Finding contours and midpoints of color squares in an image

Question

I have an image with color squares in it:

I am trying find contours for the color squares, as well as the midpoints of the color squares to find the pixel value.

Answer 1

You can use HSV colour space, but you have to pick a range of colour by hand.

change the H value based on colour and keep the entire range of 0-255 for both S and V or you can limit these as well to be more specific.

Then you can use contours to draw a bounding box around the detected contour and find the centre.

Here's the code

import cv2
import numpy as np
from matplotlib import pyplot as plt

img = cv2.imread('UQjNf.jpg')

hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)

bi = np.zeros((hsv.shape[:2]),np.uint8)

bi[np.where((((hsv <= [20,255,255]) & (hsv >= [20,0,0])) | (hsv <= [21,255,255]) & (hsv >= [21,0,0]) | ((hsv <= [22,255,255]) & (hsv >= [22,0,0])) ).all(axis = 2))] = [255]

plt.imshow(bi)
plt.xticks([]), plt.yticks([])  # to hide tick values on X and Y axis
plt.show()

Here's one such colour that came out nicely

Hope it helps.