How to draw circles with random colors in OpenCV

问题

I am using SURF algorithm to match two images with OpenCV. And I have got the keypioints.

Now I want to draw these keypoints with random colors circles.

I know how to draw a circle in OpenCV with the function cvCircle, but the color is fixed with cvScalar(r,g,b).

I want the the color of the circle of a keypoint in a image is different to the circles near it.

The library function cv::drawMatches() in OpenCV have the effect I want. But I don't know how to realize it.

Does anyone who can tell me how to draw the circles.

Thanks!

回答1:

Suppose you want to draw circles in different colors on Mat image. Here is a way to generate random colors:

RNG rng(12345);
Mat image = Mat::zeros(500, 500, CV_8UC3);     // change to the size of your image
for (int i = 0; i < circleNum; i++) {
    Scalar color = Scalar(rng.uniform(0,255), rng.uniform(0, 255), rng.uniform(0, 255));
    circle(image, center[i], radius[i], color, -1, 8, 0);
}

回答2:

cv::drawKeypoints(matOriginal, keyPoints, matOriginal);

with this method it should be posible to draw your matches.

回答3:

Just generate a list of random numbers and then convert them to int otherwise it will give an error: TypeError: Scalar value for argument 'color' is not numeric. so convert it to int and then function for circle.

color1 = (list(np.random.choice(range(256), size=3)))  
color =[int(color1[0]), int(color1[1]), int(color1[2])]  
cv.circle(img3, (x1,y1), 2,color,2)  

put your image where you want to draw circles.

来源：https://stackoverflow.com/questions/19400376/how-to-draw-circles-with-random-colors-in-opencv