I'm attempting to use the fft module in numpy:
import Image, numpy
i = Image.open('img.png')
a = numpy.asarray(i, numpy.uint8)
b = abs(numpy.fft.rfft2(a))
b = numpy.uint8(b)
j = Image.fromarray(b)
j.save('img2.png')
However, when I try and convert the numpy array back to a PIL image, I get the error:
TypeError: Cannot handle this data type
However, both a and b arrays appear to have the same data type (uint8), and doing Image.fromarray(a)
runs fine. I do notice the shapes are slightly different (a.shape = (1840, 3264, 3) vs b.shape = (1840, 3264, 2)).
I do fix this and find out which data types PIL accepts?
I think perhaps the rfft2
is being performed over the wrong axes.
By default, it uses the last two axes: axes=(-2,-1)
. The third axis represents the RGB channels. Instead, it seems more plausible that one would want to perform an FFT over the spatial axes, axes=(0,1)
:
import Image
import numpy as np
i = Image.open('image.png').convert('RGB')
a = np.asarray(i, np.uint8)
print(a.shape)
b = abs(np.fft.rfft2(a,axes=(0,1)))
b = np.uint8(b)
j = Image.fromarray(b)
j.save('/tmp/img2.png')
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