How to fast change image brightness with python + OpenCV?

Question

I have a sequence of images. I need to average brightness of these images.

First example (very slow):

img = cv2.imread(\'test.jpg\')         


        

Answer 1

This was my solution to both increase and decrease brightness. Was having some error issues with a couple of the other answers. Function takes in a positive or negative value and alters brightness.

example in code

img = cv2.imread(path_to_image)
img = change_brightness(img, value=30) #increases
img = change_brightness(img, value=-30) #decreases

function being called

def change_brightness(img, value=30):
    hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
    h, s, v = cv2.split(hsv)
    v = cv2.add(v,value)
    v[v > 255] = 255
    v[v < 0] = 0
    final_hsv = cv2.merge((h, s, v))
    img = cv2.cvtColor(final_hsv, cv2.COLOR_HSV2BGR)
return img