dlib在android端的集成

http://dlib.net dlib 源码下载。

环境参考： android-ndk-r14b ，opencv 3.4 , dlib 19.19

1. opencv官方编译好了可用于android平台的so以及jni header 提供了jni和java版本的SDK两中调用方式，集成比较简单，不走赘述。

1. dlib 集成

1. 下载dlib源码，我使用19.19
   
   解压后的目录如下

dlib
   docs
   examples
   tools 

2. 将 dlib 目录整体拷贝到 studio 的 src/main/cpp 目录下

3. 配置 build.gradle文件

externalNativeBuild {
            cmake {
                arguments  "-DCMAKE_BUILD_TYPE=Release .."
                cppFlags "-std=c++11 -frtti -fexceptions -Os -O2"
            }
        }

4. cmake 文件处理

cmake_minimum_required(VERSION 3.4.1)

# 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.


# 设置native目录
set(NATIVE_DIR ${CMAKE_SOURCE_DIR}/src/main/cpp)
# 设置dlib
include(${NATIVE_DIR}/dlib/cmake)

include_directories(${JNI_LIBS_DIR}/includes)

set(JNI_LIBS_DIR ${CMAKE_SOURCE_DIR}/src/main/cpp)

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
        src/main/cpp/matutil.cpp
        src/main/cpp/effective.cpp
        src/main/cpp/face_detector.cpp
        )

include_directories(${CMAKE_SOURCE_DIR}/src/main/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.

add_library(libopencv_java  # 库名字
        SHARED
        IMPORTED)
set_target_properties( libopencv_java
        PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/libs/armeabi-v7a/libopencv_java.so)


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 )

# 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
                        libopencv_java
                        android
                        jnigraphics
                        dlib
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )


# 指定release编译选项
set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -s -O3 -Wall")
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -s -O3 -Wall")

5. 添加cpp源文件处理
   
   在 dlib 文件夹下添加文件 opencv_dlib_bridge.h 内容如下

#include <string>
#include <sstream>

using namespace std;
namespace std{
    template <typename T> std::string to_string(const T& n)
    {
        std::ostringstream stm;
        stm << n;
        return stm.str();
    }

    template <typename T> T round(T v)
    {
        return (v>0)?(v+0.5):(v-0.5);
    }
}

demo 参考: https://github.com/kongxs/face