Reading and Displaying Images using NumPy¶
Images can be read into numpy, and are stored as multi-dimensional arrays.
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#Needed to display images inline in Jupyter
%matplotlib inline
####################################
from numpy import *
from matplotlib.pyplot import *
from scipy.misc import imread
Reading an image in NumPy works like this:
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im = imread('bieber.jpg')
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imshow(im)
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im is a 3-D array:
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im.shape
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For example,
im[4, 5, 0] is the red component of the pixel in the upper-left corner at coordinates (4, 5)
im[4, 5, 1] is the green component of the pixel in the upper-left corner at coordinates (4, 5)
im[4, 5, 2] is the blue component of the pixel in the upper-left corner at coordinates (4, 5)
We can get the whoe pixel like this:
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im[4, 5, :]
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The pixel intensity values are of type uint8, meaning they range from 0 to 255.
We can get the red channel like this:
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r = im[:, :, 0]
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imshow(r, cmap=cm.gray)
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As you can see, in the red channel, the maple leaf is almost invisible (why?)
On the other hand, in the green channel, the maple leaf is black. (Why?)
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imshow(im[:,:,1], cmap=cm.gray)
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