Lost... doubling a single line?

You can do a centerline trace in Inkscape

Inkscape has the same trouble that any centerline trace has. When you have a t-shape intersection or one with more than two vectors at a single point, the algorithm used to determine the centerline tends to fail. I’ve also had zero success getting Inkscape’s centerline trace to work, but that could be operator error and general lack of enthusiasm.

I’ve had the same problem, and basically given up on tracing. It hardly ever provides a usable result, the best you can hope for is something that won’t take longer to fix than create from scratch. My use case is importing images of things I want to cut out, so a double line is no use to me. After a lot of experimenting my workflow now is to manually trace the part in another CAD package, then import the .dxf file it produces into LB. You can do manual tracing in LB too, but its CAD functionality is limited, and anyway I’m already familiar with my CAD package.
Can you burn the image as a straight image, without tracing it first? Like burning a picture or something? There are a couple of good instructional videos provided by LB about how to do this by adjusting the various controls.

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I’m a little confused about your reaction. Although I offer you a solution that only takes a few minutes to make, you consider it a “problem” or error of the program. - Centerline tracing is a function that is not currently supported. and not a problem. As mentioned, it takes less time to delete all inner lines after tracing, if the motif is as simple as yours, than finding it online. And if it has to be 100% precise, I will also trace it more accurately.


Thanks for the help. I think I just misunderstood what you were saying. After playing around with the software some more im understanding it a little more.

I agree. Some of the simple projects I do work fine with centerline trace, but I dropped the OP image into Inkscape and I couldn’t get it to centerline properly. I ultimately did a normal trace and deleted the lines that I wouldn’t want, effective and probably the fastest way to do it with current software.

I would like to go back to this statement and ask, how did you create this art? What software did you use and how did you construct it? As a bitmap or as a vector? If vector, you should be able to set the entire job to ‘Line’ mode and do exactly what you are after.

I appreciate everyone’s suggestion. I’m picking up things w everyone’s comments. I haven’t quite figured out how to delete the inner or outer line after tracing. The easiest solution I have come for MYSELF within my realm of knowledge with the software is to invert the image colors so instead going around the lines it goes around the larger white shapes of the image. It seemed to work that way. Hopefully they do an update for centerline soon! :sweat_smile:

This is going to take a significant amount of effort, many have tried, unsuccessfully. If ‘centerline tracing’ was an easy problem to solve, you would already be able to find good solutions available. :wink:

This may be an issue of not understanding all the options and how best to get the trace you want. Tracing Images - LightBurn Software Documentation Your task may require multiple traces of the same image, changing the settings each time to capture the desired sections. Would need to see an example to offer suggestions for your exact case, but here I use ‘Trace Image’, then remove some resulting traced elements, to isolate the outline of a dog to use as a mask.

I take, “It hardly ever provides a usable result, the best you can hope for is something that won’t take longer to fix than create from scratch.” as a challenge. I accept! :wink: So, what artwork are you trying to trace (share example), what settings did you try, and what results are you getting?

Here is a quick workup I did in Photoshop Elements and should be able to do in any editor that supports layers and has a " Fill " tool.

There may be an easier way, but each color could be treated as a seperate layer, then traced successfully, then burned as " Lines "…

The saws and axes could be treated as separate images and burned with " scan " …to get more detail without double lines.

I think others have already hinted at this work-flow…

The take away is that you need a solid image to do a successful trace.

My application is tracing plans for model aeroplanes I download from the net, a pretty basic process. Tracing shapes in FB always produces two lines which consist of multiple segments. Selecting all unwanted segments and deleting them is a time consuming and onerous task. I also find that the traces often include spurious spikes and gaps and other bits that shouldn’t be there, as the plan may have parts drawn over the top of other parts, or text may appear across the middle of a part, or there may be gaps in the lines for no apparent reason. The plans may also be quite fuzzy, (especially if they are old plans that have been photocopied) around joints for instance, which causes problems with tracing. Also, text on the plan is traced which I don’t want for cutting, so it has to be removed as well.
I have found that it is quicker for me to manually trace the parts I want using a CAD package, and produces a better result, as i can often improve the quality of the plan (or part) to remove slight deviations or imperfections in the original, and at the same time use fewer segments (lines) for each part. I find I can draw circles and curves more accurately than trace will draw them, and ensure lines that are supposed to be parallel, normal or symmetrical are, in fact, parallel, normal or symmetrical.
I get that tracing works quite well for some applications, but I have found that for me, manually tracing works better and requires less effort.
I’ve uploaded a couple of plans for you to have a look at. I haven’t tried tracing the Corsair as I was pretty sure it wouldn’t work properly, old plans like this frequently have the grain of the balsa indicated by the multiple short lines on the part, which would also be traced and take forever to clean up. Ditto the wavy lines to indicate a ply part. The Ag120 is a more modern plan that I suspect was created with CAD so may be more amenable to tracing. Enjoy.


If the intent is to generate a ‘cut-ready pattern’, then I can completely understand the requirement for significant editing to produce usable paths, using any commonly available tracing software, from these examples, yes.

A challenge I can not solve, I must admit. The source is the source of the issue here, making tracing a less reasonable solution in this case, correct.

But to say, “It hardly ever provides a usable result…”, I had to try. There are many instances where ‘Trace Image’ produces fantastic results. It all depends on the design goal. Case-sensitive. :wink:

I did some ‘Image Trace’ testing…

I have your top drawing copied and loaded into LightBurn. The miserable quality / resolution means that I do not even bother to start a trace attempt. It should be fair to judge a feature or tool. If your image is scaled up to 1:25 ???, you will not even be able to saw it out with a good band saw with a usable end product as a result. Drawings in this resolution will always require a lot of extra work. But if you find proper drawings, you could save a week’s work on such an aircraft model.
In my example, from finding a random image on the web until I posted it here, including text and small test in google-translate, it honestly took me under 5 minutes. The best thing is, if I trace and cut out my gears, they are ready to use! (without extra work)
It is about using the right tool for the right task.

It’s not a religious war I want to start, certainly not, I just think it’s a shame that people can not get the best out of the things that are available.

Fair point. I withdraw the “hardly ever” comment, or perhaps I should qualify it to “hardly ever produced results for my particular use case at my skill level and knowledge level that I was happy with.” I apologise for any perceived slur on your fine product, none was intended.

I tried it again in FB, and found that @bernd.dk’s comment is valid. Scaling up from the screenshots of the plans is never going to give a perfect image for tracing, pixellation will ensure there are always going to be wobbles and anomalies. There will be some cases where it will give a good result, for other cases it’s back to plan A, manually tracing the part.


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It depends on the accuracy you are looking for, and I am basing it on simply recreating images mathematically, where it’s about creating shapes that are symmetrical etc. Like gaskets, gears, etc. Taking @bernd.dk example, it takes longer to recreate mathematical than 5 minutes. Took me about 30 minutes. Three of the shapes are the same, just different scale and slight rotations. The other three are the same with different scale and rotations, and 1 item has the bottom chopped off. In this 6 gear example, I only had to design 1 of them, and then scale and add some inside cutouts.Gears.lbrn (92.8 KB)

RalphU, I wrote that it honestly did not take me 5 minutes.
I cut and pasted a random image into LightBurn and traced (all gears together) with the basic settings almost unchanged. When the objects are so finely delimited and the lines are intact, and if it is even a “fill” subject, it takes no time. The cut gear should only show that it is a simple cut and paste. You have already had to settle for a screenshot of a copy.

@bernd.dk I understood what you did. Tracing images in LB is OK for some things. But @mogplus8 is building scale airplanes, where the parts have to fit together. I don’t think that LB trace image for his need is the right tool. I rarely use any software for bitmap tracing, because I have the time to create the files with less nodes in CAD…hint…retired :slight_smile:

@RalphU you got it in one, Ace! Retired too, and loving it. I also have to confess to enjoying the process of manual tracing, I find it almost meditative, so for me it is not a chore. And, as you correctly state, drawing parts with precise dimensions is a requirement for them to fit together properly in the final product.

With many of the plans I work with the parts are often drawn as an approximation, and given that some (most?) were originally hand drawn, inaccuracies are inevitable. In the old days you transferred the part onto the wood to make the part (usually with a pin) then cut it out and sanded it to approximately the right shape, then modified it until it fitted properly where you wanted it to go, so the final part could be quite different to the drawing. So the part drawings were more like guidelines that precise shapes.

Today it’s possible to draw the parts with CAD and make them exactly the right shape to make them fit precisely where they are supposed to fit, then cut them out precisely with a cnc cutter and everything just clicks together! No sanding, no shaping, no slicing fingers with sharp blades, no blood all over the plan. Brilliant!

I agree with @bernd.dk though, that if you have a good source drawing, LB’s tracing function is extremely accurate and easy to use, and produces excellent results. It certainly works very well on images that would be impossible to manually trace, as in the examples @Rick has provided. But as he also mentioned a lot depends on the quality of the source image. If the quality is poor no tracing tool is going to work satisfactorily.

In my case, scaling up drawings from screenshots, pixellation is always going to be an issue, and drawings I’m trying to trace will always be average at best. So, for me, if I can use LB tracing I’ll use it. If not, it’s back to the drawing board!


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