Posted by
Gluender-4 on
URL: http://imagej.273.s1.nabble.com/Re-Signal-to-Noise-Ratio-SNR-tp3687073p3687078.html
Bonjour!
>Hi everyone,
>
>There's a MATLAB function called 'wiener2' that filters a 2D image and also
>estimates the additive noise power, which is kind of a signal-to-noise
>ratio.
As you may have seen from the paper that I've
recommended earlier (see below) this task is
ill-posed. Of course, there are cases, i.e.
images, for which sufficient estimates of the
signal-to-noise ratio are possible. However, in
order to construct a true Wiener-filter you need
to know much more details than the simple
signal-to-noise ratio. Simply spoken, you need to
know it as a function of the spatial frequency.
Getting estimates of this function is much more
involved if it is at all possible.
The approach taken in my paper is very simple,
but for the described purpose it was sufficient.
In the very case one can only speak of a very
coarse approximation of a Wiener-filter because
it was a low-pass with signal-dependent cut-off
frequency. The cut-off frequency was set to the
spatial frequency where the S + N was
_approximately_ equal to N. Both S + N and N can
sometimes be extracted from appropriate image
regions...
>Does anyone in this list know if there is an ImageJ (or even a Java)
>implementation of this filter and that also gives that sort of estimation?
I don't know of such an attempt...
I should be very careful with software that
promises to do the job and without exact
knowledge of how the signal-to-noise estimates
are determined.
>Thank you all very much.
>
>[]s
>--
>Anderson Vinícius Alves Ferreira
>Intern at Lafarge Centre de Recherche
>95 rue du Montmurier - 38291 St Quentin-Fallavier - France
Best
Herbie
=================================
>On 5 July 2010 13:35, Gluender <
[hidden email]> wrote:
>
>> Bonjour,
>>
>> I agree with Joachim Wesner's statement but maybe the background of the
>> original question is of some importance...
>>
>> In certain situations approximations, e.g.
>>
>> S + N / N
>>
>> may be of some help. See for instance:
>>
>> <
http://www.gluender.de/Writings/WritingsTexts/HardText.html#Gl-1980-1>
>>
>>
>> Hi there,
>>>
>>> Sorry but measuring the SNR of a single image without reference or any
>>> a-priori-knowledge is simply mathematically IMPOSSIBLE!
>>>
>>> How do you tell what is true data, what is noise? The human vision system
>>> might imply that it is still possible, but this relies on
>>> implicit assumptions about object structure and spatial frequency spectrum
>>> of the "true" data.
>>>
>>> Mit freundlichen Grüßen / Best regards
>>>
>>> Joachim Wesner
>>> Projektleiter Optik Technologiesysteme
>>>
>>> Leica Microsystems CMS GmbH | GmbH mit Sitz in Wetzlar | Amtsgericht
>>> Wetzlar HRB 2432
>>> Geschäftsführer: Dr. Stefan Traeger | Dr. David Roy Martyr | Colin Davis
>>> www.leica-microsystems.com
>>>
>>> ---------------------
>>>
>>> Hi,
>>>
>>> Is there any ImageJ plugin to calculate the Signal-to-Noise Ratio of a
>>> single image without a reference image?
>>>
>>> I've seen some plugins that calculate the SNR of images but in all of them
>>> reference images are necessary.
>>>
>>> Thank you.
>>>
>>> []s
>>> --
>>> Anderson Vinícius Alves Ferreira
>>> Intern at Lafarge Centre de Recherche
>>> 95 rue du Montmurier - 38291 St Quentin-Fallavier - France
>>>
>>
>> Best
>> --
>>
>> Herbie
>>
>> ------------------------
>> <
http://www.gluender.de>
>>