How to get distance between 2 pixels in IMSHOW

Hi all,

I am developing one code to get a picture, convert it to BW because I need to measure the distance between the edges of a sample that to what I have to make pictures. i have used canny filter to obtain edges, and I have the picture here if you have a look.

Then , what I would like to do is, something to measure in the picture window, this distance. I have tried with h = imdistline but I have to zoom in a lot to get preccision.

I have tried also to load impixelregion but I don't know how I can load a measure tool inside this window. That would be great to measure in this window by handling. Where I can find out about this?

Thanks a lot.

This is the picture.

http://img842.imageshack.us/img842/4342/pd0o.png