java利用opencv截取人脸， 控制最终大小在10k之内

1. 到官网下载对应版本的Windows版本，我这里下载的是4.5.3版本，下载后可以得到名为opencv的文件夹

   https://opencv.org/releases/

2. 在opencv\build\java\opencv-453.jar中找到需要引入的jar包

   在项目新建lib文件夹把该jar包放到该文件夹下

   添加maven依赖

   <dependency>
       <groupId>org.opencv</groupId>
       <artifactId>opencv</artifactId>
       <version>4.5.3</version>
       <scope>system</scope>
       <systemPath>${basedir}/lib/opencv-453.jar</systemPath>
   </dependency>
   
   <plugin>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-maven-plugin</artifactId>
       <configuration>
           <!--在打包插件中设置该值为true，会将本地jar也一起打包-->
           <includeSystemScope>true</includeSystemScope>
       </configuration>
   </plugin>
   

3. 在resources下新建opencv文件夹，将opencv\build\java\x64\opencv_java453.dll和opencv\sources\data\haarcascades\haarcascade_frontalface_alt.xml文件放到该文件夹下

   opencv_java453.dll是调用opencv的动态库文件，需要在使用前加载到jvm中

   haarcascade_frontalface_alt.xml是opencv的一个人脸识别器

4. 初始化---加载dll文件到jvm中

   这里会将resources中的opencv_java453.dll和haarcascade_frontalface_alt.xml新建一个新的文件，避免打包后在resources找不到资源导致初始失败问题

   @PostConstruct
   public void init(){
       try{
           String dirPath = "./opencv/";
           File dir = new File(dirPath);
           dir.mkdir();
           File dllFile = new File("./opencv/"+Core.NATIVE_LIBRARY_NAME + ".dll");
           if( !dllFile.exists() ){
               dllFile.createNewFile();
               InputStream inputStream = this.getClass().getResourceAsStream("/opencv/" + Core.NATIVE_LIBRARY_NAME + ".dll");
               BufferedInputStream bi = new BufferedInputStream(inputStream);
               FileOutputStream fos = new FileOutputStream("./opencv/"+Core.NATIVE_LIBRARY_NAME + ".dll");
               byte[] by = new byte[1024];
               int len = 0;
               while((len=bi.read(by))!=-1){
                   fos.write(by,0,len);
               }
               fos.close();
               bi.close();
               inputStream.close();
               dllFile = new File("./opencv/"+Core.NATIVE_LIBRARY_NAME + ".dll");
           }
           if (!dllFile.exists()) {
               log.error("找不到动态库 ".concat(dllFile.getCanonicalPath()));
               return;
           }
           System.load(dllFile.getCanonicalPath());
           log.info("openCV load success");
       }catch (Exception e){
           e.printStackTrace();
           log.error("openCV load fail");
       }
   }
   

5. 人脸识别并截取，控制最终图片大小在10k以内

   /**
    * opencv实现人脸识别
    * @param imagePath
    * @param outFile
    */
   public boolean detectFace(String imagePath, String outFile) {
       try{
           log.info("Running DetectFace ... ");
           File xmlFile = new File("./opencv/haarcascade_frontalface_alt.xml");
           if( !xmlFile.exists() ){
               InputStream inputStream = this.getClass().getResourceAsStream("/opencv/haarcascade_frontalface_alt.xml");
               BufferedInputStream bi = new BufferedInputStream(inputStream);
               FileOutputStream fos = new FileOutputStream("./opencv/haarcascade_frontalface_alt.xml");
               byte[] by = new byte[1024];
               int len = 0;
               while((len=bi.read(by))!=-1){
                   fos.write(by,0,len);
               }
               fos.close();
               bi.close();
               inputStream.close();
               xmlFile = new File("./opencv/haarcascade_frontalface_alt.xml");
           }
           CascadeClassifier faceDetector = new CascadeClassifier(xmlFile.getCanonicalPath());
           Mat image = Imgcodecs.imread(imagePath);
           // 在图片中检测人脸
           MatOfRect faceDetections = new MatOfRect();
           faceDetector.detectMultiScale(image, faceDetections);
           Rect[] rects = faceDetections.toArray();
           if(rects != null && rects.length > 1){
               log.error("超过一个脸");
               return false;
           }
           // 在每一个识别出来的人脸周围画出一个方框
           Rect rect = rects[0];
           //上y和下y为总高度的百分之15
           imageCut(imagePath, outFile, rect.x-2, (int)(rect.y-rect.height*0.15), rect.width, (int)(rect.height+rect.height*0.15));
           log.info("人脸截取成功");
           return true;
       }catch (Exception e){
           log.error("人脸截取失败");
           e.printStackTrace();
           return false;
       }
   }
   
   /**
    * 裁剪图片并重新装换大小
    * @param imagePath  
    * @param posX
    * @param posY
    * @param width
    * @param height
    * @param outFile
    */
   public void imageCut(String imagePath, String outFile, int posX, int posY, int width, int height){
       Mat image = Imgcodecs.imread(imagePath);
       //截取的区域：参数,坐标X,坐标Y,截图宽度,截图长度
       Rect rect = new Rect(posX,posY,width,height);
       Mat sub = image.submat(rect);
       Mat mat = new Mat();
       Size size = new Size(100, (float)height/width*100);
       Imgproc.resize(sub, mat, size); //将人脸进行截图并保存
       //灰度处理，灰度处理后可在最终大小上减少4-5k
       //Imgproc.cvtColor(mat, mat, Imgproc.COLOR_BGR2GRAY);
       Imgcodecs.imwrite(outFile, mat);
   }
   

6. 测试

   public static void main(String[] args) throws Exception {
       String sourceFile = "E:\\1.jpg";
       String outputFile = "E:\\2.jpg";
       OpenCVUtil.detectFace(sourceFile, outputFile);
   }
   

7. 注意点

   devtools依赖会和该jar包冲突，报出java.lang.UnsatisfiedLinkError的异常，删掉devtools依赖就不会报错

   若打包后直接引用resources的文件会报错，引用绝对路径则不会