Analyze pixels of circular roi

[logatto]

I saw several posts about this topic, but I need to do something more than extract a circular ROI. I have to analyze only the pixels are included into the circular ROI. If I use the Mask Image, the Extract ROI and then convert it with Image to Matrix, I will achieve a square matrix that included also the point masked outside the ROI. I need an array that contains only the points included into the ROI. Is there any function to do that?

Thanks a lot.

[toineroetman]

Hello,

A while back a had almost the same problem.

I needed to exclude the points in a Circle (Annulus). See word document.

Luckily some one said use the distance.

Just use the x and y from the defined annulus subtract that from your point and then calculate the distance with Pythagoras.

If the distance is within your defined radius (from the annulus) then accept this point.

If you find a faster algorithm please let me know.

With kind regards,

Toine Roetman