Hi all,
I am following Jan Erik Solem's book "Programming Computer Vision with
Python" and I'm just on the first chapter. The book asked us to create a
file imtools.py and put down helpful functions there, which we can just
call later.
There is a function created for histogram equalization of images (called *
histeq*), and saved in imtools.py. When I use this function and type this
in IDLE:
>>> from PIL import Image
>>> from numpy import *
>>> im = array(Image.open('Tulips.jpg').convert('L'))
>>> im2,cdf = imtools.histeq(im)
I get this:
Traceback (most recent call last):
File "<pyshell#59>", line 1, in <module>
im2,cdf = imtools.histeq(im)
File "C:\Python27\imtools.py", line 18, in histeq
imhist,bins = histogram(im.flatten(),nbr_bins,normed=True)
NameError: global name 'histogram' is not defined
And the relevant portion in imtools.py is:
def histeq(im,nbr_bins=256):
""" Histogram equalization of a grayscale image. """
#get image histogram
imhist,bins = histogram(im.flatten(),nbr_bins,normed=True)
cdf = imhist.cumsum() #Cumulative distribution function
cdf = 255* cdf/cdf[-1] #Normalize
#Use linear interpolation of cdf to find new pixel values
im2 = interp(im.flatten(), bins[:-1],cdf)
return im2.reshape(im.shape), cdf
------------------------------------
Can anybody point out where I'm going wrong? I have Python 2.7, NumPY,
SciPY etc.
Thanks very much
Python Newbie!
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