Re: [Gimp-user] Strugglign with Smooth Edges

[Ofnuts <ofnuts laposte net>]

On 03/09/14 19:38, NoWhizzKid wrote:
> > I think we have a question for you: how did you create that? Because
> > it's likely more an error you do than a wrong technique.
> >
> > If you want smooth outlines, you should create them using the path
> > tool
> > <http://docs.gimp.org/en/gimp-using-paths.html>, then create a
> > selection
> >from the path (Select>From path) and then bucket-fill the selection.
> > With the path tool, the smoother lines are those created with the
> > least
> > nodes, and where the tangent handles on each node are symmetrical.
> >
> > A path done using you existing foot as a guide, then used for a
> > selection and bucket-filled:
> >
> > http://imgur.com/Phb0SHA
> Oh lord, lol. I am so grateful for your reply, and the image that you have
> attached is absolutely perfect - 100% what I am after. But I'm afraid I just
> don't understand most of what you have explained to me with regards to tangent
> handles, nodes etc. I am such an amateur!
>
> I will experiment with the path tool, but is there any way you could explain
> briefly how to start? The image I attached was originally a photograph of a
> paint footprint. I used the alpha channel to remove the background, then
> smoothed out the outline as best I could with the eraser and finally colourised
> the image. I appreciate this isn't the right way of doing things as the image
> doesn't look good! But I've taught myself how to use GIMP and it's still a
> struggle as I am a real novice!
>
> Thanks so much again for your reply :)

OK, so now I start t understand what happened to you. To remove the 
background, I assume that you used the layer mask technique. This can 
work well if you use a soft brush (ie a round brush with "fuzzy 
borders"). There are a few in the standard brushes (called "Hardness 
100" (very hard), "Hardness 075" (medium hard), "Hardness 050", 
"Hardness 025"). This produces smooth lines because the edge pixels of 
the foot print are partially transparent(*). And to colourize the image 
you applied a selection from the Fuzzy select (magic wand) or the Color 
select. Unfortunately these tools do an all-or-nothing job. Either the 
pixel is fully selected or it is not selected at all. So when you apply 
paint, the pixels that were subtly partially transparent become fully 
opaque, and there are no anti-aliasing pixels left and your outline 
becomes jaggy. Instead, you should have used the alpha lock to protect 
the partial transparency of these pixels.

In other words, your technique is OK if you are careful, and the Path 
tool isn't necessary in this case (even if in many cases, it can solve 
the problem in a totally different way, as seen in my first post).


(*) see 
http://gimpforums.com/thread-proper-subject-extraction-background-removal-and-background-painting