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I want to do something similar to this post: sample code.

How can I change the given code to work for float images in "tiff"- format?

this is what I tried:

import os, numpy, PIL
from PIL import Image

# Access all PNG files in directory
os.chdir("c://users//Student///Desktop//bilder//" )
print "Current working dir : %s" % os.getcwd()

allfiles=os.listdir(os.getcwd())
imlist=[filename for filename in allfiles if  filename[-5:] in [".tiff",".tiff"]]
#imlist=[filename for filename in allfiles]

# Assuming all images are the same size, get dimensions of first image
w,h=Image.open(imlist[0]).size
N=len(imlist)

# Create a numpy array of floats to store the average (assume RGB images)
arr=numpy.zeros((h,w,1),numpy.float)

# Build up average pixel intensities, casting each image as an array of floats
for im in imlist:
    imarr=numpy.array(Image.open(im),dtype=numpy.float)
    arr+=imarr/N

# Round values in array and cast as 8-bit integer
arr=numpy.array(numpy.round(arr),dtype=numpy.uint8)

# Generate, save and preview final image
out=Image.fromarray(arr,mode="F")
out.save("Average.tiff")
out.show()

which produces this error:

File "C:\Users\Student\im_average.py", line 25, in <module>
    arr+=imarr/N
ValueError: non-broadcastable output operand with shape (250,250,1) doesn't match the broadcast shape (250,250,250)

I am not familiar with numpy arrays, so any help is welcome.

Jason Aller
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user3759978
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1 Answers1

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Doing imarr/N would do it inplace and would convert the dtype to integer of the array. So, use N=float(N)

Refer to http://docs.scipy.org/doc/numpy/user/basics.indexing.html#assigning-values-to-indexed-arrays

Please note assignments may result in changes if assigning higher types to lower types (like floats to ints) or even exceptions (assigning complex to floats or ints).

Mujtaba Hasan
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