How to detect an object from static image and crop it from the image using openCV

Use opencv. Find the contours in the image, and then crop it. Here is the sample code.

To find the contours:

1. import cv2 
2. #reading the image  
3. image = cv2.imread("example.jpg") 
4. edged = cv2.Canny(image, 10, 250) 
5. cv2.imshow("Edges", edged) 
6. cv2.waitKey(0) 
7.  
8. #applying closing function  
9. kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (7, 7)) 
10. closed = cv2.morphologyEx(edged, cv2.MORPH_CLOSE, kernel) 
11. cv2.imshow("Closed", closed) 
12. cv2.waitKey(0) 
13.  
14. #finding_contours  
15. (cnts, _) = cv2.findContours(closed.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE) 
16.  
17. for c in cnts: 
18. peri = cv2.arcLength(c, True) 
19. approx = cv2.approxPolyDP(c, 0.02 * peri, True) 
20. cv2.drawContours(image, [approx], -1, (0, 255, 0), 2) 
21. cv2.imshow("Output", image) 
22. cv2.waitKey(0) 

The image I have used for this is,

The output is,

I’m just a beginner and will upload how to crop the image using contours once I learn.

UPDATE: Adding crop image part.

1. import cv2  
2. image = cv2.imread("example.jpg") 
3. gray=cv2.cvtColor(image,cv2.COLOR_BGR2GRAY) 
4. edged = cv2.Canny(image, 10, 250) 
5. (cnts, _) = cv2.findContours(edged.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE) 
6. idx = 0 
7. for c in cnts: 
8. x,y,w,h = cv2.boundingRect(c) 
9. if w>50 and h>50: 
10. idx+=1 
11. new_img=image[y:y+h,x:x+w] 
12. cv2.imwrite(str(idx) + '.png', new_img) 
13. cv2.imshow("im",image) 
14. cv2.waitKey(0) 

This is the output which I got after running the code. It’s accuracy is almost 100% except the 3rd image.