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Cross compiling opencv project for ARM and called in go project gocv

I compiled opencv and gocv for ARM under the host Ubuntu 20.04.3 LTS follows the steps as below.

1. Apt install arm-linux-gnueabi-gcc, arm-linux-gnueabi-g++

2. Compile and install opencv

cmake -DCMAKE_C_COMPILER=arm-linux-gnueabi-gcc -DCMAKE_CXX_COMPILER=arm-linux-gnueabi-g++  -DCMAKE_TOOLCHAIN_FILE=../opencv/platforms/linux/arm-gnueabi.toolchain.cmake  ../opencv
make -j16
make install

After installed. A folder named install was created in current dir and got shared libs as below.

../arm2build/install/lib
|-- cmake
|   `-- opencv4
|       |-- OpenCVConfig-version.cmake
|       |-- OpenCVConfig.cmake
|       |-- OpenCVModules-release.cmake
|       `-- OpenCVModules.cmake
|-- libopencv_calib3d.so -> libopencv_calib3d.so.405
|-- libopencv_calib3d.so.4.5.4
|-- libopencv_calib3d.so.405 -> libopencv_calib3d.so.4.5.4
|-- libopencv_core.so -> libopencv_core.so.405
|-- libopencv_core.so.4.5.4
|-- libopencv_core.so.405 -> libopencv_core.so.4.5.4
|-- libopencv_dnn.so -> libopencv_dnn.so.405
|-- libopencv_dnn.so.4.5.4
|-- libopencv_dnn.so.405 -> libopencv_dnn.so.4.5.4
|-- libopencv_features2d.so -> libopencv_features2d.so.405
|-- libopencv_features2d.so.4.5.4
|-- libopencv_features2d.so.405 -> libopencv_features2d.so.4.5.4
|-- libopencv_flann.so -> libopencv_flann.so.405
|-- libopencv_flann.so.4.5.4
|-- libopencv_flann.so.405 -> libopencv_flann.so.4.5.4
|-- libopencv_gapi.so -> libopencv_gapi.so.405
|-- libopencv_gapi.so.4.5.4
|-- libopencv_gapi.so.405 -> libopencv_gapi.so.4.5.4
|-- libopencv_highgui.so -> libopencv_highgui.so.405
|-- libopencv_highgui.so.4.5.4
|-- libopencv_highgui.so.405 -> libopencv_highgui.so.4.5.4
|-- libopencv_imgcodecs.so -> libopencv_imgcodecs.so.405
|-- libopencv_imgcodecs.so.4.5.4
|-- libopencv_imgcodecs.so.405 -> libopencv_imgcodecs.so.4.5.4
|-- libopencv_imgproc.so -> libopencv_imgproc.so.405
|-- libopencv_imgproc.so.4.5.4
|-- libopencv_imgproc.so.405 -> libopencv_imgproc.so.4.5.4
|-- libopencv_ml.so -> libopencv_ml.so.405
|-- libopencv_ml.so.4.5.4
|-- libopencv_ml.so.405 -> libopencv_ml.so.4.5.4
|-- libopencv_objdetect.so -> libopencv_objdetect.so.405
|-- libopencv_objdetect.so.4.5.4
|-- libopencv_objdetect.so.405 -> libopencv_objdetect.so.4.5.4
|-- libopencv_photo.so -> libopencv_photo.so.405
|-- libopencv_photo.so.4.5.4
|-- libopencv_photo.so.405 -> libopencv_photo.so.4.5.4
|-- libopencv_stitching.so -> libopencv_stitching.so.405
|-- libopencv_stitching.so.4.5.4
|-- libopencv_stitching.so.405 -> libopencv_stitching.so.4.5.4
|-- libopencv_video.so -> libopencv_video.so.405
|-- libopencv_video.so.4.5.4
|-- libopencv_video.so.405 -> libopencv_video.so.4.5.4
|-- libopencv_videoio.so -> libopencv_videoio.so.405
|-- libopencv_videoio.so.4.5.4
`-- libopencv_videoio.so.405 -> libopencv_videoio.so.4.5.4

3. Build gocv/cmd/version project with cgo

CGO_ENABLED=1 CC=arm-linux-gnueabi-gcc CXX=arm-linux-gnueabi-g++ CGO_CPPFLAGS='-I/opt/arm2build/install/include/opencv4' CGO_LDFLAGS='-L/opt/arm2build/lib -lopencv_core -lopencv_videoio -lopencv_imgproc -lopencv_highgui -lopencv_imgcodecs -lopencv_objdetect -lopencv_features2d -lopencv_video -lopencv_dnn -lopencv_calib3d -lopencv_flann -lopencv_photo' GOOS=linux GOARCH=arm go build -tags=customenv .

After do that will generate ELF

root@793d7120f9df:/opt/go/gocv/cmd/version# file version
version: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.3, BuildID[sha1]=038c80350b7a0c9e72b10021c66c31c2dbb4df2c, for GNU/Linux 3.2.0, not stripped

My questions is how to run the ELF version in android with arm processor?

I copied the static libraries in install/libs to mobile's /system/lib/. copied the version file to /data/local/tmp and grant execute privilege. Then exec the version got output "./version: No such file or directory".

130|cactus:/data/local/tmp # ./version
/system/bin/sh: ./version: No such file or directory
Solution

  • I found the reason is about dynamic link interpreter which android do not has linux platform's interpreter. After rebuild opencv with NDK got static libs. And build go project with NDK's clang compiler, the problem would be solved.