOCATION}/include/opencv2/photo/photo.hpp"
    "${OPENCV_MODULE_opencv_highgui_LOCATION}/include/opencv2/highgui/highgui.hpp"
    "${OPENCV_MODULE_opencv_ml_LOCATION}/include/opencv2/ml/ml.hpp"
    "${OPENCV_MODULE_opencv_features2d_LOCATION}/include/opencv2/features2d/features2d.hpp"
    "${OPENCV_MODULE_opencv_calib3d_LOCATION}/include/opencv2/calib3d/calib3d.hpp"
    "${OPENCV_MODULE_opencv_objdetect_LOCATION}/include/opencv2/objdetect/objdetect.hpp"
    "${OPENCV_MODULE_opencv_contrib_LOCATION}/include/opencv2/contrib/contrib.hpp")

gen.py 头文件分析，

add_custom_command(
   OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/generated0.i
   COMMAND ${PYTHON_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/src2/gen.py" "${CMAKE_CURRENT_SOURCE_DIR}/src2"
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/src2/api
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/src2/defs
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/src2/gen.py)

gen2.py 头文件分析

add_custom_command(
   OUTPUT ${cv2_generated_hdrs}
   COMMAND ${PYTHON_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/src2/gen2.py" ${CMAKE_CURRENT_BINARY_DIR} ${opencv_hdrs}
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/src2/gen2.py
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/src2/hdr_parser.py
   DEPENDS ${opencv_hdrs})

library

add_library(${the_module} SHARED src2/cv2.cpp ${CMAKE_CURRENT_BINARY_DIR}/generated0.i ${cv2_generated_hdrs} src2/cv2.cv.hpp)

cv2.cpp 为源文件，generated0.i 为gen.py转换src2目录下的文件得到，${cv2_generated_hdrs}为gen2.py转换${opencv_hdrs}得到。opencv中采用的转换方式是自己的一套，而且只有针对C++的部分特性，因此对于一些例外，需要采用手动生成python封装。如下图，在misc/python 中的文件都是为了手动转换这些例外。因此，opencv自带的一套很难被重用。