GIMP Version: 2.10.38
Operating System: Windows
GIMP Experience: Intermediate Level

List any relevant plug-ins or scripts:
G'mic

---

What I'm after:
A jagged 'broken glass' border (without fancy lighting effects, etc) or the cartoon speech balloon they use for really extreme noise/speech.

What I do:
Put guides about 100 pixels (more for big pictures) in from each edge. Layers are 800-3000 pixels.

Use the freehand tool, clicking only, to draw a crude sawtooth from the outside edge to the inner edge of the border, all around the layer's edge.
(if you don't make it all the way to the edge, with even one point, your border will have a glitch. If you go too far, a point will have a flattened point. Snapping helps.)

Invert selection, so the portion between the jagged line and the outside edge is selected.

Delete, replace, fill, whatever - what's selected is between the outside edge and the jagged line.

Is there a tool, procedure, or plugin I can use to draw this border, or something like it? My searches are clogged with people trying to get rid of pixel-level jaggies, and not very helpful. Even better if it works on shapes other than rectangles.

If you have a path (in blue, below), you can use my path-waves script to make a triangular wave around it (red):

That's most of the hard stuff. Thanks.

If I could modulate the asymmetry with randomness that would be close to really nice. Modulate the asymmetry AND frequency, either from noise or more waveforms, or color values - hog heaven. But that's my modular synth background - EVERY reasonable plugin parameter should be able to be modulated, and there should be a reasonable selection of modulation sources - bitmap values, phase and distance or proportion around a center point, height, width, random sources...

Looks like I'll go and see if I can wrestle the python. The pseudocode is straightforward enough...
The other option, I suppose, is to start with that then attack it with other editing tools.

If you did that in a really long, really tight spiral with the CD data, you could Rickroll people with basically a facsimile of the vinyl.

After some Roller experimentation, I was able to make an icy-jag edge with on an ellipse using a Plaque/Mask/Fringe.

That's a different approach. I'll mess with that. So far I've been baffled by the plethora of brushes, and just use the same three or four.