I am trying to utilise OpenCV 4 on the Raspberry Pi Zero W, running Raspbian Buster (10). When doing any transformations on a captured image, the application exits with a floating-point exception.
I have cross-compiled OpenCV with various options, most notably the ENABLE_VFPV3 option, with no luck. I always get the floating-point exception. I use crosstool-ng for the cross-compilation on macOS, and CMake (through Jetbrains CLion, mostly).
OpenCV is configured with the following options before being built:
-DCMAKE_TOOLCHAIN_FILE=armv6-rpi-linux-gnueabi-toolchain.cmake -DBUILD_JPEG=ON -DBUILD_PNG=ON -DBUILD_TIFF=ON -DWITH_V4L=ON -DENABLE_VFPV3=ON -DBUILD_TESTS=OFF -DCMAKE_BUILD_TYPE=Debug -DBUILD_SHARED_LIBS=OFF
OpenCV builds without any issues, and so do the applications that utilise the libraries. I don't build the shared libs, as I want the compiled application to not be dependent on 3rd party libraries to be installed.
The toolchain file that I use for cross-compilation of both OpenCV and the test application:
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR arm)
set(CMAKE_CXX_FLAGS "-static-libstdc++")
set(CMAKE_SYSROOT /Volumes/crosstool/x-tools/armv6-rpi-linux-gnueabi/armv6-rpi-linux-gnueabi/sysroot)
set(CMAKE_OSX_SYSROOT /Volumes/crosstool/x-tools/armv6-rpi-linux-gnueabi/armv6-rpi-linux-gnueabi/sysroot)
set(CMAKE_C_COMPILER "/Volumes/crosstool/x-tools/armv6-rpi-linux-gnueabi/bin/armv6-rpi-linux-gnueabi-gcc")
set(CMAKE_CXX_COMPILER "/Volumes/crosstool/x-tools/armv6-rpi-linux-gnueabi/bin/armv6-rpi-linux-gnueabi-g++")
I have successfully compiled and run various applications with no issues up to this point, using this same setup.
A simple test application to reproduce the error:
#include <iostream>
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/video/video.hpp"
#include "opencv2/videoio/videoio.hpp"
using namespace cv;
using namespace std;
int main( int argc, char** argv )
{
VideoCapture cap(0); //capture the video from web cam
if ( !cap.isOpened() ) // if not success, exit program
{
cout << "Cannot open the web cam" << endl;
return -1;
}
while (true)
{
Mat image;
bool bSuccess = cap.grab();
if (!bSuccess) //if not success, break loop
{
cout << "Cannot read a frame from video stream" << endl;
break;
}
cap.retrieve(image);
cvtColor(image, image, COLOR_BGR2GRAY);
}
return 0;
}
The CMakefiles.txt:
cmake_minimum_required(VERSION 3.14)
project(vision)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_FLAGS "-static-libstdc++")
message( STATUS "Profile: ${PROFILE}" )
if ("${PROFILE}" STREQUAL "macos")
include_directories(
/usr/local/include/opencv4
)
link_directories(
/usr/local/lib
/usr/local/lib/opencv4/3rdparty
)
elseif ("${PROFILE}" STREQUAL "arm")
include_directories(
../opencv-arm/build/install/include/opencv4
)
link_directories(
../zlib/install/lib
../opencv-arm/build/install/lib
../opencv-arm/build/install/lib/opencv4/3rdparty
)
else()
message( ERROR "unsupported build profile" )
return()
endif()
add_executable(vision main.cpp)
target_link_libraries(
vision
# video
opencv_videoio
opencv_video
# gui
opencv_highgui
# image processing
opencv_imgcodecs
opencv_imgproc
opencv_core
libjpeg-turbo
libjasper
libtiff
libpng
libwebp
ittnotify
dl
z
)
if ("${PROFILE}" STREQUAL "arm")
target_link_libraries(
vision
tegra_hal
pthread
)
endif()
After attempting the color transformation (or any other transformation) on the RPi Zero, the application exits with a Floating point exception. Compiling and running on macOS works without any issues (-DPROFILE=macos).
My only thoughts at this stage are that the OpenCV compilation needs to do something special for the RPi Zero for the floating-point calculations to work. Any help/direction will be greatly appreciated.
