def change_light(image, value, channel="v"):
""" Change the light intensity of an image."""
channelDic = {"h": 0, "s":1, "v":2}
# "translate" image channel to channel index
if not channel in channelDic:
raise AttributeError("invalid channel value. Valid values are h, s, or v")
# which format (ConvNet (3, w, h) vs. Normal (w, h, 3)
reshape = False
prevShape = image.shape
if image.shape[0] == 3 or image.shape[0] == 1:
reshape = True
if image.shape[0] == image.shape[1] or (image.shape[0] == 1 and image.shape[1] == 3): # grayscale 1L, 1L, h, w OR color 1L, 3L, h, w
reshapeVector = (image.shape[2], image.shape[3], image.shape[1])
else:
reshapeVector = (image.shape[1], image.shape[2], image.shape[0]) # single row color or grayscale 1L/3L, h, w
image = image.reshape(reshapeVector)
#print "Shape",image.shape
#print "dtype",image.dtype
# convert to hsv
hsv = cv.cvtColor(image, cv.COLOR_BGR2HSV)
# hsv[:,:,2] += value - would be way faster but this does not prevent overflow (a high value gets even higher and becomes 0)
channels = cv.split(hsv)
for row in xrange(len(channels[channelDic[channel]])):
for col in xrange(len(channels[channelDic[channel]][0])):
channels[channelDic[channel]][row][col] = max(min(255, channels[channelDic[channel]][row][col]*value),0)
image = cv.cvtColor(cv.merge(channels), cv.COLOR_HSV2BGR)
# reshape back
if reshape:
image = image.reshape(prevShape)
return image
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