#include <jni.h>
#include <string>
#include <vector>
#include <iostream>#include "face_detection/dlib/image_io.h"
#include "face_detection/dlib/image_processing.h"
#include "face_detection/dlib/image_processing/frontal_face_detector.h"#include <ctime>dlib::frontal_face_detector m_facedetector=dlib::get_frontal_face_detector();
//获取人脸框
std::vector<int > getfacerect(const std::vector<int>img,int height,int width)
{dlib::array2d<unsigned char>image;image.set_size(height,width);for (int i = 0; i < height; i++){for(int j=0;j<width;j++){int clr = img[i*width+j];int red = (clr & 0x00ff0000) >> 16; // 取高两位int green = (clr & 0x0000ff00) >> 8; // 取中两位int blue = clr & 0x000000ff; // 取低两位unsigned char gray=red*0.299+green*0.587+blue*0.114;//dlib::rgb_pixel pt(red,green,blue);image[i][j]=gray;}}clock_t begin = clock();std::vector<dlib::rectangle> dets= m_facedetector(image);std::vector<int >rect;if (!dets.empty()){rect.push_back(dets[0].left());rect.push_back(dets[0].top());rect.push_back(dets[0].width());rect.push_back(dets[0].height());}return rect;}extern "C" jintArray  Java_image_imageapp_MainActivity_stringFromJNI(JNIEnv *env, jobject /* this */,jintArray image_data,jint image_height,jint image_widht)
{//const char* cha = env->GetStringUTFChars(imagepath, nullptr);// char* 转 string// std::string image_str(cha);// if(cha == NULL) {//return NULL;// }//jstring rtstr = env->NewStringUTF(image_str.c_str());//env->NewStringUTF(hello.c_str());// return rtstr;std::vector<int>image_datacpp(image_height*image_widht);jsize len = env->GetArrayLength(image_data);jint *body = env->GetIntArrayElements(image_data, 0);for (jsize i=0;i<len;i++){image_datacpp[i]=(int)body[i];}std::vector<int>rect=getfacerect(image_datacpp,image_height,image_widht);jintArray result =env->NewIntArray(4);env->SetIntArrayRegion(result, 0, 4, &rect[0]);return result;}

2、MainActivity.JAVA中调用库函数：

    private int[] face_detection(Bitmap origin_image){float scale = 240.f/ Math.max(origin_image.getHeight(), origin_image.getWidth());int width = (int)(origin_image.getWidth()*scale);int height = (int)(origin_image.getHeight()*scale);Bitmap resize_image=Bitmap.createScaledBitmap(origin_image,width,height , false);// 保存所有的像素的数组，图片宽×高int[] pixels = new int[width * height];resize_image.getPixels(pixels, 0, width, 0, 0, width, height);int[] rect=stringFromJNI(pixels,height,width);int[] result_rect=new int[4];result_rect[0]=(int)(rect[0]/scale);result_rect[1]=(int)(rect[1]/scale);result_rect[2]=(int)(rect[2]/scale);result_rect[3]=(int)(rect[3]/scale);result_rect[2]=result_rect[2]+result_rect[0];result_rect[3]=result_rect[3]+result_rect[1];return  result_rect;}

3、显示绘制结果

            int[] rect=face_detection(scaled);Canvas canvas=new Canvas(scaled);Paint p=new Paint();p.setColor(Color.RED);p.setStrokeWidth(3.0f);canvas.drawLine(rect[0], rect[1], rect[2], rect[1], p);//upcanvas.drawLine(rect[0], rect[1], rect[0], rect[3], p);//leftcanvas.drawLine(rect[0], rect[3], rect[2], rect[3], p);//downcanvas.drawLine(rect[2], rect[1], rect[2], rect[3], p);//cnvs.drawRect(rectangle,paint);imageView.setImageBitmap(scaled);