一、安装交叉编译器

目标平台为arm7l，此为32位ARM架构，要安装合适的编译器

sudo apt install arm-linux-gnueabihf-gcc
sudo apt install arm-linux-gnueabihf-g++

注意：64位ARM架构的编译器与32位ARM架构的编译器不能通用

二、opencv交叉编译

opencv的交叉编译工具链在../opencv3.2.0/platforms/linux 路径下，linux文件夹下是一些.cmake文件，对应不同的移植对象，我需要在rv1126上部署模型，所以选择platform/linux/arm-gnueabi.toolchain.cmake

你也可以对其作出修改（添加编译器所在位置）：

set(GCC_COMPILER_VERSION "" CACHE STRING "GCC Compiler version")
set(GNU_MACHINE "arm-linux-gnueabi" CACHE STRING "GNU compiler triple")



set(CMAKE_C_COMPILER /usr/bin/arm-linux-gnueabihf-gcc)
set(CMAKE_CXX_COMPILER /usr/bin/arm-linux-gnueabihf-g++)

include("${CMAKE_CURRENT_LIST_DIR}/arm.toolchain.cmake")

接下来执行交叉编译命令

mkdir build && cd build
sudo cmake -D CMAKE_BUILD_TYPE=Release -D CMAKE_INSTALL_PREFIX=/mnt/usr/local -D OPENCV_EXTRA_MODULES_PATH=/opt/opencv/opencv_contrib/modules/ -D OPENCV_ENABLE_NONFREE=True -DCMAKE_TOOLCHAIN_FILE=/opt/opencv/platforms/linux/arm-gnueabi.toolchain.cmake ..

sudo make -j8
sudo make install

编译结束后进入 build 文件夹，里面生成bin,include,lib,share四个文件夹

三、Linux上生成ARM架构下可执行文件

创建测试用例test.cpp,内容如下

#include <opencv2/opencv.hpp>
 
using namespace cv; 
 
int main( int argc, char** argv )  
{  
	Mat image;  
 
	image = imread( "7.bmp", 1 );  
	if( !image.data )  
	{  
		printf( "No image data \n" );  
		return -1;  
	}   
 
	cv::Point lu = cv::Point(180, 60); 
	cv::Point rd = cv::Point(400, 260);   
 
	cv::rectangle(image, lu, rd, cv::Scalar( 255, 20, 0 ), 1, cv::LINE_AA );                 	
 
	imwrite("8.bmp", image);        
 
	return 0;  
}

CMakeList.txt

cmake_minimum_required(VERSION 2.8.4)

project(draw_image)
include ($ENV{HOME}/configs/cross.cmake)

find_package(OpenCV REQUIRED)
add_executable(${CMAKE_PROJECT_NAME} test.cpp)
target_include_directories(draw_image PUBLIC ${OpenCV_INCLUDE_DIRS})
target_link_libraries(draw_image PRIVATE ${OpenCV_LIBS})
~

在终端执行：

mkdir build && cd buid
cmake ..
make

在test.cpp同一目录下会生成可执行文件 draw_image,利用file draw_image检查可执行文件格式是否支持arm

draw_image: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, BuildID[sha1]=6030f6191b409626a1f54c996cebb91aad644061, for GNU/Linux 3.2.0, not stripped

出现如上结果说明可执行文件支持ARM7l