mirror of
https://github.com/Hopiu/django-imagekit.git
synced 2026-03-17 05:40:25 +00:00
18 lines
574 B
Python
18 lines
574 B
Python
import math
|
|
from imagekit.lib import Image
|
|
|
|
|
|
def histogram_entropy(im):
|
|
"""
|
|
Calculate the entropy of an images' histogram. Used for "smart cropping" in easy-thumbnails;
|
|
see: https://raw.github.com/SmileyChris/easy-thumbnails/master/easy_thumbnails/utils.py
|
|
|
|
"""
|
|
if not isinstance(im, Image.Image):
|
|
return 0 # Fall back to a constant entropy.
|
|
|
|
histogram = im.histogram()
|
|
hist_ceil = float(sum(histogram))
|
|
histonorm = [histocol / hist_ceil for histocol in histogram]
|
|
|
|
return -sum([p * math.log(p, 2) for p in histonorm if p != 0])
|