How to threshold a circular symmetric gaussian kernel filter?

Two matched-filters, tuned to objects of different sizes, are applied to the tophat image, each of which are thresholded separately and combined using a binary OR operation.

The above said is a step explained in a paper I am referring currently. Here the matched filters used are Circular symmetric Gaussian, kernel ,width= 17 (pixels), sigma = 2.38 (pixels)and Circular symmetric Gaussian, kernel width= 13 (pixels), sigma = 1.5 (pixels). I created the filters using the function 'fspecial' and filtered it using 'imfilter'. Can anyone explain what does 'thresholded separately' means here.

Thanks in advance

Answer 1

[Image Analyst]

You apply one filter to the image, then threshold it to get binaryImage1. Then you apply the second filter and threshold it to get binaryImage2.

[Jyothis Jose]

Sir, in the paper to find the threshold value the following steps are done: i) The second moment of pixel values within the matched filter image are found ii) then threshold is given by T=5.25*sqrt(moment)

But when I calculated the moment I got a matrix. But the threshold value should be a single value. Can we use the function 'moment' to calculate moment of an image?

[Image Analyst]

Yes of course:

binaryImage = momentMatrix > T;

but if the moment is a matrix, then sqrt(moment) will also be a matrix!