threshold values

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

Answer 1

[the cyclist]

Does this do what you want?

p = 255*(p>=0.9);

[Sivakumaran Chandrasekaran]

Thanks cyclist.

In an image, i have to find the threshold value.

the pixels having threshold values less than 0.9 should be converted to zero.

Your code does not matches my requirement

[Image Analyst]

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]

+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?

Answer 2

[Ricky]

you could try this:

p = 255;

i = find(p < 0.9);

p(i) = 0;

[Geoff]

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.

Answer 3

[Sivakumaran Chandrasekaran]

Hi, Thanks all for guiding me

Answer 4

[Neesha Sahl]

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.