CODEWITHSUNDEEP
pythonopencv
RyeRai
RyeRai

Reputation: 118

OpenCV Python count pixels

I'm working with a little project with application of OpenCV and I'm stuck with something that I don't know how to implement. Suppose I have an image (1024x768). In this image there is a red bounding box at the center.

Is it possible to count the pixels inside the red box using OpenCS? given that the image is 1024x768 in dimension.

I tried to use bounding rectangle by thresholding the red color and tried using convexhull but then I can't extract how many pixels are inside the red marker.

Upvotes: 6

Views: 20346

Answers (1)

I.Newton
I.Newton

Reputation: 1783

That's simple. Clearly the inner gray and outer colour are different. just threshold the image. 

ret,thresh=cv2.threshold(img,133,255,cv2.THRESH_BINARY_INV)

Then use:

cv2.countNonZero(your_thresh_img)

That gives you the number of white pixels, which is the count you need. In your Image, it was 183920 pixels.

Edit

import numpy as np
import cv2

img=cv2.imread("your_image.png",0)

def nothing(x):
  pass

cv2.namedWindow('image')

cv2.createTrackbar('min','image',0,255,nothing)
cv2.createTrackbar('max','image',0,255,nothing)

while(1):

 a = cv2.getTrackbarPos('min','image')
 b = cv2.getTrackbarPos('max','image')
 ret,thresh=cv2.threshold(img,a,b,cv2.THRESH_BINARY_INV)
 cv2.imshow("output",thresh)
 k = cv2.waitKey(10) & 0xFF
 if k == 27:
    break
print cv2.countNonZero(thresh)
cv2.destroyAllWindows()

Upvotes: 12

Related Questions