How to find the width of the red area using opencv or any other python library?

Question

The red image above is the health meter for enemy units in a game. I got a python application that takes a screenshot and it must be able to determine the percentage of health remaining. In this case it would be ~70%, given the size of the red bar. I tried several ways from google Bard AI suggestions but none work 100%. How should I proceed?

Answer 1

Here is one way to do that in Python/OpenCV. Just threshold using cv2.inRange(). Then get the bounding box of the white region from the thresholded image. Then get the width of the bounding box as a percentage of the width of the image.

Input:

import cv2
import numpy as np

# read input
img = cv2.imread('red_bar.png')
hh, ww = img.shape[:2]

# threshold on red
lower=(0,0,140)
upper=(40,40,220)
thresh = cv2.inRange(img, lower, upper)

# get bounding box
x,y,w,h = cv2.boundingRect(thresh)

# print width of red as percent of width of image
width = 100*(w-x)/ww
print("percent width:", width)

# save results
cv2.imwrite('red_bar_thresh.png', thresh)

# show results
cv2.imshow('thresh', thresh)
cv2.waitKey(0)

Thresholded Image:

Text Output:

percent width: 60.13986013986014