image processing python

Question

I need to construct a 15x15 mean filter for an image using python.

The following is the error my code keeps producing:

Traceback (most recent call last):
  File "C:\Documents and Settings\User\My Documents\school\HUB\coding\first attempt.py", line 43, in <module>
    Array.append(Im1.getpixel((X,Y)))
  File "C:\Python27\lib\site-packages\PIL\Image.py", line 950, in getpixel
    return self.im.getpixel(xy)
IndexError: image index out of range

This is my code:

import numpy as np
from matplotlib import pyplot as plt
import Image as im
import math
import scipy as sp, Image as im, sys

def median(Array):
    sorts = sorted(Array)
    length = len(sorts)
    if not length % 2:
        return (sorts[length / 2] + sorts[length / 2-1]) / 2.0
    return sorts[length / 2]



Im1 =im.open('malaria.jpg')
#Im1.show()

[ymax,xmax] = Im1.size
print 'height =',ymax,'pixels'
print 'length =',xmax,'pixels'

Array =[]
Im2 = im.new ('RGB', (xmax-5, ymax-5))

i=5
for i in range (5, (xmax-8)):
    j=5
    for j in range(5, (ymax-8)):
        Array=[]
        k=0
        for k in range (0, 9):
            l=0
            for l in range (0, 9):
                X=(i-5+k)
                Y=(j-5+l)
                Array.append(Im1.getpixel((X,Y)))
                l+=1
            k=+1
        k=0

        m= int(np.mean(Array))
        pixel=mean,mean,mean
        Im2.putpixel ((i-5,j-5),(pixel))
        j+=1
    i+=1
print "new Image"
Im2.save('output.jpg')
Im2.show()

reptilicus · Accepted Answer · 2013-03-11 20:38:46Z

3

You should use np.convolve() to get the smoothed image. Something like

npix=15
smoothed = np.convolve(Im1, np.ones((npix, npix))/(npix**2))

should do the trick if you really want a mean filter. For the median filter use scipy.signal.medfilt

smoothed = scipy.signal.medfilt(Im1, (15, 15))

edited Mar 11, 2013 at 20:38

answered Mar 11, 2013 at 20:33

reptilicus

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iec2011007 · Accepted Answer · 2015-09-06 05:39:12Z

-1

Check out this link. And as far as mean goes mean filter is analogous to blurring or convolving with a matrix of ones(you should also normalize it) for a proper description see this

answered Sep 6, 2015 at 5:39

iec2011007

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1 Comment

kleopatra Over a year ago

Note that link-only answers are discouraged, SO answers should be the end-point of a search for a solution (vs. yet another stopover of references, which tend to get stale over time). Please consider adding a stand-alone synopsis here, keeping the link as a reference

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