How to remove the background/background noise from the images that comprise my video?

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Yagnaseni Roy 2011-11-1

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编辑： DGM 2023-2-13

Hi,

I have a video in which a cell moves along a channel...however, the background i.e. the channel is near the brightness of that of my cell, so when I convert the video into images of its frames, and turn them into grayscale images, I cannot isolate the cell from its background very clearly, though I can faintly see it move against the background.

I tried frame subtraction..after subtracting the first frame that does not contain the cell from the remaining, I still get a lot of background noise. *Thus, when I try locating the cell by trying to identify the maximum brightness spot, *I get the locations of different other points with the greater brightness than the cell.

Can you suggest what I can do?

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Image Analyst 2011-11-3

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You can get a fairly comprehensive overview of several of the main noise removal techniques here: http://www.stanford.edu/~slansel/tutorial/software.htm The methods the web page discusses are generally thought of as the best, state of the art methods, from among thousands that have been invented and more that are invented every month.

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Yagnaseni Roy 2011-11-4

编辑：DGM 2023-2-13

I uploaded some images and they're on the links

http://imgur.com/4Yvy5

http://i.imgur.com/J1Zz2.jpg

based on what u see, is there any one of those toolbars that you would reccommend? Or could you categorize the kind of filtering I need?..or should i just download and use any one?

Yagnaseni Roy 2011-11-4

编辑：DGM 2023-2-13

D60kG.jpeg

AFTER FILTERING TWICE BY MEDFILT2....

I get the following image:

http://imgur.com/D60kG

However, the cell is NOT THE BIGHTEST SPOT here, so I cannot use the code to find the brightest spot in order to locate the cell...so do I go for any other filter, or do I choose some other criterion to locate the cell?

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更多回答（3 个）

Image Analyst 2011-11-2

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I'd suggest you post a few frames of your video somewhere so people can make informed suggestions.

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Yagnaseni Roy 2011-11-12

编辑：DGM 2023-2-13

在 MATLAB Online 中打开

its ok, i got it using:

for ii= 1:N
    hold on
    plot(x(ii),y(ii),'ro')
    hold off
end

Yagnaseni Roy 2011-11-12

SO before I end off, I'd just like to ask if there is any other function that I could try out...i didn't know about ginput before this, so I'm wondering if there are others that would serve a similar purpose...or maybe even better

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Bjorn Gustavsson 2011-11-3

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In addition to medfilt2, you can also play around with wiener2 (Lee's sigma filter). Then there are a bunc of filter functions on the file exchange. One that I'd suggest you could try is bilateral or susan filters, there are a couple of those. Then there is a few nonlinear diffusion filters - they are really fancy and powerful but might be on the slow side when it comes to filtering a large number of frames. These two types of "more advanced" filters are my favourites outside of medfilt2 and wiener2, but tastes might vary.

Another point you might have to take into account (couldn't see your images so I'm really shooting in the dark here) is that you might have photo-respons non-uniformities - pixel-to-pixel variation in sensitivity. That is something you might be able to correct for by calculating the average of the ratio between medfilt2(frame,[5,5])./frame over all frames. That might give you a correction factor for PRNU, that might make filtering easier.

Then you might have a few bright or dark spots that eats up most of your grayscale. That you can overcome by setting the intensity limits manually or by doing some histogram clipping automatically.

I'm just tossing up a few ideas that I know can be useful, hopefully some of them helps.

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Yagnaseni Roy 2011-11-4

Also, please note that in some other videos that I will be working on with MATLAB, there are multiple cells(looking exactly like the cell i showed in the images)....but I need to trace the position and velocity of any one of those...so would the filters that you are referring to meet this requirement? i.e. can i eliminate one of two completely similar looking objects?

Yagnaseni Roy 2011-11-4

编辑：DGM 2023-2-13

AFTER FILTERING TWICE BY MEDFILT2....

I get the following image:

https://www.mathworks.com/matlabcentral/answers/uploaded_files/1293760/D60kG.jpeg

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i Venky 2011-11-4

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Use top hat or bottom hat. It is used to reduce illumination

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Yagnaseni Roy 2011-11-7

移动：DGM 2023-2-13

it didn't work too well with me...since the cell is so similar to its background, it itself gets invisible when I use imtophat..any other suggestions?

Yagnaseni Roy 2011-11-11

移动：DGM 2023-2-13

The problem is that my background isn't constant at all. Even after applying imtophat or imbothat, it doesn't completely help.

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