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high pass filter for digital image to remove noise in real time

Hi all,

             I am trying to write a code for filtering noise from a speckled image. I am working on speckle interferometry, and need some help to improve to quality of the images. I am looking for 2D high pass or low pass filter which can filter a digital image in 1/50 of a sec ( with CCD camera frame rate). If some body has any idea about this please let me know, it would be great help. All i have to do is acquiring an image which i can do now with a LabView programme and using IMAC 1409, after acquiring this image i need to filter it and also subtract with subsequent frame.

 

 

Regards

Visu

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Many people did this before you, so it really makes no sense to make this
yourself. Unless you are working on a real time target, you can use external
libraries.

There are a lot of libraries out there, for AX, .NET, c#, c++, c, and many
others, like phyton. I'd search for a library that has a C API, and
preferably has a binary dll for download. Then all you need to do is find
out how it works, and how to connect your IMAQ image to it...

Whether you can do this in real time depends on your resolution, processor
speed, nr of processors, processor type, available memory, memory speed, and
probably most important, your image resolution.

Regards,

Wiebe.


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Hi Visu

 

There is a Lowpass filter writen within LabVIEW (IMAQ LowPass) this has been optimized for multicore prosessing and runs pretty efficiently - what kind of speeds are you getting using this filter?

 

If you want a High pass then you could create one of these within LabVIEW - do a gradient filter to detect the scale of the peaks/noise that you have. Threshhold this and use the threshold image as a mask for doing an averaging filter. This would average out the smaller noise variation without effecting the larger jumps.

 

Which of these two filter processes do you need High or low pass?

Is the speed of your system the main issue with low pass or is it the filtering itself?

 

best regards

Graham Green

Sr. Product Marketing Manager

National instruments
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Hi, Graham,

 

You wrote: "...There is a Lowpass filter writen within LabVIEW (IMAQ LowPass) this has been optimized for multicore prosessing and runs pretty efficiently..."

 

Sorry, but I can't recognize any advantages of IMAQ LowPass on the DualCore system. See attachment. When this VI running, then I have approx. 50% CPU load, and no any effect when I set 2 cores with IMAQ Multi-Core Options. This take always approx. 60 - 70 ms for 5x5 low pass on 1024x1024 8 bit image.

 

I'm missing something?

 

Upd:

Sorry, forgot technical data:

LabVIEW 8.6f1; Vision 8.6.1; WinXP Prof SP3; Intel Core2 6700 CPU

 

Andrey.

 

Message Edited by Andrey Dmitriev on 11-19-2008 02:21 PM
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Hi all,

          Thanks for the reply. It was very useful. i tried low pass filter built in IMAC vision. I saw some sratnge noise when the VI was executed. i dont know reasons but it is working. I actually need HIgh pass filter. Thanks Beiwe  for the VI but i could open it because i am using LV8.2 version. As Grahams said i will try to design high pass filter and will see if it works or not. If it works then i will post in here.

 

if any has high pass filter already please post here i will adjust settings according to the image requirement in my work.

 

Cheers

Visu 

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"...(IMAQ LowPass) this has been optimized for multicore prosessing and runs pretty efficiently..."

 

Definitively not. Just perform comparizon between different Vision versions and see:

 

 

 

Now interesting, which functions are optimized for multicore, and which not yet? 

Andrey.

 

Message Edited by Andrey Dmitriev on 11-20-2008 07:33 PM
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Hi Andrey,

 

If you look at the LabVIEW Vision Development Module 8.6 readme this will give you a list of functions that have been optimsed for multicore systems.

 

You are right in stating the IMAQ Low Pass has not been optimised in this release.

Please let me aplogise about the earlier posting suggesting otherwise.

 

I hope the readme document will tell you all you need to know regarding the improvements to the VDM.

 

Regards
JamesC
NIUK and Ireland

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