OpenCV 相机预览中未显示蒙版

我想制作一个简单的 Android 应用程序，它在使用 OpenCV 检测到的面部上放置面具，如下例所示：

人脸面具检测教程 http://opencvexamples.blogspot.com/2013/11/putting-mask-on-face-using-opencv.html

我将 C++ 翻译成 Java 来用于我的应用程序。遮罩的大小得到了很好的调整，白色部分被消除了（我在预览中的 ImageView 中显示了测试结果），但遮罩从未出现在绿色矩形中检测到的脸上：

结果截图 https://i.stack.imgur.com/rDRH6.jpg

我的代码：

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
             [...]

    for( int i = 0; i < facesArray.length; i++)
        min_face_size = facesArray[0].width*0.7;
        max_face_size = facesArray[0].width*1.5;
        Point center=new Point (facesArray[i].x + facesArray[i].width/2, facesArray[i].y + facesArray[i].height/2);
        mRgba=putMask(mRgba,center, new Size(facesArray[i].width, facesArray[i].height));
    }
    return mRgba;
}

Mat putMask(Mat src, Point center, Size face_size)
{

    //mask : loaded mask image
    Mat mask1 = new Mat(); //resized mask
    src1 = new Mat(); //ROI
    m = new Mat();

    Imgproc.resize(mask ,mask1,face_size);

    // ROI selection
    roi = new Rect((int) (center.x - face_size.width/2), (int) (center.y - face_size.height/2),(int) face_size.width, (int) face_size.height);
    //Rect roi = new Rect(100, 100, (int) face_size.width, (int) face_size.height);
    src.submat(roi).copyTo(src1);


    // to make the white region transparent
    Mat mask2 = new Mat(); //greymask
    m1= new Mat();
    Imgproc.cvtColor(mask1,mask2, Imgproc.COLOR_BGR2GRAY);
    Imgproc.threshold(mask2,mask2,230,255, Imgproc.THRESH_BINARY_INV);

    ArrayList<Mat> maskChannels = new ArrayList<>(3);
    ArrayList<Mat> result_mask = new ArrayList<>(3);
    result_mask.add(new Mat());
    result_mask.add(new Mat());
    result_mask.add(new Mat());

    Core.split(mask1, maskChannels);

    Log.e(TAG, "MASK maskChannels :"+maskChannels.get(0).size());
    Log.e(TAG, "MASK mask2 :"+mask2.size());

    Core.bitwise_and(maskChannels.get(0),mask2, result_mask.get(0));
    Core.bitwise_and(maskChannels.get(1),mask2, result_mask.get(1));
    Core.bitwise_and(maskChannels.get(2),mask2, result_mask.get(2));
    Core.merge(result_mask, m);        


    Core.subtract(mask2, new Scalar(255), mask2);

    ArrayList<Mat> srcChannels = new ArrayList<>(3);
    Core.split(src1, srcChannels);
    Core.bitwise_and(srcChannels.get(0),mask2, result_mask.get(0));
    Core.bitwise_and(srcChannels.get(1),mask2, result_mask.get(1));
    Core.bitwise_and(srcChannels.get(2),mask2, result_mask.get(2));
    Core.merge(result_mask,m1);        


    Core.addWeighted(m,1,m1,1,0,m1);    

    m1.copyTo(src.submat(roi));

    return src;
}

=============

感谢@hariprasad :)这里是工作代码：

 onCreate(){
          [...]
                try {
                    File file = new File(Environment.getExternalStorageDirectory(), "1-alpha.png");

                    mask = Imgcodecs.imread(file.getPath(), -1);

                }catch (Exception e){
                    e.printStackTrace();
                }
        }


Mat putMask(Mat src, Point center, Size face_size)
{

    //mask : masque chargé depuis l'image
    Mat mask_resized = new Mat(); //masque resizé
    src_roi = new Mat(); //ROI du visage croppé depuis la preview
    roi_gray = new Mat();


    Imgproc.resize(mask ,mask_resized,face_size);

    // ROI selection
    roi = new Rect((int) (center.x - face_size.width/2), (int) (center.y - face_size.height/2),(int) face_size.width, (int) face_size.height);
    //Rect roi = new Rect(10, 10, (int) face_size.width, (int) face_size.height);

    src.submat(roi).copyTo(src_roi);

    Log.e(TAG, "MASK SRC1 :"+ src_roi.size());

    // to make the white region transparent
    Mat mask_grey = new Mat(); //greymask
    roi_rgb = new Mat();
    Imgproc.cvtColor(mask_resized,mask_grey, Imgproc.COLOR_BGRA2GRAY);
    Imgproc.threshold(mask_grey,mask_grey,230,255, Imgproc.THRESH_BINARY_INV);

    ArrayList<Mat> maskChannels = new ArrayList<>(4);
    ArrayList<Mat> result_mask = new ArrayList<>(4);
    result_mask.add(new Mat());
    result_mask.add(new Mat());
    result_mask.add(new Mat());
    result_mask.add(new Mat());

    Core.split(mask_resized, maskChannels);

    Core.bitwise_and(maskChannels.get(0),mask_grey, result_mask.get(0));
    Core.bitwise_and(maskChannels.get(1),mask_grey, result_mask.get(1));
    Core.bitwise_and(maskChannels.get(2),mask_grey, result_mask.get(2));
    Core.bitwise_and(maskChannels.get(3),mask_grey, result_mask.get(3));

    Core.merge(result_mask, roi_gray);        

    Core.bitwise_not(mask_grey,mask_grey);

    ArrayList<Mat> srcChannels = new ArrayList<>(4);
    Core.split(src_roi, srcChannels);
    Core.bitwise_and(srcChannels.get(0),mask_grey, result_mask.get(0));
    Core.bitwise_and(srcChannels.get(1),mask_grey, result_mask.get(1));
    Core.bitwise_and(srcChannels.get(2),mask_grey, result_mask.get(2));
    Core.bitwise_and(srcChannels.get(3),mask_grey, result_mask.get(3));

    Core.merge(result_mask, roi_rgb);          

    Core.addWeighted(roi_gray,1, roi_rgb,1,0, roi_rgb); 

    roi_rgb.copyTo(new Mat(src,roi));

    return src;
}

src.submat(roi)不等于src(roi)在 C++ 中。因为在 C++ 中src(roi)实际上修改的是src数据矩阵在 roi 区域但在 java 中submat正在克隆 src 的 roi。因此对 roi 所做的任何更改都不会影响 src，这就是为什么您在相机预览中没有任何内容。 要使其正确，您需要使用像 C++ 这样的构造函数 即使用

m1.copyTo(new Mat(src,roi));

代替

 m1.copyTo(src.submat(roi));