CODEWITHSUNDEEP
pythonimagenumpyopencv
ClassicWhat
ClassicWhat

Reputation: 25

Coordinates of an object Python

Image

I am trying to find the position of the rectangle in the image. Considering the top part of the image as reference, how can I find the position of the rectangle? I want the coordinates of the four vertices.

I have tried findContours and bounded rectangle method but have not been able to get the coordinates. Help would be appreciated.

Upvotes: 0

Views: 3116

Answers (2)

kevinkayaks
kevinkayaks

Reputation: 2726

just adapting the cv2 tutorial, you can find the largest contour and then obtain its bounding rectangle.

img = cv2.imread('/home/kvnp/Desktop/v02J6.jpg',0) #read in the image with correct dtype 

_,thresh = cv2.threshold(img,200,255,0) # threshold the image 

_,contours,_ = cv2.findContours(thresh, 1, 2) # find the contours

cnt = sorted(contours, key = lambda c: -len(c))[0] # order from largest to smallest and select the largest 

x,y,w,h = cv2.boundingRect(cnt) # make bounding rectangle around the largest contour 

corners = np.array([[x,y],[x+w,y],[x+w,y+h],[x,y+h]]) # make array of corners sorted clockwise

This image I get 

>>> corners 

array([[371,   1],
   [900,   1],
   [900, 430],
   [371, 430]])

Upvotes: 1

Lev Zakharov
Lev Zakharov

Reputation: 2427

Just get contour and then find bounding rectangle. Check this tutorial from official documentation. 

import cv2

img = cv2.imread('image.jpg')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
ret, thresh = cv2.threshold(gray, 80, 255, cv2.THRESH_BINARY)

_, contours, _ = cv2.findContours(thresh,
                                  cv2.RETR_TREE,
                                  cv2.CHAIN_APPROX_NONE)

x1, y1, w, h = cv2.boundingRect(contours[0])
x2, y2 = x1 + w, y1 + h
print((x1, y1), (x2, y2)) 
cv2.rectangle(img, (x1, y1), (x2, y2), (0, 255, 0), 2)

cv2.imwrite('res.jpg', img)

Coordinates of upper-left and lower-right points of rectangle ((x1, y1), (x2, y2)):

(369, 0) (901, 433)

Result:

res.jpg

Upvotes: 2

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