I have a sharp edge, black to white. I want blur this edge but just in one direction. So after the blur the gradient should start where the edge was and go in either one of the two directions.
To clarify, if I just blur then the middle of the gradient will be where the edge was. This is not what I want!
Any ideas how I can accomplish this in Gimp or Gmic?
Like a smear?
I don’t know specifically how to do it with the programs but you just convolve with a gradient kernel and it’ll have a sharp edge on one side and fade out to the other.
Make a selection and fill the selection with the gradient tool.
ninja’d by paperdigits while making screenshots
Can you not just constrain the blur area with a selection and use the motion blur tool?
Something like this: http://imgur.com/FQpEmYH
Which gives a blur along the original as: http://imgur.com/Mx07VMO
edit: a couple more (better) screenshots with a curved boundary and reversed direction (180 deg)
http://imgur.com/9KbMlAc and http://imgur.com/9yb3Xy6
Thanks for the replies so far, made me notice that I need to be more specific.
I start with this:
And I want to have either this (with the red line marking the old edge):
Or this (with the red line again marking the old edge):
BUT I’d like to have this on any kind of edge shape, e.g.:
In this last example I don’t see motion blur working.
I need this for transitions between visible (white) and invisible (black) areas in masks. So the shape could be anything.
Any ideas?
Isn’t there a motion blur filter in gimp > filters > blur
Yes but ti is one directional.It would need to recognise the normal to the edge and then motion blur parallel to the normal for each point on the edge…
ok…understand your idea…but I also don’t how to do this in gimp or gmic. 
Ha, got it!
If it is a mask you’re working with, you can also do Mask to Selection. If you’re using gimp 2.9, hit / and start typing.
