Python opencv fill circle

In all the above functions, you will see some common arguments as given below:

img : The image where you want to draw the shapes
color : Color of the shape. for BGR, pass it as a tuple, eg: (255,0,0) for blue. For grayscale, just pass the scalar value.
thickness : Thickness of the line or circle etc. If -1 is passed for closed figures like circles, it will fill the shape. default thickness = 1
lineType : Type of line, whether 8-connected, anti-aliased line etc. By default, it is 8-connected.cv.LINE_AA gives anti-aliased line which looks great for curves.

Drawing Line

To draw a line, you need to pass starting and ending coordinates of line. We will create a black image and draw a blue line on it from top-left to bottom-right corners.

Drawing Rectangle

To draw a rectangle, you need top-left corner and bottom-right corner of rectangle. This time we will draw a green rectangle at the top-right corner of image.

Drawing Circle

To draw a circle, you need its center coordinates and radius. We will draw a circle inside the rectangle drawn above.

Drawing Ellipse

To draw the ellipse, we need to pass several arguments. One argument is the center location (x,y). Next argument is axes lengths (major axis length, minor axis length). angle is the angle of rotation of ellipse in anti-clockwise direction. startAngle and endAngle denotes the starting and ending of ellipse arc measured in clockwise direction from major axis. i.e. giving values 0 and 360 gives the full ellipse. For more details, check the documentation of cv.ellipse(). Below example draws a half ellipse at the center of the image.

Drawing Polygon

To draw a polygon, first you need coordinates of vertices. Make those points into an array of shape ROWSx1x2 where ROWS are number of vertices and it should be of type int32. Here we draw a small polygon of with four vertices in yellow color.

Note If third argument is False, you will get a polylines joining all the points, not a closed shape. cv.polylines() can be used to draw multiple lines. Just create a list of all the lines you want to draw and pass it to the function. All lines will be drawn individually. It is a much better and faster way to draw a group of lines than calling cv.line() for each line.

Adding Text to Images:

To put texts in images, you need specify following things.

Text data that you want to write
Position coordinates of where you want put it (i.e. bottom-left corner where data starts).
Font type (Check cv.putText() docs for supported fonts)
Font Scale (specifies the size of font)
regular things like color, thickness, lineType etc. For better look, lineType = cv.LINE_AA is recommended.

We will write OpenCV on our image in white color.

Result

So it is time to see the final result of our drawing. As you studied in previous articles, display the image to see it.

Additional Resources

Exercises

doxygen

Generated on Tue Jul 18 2023 23:26:23 for OpenCV by 1.8.13

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Python opencv fill circle

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How to Draw Filled Circle in OpenCV Python

You can draw a filled circle in OpenCV Python by following the given steps. I highly recommend you get the “Computer Vision: Models, Learning, and Inference Book” to learn Computer Vision. How to Draw Filled Circle in OpenCV Python

Step 1

Import the OpenCV library. If OpenCV is not installed in your system then first install it using This Method.

import cv2 #cv2 is used for OpenCV library

Step 2

Now read the image from the location. In my case “C:\\AiHints” is the location and “AI.jpg” is the name of the image. Change it according to your image location and name.

image = cv2.imread("C:\\AiHints\\AI.jpg") #imread is use to read an image from a location

Step 3

Now I will draw a filled circle on the image using the following code. In the code, (80,80) is the center point, and 50 is the diameter of the circle. After that, I will specify a color for the circle (0,255,0) that is green color. The last parameter in both methods is for the filled circle. You can change any value according to your requirement.

# Both methods will give same results. You can use any method to draw filled circle. image2 = cv2.circle(image,(80,80), 50, (0,255,0),-1) #Method 1 image2 = cv2.circle(image,(80,80), 50, (0,255,0),cv2.FILLED) #Method 2

Step 4

To display the image in a specified window use ”imshow” function.

cv2.imshow("Green Filled Circle on Image",image2)

Step 5

“waitKey(0)” will display a window until any key is pressed. “destroyAllWindows()” will destroy all the windows that we created.

cv2.waitKey(0) cv2.destroyAllWindows()

Output

Green Filled Circle on Image using OpenCV

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