OpenCV开发之——人脸识别库生成so文件

一 概述

  • 本文介绍通过ndk-build和cmake分别编译过程
  • 人脸识别库由face-detection下的jni生成的so文件和sdk生成的so合并后成为app的so文件

二 ndk-build和cmake编译

2.1 ndk-build编译

运行环境(ndk添加到环境变量中)

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path=D:\SoftWare\Android\SDK\ndk\android-ndk-r15c

执行ndk-build执行,显示如下消息说明ndk配置成功

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C:\Users\Admin>ndk-build
Android NDK: Could not find application project directory !
Android NDK: Please define the NDK_PROJECT_PATH variable to point to it.
D:\SoftWare\Android\SDK\ndk\android-ndk-r15c\build\\..\build\core\build-local.mk:151: *** Android NDK: Aborting . Stop.

ndk-build构建依赖文件

Application.mk:指定 ndk-build 的项目级设置。如ABI,Platform

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APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a
APP_PLATFORM := android-8

Android.mk:文件位于项目 jni/ 目录的子目录中,用于向构建系统描述源文件和共享库

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LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

#OPENCV_INSTALL_MODULES:=off
#OPENCV_LIB_TYPE:=SHARED
ifdef OPENCV_ANDROID_SDK
ifneq ("","$(wildcard $(OPENCV_ANDROID_SDK)/OpenCV.mk)")
include ${OPENCV_ANDROID_SDK}/OpenCV.mk
else
include ${OPENCV_ANDROID_SDK}/sdk/native/jni/OpenCV.mk
endif
else
include ../../sdk/native/jni/OpenCV.mk
endif

LOCAL_SRC_FILES := DetectionBasedTracker_jni.cpp
LOCAL_C_INCLUDES += $(LOCAL_PATH)
LOCAL_LDLIBS += -llog -ldl
LOCAL_MODULE := detection_based_tracker
include $(BUILD_SHARED_LIBRARY)

ndk-build编译face-detection/jni文件

  • 在项目/jni上右键—>Open In—>Terminal

  • 在打开后的终端,执行ndk-build指令

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    Android NDK: android-8 is unsupported. Using minimum supported version android-14.
    Android NDK: WARNING: APP_PLATFORM android-14 is higher than android:minSdkVersion 1 in D:/Code/Android/OpenCV-android-sdk-453/samples/face-detection/AndroidManifest.xml. NDK binaries will *not* be comptible with
    devices older than android-14. See https://android.googlesource.com/platform/ndk/+/master/docs/user/common_problems.md for more information.
    D:/Code/Android/OpenCV-android-sdk-453/samples/face-detection/jni/Android.mk:14: ../../sdk/native/jni/OpenCV.mk: No such file or directory
    make: *** No rule to make target `../../sdk/native/jni/OpenCV.mk'. Stop.
  • 根据提示信息做如下修改

    Android.mk

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    include ../../sdk/native/jni/OpenCV.mk 修改为 include ../../../sdk/native/jni/OpenCV.mk
    #LOCAL_SRC_FILES := DetectionBasedTracker_jni.cpp(注释掉)


    Application.mk

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    APP_ABI := armeabi-v7a 修改为 APP_ABI := armeabi-v7a arm64-v8a
  • 重新执行ndk-build执行,libs和obj文件夹下生成对应的so文件

2.2 cmake编译

Cmake运行环境

官网下载地址:https://cmake.org/download/

环境变量配置

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path=D:\SoftWare\cmake-3.18.2-win64-x64
path=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30133\bin\Hostx64\x64

Cmake构建文件

CMakeLists.txt:编译配置工具

终端执行camek指令

  • jni文件夹下新建build文件夹(用于cmake指令的生成目录)

  • 右键build,依次选择:Open In——>Terminal,在终端中打开build

  • 在终端中执行如下cmake指令

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    cmake .. -DOpenCV_DIR=..\..\..\sdk\native\jni\abi-arm64-v8a -DANDROID_TOOLCHAIN=clang -DANDROID_STL=c++_shared

    指令说明:

    • ..表示执行上一层目录下的CMakeLists.txt文件
    • OpenCV_DIR,ANDROID_TOOLCHAIN,ANDROID_STL表示build.gradle中执行cmake时传递进来的参数,用等号链接
  • 执行后的效果图

cmake-gui.exe执行编译

  • 找到cmake安装目录,打开cmake-gui

  • 分别选择source code和 build生成文件夹

  • 点击Configure按钮,在弹出的对话框中设置对应选项

  • 按照配置检查有无错误

    编译错误 错误原因
  • 修改OpenCV_DIR后重新执行Configure按钮,检查是否有错误

  • 点击Generate,查看build目录下生成内容

    三 android studio生成so文件

  • 打开android studio,执行Build—>Rebuild Project按钮或者执行Gradle—>Tasks—>Build指令

  • 执行完毕后,在build/intermediates/cmake/debug/obj下生成对应的so文件

  • 同理,依赖sdk的build/intermediates/cmake/debug/obj下生成对应的so文件

  • app下的abi和sdk下的abi合并后就是app的abi

四 参考

  • 在命令行中使用 cl.exe 编译器