[SciPy-User] Image with black points

[Nicolau Werneck]

What result are you expecting anyway? This all looks very natural to
me. The FFT is always symmetric, and your black points are the
locations where the curves cross the zero from negative to positive
values. They are also happening a lot more in the noisy,
high-frequency regions, that probably don't matter much to your
application. (Face image analysis?)

++nic


On Wed, Apr 27, 2011 at 9:04 PM, Paulo Henrique Junqueira Amorim
<paulojamorim at gmail.com> wrote:
> Hi Bruno,
>
> Yeah Bruno, how could only one of them?
>
> Thx,
> Paulo
>
>
> On 26 April 2011 23:10, Bruno George <bgeorge98121 at gmail.com> wrote:
>>
>> Hi,
>> You know the two images are mirroring (flopped) to each other?
>>
>> Bruno George
>>
>> On Mon, Apr 25, 2011 at 10:15 AM, Zachary Pincus <zachary.pincus at yale.edu>
>> wrote:
>>>
>>> On Apr 24, 2011, at 10:22 PM, Paulo Henrique Junqueira Amorim wrote:
>>>
>>> > Hi,
>>> >
>>> > I'm computing the 1D fft from image, and saving the image of
>>> > frequency.
>>> >
>>> > But the saved image appears black point's (example image), it seems
>>> > that do not belong.
>>> >
>>> > Is this correct? How could I remove it?
>>> >
>>> > Example image - http://img818.imageshack.us/i/fftthreshold.png/
>>> >
>>> > Code:
>>> >
>>> > import scipy
>>> > import numpy
>>> >
>>> > r = scipy.misc.pilutil.imread('face.jpg', 'F')
>>> >
>>> > fft = numpy.fft.fftshift(numpy.fft.fft(r).real)
>>> > fft_2d = numpy.log10(numpy.abs(fft))
>>> > pil_array = scipy.misc.pilutil.toimage(fft_2d)
>>> >
>>> > scipy.misc.pilutil.imsave('fft.tif', pil_array)
>>> >
>>>
>>> If you could provide the input image that would be helpful for people
>>> trying to determine what the issue is.
>>>
>>> As a stab in the dark -- have you checked (from python) what the
>>> values of at the "black points" are? Are they NaNs? (Perhaps from the
>>> log10 operation?)
>>>
>>> Zach
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>>
>>
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-- 
Nicolau Werneck <nwerneck at gmail.com>         C3CF E29F 5350 5DAA 3705
http://www.lti.pcs.usp.br/~nwerneck                   7B9E D6C4 37BB DA64 6F15
Linux user #460716