java - OpenCV检测ROI，创建子垫并复​​制到原始垫

我正在尝试使图像中所有人的脸变灰。虽然我可以检测到他们的脸并将它们变灰成较小的垫子，但是我无法将灰色的脸“复制”到原始垫子上。这样最终结果将具有所有面为灰色的垫。

        faceDetector.detectMultiScale(mat, faceDetections);
        for (Rect rect : faceDetections.toArray())
        {
            Rect rectCrop = new Rect(rect.x, rect.y, rect.width, rect.height);
            Mat imageROI = new Mat(mat,rectCrop);

            //convert to B&W
            Imgproc.cvtColor(imageROI, imageROI, Imgproc.COLOR_RGB2GRAY);

            //Uncomment below will grayout the faces (one by one) but my objective is to have them grayed out on the original mat only.
            //Highgui.imwrite(JTestUtil.DESKTOP_PATH+"cropImage_"+(++index)+".jpg",imageROI);

            //add to mat? doesn't do anything :-(
            mat.copyTo(imageROI);
        }

最佳答案

imageROI是3或4通道图像。将cvtColor转换为灰色可提供单通道输出，并且可能会破坏imageROI对mat的引用。

使用缓冲区进行灰度转换，并以dst作为imageROI转换回RGBA或RGB。

faceDetector.detectMultiScale(mat, faceDetections);
    for (Rect rect : faceDetections.toArray())
    {
        Rect rectCrop = new Rect(rect.x, rect.y, rect.width, rect.height);
        //Get ROI
        Mat imageROI = mat.submat(rectCrop);

        //Move this declaration to onCameraViewStarted
        Mat bw = new Mat();

        //Use Imgproc.COLOR_RGB2GRAY for 3 channel image.
        Imgproc.cvtColor(imageROI, bw, Imgproc.COLOR_RGBA2GRAY);
        Imgproc.cvtColor(bw, imageROI, Imgproc.COLOR_GRAY2RGBA);
    }

结果看起来像