Android动态人脸检测的示例代码（脸数可调）

public class findfaceview extends surfaceview implements surfaceholder.callback {

  private surfaceholder holder;
  private int mwidth;
  private int mheight;
  private float eyesdistance;

  public findfaceview(context context, attributeset attrs) {
    super(context, attrs);
    holder = getholder();
    holder.addcallback(this);
    holder.setformat(pixelformat.transparent);
    this.setzorderontop(true);
  }

  @override
  public void surfacechanged(surfaceholder holder, int format, int width,
                int height) {
    mwidth = width;
    mheight = height;
  }

  @override
  public void surfacecreated(surfaceholder holder) {

  }

  @override
  public void surfacedestroyed(surfaceholder holder) {

  }

  public void drawrect(facedetector.face[] faces, int numberoffacedetected) {
    canvas canvas = holder.lockcanvas();
    if (canvas != null) {
      paint clippaint = new paint();
      clippaint.setantialias(true);
      clippaint.setstyle(paint.style.stroke);
      clippaint
          .setxfermode(new porterduffxfermode(porterduff.mode.clear));
      canvas.drawpaint(clippaint);
      canvas.drawcolor(getresources().getcolor(color.transparent));
      paint paint = new paint();
      paint.setantialias(true);
      paint.setcolor(color.green);
      paint.setstyle(style.stroke);
      paint.setstrokewidth(5.0f);
      for (int i = 0; i < numberoffacedetected; i++) {
        face face = faces[i];
        pointf midpoint = new pointf();
        // 获得两眼之间的中间点
        face.getmidpoint(midpoint);
        // 获得两眼之间的距离
        eyesdistance = face.eyesdistance();
        // 换算出预览图片和屏幕显示区域的比例参数
        float scale_x = mwidth / 500;
        float scale_y = mheight / 600;
        log.e("eyesdistance=", eyesdistance + "");
        log.e("midpoint.x=", midpoint.x + "");
        log.e("midpoint.y=", midpoint.y + "");
        // 因为拍摄的相片跟实际显示的图像是镜像关系，所以在图片上获取的两眼中间点跟手机上显示的是相反方向
        canvas.drawrect((int) (240 - midpoint.x - eyesdistance)
                * scale_x, (int) (midpoint.y * scale_y),
            (int) (240 - midpoint.x + eyesdistance) * scale_x,
            (int) (midpoint.y + 3 * eyesdistance) * scale_y, paint);
      }
      holder.unlockcanvasandpost(canvas);
    }
  }
}

 holder.setformat(pixelformat.transparent);
 this.setzorderontop(true);

public class facerecognitiondemoactivity extends activity implements
    onclicklistener {

  private surfaceview preview;
  private camera camera;
  private camera.parameters parameters;
  private int orientionofcamera;// 前置摄像头的安装角度
  private int facenumber;// 识别的人脸数
  private facedetector.face[] faces;
  private findfaceview mfindfaceview;
  private imageview iv_photo;
  private button bt_camera;
  textview mtv;

  /**
   * called when the activity is first created.
   */
  @override
  public void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.main);
  }

  @override
  protected void onstart() {
    super.onstart();
    iv_photo = (imageview) findviewbyid(r.id.iv_photo);
    bt_camera = (button) findviewbyid(r.id.bt_camera);
    mtv = (textview) findviewbyid(r.id.show_count);
    bt_camera.setonclicklistener(this);

    mfindfaceview = (findfaceview) findviewbyid(r.id.my_preview);

    preview = (surfaceview) findviewbyid(r.id.preview);
    // 设置缓冲类型（必不可少）
    preview.getholder().settype(surfaceholder.surface_type_push_buffers);
    // 设置surface的分辨率
    preview.getholder().setfixedsize(176, 144);
    // 设置屏幕常亮（必不可少）
    preview.getholder().setkeepscreenon(true);

    preview.getholder().addcallback(new surfacecallback());
  }

  private final class mypicturecallback implements picturecallback {

    @override
    public void onpicturetaken(byte[] data, camera camera) {
      try {
        bitmap bitmap = bitmapfactory.decodebytearray(data, 0,
            data.length);
        matrix matrix = new matrix();
        matrix.setrotate(-90);
        bitmap bmp = bitmap.createbitmap(bitmap, 0, 0, bitmap
            .getwidth(), bitmap.getheight(), matrix, true);
        bitmap.recycle();
        iv_photo.setimagebitmap(bmp);
        camera.startpreview();
      } catch (exception e) {
        e.printstacktrace();
      }
    }

  }

  private final class surfacecallback implements callback {

    @override
    public void surfacechanged(surfaceholder holder, int format, int width,
                  int height) {
      if (camera != null) {
        parameters = camera.getparameters();
        parameters.setpictureformat(pixelformat.jpeg);
        // 设置预览区域的大小
        parameters.setpreviewsize(width, height);
        // 设置每秒钟预览帧数
        parameters.setpreviewframerate(20);
        // 设置预览图片的大小
        parameters.setpicturesize(width, height);
        parameters.setjpegquality(80);
      }
    }

    @override
    public void surfacecreated(surfaceholder holder) {
      int cameracount = 0;
      camera.camerainfo camerainfo = new camera.camerainfo();
      cameracount = camera.getnumberofcameras();
      //设置相机的参数
      for (int i = 0; i < cameracount; i++) {
        camera.getcamerainfo(i, camerainfo);
        if (camerainfo.facing == camera.camerainfo.camera_facing_front) {
          try {
            camera = camera.open(i);
            camera.setpreviewdisplay(holder);
            setcameradisplayorientation(i, camera);
            //最重要的设置 帧图的回调
            camera.setpreviewcallback(new mypreviewcallback());
            camera.startpreview();
          } catch (exception e) {
            e.printstacktrace();
          }
        }
      }
    }

    @override
    public void surfacedestroyed(surfaceholder holder) {
    //记得释放，避免oom和占用
      if (camera != null) {
        camera.setpreviewcallback(null);
        camera.stoppreview();
        camera.release();
        camera = null;
      }
    }

  }

  private class mypreviewcallback implements previewcallback {

    @override
    public void onpreviewframe(byte[] data, camera camera) {
    //这里需要注意，回调出来的data不是我们直接意义上的rgb图 而是yuv图，因此我们需要
    //将yuv转化为bitmap再进行相应的人脸检测，同时注意必须使用rgb_565，才能进行人脸检测，其余无效
      camera.size size = camera.getparameters().getpreviewsize();
      yuvimage yuvimage = new yuvimage(data, imageformat.nv21,
          size.width, size.height, null);
      bytearrayoutputstream baos = new bytearrayoutputstream();
      yuvimage.compresstojpeg(new rect(0, 0, size.width, size.height),
          80, baos);
      byte[] bytearray = baos.tobytearray();
      detectionfaces(bytearray);
    }
  }

  /**
   * 检测人脸
   *
   * @param data 预览的图像数据
   */
  private void detectionfaces(byte[] data) {
    bitmapfactory.options options = new bitmapfactory.options();
    bitmap bitmap1 = bitmapfactory.decodebytearray(data, 0, data.length,
        options);
    int width = bitmap1.getwidth();
    int height = bitmap1.getheight();
    matrix matrix = new matrix();
    bitmap bitmap2 = null;
    facedetector detector = null;
    //设置各个角度的相机，这样我们的检测效果才是最好
    switch (orientionofcamera) {
      case 0:
        //初始化人脸检测（下同）
        detector = new facedetector(width, height, 10);
        matrix.postrotate(0.0f, width / 2, height / 2);
        // 以指定的宽度和高度创建一张可变的bitmap（图片格式必须是rgb_565，不然检测不到人脸）
        bitmap2 = bitmap.createbitmap(width, height, bitmap.config.rgb_565);
        break;
      case 90:
        detector = new facedetector(height, width, 1);
        matrix.postrotate(-270.0f, height / 2, width / 2);
        bitmap2 = bitmap.createbitmap(height, width, bitmap.config.rgb_565);
        break;
      case 180:
        detector = new facedetector(width, height, 1);
        matrix.postrotate(-180.0f, width / 2, height / 2);
        bitmap2 = bitmap.createbitmap(width, height, bitmap.config.rgb_565);
        break;
      case 270:
        detector = new facedetector(height, width, 1);
        matrix.postrotate(-90.0f, height / 2, width / 2);
        bitmap2 = bitmap.createbitmap(height, width, bitmap.config.rgb_565);
        break;
    }
    //设置支持的面数（最大支持检测多少人的脸 ，可以根据需要调整，不过需要与findfaces中的参数数值相同，否则会抛出异常）
    faces = new facedetector.face[10];
    paint paint = new paint();
    paint.setdither(true);
    canvas canvas = new canvas();
    canvas.setbitmap(bitmap2);
    canvas.setmatrix(matrix);
    // 将bitmap1画到bitmap2上（这里的偏移参数根据实际情况可能要修改）
    canvas.drawbitmap(bitmap1, 0, 0, paint);
    //这里通过向findfaces中传递帧图转化后的bitmap和最大检测的人脸数face，返回检测后的人脸数
    facenumber = detector.findfaces(bitmap2, faces);
    mtv.settext("facnumber----" + facenumber);
    mtv.settextcolor(color.red);
    //这里就是我们的人脸识别，绘制识别后的人脸区域的类
    if (facenumber != 0) {
      mfindfaceview.setvisibility(view.visible);
      mfindfaceview.drawrect(faces, facenumber);
    } else {
      mfindfaceview.setvisibility(view.gone);
    }
    bitmap2.recycle();
    bitmap1.recycle();
  }

  /**
   * 设置相机的显示方向（这里必须这么设置，不然检测不到人脸）
   *
   * @param cameraid 相机id(0是后置摄像头，1是前置摄像头）
   * @param camera  相机对象
   */
  private void setcameradisplayorientation(int cameraid, camera camera) {
    camera.camerainfo info = new camera.camerainfo();
    camera.getcamerainfo(cameraid, info);
    int rotation = getwindowmanager().getdefaultdisplay().getrotation();
    int degree = 0;
    switch (rotation) {
      case surface.rotation_0:
        degree = 0;
        break;
      case surface.rotation_90:
        degree = 90;
        break;
      case surface.rotation_180:
        degree = 180;
        break;
      case surface.rotation_270:
        degree = 270;
        break;
    }

    orientionofcamera = info.orientation;
    int result;
    if (info.facing == camera.camerainfo.camera_facing_front) {
      result = (info.orientation + degree) % 360;
      result = (360 - result) % 360;
    } else {
      result = (info.orientation - degree + 360) % 360;
    }
    camera.setdisplayorientation(result);
  }

  @override
  public void onclick(view v) {
    switch (v.getid()) {
      case r.id.bt_camera:
        if (camera != null) {
          try {
            camera.takepicture(null, null, new mypicturecallback());
          } catch (exception e) {
            e.printstacktrace();
          }
        }
        break;
    }
  }
}