skintones.py

#!/usr/bin/env python3

import os
import sys
import numpy as np
import cv2

if __name__ == '__main__':
	def predicate(pixel):
		B, G, R = pixel
		#return G < 140
		return R > 1.08*G and R > 1.08*B and G > 30 and G < 140

	def repaint(V):
		global bgr
		# HSV
		sat = np.arange(0.0, 1.0, 1/256)
		hue = np.arange(0.0, 360.0, 1.0)
		H,S = np.meshgrid(hue, sat)

		picture = np.zeros((len(sat), len(hue), 3), dtype=np.float32)
		picture[:,:,0] = H
		picture[:,:,1] = S
		picture[:,:,2] = V

		bgr = cv2.cvtColor(picture, cv2.COLOR_HSV2BGR)
		bgr = (bgr * 255).astype(np.uint8)



		mask = np.apply_along_axis(predicate, 2, bgr)
		bgr[~mask] = 0

		cv2.imshow("display", bgr)


	def ontrackbar(val):
		repaint(val/255)

	cv2.namedWindow("display")
	cv2.createTrackbar('Y', 'display', 255, 256, ontrackbar)
	repaint(1.0)

	while True:
		key = cv2.waitKey(100)
		if key == -1: continue
		if key == 27: break

	cv2.destroyAllWindows()