import cv2
import numpy as np

# Minimum percentage of pixels of same hue to consider dominant colour
MIN_PIXEL_CNT_PCT = (1.0/20.0)

image = cv2.imread('colourblobs.png')
image_hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
h,_,_ = cv2.split(image_hsv)
bins = np.bincount(h.flatten())
peaks = np.where(bins > (h.size * MIN_PIXEL_CNT_PCT))[0]

for i,peak in enumerate(peaks):
    mask = cv2.inRange(h, peak, peak)
    blob = cv2.bitwise_and(image, image, mask=mask)
    cv2.imwrite("colourblobs-%d-hue_%03d.png" % (i, peak), blob)