JAVA应用JNI调用OpenCV实现人脸检测(1)

原文转载于：http://blog.csdn.net/wangkr111/article/details/7855648

貌似上面地址也是转载的，但是我找不到最原始的出处了。

主要思想：使用JNI进行C++编程，将功能模块编译为DLL链接库，在Android开发中直接调用DLL链接。

1.JAVA的JNI部分 
调用JNI的基类 

 package lveyo.bcndyl.jni.opencv;
 public class JNIBase {

     public JNIBase(){}

     public JNIBase(String libraryName){
         loadLibrary(libraryName);
     }

     private static void loadLibrary(String libraryName){
         System.loadLibrary(libraryName);
     }

 }

实现这个基类 

 package lveyo.bcndyl.jni.opencv;

 public class JNIOpencv extends JNIBase{

     public JNIOpencv (String libraryName){
         super(libraryName);
     }

     public JNIOpencv(){
         System.loadLibrary("jniOpenCV");
     }

     public native int[] detectFace(int minFaceWidth, int minFaceHeight,
                                    String cascade, String filename);

 }

类中定义了一个detectFace方法，是要用C来实现的。 

编译好这个类后，要用在命令行用javah命令生成需要的.h的头文件： 

引用

javah lveyo.bcndyl.jni.opencv.JNIOpencv 

会生成一个名为lveyo_bcndyl_jni_opencv_JNIOpencv.h的头文件： 

 /* DO NOT EDIT THIS FILE - it is machine generated */
 #include <jni.h>
 /* Header for class lveyo_bcndyl_jni_opencv_JNIOpencv */

 #ifndef _Included_lveyo_bcndyl_jni_opencv_JNIOpencv
 #define _Included_lveyo_bcndyl_jni_opencv_JNIOpencv
 #ifdef __cplusplus
 extern "C" {
 #endif
 /*
  * Class:     lveyo_bcndyl_jni_opencv_JNIOpencv
  * Method:    detectFace
  * Signature: (IILjava/lang/String;Ljava/lang/String;)[I
  */
 JNIEXPORT jintArray JNICALL Java_lveyo_bcndyl_jni_opencv_JNIOpencv_detectFace
   (JNIEnv *, jobject, jint, jint, jstring, jstring);

 #ifdef __cplusplus
 }
 #endif
 #endif

2.C程序部分 
按照 http://www.opencv.org.cn/index.php/Template:Install 安装OpenCV并配置相应的开发环境，我这里用的是VS2005，同时要将JDK中的include目录和include/win32目录都加入到VS2005的Include Files中。 
新建一个win32 MFC DLL项目jniOpenCV，把刚才生成的lveyo_bcndyl_jni_opencv_JNIOpencv.h头文件加入到项目，并且修改jniOpenCV.cpp文件： 

 #include "stdafx.h"
 #include <jni.h>
 #include "lveyo_bcndyl_jni_opencv_JNIOpencv.h"
 #include "cv.h"
 #include "highgui.h"

 JNIEXPORT jintArray JNICALL Java_lveyo_bcndyl_jni_opencv_JNIOpencv_detectFace
   (JNIEnv *env, jobject obj, jint width, jint height, jstring cascade, jstring filename)
 {
     const char *str_cascade, *str_filename;
     str_cascade = env->GetStringUTFChars(cascade, false);
     str_filename = env->GetStringUTFChars(filename, false);

     jintArray faceArray;
     CvHaarClassifierCascade *cv_cascade = (CvHaarClassifierCascade*)cvLoad( str_cascade );
     IplImage *image = cvLoadImage( str_filename, 1 );

     if(image!=0){

         CvMemStorage* storage = cvCreateMemStorage(0);
         CvSeq* faces;

         //double t = (double)cvGetTickCount();
         /* use the fastest variant */
         faces = cvHaarDetectObjects( image, cv_cascade, storage, 1.2, 2,
                                    CV_HAAR_DO_CANNY_PRUNING, cvSize(width, height) );
         //t = (double)cvGetTickCount() - t;
         //printf( "detection time = %gms\n", t/((double)cvGetTickFrequency()*1000.) );


         const int total = faces->total;

         faceArray = env-> NewIntArray(4*total);
         jint faceBuf[4];

         for( int i = 0; i < total; i++ )
         {
             CvRect face_rect = *(CvRect*)cvGetSeqElem( faces, i );
             int pointX = face_rect.x;
             int pointY = face_rect.y;
             int faceWidth = face_rect.width;
             int faceHeight = face_rect.height;

             //printf("i %d, x %d, y %d, width %d, height %d\n",
                         //        i,pointX,pointY,faceWidth,faceHeight);


             faceBuf[0] = pointX;
             faceBuf[1] = pointY;
             faceBuf[2] = faceWidth;
             faceBuf[3] = faceHeight;


             env->SetIntArrayRegion(faceArray,i*4,4,faceBuf);

         }

         cvReleaseMemStorage( &storage );
         cvReleaseImage( &image );
     }
     cvReleaseHaarClassifierCascade( &cv_cascade );


     env->ReleaseStringUTFChars(cascade, str_cascade);
     env->ReleaseStringUTFChars(filename, str_filename);
     return faceArray;
 }

编译生成jniOpenCV.dll。此处的检测代码是根据OpenCV的文档和示例程序修改，由于本人对c++程序不是很熟练，所以对此段代码是否会有潜在危险和内存泄露不是很肯定，还请熟悉c使用的朋友帮忙检查一下。 
别忘记将生成的jniOpenCV.dll文件复制到%JAVA_HOME%/bin中，如果在没安装OpenCV的机器上运行，还需要将OpenCV安装目录中bin目录下所有dll文件一起复制到%JAVA_HOME%/bin中。 

3.实现JAVA的调用 

 package lveyo.bcndyl.jni.opencv;

 public class Test {

     public static void main(String[] args) {

         //初始化JNI调用类JNIOpencv
         JNIOpencv open = new JNIOpencv("jniOpenCV");

         //要检测的图片文件
         String filename = "d:/80010.jpg";

         //OpenCv提供的人间的特征文件
         String cascade = "d:/haarcascade_frontalface_alt2.xml";

         //人脸检测，前两个参数为可检测的最小人脸的宽度和高度
         //返回值为人脸在图中的坐标和宽高，{x, y, width, height}
         int[] faces = open.detectFace(40, 40, cascade, filename);
         if(faces != null && faces.length!=0){

             //返回的人脸总数
             System.out.println( "faces " + faces.length/4 );

             //分别输出每个人脸的坐标信息
             for (int temp : faces) {
                 System.out.println(temp);
             }
         }
     }
 }