this post was submitted on 07 Mar 2024
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I know this might be a bit too specific, but I'll ask anyway.

Is there any FOSS app for Android that supports tracing photos that can export the trace to SVG? I suppose this means it would have to support layers, and also support the ability to export individual layers instead of the whole project as SVG.

The intent is to use my Galaxy Tab with S-pen to trace objects in a photo in order create an SVG I can import into an app like Carbide Create (not FOSS either, but it's all I know how to sorta use at the moment) for cutting on a CNC. An example is a photo of one of my chickens. I wanted to turn this photo into a silhouette of said chicken and be able to cut that on a plank of wood. I did try Inkscape, but due to the background elements it would not pick up just the chicken during the "Trace Bitmap" operation. And honestly seems like a shame to not be able to use the S-pen for this type of project.

I run Linux on my home PC and I'm not sure if it will support using the tablet like a drawing tablet (Wacom type) like Windows can, but I suppose that is an option.

I looked at Infinite Design (not FOSS) but could not seem to find a free trace tool. There is a "pen" tool, but it wants to constrain it to a line and then you sorta pull the curves out of it. I apologize, I'm not really sure what all of the terms are.

I also looked at Excalidraw, which while being web app, runs reasonably well on Android. But some of the functions either don't work at all or I'm doing something wrong. I was able to import a photo and trace it, but couldn't find a way to export just the trace outline.

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[–] [email protected] 7 points 8 months ago (1 children)

If you're OK with using inkscape and GIMP, if the background color is different than the chicken, you could apply a color filter to simplify the image to "chicken" and "not chicken" (basically, reduce the number of total colors to 16 or less), then use inkscape Trace Bitmap in Colors mode.

Tracing a bitmap to an SVG is really only practical if it's a line drawing or if it has less than 16 (preferably less than 8) colors, because each color becomes a different vector object. Its really not intended for full on photos, unfortunately.

[–] [email protected] 3 points 8 months ago (1 children)

That makes sense, I'll have to try that. It would be a silhouette of said chicken. Thanks!

[–] [email protected] 2 points 8 months ago (1 children)
[–] [email protected] 4 points 8 months ago (1 children)
[–] [email protected] 3 points 8 months ago (1 children)

If you're ok with using your tablet as a drawing tablet with your PC, I use an app called Virtual Tablet for that. Sadly it appears to be Windows and MacOS only, but a quick search led to Weylus. I have no idea how well this works and never tried it, but from the readme it sounds pretty good.

[–] [email protected] 2 points 8 months ago

That looks promising! Thank you.

[–] [email protected] 2 points 8 months ago (1 children)

I also looked at Excalidraw, which while being web app, runs reasonably well on Android. But some of the functions either don't work at all or I'm doing something wrong. I was able to import a photo and trace it, but couldn't find a way to export just the trace outline.

After you trace the photo, can't you delete the photo from the canvas and just save as SVG? Won't it save just the trace if that's all there is?

[–] [email protected] 1 points 8 months ago* (last edited 8 months ago)

See? This is why I asked. I figured if nothing else, someone would have a better idea than what I've been trying! That totally works! I'll have to try it more to see if it can do what I want. Thanks!

EDIT: yep, this idea works!

[–] [email protected] 1 points 8 months ago (1 children)

Just manually trace it using your mouse. It'll take like 5 minutes, at most.

[–] [email protected] 2 points 8 months ago

I suppose you're right. But I've got this neat tablet here and I wanna use it! That and I want to do this on multiple projects, not just this example.

[–] [email protected] 1 points 8 months ago

Inkscape has a bmp to vector tool. It's quite good too. Depending on input of course.