Drawing images and shapes using OpenCV

Let's start off my making a black square



In [1]:

    
import cv2
import numpy as np

# Create a black image
image = np.zeros((512,512,3), np.uint8)

# Can we make this in black and white?
image_bw = np.zeros((512,512), np.uint8)

cv2.imshow("Black Rectangle (Color)", image)
cv2.imshow("Black Rectangle (B&W)", image_bw)

cv2.waitKey(0)
cv2.destroyAllWindows()

Let's draw a line over our black sqare

cv2.line(image, starting cordinates, ending cordinates, color, thickness)



In [3]:

    
# Draw a diagonal blue line of thickness of 5 pixels
image = np.zeros((512,512,3), np.uint8)
cv2.line(image, (0,0), (511,511), (255,127,0), 5)
cv2.imshow("Blue Line", image)

cv2.waitKey(0)
cv2.destroyAllWindows()

Let's now draw a rectangle

cv2.rectangle(image, starting vertex, opposite vertex, color, thickness)



In [4]:

    
# Draw a Rectangle in
image = np.zeros((512,512,3), np.uint8)

cv2.rectangle(image, (100,100), (300,250), (127,50,127), -1)
cv2.imshow("Rectangle", image)
cv2.waitKey(0)
cv2.destroyAllWindows()

How about cirlcles?

cv2.cirlce(image, center, radius, color, fill)



In [5]:

    
image = np.zeros((512,512,3), np.uint8)

cv2.circle(image, (350, 350), 100, (15,75,50), -1) 
cv2.imshow("Circle", image)
cv2.waitKey(0)
cv2.destroyAllWindows()

And polygons?



In [6]:

    
image = np.zeros((512,512,3), np.uint8)

# Let's define four points
pts = np.array( [[10,50], [400,50], [90,200], [50,500]], np.int32)

# Let's now reshape our points in form  required by polylines
pts = pts.reshape((-1,1,2))

cv2.polylines(image, [pts], True, (0,0,255), 3)
cv2.imshow("Polygon", image)
cv2.waitKey(0)
cv2.destroyAllWindows()

Let's even add text with cv2.putText

cv2.putText(image, 'Text to Display', bottom left starting point, Font, Font Size, Color, Thickness)

FONT_HERSHEY_SIMPLEX, FONT_HERSHEY_PLAIN
FONT_HERSHEY_DUPLEX,FONT_HERSHEY_COMPLEX
FONT_HERSHEY_TRIPLEX, FONT_HERSHEY_COMPLEX_SMALL
FONT_HERSHEY_SCRIPT_SIMPLEX
FONT_HERSHEY_SCRIPT_COMPLEX



In [7]:

    
image = np.zeros((512,512,3), np.uint8)

cv2.putText(image, 'Hello World!', (75,290), cv2.FONT_HERSHEY_COMPLEX, 2, (100,170,0), 3)
cv2.imshow("Hello World!", image)
cv2.waitKey(0)
cv2.destroyAllWindows()



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