creating a boundary of object as separate image?

STCB

I have a circular object in a binary image. I assumed I could run a "distance map" (2D morphology filter) and the boundary of the object would be represented by pixels which have an intensity of "1". I could then threshold the distance map image with threshold limits of 1 and 1 and this would give me a single pixel boundary image? When i ran the distance map however and inspected the bitmap i could not find any pixels with value of 1? distance map image attached.

YuriG

Distance map in 2D filters creates a 16-bit image where pixel intensities are scaled.
Distance map of 3D filters creates a floating point image without intensity scaling, so please check 30 distance map, you will have intensity of 1 there.

Yuri

DavidW

Another way to extract the boundary of the object would be to apply a Sobel or Roberts filter to your mask instead to extract the edge. You can apply a thinning filter to it afterwards if needed to make sure it is only a pixel thick.