Thinning out lines?

[awow27]

Hi everyone! I'm fairly new to gimp.

So, I want to make the lines of this diamond render thinner than they are.



I'm planning to use it as a border for another image, so really the thinnest line possible would be great. I've tried using the eraser, but it ends up being uneven. I've also tried just using different selection tools so I could cut it, but I can't find one that will select it in the shape I need (ie not in a horizontal rectangle/circle).

Any help would be greatly appreciated

[Espermaschine]

You will get the best possible quality result by drawing a path and then stroking the path. Even with very thin, or curved lines.

Its possible to use a filter like Generic -> Dilate or G'MIC Morphological, but stroking a path is what i would strongly recommend !

[Ofnuts]

Yes, making  a diamond takes a few seconds, so better do your own diamond from scratch using paths.

[TechnicGeek]

@Espermaschine

How would you make lines thinner by stroking path? You would reduce selection then and hit "Del" key or you would do the opposite of "Grow" (if that's possible) and then reduce selection by a few pixels from edges, do invert selection and hit "Del" key?

[Ofnuts]

(01-23-2018, 10:34 AM)TechnicGeek Wrote: @Espermaschine

How would you make lines thinner by stroking path? You would reduce selection then and hit "Del" key or you would do the opposite of "Grow" (if that's possible) and then reduce selection by a few pixels from edges, do invert selection and hit "Del" key?

You create  a path (perhaps using the old image as a template)(four clicks...), add a new layer, stroke the path on that new layer, and discard the initial image.

   

This gives you plenty of options, such as thickness of the line, color, sharp or round summits...

[Espermaschine]

Yeah, thats a misunderstanding. You dont make the existing lines thinner by stroking a path.

Some beginners seem to think its a good idea to dabble around with Gimp and then fix what they have done.
Thats not a very efficient approach.

You learn the tools and build your designs with the possibilitis you have.
In this case the best way of making lines is stroking a path.

In some cases you can use the Brush/Pencil Tool with Shift (to make a line) and CTRL (to restrict angle), but its not as flexible or editable like paths.

[gramp]

OTOH, if you "really" had to thin some thick lines, it might be done by subtracting one selection from another.

Let's say you have a drawing with 5px-wide lines. Select the outside edge of the figure, shrink it by 3 px, and save the selection to a path, say, "Minus3." Do the same with a path shrunk only 2px, saved to "Minus2."

On the Paths tab, right-click on the Minus2 path and choose Path-to-Selection. Then right-click Minus3 and "Subtract from Selection", leaving, theoretically at least, a 1 px interior. Invert the selection and hit delete key to get rid of the unselected fat parts.

(I like to start from outside and shrink, rather than inside and grow, because the former tends to preserve detail, while the latter doesn't know what to do at sharp corners, so rounds them.)

[Espermaschine]

Nine days and no reply.

[gramp]

There is also an interest in the general case of "thinning regions to their central lines". The central line can be guessed at by selecting the region and "shrinking" to smaller and smaller selections, but the process doesn't care anything about preserving single pixels in a line.

I was trying to find out more about it a few days ago:
https://stackoverflow.com/questions/6955...ong-region
which references this project (which then discusses Hilditch's Algorithm):
http://cgm.cs.mcgill.ca/~godfried/teachi...tml#define

A skeletonizing tool would be useful for finding the centerlines for later stroking, to replace a rough area with a smoother one.