lib_image_processing/contrast_brightness_lib.py

import cv2 

def controller(img, brightness=255, 
			contrast=127): 
	
	brightness = int((brightness - 0) * (255 - (-255)) / (510 - 0) + (-255)) 

	contrast = int((contrast - 0) * (127 - (-127)) / (254 - 0) + (-127)) 

	if brightness != 0: 

		if brightness > 0: 

			shadow = brightness 

			max = 255

		else: 

			shadow = 0
			max = 255 + brightness 

		al_pha = (max - shadow) / 255
		ga_mma = shadow 

		# The function addWeighted calculates 
		# the weighted sum of two arrays 
		cal = cv2.addWeighted(img, al_pha, 
							img, 0, ga_mma) 

	else: 
		cal = img 

	if contrast != 0: 
		Alpha = float(131 * (contrast + 127)) / (127 * (131 - contrast)) 
		Gamma = 127 * (1 - Alpha) 

		# The function addWeighted calculates 
		# the weighted sum of two arrays 
		cal = cv2.addWeighted(cal, Alpha, 
							cal, 0, Gamma) 

	# # putText renders the specified text string in the image. 
	# cv2.putText(cal, 'B:{},C:{}'.format(brightness, 
	# 									contrast), (10, 30), 
	# 			cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 0, 255), 2) 

	return cal