Android 中对“cv::initModule_nonfree()"的未定义引用 [英] Undefined Reference To 'cv::initModule_nonfree()' In Android

问题描述

我想创建一个 Android 应用程序，它在本机(使用 C++)中使用 BOW + SVM 进行预测.不幸的是，我在构建本机部分时遇到了问题.由于Android的OpenCV SDK中不包含非免费模块，我需要自己构建模块，使用本教程.看来我成功构建了 .so 文件.这是输出:

[armeabi-v7a] 预构建:libopencv_java.so <=/home/crash-id/Development/SDK/OpenCV-2.4.9-android-sdk/sdk/native/jni/../libs/armeabi-v7a/[armeabi-v7a] 共享库:libnonfree.so[armeabi-v7a] 安装:libnonfree.so =>库/armeabi-v7a/libnonfree.so[armeabi-v7a] 安装:libopencv_java.so =>库/armeabi-v7a/libopencv_java.so

所以问题就来了，当我必须将这个 .so 文件添加到我的项目时.我将 libnonfree.so 添加到我的 jni 文件夹中.然后我编辑了Android.mk.我在这里提供我的 .mk 文件.

Android.mk

LOCAL_PATH := $(call my-dir)包括 $(CLEAR_VARS)LOCAL_MODULE := nonfree_prebuiltLOCAL_SRC_FILES := libnonfree.so包括 $(PREBUILT_SHARED_LIBRARY)包括 $(CLEAR_VARS)OPENCV_CAMERA_MODULES := onOPENCV_INSTALL_MODULES := on包括/home/crash-id/Development/SDK/OpenCV-2.4.9-android-sdk/sdk/native/jni/OpenCV.mk#LOCAL_SHARED_LIBRARIES := nonfree_prebuilt #如果我添加了这个，它表示 cv 命名空间中的所有内容的未定义引用.LOCAL_SRC_FILES := SVMDetector.cppLOCAL_MODULE := svm_detectorLOCAL_C_INCLUDES +=/home/crash-id/Development/SDK/OpenCV-2.4.9-android-sdk/sdk/native/jni/includeLOCAL_CFLAGS := -Werror -O3 -ffast-mathLOCAL_LDLIBS += -llog -ldl包括 $(BUILD_SHARED_LIBRARY)

Application.mk

APP_STL := gnustl_staticAPP_CPPFLAGS := -frtti -fexceptionsAPP_ABI := armeabi-v7aAPP_PLATFORM := android-15

但这行不通.当我尝试构建应用程序时，出现以下错误:

./obj/local/armeabi-v7a/objs/svm_detector/SVMDetector.o: 在函数 Java_org_elsys_thesisdiploma_cammect_FrameProcess_SVMDetect:jni/SVMDetector.cpp:23: 错误: 未定义引用 'cv::initModule_nonfree()'

当我在 initModule_nonfree(); 上单击右键时，Eclipse 会打开 nonfree.hpp 文件，其内容如下:

#ifndef __OPENCV_NONFREE_HPP__#define __OPENCV_NONFREE_HPP__#include "opencv2/nonfree/features2d.hpp"命名空间{CV_EXPORTS_W bool initModule_nonfree();}#万一

但我不确定链接器是否知道此方法的实现在哪里.因为它给出了错误，所以它没有.

编辑

如果我添加LOCAL_ALLOW_UNDEFINED_SYMBOLS := true，项目编译成功但会导致运行时错误:

 02-17 00:15:58.197: E/AndroidRuntime(8793): 致命异常: main02-17 00:15:58.197:E/AndroidRuntime(8793):进程:com.example.cammect，PID:879302-17 00:15:58.197: E/AndroidRuntime(8793): java.lang.UnsatisfiedLinkError: dlopen 失败: 无法找到libsvm_detector.so"引用的符号_ZN2cv18initModule_nonfreeEv"...

你知道我做错了什么吗?提前致谢！

解决方案

我的开发环境设置如下:

• android-ndk-r10d(安装路径:D:adt-bundle-windows-x86_64-20140702android-ndk-r10d)
• OpenCV-2.4.10-android-sdk(安装路径:D:CODEOpenCV-2.4.10-android-sdk)，下载链接
• OpenCV-2.4.10(安装路径:D:CODEOpenCV-2.4.10)、下载链接

构建非自由模块

1. 我们其实只需要从OpenCV-2.4.10源代码中复制几个文件到OpenCV-2.4.10-android-sdk，即:
   从 OpenCV-2.4.10sourcesmodules onfreeinclude 复制 nonfree 文件夹opencv2 到 OpenCV-2.4.10-android-sdksdk ativejniincludeopencv2.

2. 为libnonfree.so 创建一个文件夹来保存我们的新项目.在这里，我称之为libnonfree.在 libnonfree 下创建一个 jni 文件夹.将以下文件从 OpenCV-2.4.10sourcesmodules onfreesrc 复制到 libnonfreejni 文件夹:

   • nonfree_init.cpp
   • precomp.hpp
   • sift.cpp(使用原始文件em>)
   • surf.cpp(使用原始文件em>)

3. 构建libnonfree.so:
   创建 Android.mk 和 Application.mk 脚本.这个Android.mk用于构建libnonfree.so.

   • Application.mk
   • Android.mk(你应该修改OPENCV_PATH 你的 OpenCV-2.4.10-android-sdk 在哪里)

   cd 进入项目文件夹 libnonfree 并键入 ndk-build 以构建 libnonfree.so.

到目前为止，您已经在 libnonfreelibs 中获得了 libnonfree.so 以及 libopencv_java.so 和 libgnustl_shared.soarmeabi-v7a 文件夹.
您可以使用这些库轻松构建任何 SIFT 或 SURF 应用程序.如果你想在你的Android应用程序中使用JAVA代码中的SIFT和SURF，你只需要为你要使用的功能编写JNI接口即可.

构建示例应用

1. 创建一个项目文件夹调用libnonfree_demo.在项目文件夹中创建一个 jni 文件夹.然后将libnonfree.so 连同libopencv_java.so 和libgnustl_shared.so 复制到jni 中.

2. 在 jni 中创建一个 nonfree_jni.cpp.它是简单的 SIFT 测试程序.它基本上读取图像并检测关键点，然后提取特征描述符，最后将关键点绘制到输出图像中.

3. 在jni中创建Android.mk和Application.mk:

   • Application.mk
   • Android.mk(你应该修改OPENCV_PATH 你的 OpenCV-2.4.10-android-sdk 在哪里)

   cd 进入项目文件夹 libnonfree_demo 并键入 ndk-build 以构建 libnonfree_demo.so.

此时，您可以使用 SVMDetector 轻松扩展示例应用程序.只需将源文件和包含文件 int 复制到文件夹 libnonfree_demojni 并将 cpp 文件添加到 Android.mk 中的 LOCAL_SRC_FILES.

整个源码可以从:https://github.com/bkornel/opencv_android_nonfree下载.

原文来自:http://web.guohuiwang.com/technical-notes/sift_surf_opencv_android

I want to create an Android app which uses BOW + SVM in native (using C++) for predicting. Unfortunately I have problem with building the native part. Since the non-free module is not included in the OpenCV SDK for Android, I need to build the module myself, using this tutorial. It seems I built the .so file successfully. Here is the output:

[armeabi-v7a] Prebuilt       : libopencv_java.so <= /home/crash-id/Development/SDK/OpenCV-2.4.9-android-sdk/sdk/native/jni/../libs/armeabi-v7a/
[armeabi-v7a] SharedLibrary  : libnonfree.so
[armeabi-v7a] Install        : libnonfree.so => libs/armeabi-v7a/libnonfree.so
[armeabi-v7a] Install        : libopencv_java.so => libs/armeabi-v7a/libopencv_java.so

So the problem comes here, when I have to add this .so file to my project. I added libnonfree.so to my jni folder. Then I edited the Android.mk. Here I provide my .mk files.

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE    := nonfree_prebuilt
LOCAL_SRC_FILES := libnonfree.so
include $(PREBUILT_SHARED_LIBRARY)


include $(CLEAR_VARS)
OPENCV_CAMERA_MODULES   := on
OPENCV_INSTALL_MODULES  := on

include /home/crash-id/Development/SDK/OpenCV-2.4.9-android-sdk/sdk/native/jni/OpenCV.mk
#LOCAL_SHARED_LIBRARIES := nonfree_prebuilt #if I add this, it says undefined reference for everything in the cv namespace.
LOCAL_SRC_FILES  := SVMDetector.cpp
LOCAL_MODULE     := svm_detector

LOCAL_C_INCLUDES        += /home/crash-id/Development/SDK/OpenCV-2.4.9-android-sdk/sdk/native/jni/include

LOCAL_CFLAGS            := -Werror -O3 -ffast-math 
LOCAL_LDLIBS            += -llog -ldl 

include $(BUILD_SHARED_LIBRARY)

Application.mk

APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions

APP_ABI := armeabi-v7a

APP_PLATFORM := android-15

But this doesn't work. When I try to build the app, I get the following error:

./obj/local/armeabi-v7a/objs/svm_detector/SVMDetector.o: in function Java_org_elsys_thesisdiploma_cammect_FrameProcess_SVMDetect:jni/SVMDetector.cpp:23: error: undefined reference to 'cv::initModule_nonfree()'

When I click right button on initModule_nonfree();, Eclipse opens the nonfree.hpp file and here are it's contents:

#ifndef __OPENCV_NONFREE_HPP__
#define __OPENCV_NONFREE_HPP__

#include "opencv2/nonfree/features2d.hpp"

namespace cv
{

CV_EXPORTS_W bool initModule_nonfree();

}

#endif

But I'm not sure the linker knows where is the implementation of this method. Since it gives an error, it doesn't.

EDIT

If I add LOCAL_ALLOW_UNDEFINED_SYMBOLS := true, the project compiles successfully but it causes run time error:

 02-17 00:15:58.197: E/AndroidRuntime(8793): FATAL EXCEPTION: main
02-17 00:15:58.197: E/AndroidRuntime(8793): Process: com.example.cammect, PID: 8793
02-17 00:15:58.197: E/AndroidRuntime(8793): java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol "_ZN2cv18initModule_nonfreeEv" referenced by "libsvm_detector.so"...

Do you know what am I doing wrong? Thanks in advance!

解决方案

My development environment is set up as follows:

• android-ndk-r10d (install path: D:adt-bundle-windows-x86_64-20140702android-ndk-r10d)
• OpenCV-2.4.10-android-sdk (install path: D:CODEOpenCV-2.4.10-android-sdk), Download link
• OpenCV-2.4.10 (install path: D:CODEOpenCV-2.4.10), Download link

Building the nonfree module

1. We actually only need to copy a few files from OpenCV-2.4.10 source code to OpenCV-2.4.10-android-sdk, namely:
   Copy the nonfree folder from OpenCV-2.4.10sourcesmodules onfreeincludeopencv2 to OpenCV-2.4.10-android-sdksdk ativejniincludeopencv2.

2. Create a folder to hold our new project for libnonfree.so. Here, I call it libnonfree. Create a jni folder under libnonfree. Copy the following files from OpenCV-2.4.10sourcesmodules onfreesrc to libnonfreejni folder:

   • nonfree_init.cpp
   • precomp.hpp
   • sift.cpp (use the original file)
   • surf.cpp (use the original file)

3. Building libnonfree.so:
   Create Android.mk and Application.mk scripts. This Android.mk is used to build libnonfree.so.

   • Application.mk
   • Android.mk (you should modify OPENCV_PATH where your OpenCV-2.4.10-android-sdk is)

   cd into the project folder libnonfree and type ndk-build to build the libnonfree.so.

So far, you have got libnonfree.so along with libopencv_java.so and libgnustl_shared.so in libnonfreelibsarmeabi-v7a folder.
You can easily build any SIFT or SURF applications using those libraries. If you want to use SIFT and SURF in JAVA code in your Android application, you only need to write JNI interfaces for the functions you want to use.

Building a sample application

1. Create a project folder call libnonfree_demo. Create a jni folder inside the project folder. Then copy libnonfree.so along with libopencv_java.so and libgnustl_shared.so into jni.

2. Create a nonfree_jni.cpp in jni. It is simple SIFT test program. It basically reads an image and detects the keypoints, then extracts feature descriptors, finally draws the keypoints to an output image.

3. Create Android.mk and Application.mk inside jni:

   • Application.mk
   • Android.mk (you should modify OPENCV_PATH where your OpenCV-2.4.10-android-sdk is)

   cd into the project folder libnonfree_demo and type ndk-build to build the libnonfree_demo.so.

At this point you can easily extend the sample app with your SVMDetector. Just copy the source and include files int to the folder libnonfree_demojni and add cpp files to LOCAL_SRC_FILES in Android.mk.

The whole source can be downloaded from: https://github.com/bkornel/opencv_android_nonfree.

Original source from: http://web.guohuiwang.com/technical-notes/sift_surf_opencv_android

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