How can I count pixels which are touching each other?

Hi everyone, I am new to MATLAB and I need to find out how to count Red color pixels above a certain threshold which are touching each other. By knowing the size of one pixel in [mm] I would like to get the length of the pixels touching each other. Could you help me to develop a code for that? Thank you in advance.

[John BG]

Hi Mustafa

this is John BG <mailto:[e-mail] [e-mail]>

would it be possible for you to attach an image to your question, and then tell what 'reds' do you consider above threshold, and what 'reds' should be ignored.

As you well point out, there has to be a threshold to whether tell a pixel is 'attached' to the pixel being observed, or to discard the neighbour pixels as 'not red enough'.

100% saturated red has RGB values [1 0 0].

But [.8 0 0] is also red. Or [.8 .1 .1] too.

So what kind of threshold do you have in mind to make the decision?

John BG

<mailto:[e-mail] [e-mail]>

[BAM]

Sorry for the unclear question. Saying red pixels I mean only red color channel from RGB ( interested in thresholding only the Red channel pixels brightness). I would like to threshold video frames which have brightness value 1.10 times more than the first frame (used as a reference brightness value).