How to Draw a rectangle in Opencv Python

As we all know a image in nothing a 2d graph in which several pixels are there arranging rows and colum

Note : I am assuming that you image is in the same folder where your python code is saving if you then you need to give proper directory

Input image :

import cv2

a = cv2.imread("1.jpg")

l = cv2.rectangle(a,(0,0),(250,250),(250,0,0),3)

cv2.imshow("rectangle",l)

cv2.waitKey(0)

In cv2.rectangel : a is image name on which rectangel is going to draw
the second parameter is (0,0) it is the starting point of the rectangle

the third parameter is (250,250) it is the ending point of the rectangle 
Note: the second and third parameter are the diagonal points of the rectangle

Fourth parameter is color of the rectangle (255,0,0) it means blue color
remember opencv by convention accept BGR color format

the last parameter the thickness of the rectangle if you put -1 here it will fill the rectangle

cv2 rectangle fill

Output image :