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# | |
# The Python Imaging Library. | |
# $Id$ | |
# | |
# global image statistics | |
# | |
# History: | |
# 1996-04-05 fl Created | |
# 1997-05-21 fl Added mask; added rms, var, stddev attributes | |
# 1997-08-05 fl Added median | |
# 1998-07-05 hk Fixed integer overflow error | |
# | |
# Notes: | |
# This class shows how to implement delayed evaluation of attributes. | |
# To get a certain value, simply access the corresponding attribute. | |
# The __getattr__ dispatcher takes care of the rest. | |
# | |
# Copyright (c) Secret Labs AB 1997. | |
# Copyright (c) Fredrik Lundh 1996-97. | |
# | |
# See the README file for information on usage and redistribution. | |
# | |
from __future__ import annotations | |
import math | |
class Stat: | |
def __init__(self, image_or_list, mask=None): | |
try: | |
if mask: | |
self.h = image_or_list.histogram(mask) | |
else: | |
self.h = image_or_list.histogram() | |
except AttributeError: | |
self.h = image_or_list # assume it to be a histogram list | |
if not isinstance(self.h, list): | |
msg = "first argument must be image or list" | |
raise TypeError(msg) | |
self.bands = list(range(len(self.h) // 256)) | |
def __getattr__(self, id): | |
"""Calculate missing attribute""" | |
if id[:4] == "_get": | |
raise AttributeError(id) | |
# calculate missing attribute | |
v = getattr(self, "_get" + id)() | |
setattr(self, id, v) | |
return v | |
def _getextrema(self): | |
"""Get min/max values for each band in the image""" | |
def minmax(histogram): | |
res_min, res_max = 255, 0 | |
for i in range(256): | |
if histogram[i]: | |
res_min = i | |
break | |
for i in range(255, -1, -1): | |
if histogram[i]: | |
res_max = i | |
break | |
return res_min, res_max | |
return [minmax(self.h[i:]) for i in range(0, len(self.h), 256)] | |
def _getcount(self): | |
"""Get total number of pixels in each layer""" | |
return [sum(self.h[i : i + 256]) for i in range(0, len(self.h), 256)] | |
def _getsum(self): | |
"""Get sum of all pixels in each layer""" | |
v = [] | |
for i in range(0, len(self.h), 256): | |
layer_sum = 0.0 | |
for j in range(256): | |
layer_sum += j * self.h[i + j] | |
v.append(layer_sum) | |
return v | |
def _getsum2(self): | |
"""Get squared sum of all pixels in each layer""" | |
v = [] | |
for i in range(0, len(self.h), 256): | |
sum2 = 0.0 | |
for j in range(256): | |
sum2 += (j**2) * float(self.h[i + j]) | |
v.append(sum2) | |
return v | |
def _getmean(self): | |
"""Get average pixel level for each layer""" | |
return [self.sum[i] / self.count[i] for i in self.bands] | |
def _getmedian(self): | |
"""Get median pixel level for each layer""" | |
v = [] | |
for i in self.bands: | |
s = 0 | |
half = self.count[i] // 2 | |
b = i * 256 | |
for j in range(256): | |
s = s + self.h[b + j] | |
if s > half: | |
break | |
v.append(j) | |
return v | |
def _getrms(self): | |
"""Get RMS for each layer""" | |
return [math.sqrt(self.sum2[i] / self.count[i]) for i in self.bands] | |
def _getvar(self): | |
"""Get variance for each layer""" | |
return [ | |
(self.sum2[i] - (self.sum[i] ** 2.0) / self.count[i]) / self.count[i] | |
for i in self.bands | |
] | |
def _getstddev(self): | |
"""Get standard deviation for each layer""" | |
return [math.sqrt(self.var[i]) for i in self.bands] | |
Global = Stat # compatibility | |