Morphological Operations

Hi all,

I am stuck again with a problem and wanted to ask for some advice.

I have bin images like this one: 

https://www.dropbox.com/s/tgulsr1amo9asrq/Image.tif?dl=0

And I want to be those (red marked) boarders as clear as possible. They should be idealy white lines:

https://www.dropbox.com/s/2xx5xph0nbde5rk/imageA.tif?dl=0

So I'm playing around with Morphologial Image Operations but I don't get it right. Or should I try something totaly different?

Any help would be great.

Thanks,

Flo