Android、OpenCV：检测颜色和绘制轮廓

Question

如何只在黑色物体上绘制轮廓，而将背景中的其他所有物体填充为白色？我的代码目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);

Answer 1

您应该创建并应用遮罩，就像回答 this 问题一样。例如，您可以通过这种方式执行此操作（在您的 Imgproc.findContours() 调用而不是 for (int contourIdx = ...:

之后插入下面的代码

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

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

Android、OpenCV：检测颜色和绘制轮廓

Android, OpenCV: Detect color & Draw Contours

android

opencv

mask

image-processing

opencv-contour