Cross compiling OpenCV for a ARM based linux system (Xilinx)

edit

I have successfully built OpenCV for a Arm Based linux system (Xilinx) under Ubuntu 18.04. Because i spent a lot of time on this i want to share my methode in this post.

Building Lapack:

The lapack (Linear Algebra PACKage) library is required. To use OpenCV for arm you have to manual build and install lapack. First you have to create a toolchain.make file.

$ gedit toolchain.make

• Insert the flowing configuration and set your path-to-xilinx-compiler and other params.

  set( CMAKE_SYSTEM_NAME Linux )
  set( CMAKE_SYSTEM_PROCESSOR arm )
  set( CMAKE_C_COMPILER path-to-xilinx-compiler/arm-linux-gnueabihf-gcc )
  set( CMAKE_CXX_COMPILER path-to-xilinx-compiler/arm-linux-gnueabihf-g++ )
  set( CMAKE_INSTALL_PREFIX /usr/lib/arm )
  set( CMAKE_FIND_ROOT_PATH /usr/lib/arm )
  

  Then download, build and install lapack.

  cwd=$(pwd)
  git clone https://github.com/Reference-LAPACK/l...
  cd lapack/
  mkdir build
  cd build/
  cmake -D CMAKE_TOOLCHAIN_FILE=$toolchainpath ..
  make -j8 #multithreading make
  sudo make install
  

Building OpenCV:

It is important that the libraries libatlas3-base, libatlas-base-dev and libhdf5-dev are not installed on the system because OpenCV will include them but you wont be able to link them without building the system specific version yourself.

• configure cmake: you can use the exported cmake command or configure it yourself using cmake-gui like below

  -set these flags and configure a few times

  BUILD_SHARED_LIBS = OFF
  OPENCV_EXTRA_MODULES_PATH = "<extra_modules_path>"
  CMAKE_INSTALL_PREFIX = "<install_prefix_path>"

  -set all these flags to OFF

  WITH_1394
  WITH_CUDA
  WITH_CUFFT X
  WITH_EIGEN
  WITH_GSTREAMER
  WITH_GTK
  WITH_JASPER
  WITH_JPEG
  WITH_OPENEXR
  WITH_PNG
  WITH_PVAPI
  WITH_QT
  WITH_TBB
  WITH_TIFF
  WITH_UNICAP X
  WITH_V4L
  WITH_XINE
  
  WITH_EIGEN
  WITH_IPP
  BUILD_ZLIB
  BUILD_opencv_gapi
  BUILD_IPP_IW

  -delete EIGEN_INCLUDE_PATH
  -delete all HDF paths
  -set right compiler

  CMAKE_CXX_COMPILER
  CMAKE_C_COMPILER
  

• build:

  make -j8

• install:

  sudo make install

• pkg-config setup:

  sed -i 's/-lfreetype //g' unix-install/opencv4.pc #remove -lfreetype from file
  sed -i 's/-lharfbuzz //g' unix-install/opencv4.pc #remove -lharfbuzz from file
  sudo cp unix-install/opencv4.pc /usr/lib/x86_64-linux-gnu/pkgconfig

  Sample Program

#include <stdio.h>
#include <opencv2/opencv.hpp>
int main( int argc, char** argv )
{
  cv::Mat testmat;
  printf("Test\n");
  return 0;
} 

• Add Lapack lib path

  dont forget to add the lapack lib path "-L/usr/lib/arm/lib" to the build command/makefile.

• build:

  g++ TestApp.cpp -o TestApp `pkg-config --cflags --libs opencv4` -L/usr/lib/arm/lib

I hope this will help someone.