threshold values

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Sivakumaran Chandrasekaran
Answered: Neesha Sahl on 3 Apr 2019
My threshold value=0.9
If the pixel value is less than 0.9, I have to set it to zero...
else set it to 255.
What command should be used for this

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Answers (4)

the cyclist
the cyclist on 22 May 2012
Does this do what you want?
p = 255*(p>=0.9);
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Image Analyst
Image Analyst on 22 May 2012
Assuming p is your image array, it does match your requirement. If it doesn't you need to say why not, because then there would be something you didn't tell us. In your original question you did NOT say anything about "finding" a threshold value - you said that it was 0.9.
Geoff
Geoff on 22 May 2012
+1 : this does exactly what you have requested, but you might not understand why. The call (p>=0.9) returns an array of 0 or 1: 0 if the value is less than 0.9 and 1 otherwise. By multiplying by 255, this achieves your two tasks (set to zero or set to 255) simultaneously. Did you actually try it?

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Ricky
Ricky on 22 May 2012
you could try this:
p = 255;
i = find(p < 0.9);
p(i) = 0;
  1 Comment
Geoff
Geoff on 22 May 2012
This code will turn the image into a single value (255), and then do a find which will fail, rendering the last two lines of code pointless.

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Sivakumaran Chandrasekaran
Hi, Thanks all for guiding me
Neesha Sahl
Neesha Sahl on 3 Apr 2019
Can someone explain to me threshold values in simple English? Such as why I need to set a threshold value when I am running Optical Flow and how to pick the best threshold value.

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