November 2018
Intermediate to advanced
492 pages
12h 19m
English
Content preview from Hands-On Image Processing with Python
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Down-sampling and anti-aliasing
As we have seen, down-sampling is not very good for shrinking images as it creates an aliasing effect. For instance, if we try to resize (down-sample) the original image by reducing the width and height a factor of 5, we shall get such patchy and bad output.
Anti-aliasing
The problem here is that a single pixel in the output image corresponds to 25 pixels in the input image, but we are sampling the value of a single pixel instead. We should be averaging over a small area in the input image. This can be done using ANTIALIAS (a high-quality down-sampling filter); this is how you can do it:
im = im.resize((im.width//5, im.height//5), Image.ANTIALIAS)pylab.figure(figsize=(15,10)), pylab.imshow(im), pylab.show() ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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