reading values from an image

If I have a matrix of coordiantes (centres=[xii, yii]) for the locations of objects on an image.

How can I read an average of all the values back within a 2 pixel radius of each of the spots.

and any ideas on how to measure approximately the backgorund?

Thanks

[Geoff Hayes]

Jason - do your coordinates correspond to the red dots in the above figure? Would your values within a 2 pixel radius of each of the spots correspond to a 5x5 block/window whose centre is the spot?

[Jason]

Hi, yes teh red dots correpsond to my coordinates. I would really like to have a userdefined radius (say 2 to begin with) but a circle not a square block.

I've worked out how to create a binary image from these red dot locations and was wondering if it was the best way to use that as a mask?

[Adam]

Have you tried using imdilate on your binary image?

[Jason]

Yes this is a great idea, thankyou.