How to draw a rounded rectangle (a rounded rectangle) using OpenCV?

Question

How to draw a rounded rectangle in OpenCV? I know that the ellipse () and line () functions can simply be built to draw. I'm just wondering if someone has done this before and put it in the correct function so that I can use it? Ideally, the angle radius should be calibrated with a parameter.

I searched a lot for this, but it seems like he didn’t have this problem before. If no one has such a function, I will probably post my solution here in a few days.

Answer 1

I realized this is a lot easier than I thought. Here is my function. I hope this will be helpful to someone.

/** * Draws a rectangle with rounded corners, the parameters are the same as in the OpenCV function @see rectangle(); * @param cornerRadius A positive int value defining the radius of the round corners. * @author K */ void rounded_rectangle( Mat& src, Point topLeft, Point bottomRight, const Scalar lineColor, const int thickness, const int lineType , const int cornerRadius) { /* corners: * p1 - p2 * | | * p4 - p3 */ Point p1 = topLeft; Point p2 = Point (bottomRight.x, topLeft.y); Point p3 = bottomRight; Point p4 = Point (topLeft.x, bottomRight.y); // draw straight lines line(src, Point (p1.x+cornerRadius,p1.y), Point (p2.x-cornerRadius,p2.y), lineColor, thickness, lineType); line(src, Point (p2.x,p2.y+cornerRadius), Point (p3.x,p3.y-cornerRadius), lineColor, thickness, lineType); line(src, Point (p4.x+cornerRadius,p4.y), Point (p3.x-cornerRadius,p3.y), lineColor, thickness, lineType); line(src, Point (p1.x,p1.y+cornerRadius), Point (p4.x,p4.y-cornerRadius), lineColor, thickness, lineType); // draw arcs ellipse( src, p1+Point(cornerRadius, cornerRadius), Size( cornerRadius, cornerRadius ), 180.0, 0, 90, lineColor, thickness, lineType ); ellipse( src, p2+Point(-cornerRadius, cornerRadius), Size( cornerRadius, cornerRadius ), 270.0, 0, 90, lineColor, thickness, lineType ); ellipse( src, p3+Point(-cornerRadius, -cornerRadius), Size( cornerRadius, cornerRadius ), 0.0, 0, 90, lineColor, thickness, lineType ); ellipse( src, p4+Point(cornerRadius, -cornerRadius), Size( cornerRadius, cornerRadius ), 90.0, 0, 90, lineColor, thickness, lineType ); } 

Answer 2

The Python implementation is implemented here (in case someone was looking for it): it draws a rounded corner (random radius and line thickness --- change this if you want) on the border around the image:

 def addRoundedRectangleBorder(img): height, width, channels = img.shape border_radius = int(width * random.randint(1, 10)/100.0) line_thickness = int(max(width, height) * random.randint(1, 3)/100.0) edge_shift = int(line_thickness/2.0) red = random.randint(230,255) green = random.randint(230,255) blue = random.randint(230,255) color = (blue, green, red) #draw lines #top cv2.line(img, (border_radius, edge_shift), (width - border_radius, edge_shift), (blue, green, red), line_thickness) #bottom cv2.line(img, (border_radius, height-line_thickness), (width - border_radius, height-line_thickness), (blue, green, red), line_thickness) #left cv2.line(img, (edge_shift, border_radius), (edge_shift, height - border_radius), (blue, green, red), line_thickness) #right cv2.line(img, (width - line_thickness, border_radius), (width - line_thickness, height - border_radius), (blue, green, red), line_thickness) #corners cv2.ellipse(img, (border_radius+ edge_shift, border_radius+edge_shift), (border_radius, border_radius), 180, 0, 90, color, line_thickness) cv2.ellipse(img, (width-(border_radius+line_thickness), border_radius), (border_radius, border_radius), 270, 0, 90, color, line_thickness) cv2.ellipse(img, (width-(border_radius+line_thickness), height-(border_radius + line_thickness)), (border_radius, border_radius), 10, 0, 90, color, line_thickness) cv2.ellipse(img, (border_radius+edge_shift, height-(border_radius + line_thickness)), (border_radius, border_radius), 90, 0, 90, color, line_thickness) return img