在Android中使用OpenCv

oskycar 2011-07-18

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编译环境:ubuntu 10.10
opencv版本:2.2

1.首先需要下载以下文件:

OpenCV-2.2.0.tar.bz2

android-ndk-r4-linux-x86-crystax-4.tar.bz2

2.ubuntu需要以下包

sudo apt-get install build-essential
sudo apt-get install cmake
sudo apt-get install libgtk2.0-dev
sudo apt-get install swig
sudo apt-get install libpython2.6 python-dev python2.6-dev

3.解压缩opencv后,在其目录进行以下操作
cd release
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D BUILD_PYTHON_SUPPORT=ON
-D BUILD_EXAMPLES=ON ..
make

编译完成后安装进系统库中
sudo make install
sudo ldconfig

如果想测试效果可以进入samples/c目录中执行
. build_all.sh
来编译示例程序,然后运行find_obj来看看opencv中surf的效果

4.接下来是编译android的版本
在编译之前需要解压缩android-ndk-r4-linux-x86-crystax-4.tar.bz2到用户目录下,因为opencv默认在用户目录下寻找,当然大家也可以更改配置文件

进入android目录中,执行以下操作:
mkdir build
cd build
cmake ..
make

这就编译好android的库文件了,下面来新建一个android程序来测试一下

5.创建一个android工程,工程名为opencvtest,包名为com.opencvtest
在工程的根目录下创建一个jni文件夹,然后分别创建Android.mk和hello-jni.cpp两个文件
Android.mk的内容如下:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

include /home/ms/opencv/OpenCV-2.2.0/android/build/android-opencv.mk

LOCAL_LDLIBS += $(OPENCV_LIBS)

LOCAL_C_INCLUDES += $(OPENCV_INCLUDES)

LOCAL_MODULE := hello-jni

LOCAL_SRC_FILES := hello-jni.cpp

include $(BUILD_SHARED_LIBRARY)

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其中需要注意的是要更改include /home/ms/opencv/OpenCV-2.2.0到自己的opencv目录下
hello-jni.cpp的内容如下:

#include <jni.h>

#include <cstdlib>

#include <stdexcept>

#include <string>

#include <opencv2/core/core.hpp>

#include <opencv2/features2d/features2d.hpp>

#include <opencv2/highgui/highgui.hpp>

#include <opencv2/imgproc/imgproc.hpp>

#include <opencv2/calib3d/calib3d.hpp>

#include <opencv2/imgproc/imgproc_c.h>

static CvScalar colors[] =

{

{{0,0,255}},

{{0,128,255}},

{{0,255,255}},

{{0,255,0}},

{{255,128,0}},

{{255,255,0}},

{{255,0,0}},

{{255,0,255}},

};

extern "C"

jint Java_com_opencvtest_opencvtest_getKeypointNum(JNIEnv* env,jobject thiz)

{

IplImage* object = cvLoadImage( "/sdcard/src.jpg", CV_LOAD_IMAGE_GRAYSCALE );

if(object != NULL){

CvSURFParams params = cvSURFParams(500, 1);

CvMemStorage* storage = cvCreateMemStorage(0);

IplImage* object_color = cvCreateImage(cvGetSize(object), 8, 3);

CvSeq *objectKeypoints = 0;

CvSeq *objectDescriptors = 0;

cvCvtColor( object, object_color, CV_GRAY2BGR );

cvExtractSURF( object, 0, &objectKeypoints, &objectDescriptors, storage, params);

for( int i = 0; i < objectKeypoints->total; i++ )

{

CvSURFPoint* r = (CvSURFPoint*)cvGetSeqElem( objectKeypoints, i );

CvPoint center;

int radius;

center.x = cvRound(r->pt.x);

center.y = cvRound(r->pt.y);

radius = cvRound(r->size*1.2/9.*2);

cvCircle( object_color, center, radius, colors[0], 1, 8, 0 );

}

cvSaveImage( "/sdcard/src_surf.jpg" , object_color);

return objectKeypoints->total;

}

return 0;

}

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需要注意的是,如果创建的工程名和我不一样的话,需要更改JNI函数的函数名

更改好之后在工程的根目录下运行
~/android-ndk-r4-crystax/ndk-build
即可进行编译,~/android-ndk-r4-crystax指向了我自己的目录,大家可以根据自己的情况修改

编译完成后会创建libs和obj两个目录出来,同时需要注意的是要刷新android的工程来同步这两个目录下的内容

最后更改opencvtest.java文件来调用JNI,我的代码如下:

package com.opencvtest;

import android.app.Activity;

import android.os.Bundle;

import android.widget.TextView;

public class opencvtest extends Activity {

private TextView mTextView;

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

mTextView = (TextView) this.findViewById(R.id.textview);

mTextView.setText(Integer.toString(getKeypointNum()));

}

public native int getKeypointNum();

static {

System.loadLibrary("hello-jni");

}

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6. 这时候编译出来的程序还不能在虚拟机中运行,一运行就会闪一下跳出来,这是因为opencv的android库中有V5和V7两种ARM架构的库,我发现一般都会优先运行V7架构的ARM库,但是虚拟机应该是个V5架构的,所以会马上退出,我的G2手机也一样,所以这时候还要对OpenCV-2.2.0/android/build/android-opencv.mk文件进行修改来让程序在V5架构的ARM上运行,修改内容如下:

--- android-opencv.mk_backup 2011-02-27 05:31:41.813090978 -0800

+++ android-opencv.mk 2011-02-27 06:30:09.605091003 -0800

@@ -19,14 +19,10 @@

ANDROID_OPENCV_INCLUDES := $(OPENCV_ROOT)/android/android-jni/jni

ARMOBJS := local/armeabi

-ARMOBJS_V7A := local/armeabi-v7a

-OPENCV_LIB_DIRS := -L$(OPENCV_BUILD_ROOT)/obj/$(ARMOBJS_V7A) \

- -L$(OPENCV_BUILD_ROOT)/obj/$(ARMOBJS) -L$(OPENCV_BUILD_ROOT)/bin/ndk/$(ARMOBJS) \

- -L$(OPENCV_BUILD_ROOT)/bin/ndk/$(ARMOBJS_V7A)

+OPENCV_LIB_DIRS := -L$(OPENCV_BUILD_ROOT)/obj/$(ARMOBJS) -L$(OPENCV_BUILD_ROOT)/bin/ndk/$(ARMOBJS)

-ANDROID_OPENCV_LIB_DIRS := -L$(OPENCV_ROOT)/android/android-jni/libs/armeabi-v7a \

- -L$(OPENCV_ROOT)/android/android-jni/libs/armeabi