android - Android，OpenCV:检测颜色并绘制轮廓

如何仅在黑色物体上绘制轮廓，并在背景白色中填充其他所有内容？
我的代码当前能够在图像上绘制轮廓:

Bitmap b = BitmapFactory.decodeByteArray(getIntent().getByteArrayExtra("byteArray"),0,getIntent().getByteArrayExtra("byteArray").length);
srcMat= new Mat();
Utils.bitmapToMat(b,srcMat);

Mat gray = new Mat();
Imgproc.cvtColor(srcMat, gray, Imgproc.COLOR_RGBA2GRAY);

Imgproc.Canny(gray, gray, 20, 20*3, 3, true);
List<MatOfPoint> contours = new ArrayList<>();
Mat hierarchy = new Mat();

Imgproc.findContours(gray,contours,hierarchy,Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
for (int contourIdx = 0; contourIdx < contours.size(); contourIdx++) {
    Imgproc.drawContours(srcMat, contours, contourIdx, new Scalar(0, 0, 255), -1);
}

Utils.matToBitmap(gray, b);
imgR.setImageBitmap(b);

最佳答案

您应该创建并应用遮罩，例如回答this问题。例如，您可以通过这种方式执行此操作(在Imgproc.findContours()调用之后而不是for (int contourIdx = ...后面插入代码:

// create Mat for mask
Mat mask =  new Mat(new Size(srcMat.cols(), srcMat.rows() ), CvType.CV_8UC1);
mask.setTo(new Scalar(0.0));

// create Scalar for color of mask objects
Scalar white = new Scalar(255, 255, 255);

// draw contours border and fill them
Imgproc.drawContours(mask, contours, -1, white, 10);
for (MatOfPoint contour: contours) {
    Imgproc.fillPoly(mask, Arrays.asList(contour), white);
}

// create mat foe masked image
Mat masked = new Mat();

// apply mask to srcMat and set result to masked
srcMat.copyTo(masked, mask);

然后将gray调用中的Utils.matToBitmap()垫更改为masked:

Utils.matToBitmap(masked, b);
imgR.setImageBitmap(b);