how com from the number of neighborhood size of adaptthresh

Hello all,

I've tried the neighborhood size as default for adaptthresh as in figure attached.

The value 42 I know it come from, But I dont know how come the value 26 from?

anyone can explain to me?

>> bb=2*floor(size(spect)/16)+10

bb =

    42    42    26

[Image Analyst]

What is the size of your image, and what is the size of spect?

[mohd akmal masud]

My image is spect

the spect size is 256x256x142

[DGM]

That parameter is the size of a rectangular window which has odd geometry and is at least size(I)/16 in radius. Note two things. First, the trailing addend is 1, not 10.

x = [256 256 142];
y = 2*floor(x/16)+1

y = 1×3

33 33 17

Second, if you want the window width to be 2*floor(size(I)/16)+1, you don't need to specify it. That's just how it's calculated internally by default.

As to why it needs to be odd, that's often desirable for one of two reasons. First, an odd window gives you a clear center pixel. Second, since the median is being calculated, it gives you a clear central order statistic.

As to why it's size(I)/16, I don't know off the top of my head. I'd have to look at the references and the code.

[mohd akmal masud]

Thank you @Image Analyst and @DGM, I understand.