Draw geometric shapes on images using OpenCV
Last Updated :
04 Jan, 2023
OpenCV provides many drawing functions to draw geometric shapes and write text on images. Let’s see some of the drawing functions and draw geometric shapes on images using OpenCV.
Some of the drawing functions are :
cv2.line() : Used to draw line on an image.
cv2.rectangle() : Used to draw rectangle on an image.
cv2.circle() : Used to draw circle on an image.
cv2.putText() : Used to write text on image.
To demonstrate the uses of the above-mentioned functions we need an image of size 400 X 400 filled with a solid color (black in this case). Inorder to do this, We can utilize numpy.zeroes function to create the required image.
Python3
import numpy as np
import cv2
img = np.zeros(( 400 , 400 , 3 ), dtype = "uint8" )
cv2.imshow( 'dark' , img)
cv2.waitKey( 0 )
cv2.destroyAllWindows()
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Output :
Now, let’s draw some geometric shapes on this solid black image.
Draw a line :
cv2.line(imageObjectName, (‘start_coordinates’), (‘end_coordinates’), (‘color_in_bgr’), ‘line_thickness’)
Python3
import numpy as np
import cv2
img = np.zeros(( 400 , 400 , 3 ), dtype = "uint8" )
cv2.line(img, ( 20 , 160 ), ( 100 , 160 ), ( 0 , 0 , 255 ), 10 )
cv2.imshow( 'dark' , img)
cv2.waitKey( 0 )
cv2.destroyAllWindows()
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Output :
Draw a rectangle :
cv2.rectangle(imageObjectName, (‘top_left_vertex_coordinates’), (‘lower_right_vertex_coordinates’), (‘stroke_color_in_bgr’), ‘stroke_thickness’)
Python3
import numpy as np
import cv2
img = np.zeros(( 400 , 400 , 3 ), dtype = "uint8" )
cv2.rectangle(img, ( 30 , 30 ), ( 300 , 200 ), ( 0 , 255 , 0 ), 5 )
cv2.imshow( 'dark' , img)
cv2.waitKey( 0 )
cv2.destroyAllWindows()
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Output :
Draw a Circle :
cv2.circle(imageObjectName, (‘center_coordinates’), (‘circle_radius’), (‘color_in_bgr’), ‘stroke_thickness’)
Python3
import numpy as np
import cv2
img = np.zeros(( 400 , 400 , 3 ), dtype = "uint8" )
cv2.circle(img, ( 200 , 200 ), 80 , ( 255 , 0 , 0 ), 3 )
cv2.imshow( 'dark' , img)
cv2.waitKey( 0 )
cv2.destroyAllWindows()
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Output :
Writing text :
cv2.putText(imageObjectName, ‘TextContent’, (‘text_starting_point_coordinates’), ‘fontToBeUsed’, ‘font_size’, (‘text_color’, ‘text_thickness’, ‘line_type’)
Python
import numpy as np
import cv2
img = np.zeros(( 400 , 400 , 3 ), dtype = "uint8" )
font = cv2.FONT_HERSHEY_SIMPLEX
cv2.putText(img, 'GeeksForGeeks' , ( 50 , 50 ),
font, 0.8 , ( 0 , 255 , 0 ), 2 , cv2.LINE_AA)
cv2.imshow( 'dark' , img)
cv2.waitKey( 0 )
cv2.destroyAllWindows()
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Output :
Applications of drawing shapes on images :
- Drawing geometrical shapes can help us highlight the particular portions of an image.
- Geometrical shapes like line can help us point or identify particular regions in image.
- Writing text on certain regions of images can add description to that region.
Reference :
https://docs.opencv.org/2.4/modules/core/doc/drawing_functions.html
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