Drawing bounding rectangles around multiple objects in binary image in python

Drawing bounding rectangles around multiple objects in binary image in python

The simplest way to do that in Python/OpenCV is to get the contours. Then loop over each contour and get its bounding box and draw it on the image and print it.

Input:

import cv2
import numpy as np

# read image
img = cv2.imread(two_blobs.jpg)

# convert to grayscale
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

# threshold
thresh = cv2.threshold(gray,128,255,cv2.THRESH_BINARY)[1]

# get contours
result = img.copy()
contours = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
contours = contours[0] if len(contours) == 2 else contours[1]
for cntr in contours:
    x,y,w,h = cv2.boundingRect(cntr)
    cv2.rectangle(result, (x, y), (x+w, y+h), (0, 0, 255), 2)
    print(x,y,w,h:,x,y,w,h)
 
# save resulting image
cv2.imwrite(two_blobs_result.jpg,result)      

# show thresh and result    
cv2.imshow(bounding_box, result)
cv2.waitKey(0)
cv2.destroyAllWindows()

Bounding boxes image:

Texual results:

x,y,w,h: 262 267 37 45
x,y,w,h: 212 143 97 55

Drawing bounding rectangles around multiple objects in binary image in python