I need a little help with blurring

[bobhwantstoknow]

Hello,

I have a very simple black and white image that I will use as a mask. I would like to blur the image to smooth the hard edges. But I do not want the black parts of the image to get any lighter. I only want the white parts to get darker. Is there an easy way to do that?

Thanks

[fmw42]

-blur 0xsigma -level 50x100%

or

-blur radiusx65000 -level 50x100%

for a proper linear blur that the -level can split at the halfway part

[bobhwantstoknow]

This works great. Thankyou.