OpenCV简介
OpenCV，全称Open Source Computer VisionLibrary，是基于C/C++编写的，是BSD开源许可的计算机视觉开发框架，其开源协议允许在学术研究与商业应用开发中免费使用它。OpenCV支持Windows、Linux、Mac OS、iOS与Android操作系统上的应用开发。
下载
- 官网OpenCV官网Android最新版本SDK（我自己再用的是4.5.0）
- 选择OpenCV对应版本下的Android平台
SDK概述
SDK目录结构如下：
OpenCV-android-sdk
|_ samples
|_ sdk
| |_ etc
| |_ java
| |_ libcxx_helper
| |_ native
| |_ 3rdparty
| |_ jni
| |_ abi-arm64-v8a
| |_ abi-armeabi-v7a
| |_ abi-x86
| |_ abi-x86_64
| |_ include
| |_ libs
| |_ arm64-v8a
| |_ armeabi-v7a
| |_ x86
| |_ x86_64
| |_ staticlibs
| |_ arm64-v8a
| |_ armeabi-v7a
| |_ x86
| |_ x86_64
|
|_ LICENSE
|_ README.android
| 目录 | 文件 |
|---|---|
| samples | OpenCV运行案例 |
| sdk | OpenCV API以及依赖库 |
| sdk/etc | Haar和LBP级联分类器 |
| sdk/java | OpenCV Java API |
| sdk/libcxx_helper | bring libc++_shared.so into packages |
| sdk/native | OpenCV 静态库、动态库以及JNI文件 |
集成OpenCV SDK
在Android应用中调用OpenCV进行图像处理的方法有很多种，考虑到性能问题，本人推荐使用NDK进行开发，毕竟C/C++要比Java性能好的多。
一、集成OpenCV
OpenCV集成还是很简单的，不需要我们自己去交差编译生成动/静态库，解压后的文件已经包含了动态库。一般套路都是这样，下载库、导入.h和动/静态库、配置CmakeList。详细步骤：
1.下载最新OpenCV SDK
2.新建项目
新建工程一定要勾选“Include C++ support”，这样新建的Android工程会直接支持NDK开发，避免各种配置问题，如果提示没有NDK，请下载NDK，并在工程“Project Structure”中导入即可：
新建工程勾选了“Include C++ support”，就已经支持NDK开发了（即native-lib），我们需要做的是，根据自己项目需要，增加JNI接口。
3.导入.h文件和.so动态库
20201204135918.png
把OpenCV SDK的include文件复制到cpp文件夹下，把opencv的动态库引入jniLibs文件下
4.CMakeLists.txt配置
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# Sets the minimum version of CMake required to build the native library.
cmake_minimum_required(VERSION 3.10.2)
# Declares and names the project.
project("learning")
set(libs "${CMAKE_SOURCE_DIR}/src/main/jnilibs")
#导入libopencv_java4库文件
add_library(libopencv SHARED IMPORTED)
set_target_properties(libopencv PROPERTIES
IMPORTED_LOCATION "${libs}/${ANDROID_ABI}/libopencv_java4.so")
#导入头文件
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/include)
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
add_library( # Sets the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main/cpp/native-lib.cpp)
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
find_library( # Sets the name of the path variable.
log-lib
# Specifies the name of the NDK library that
# you want CMake to locate.
log)
find_library( # Sets the name of the path variable.
jnigraphics-lib
jnigraphics)
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
native-lib
#添加opencv_java4
libopencv
${jnigraphics-lib}
# Links the target library to the log library
# included in the NDK.
${log-lib})
5.修改build文件
android {
compileSdkVersion 30
buildToolsVersion "30.0.2"
defaultConfig {
····
externalNativeBuild {
cmake {
cppFlags "-std=c++17"
arguments "-DANDROID_STL=c++_shared"
//生成.so库的目标平台
abiFilters 'armeabi-v7a', 'arm64-v8a'
}
}
}
····
externalNativeBuild {
cmake {
path "CMakeLists.txt"// CMakeLists.txt路径
version "3.10.2"//CMakeLists.txt版本
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
clean一下，并重新编译，这样NDK就支持OpenCV开发了。
PS：到这里，只是表示NDK C++层可以支持OpenCV开发了，要是想在Java层中，直接使用OpenCV的Java包，还需要导入“OpenCV-android-sdk”的Java，方法是可以参考：http://blog.csdn.net/u010097644/article/details/56849758
