使用Android NDK编译OpenCV应用r人脸检测

最新推荐文章于 2023-06-18 04:56:23 发布

转载最新推荐文章于 2023-06-18 04:56:23 发布 · 2.3k 阅读

文章标签：

#android #xml #image #jni #string #input

本文介绍如何在Android设备上使用OpenCV库进行人脸检测应用开发，包括使用NDK编译so库，设置环境变量，创建Android工程，实现图像人脸检测等功能。通过示例代码展示了如何捕获图像，加载预训练的人脸检测模型，检测并绘制人脸矩形框，最终将处理后的图像保存为文件。

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OpenCV 在 Android 中的应用

使用 Android NDK 编译 so 库

简介

在 linuxt 系统下使用 OpenCV2.3 + NDK R6 编译 OpenCV 人脸检测应用

准备

Android NDK ( r5 或更高版本 ) http://developer.android.com/sdk/ndk/index.html

OpenCV Android 包 http://sourceforge.net/projects/opencvlibrary/files/opencv-android/2.3/

cmake( 可选，替代 NDK) http://www.cmake.org/

注： http://code.google.com/p/android-opencv/ 网站上说要使用crystax ndk r4代替 NDK 。估计可能是对于较旧的 Android 版本需要这样。如果 NDK 无法编译，请尝试使用 crystax ndk r4 编译。

OpenCV 设置

从网站上下载 OpenCV 2.3.0 for Android 后，解压到某个目录，如 ~/ 目录下

设置 OPENCV_PACKAGE_DIR 环境变量

$ export OPENCV_PACKAGE_DIR=~/enCV-2.3.0/

新建一个 Android 工程

在 eclipse 中新建一个 android 工程如 study.opencv ，并且在工程根目录下新建一个名为 jni 的目录。将下载的 android-ndk-r6 解压到某个目录下，如 ~/

从 ~/android-ndk-r6/sample 下某个 sample 中拷贝 Android.mk, Application.mk 到 study.opencv/jni 目录

设置编译脚本

在 Android.mk 中， include $(CLEAR_VARS) 后面，加入下行

include $(OPENCV_PACKAGE_DIR)/$(TARGET_ARCH_ABI)/share/opencv/OpenCV.mk

如果应用支持 ARM NEON 那么还需要加入以下行

include $(OPENCV_PACKAGE_DIR)/armeabi-v7a-neon/share/opencv/OpenCV.mk

LOCAL_ARM_NEON := true

在 Application.mk 中加入以下行

APP_STL := gnustl_static

APP_CPPFLAGS := -frtti -fexceptions

注：关于 Android.mk 与 Application.mk 的详细说明，请参考 ndk/docs 下 Android-mk.html 和 Application-mk.html 。

Java 层定义 native 接口

新建 study.opencv.FaceRec 类，定义一个人脸检测的本地接口

/**

* detect front face from image.

* @param xml

* opencv haarcascade xml file path

* @param infile

* input image file path

* @param outfile

* output image file path

public native void detect(String xml, String infile, String outfile);

生成 jni 头文件

使用 javah 命令生成 jni 头文件

$ cd ~/workspace/study.opencv/bin

$ javah study.opencv.FaceRec

会在 bin 目录生成一个 study_opencv_FaceRec.h 文件。将此文件拷贝到 ../jni 目录中

注：如果接口有变更，请先手动删除生成的 .h 文件。以防止一些意外的错误。

在 c 层实现图像人脸检测

在 jni 目录中使用文本编辑器新建一个 facedetect.cpp ，实现图像人脸检测

Cpp代码

#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <float.h>
#include <limits.h>
#include <time.h>
#include <ctype.h>
#include <android/log.h>
#include <study_opencv_FaceRec.h>
#include <jni.h>
#define LOG_TAG "opencv_face_detect"
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
static CvMemStorage* storage = 0;
static CvHaarClassifierCascade* cascade = 0;
void detect_and_draw( IplImage* image );
const char* cascade_name =
"haarcascade_frontalface_alt.xml";
/* "haarcascade_profileface.xml";*/
/*int captureFromImage(char* xml, char* filename);*/
char* jstring2String(JNIEnv*, jstring);
int captureFromImage(char* xml, char* filename, char* outfile)
{
LOGI("begin: ");
// we just detect image
// CvCapture* capture = 0;
IplImage *frame, *frame_copy = 0;
const char* input_name = "lina.png";
if(xml != NULL)
{
cascade_name = xml;
}
if(filename != NULL)
{
input_name = filename;
}
LOGI("xml=%s,filename=%s", cascade_name, input_name);
// load xml
cascade = (CvHaarClassifierCascade*)cvLoad( cascade_name, 0, 0, 0 );
LOGI("load cascade ok ? %d", cascade != NULL ? 1 : 0);
if( !cascade )
{
LOGI("ERROR: Could not load classifier cascade\n" );
// I just won't write long full file path, to instead of relative path, but I failed.
FILE * fp = fopen(input_name,"w");
if(fp == NULL){
LOGE("create failed");
}
return -1;
}
storage = cvCreateMemStorage(0);
// cvNamedWindow( "result", 1 );
IplImage* image = cvLoadImage( input_name, 1 );
if( image )
{
LOGI("load image successfully");
detect_and_draw( image );
// cvWaitKey(0);
if(outfile != NULL)
{
LOGI("after detected save image file");
cvSaveImage(outfile, image);//把图像写入文件
}
cvReleaseImage( &image );
}
else
{
LOGE("can't load image from : %s ", input_name);
}
}
void detect_and_draw( IplImage* img )
{
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}}
};
double scale = 1.3;
IplImage* gray = cvCreateImage( cvSize(img->width,img->height), 8, 1 );
IplImage* small_img = cvCreateImage( cvSize( cvRound (img->width/scale),
cvRound (img->height/scale)),
8, 1 );
int i;
cvCvtColor( img, gray, CV_BGR2GRAY );
cvResize( gray, small_img, CV_INTER_LINEAR );
cvEqualizeHist( small_img, small_img );
cvClearMemStorage( storage );
if( cascade )
{
double t = (double)cvGetTickCount();
CvSeq* faces = cvHaarDetectObjects( small_img, cascade, storage,
1.1, 2, 0/*CV_HAAR_DO_CANNY_PRUNING*/,
cvSize(30, 30) );
t = (double)cvGetTickCount() - t;
LOGI( "detection time = %gms\n", t/((double)cvGetTickFrequency()*1000.) );
for( i = 0; i < (faces ? faces->total : 0); i++ )
{
CvRect* r = (CvRect*)cvGetSeqElem( faces, i );
CvPoint center;
int radius;
center.x = cvRound((r->x + r->width*0.5)*scale);
center.y = cvRound((r->y + r->height*0.5)*scale);
radius = cvRound((r->width + r->height)*0.25*scale);
cvCircle( img, center, radius, colors[i%8], 3, 8, 0 );
}
}
// cvShowImage( "result", img );
cvReleaseImage( &gray );
cvReleaseImage( &small_img );
}
JNIEXPORT void JNICALL Java_study_opencv_FaceRec_detect
(JNIEnv * env, jobject obj, jstring xml, jstring filename, jstring outfile)
{
LOGI("top method invoked! ");/*LOGI("1");
char * c_xml = (char *)env->GetStringUTFChars(xml, JNI_FALSE);
LOGI("char * = %s", c_xml);
if(c_xml == NULL)
{
LOGI("error in get char*");
return;
}
char * c_file = env->GetStringCritical(env, filename, 0);
if(c_xml == NULL)
{
LOGI("error in get char*");
return;
}
captureFromImage(c_xml, c_file);
env->ReleaseStringCritical(env, xml, c_xml);
env->ReleaseStringCritical(env, file_name, c_file);
*/
captureFromImage(jstring2String(env,xml), jstring2String(env,filename), jstring2String(env,outfile));
}
//jstring to char*
char* jstring2String(JNIEnv* env, jstring jstr)
{
if(jstr == NULL)
{
LOGI("NullPointerException!");
return NULL;
}
char* rtn = NULL;
jclass clsstring = env->FindClass("java/lang/String");
jstring strencode = env->NewStringUTF("utf-8");
jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");
jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);
jsize alen = env->GetArrayLength(barr);
jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);
if (alen > 0)
{
rtn = (char*)malloc(alen + 1);
memcpy(rtn, ba, alen);
rtn[alen] = 0;
}
env->ReleaseByteArrayElements(barr, ba, 0);
LOGI("char*=%s",rtn);
return rtn;
}

#include "cv.h"#include "highgui.h"#include <stdio.h>#include <stdlib.h>#include <string.h>#include <assert.h>#include <math.h>#include <float.h>#include <limits.h>#include <time.h>#include <ctype.h>#include <android/log.h>#include <study_opencv_FaceRec.h>#include <jni.h>#define  LOG_TAG    "opencv_face_detect"#define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)static CvMemStorage* storage = 0;static CvHaarClassifierCascade* cascade = 0;void detect_and_draw( IplImage* image );const char* cascade_name =    "haarcascade_frontalface_alt.xml";/*    "haarcascade_profileface.xml";*//*int captureFromImage(char* xml, char* filename);*/char* jstring2String(JNIEnv*, jstring);int captureFromImage(char* xml, char* filename, char* outfile){	LOGI("begin: ");	// we just detect image	// CvCapture* capture = 0;    IplImage *frame, *frame_copy = 0;    const char* input_name = "lina.png";	if(xml != NULL)	{		cascade_name = xml;		}	if(filename != NULL)	{		input_name = filename;	}	LOGI("xml=%s,filename=%s", cascade_name, input_name);	// load xml     cascade = (CvHaarClassifierCascade*)cvLoad( cascade_name, 0, 0, 0 );	LOGI("load cascade ok ? %d", cascade != NULL ? 1 : 0);	if( !cascade )    {        LOGI("ERROR: Could not load classifier cascade\n" );		// I just won't write long full file path, to instead of relative path, but I failed.		FILE * fp = fopen(input_name,"w");		if(fp == NULL){			LOGE("create failed");		}        return -1;    }	storage = cvCreateMemStorage(0);	// cvNamedWindow( "result", 1 );    IplImage* image = cvLoadImage( input_name, 1 );    if( image )    {		LOGI("load image successfully");        detect_and_draw( image );        // cvWaitKey(0);		if(outfile != NULL)		{			LOGI("after detected save image file");			cvSaveImage(outfile, image);//把图像写入文件		}        cvReleaseImage( &image );    }	else	{		LOGE("can't load image from : %s ", input_name);	}}void detect_and_draw( IplImage* img ){    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}}    };    double scale = 1.3;    IplImage* gray = cvCreateImage( cvSize(img->width,img->height), 8, 1 );    IplImage* small_img = cvCreateImage( cvSize( cvRound (img->width/scale),                         cvRound (img->height/scale)),                     8, 1 );    int i;    cvCvtColor( img, gray, CV_BGR2GRAY );    cvResize( gray, small_img, CV_INTER_LINEAR );    cvEqualizeHist( small_img, small_img );    cvClearMemStorage( storage );    if( cascade )    {        double t = (double)cvGetTickCount();        CvSeq* faces = cvHaarDetectObjects( small_img, cascade, storage,                                            1.1, 2, 0/*CV_HAAR_DO_CANNY_PRUNING*/,                                            cvSize(30, 30) );        t = (double)cvGetTickCount() - t;        LOGI( "detection time = %gms\n", t/((double)cvGetTickFrequency()*1000.) );        for( i = 0; i < (faces ? faces->total : 0); i++ )        {            CvRect* r = (CvRect*)cvGetSeqElem( faces, i );            CvPoint center;            int radius;            center.x = cvRound((r->x + r->width*0.5)*scale);            center.y = cvRound((r->y + r->height*0.5)*scale);            radius = cvRound((r->width + r->height)*0.25*scale);            cvCircle( img, center, radius, colors[i%8], 3, 8, 0 );        }    }    // cvShowImage( "result", img );    cvReleaseImage( &gray );    cvReleaseImage( &small_img );}JNIEXPORT void JNICALL Java_study_opencv_FaceRec_detect  (JNIEnv * env, jobject obj, jstring xml, jstring filename, jstring outfile){	LOGI("top method invoked! ");/*LOGI("1");	char * c_xml = (char *)env->GetStringUTFChars(xml, JNI_FALSE);	LOGI("char * = %s", c_xml);	if(c_xml == NULL)	{		LOGI("error in get char*");		return;	}	char * c_file = env->GetStringCritical(env, filename, 0);	if(c_xml == NULL)	{		LOGI("error in get char*");		return;	}	captureFromImage(c_xml, c_file);	env->ReleaseStringCritical(env, xml, c_xml);	env->ReleaseStringCritical(env, file_name, c_file);	*/	captureFromImage(jstring2String(env,xml), jstring2String(env,filename), jstring2String(env,outfile));}//jstring to char*char* jstring2String(JNIEnv* env, jstring jstr){	if(jstr == NULL)	{		LOGI("NullPointerException!");		return NULL;	}	char* rtn = NULL;	jclass clsstring = env->FindClass("java/lang/String");	jstring strencode = env->NewStringUTF("utf-8");	jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");	jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);	jsize alen = env->GetArrayLength(barr);	jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);	if (alen > 0)	{		rtn = (char*)malloc(alen + 1);		memcpy(rtn, ba, alen);		rtn[alen] = 0;	}	env->ReleaseByteArrayElements(barr, ba, 0);	LOGI("char*=%s",rtn);	return rtn;}