opencv 图片变亮

def bianLiang(img):
    '''
      图片变亮
    '''
    gamma=0.4
    lookup=np.empty((1,256),np.uint8)
    for i in range(256):
        lookup[0,i]=np.clip(pow(i/255.0,gamma)*255.0,0,255)
    
    res=cv2.LUT(img,lookup)
    return res

去年写的, 忘记啥意思了. 备注一下吧.