opencv version: 3.4.3
NDK: 25.2
ubnutu: 20.04
ps: opencv 的版本最好是opencv3,我一开始使用opencv4.6.0的时候编译时候会报错
1 安装NDK
从下面的链接下载NDK,并解压:
https://developer.android.google.cn/ndk/downloads/
记住解药后的路径
如果你是在Android Studio里面下载的ndk,那么安装路径可以参加下面
/home/peter/Android/Sdk/ndk/25.2.9519653
2 安装Opencv
https://github.com/opencv/opencv/releases?page=4
下载压缩包,比如: opencv-3.4.3.zip
并解压到当前目录
3 交叉编译Opencv
cd opencv-3.4.3/
rm -rf build
mkdir build && cd build
export ANDROID_NDK=/home/peter/Android/Sdk/ndk/25.2.9519653
sudo cmake -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
-DCMAKE_ANDROID_NDK=$ANDROID_NDK \
-DANDROID_NATIVE_API_LEVEL=26 \
-DBUILD_ANDROID_PROJECTS=OFF \
-DBUILD_ANDROID_EXAMPLES=OFF \
-DCMAKE_BUILD_TYPE=Release \
-DBUILD_JAVA=OFF \
-DANDROID_ABI=arm64-v8a \
-DCMAKE_INSTALL_PREFIX=/home/temp/programs/opencv343_android ..
sudo make -j8
sudo make install
这里编译的是arm64
的,其他可修改编译选项。
安装目录是 /home/temp/programs/opencv343_android
, 可修改。
编译好之后,库文件在 安装目录 /sdk/native
下
上面默认是生成静态库。
如果要生成动态库,加上以下cmake
选项
-DANDROID_STL=c++_shared \
-DBUILD_SHARED_LIBS=ON \
4 交叉编译Android下的OpenCV demo
写一个使把图像test.jpg模糊成result.jpg的例子
4.1 源文件 boxfilter_arm.cpp
#include "opencv2/opencv.hpp"
int main()
{
//read picture
cv::Mat img = cv::imread("test.jpg");
cv::Mat out;
cv::boxFilter(img, out, -1, cv::Size(5, 5));
cv::imwrite("result.jpg", out);
return 0;
}
4.2 CMakeLists.txt
cmake_minimum_required(VERSION 2.8.3)
project(boxfilter_arm)
add_definitions("-Wall -g")
set(OpenCVHome /home/temp/programs/opencv343_android/sdk/native)
include_directories(${OpenCVHome}/jni/include)
link_directories(${OpenCVHome}/staticlibs/arm64-v8a
${OpenCVHome}/3rdparty/libs/arm64-v8a)
link_libraries(
opencv_imgcodecs
opencv_imgproc
opencv_highgui
opencv_core
opencv_video
opencv_features2d
opencv_videoio
cpufeatures
tegra_hal
IlmImf
libjasper
libjpeg-turbo
libpng
libprotobuf
libtiff
libwebp
# quirc
log
z
)
add_executable(${PROJECT_NAME} boxfilter_arm.cpp)
install(TARGETS ${PROJECT_NAME}
RUNTIME DESTINATION ${PROJECT_SOURCE_DIR})
4.3 cmake 编译
export ANDROID_NDK=/home/peter/Android/Sdk/ndk/25.2.9519653
rm -r build
mkdir build && cd build
sudo cmake -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
-DANDROID_ABI="arm64-v8a" \
-DANDROID_NDK=$ANDROID_NDK \
-DANDROID_PLATFORM=android-26 \
..
sudo make
sudo make install
cd ..
5 放到Android 上执行
5.1 安装adb工具
sudo apt install android-tools-adb android-tools-fastboot
5.2 push 到手机上
adb push boxfilter_arm /data/local/tmp
adb push test.jpg /data/local/tmp
5.3 给boxfilter_arm执行权限
adb shell
cd /data/local/tmp
chmod +x boxfilter_arm
5.4 执行boxfilter_arm
./boxfilter_arm
如果没有报错,就会在当前目录下生成result.jpg
通过下面的命令取出来
adb pull /data/local/tmp/result.jpg .
6 注意事项
armv7和arm64-v8a的差别
差别在CMAKE_ANDROID_ARCH_ABI和ANDROID_ABI, CMAKE_ANDROID_ARCH_ABI有没有有用不知道,但是arm64-v8a要用-DANDROID_ABI=arm64-v8a,否则生成默认的armv7的
armv7的cmake选项如下:
cmake -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
-DCMAKE_ANDROID_NDK=$ANDROID_NDK \
-DANDROID_NATIVE_API_LEVEL=26 \
-DBUILD_ANDROID_PROJECTS=OFF \
-DBUILD_ANDROID_EXAMPLES=OFF \
-DCMAKE_BUILD_TYPE=Release \
-DBUILD_JAVA=OFF \
-DCMAKE_ANDROID_ARCH_ABI=armeabi-v7a \
-DCMAKE_INSTALL_PREFIX=/home/temp/programs/opencv343_android ..
arm64-v8a的cmake选项则如下:
要设置ANDROID_ABI=arm64-v8a,而不是ANDROID_ARCH_ABI=arm64-v8a
cmake -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
-DCMAKE_ANDROID_NDK=$ANDROID_NDK \
-DANDROID_NATIVE_API_LEVEL=26 \
-DBUILD_ANDROID_PROJECTS=OFF \
-DBUILD_ANDROID_EXAMPLES=OFF \
-DCMAKE_BUILD_TYPE=Release \
-DBUILD_JAVA=OFF \
-DANDROID_ABI=arm64-v8a \
-DCMAKE_INSTALL_PREFIX=/home/temp/programs/opencv343_android ..
7. 参考
https://www.jianshu.com/p/78875d220dbf
https://www.sisik.eu/blog/android/ndk/opencv-without-java
https://juejin.im/post/6844903793650302989
https://www.jianshu.com/p/925614d6e9e0