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I've got an cylindrical object that has already been laser engraved. And I've got an identical object, with sticker instead of engraving. I want to capture the lettering, generate a SVG file and laser non-engraved objects by a professional. They can engrave round objects, but need the corresponding SVG.

The surface is evenly cylindrical, therefore no distortion in height towards the lens/transferring surface. I already tried photogrammetry, tracing using thin paper + scanning and panaroma-mode (phone). These methods have too much error in perspective, line-precision and sharpness..

My next idea was to use a motor to evenly turn it (like a "kebab machine" or lathe) and capture a video. But how to post-process it?

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  • I suppose that the stickers do not have the lettering... You could peal some and scan them in a flat bed scanner.
    – Rafael
    Mar 7, 2022 at 9:48
  • @Rafael thanks, but these are different to the ones with engraved lettering and not acceptable :)
    – Tomblarom
    Mar 7, 2022 at 9:51
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    Wrap some paper around the object, use a crayon or the side of a pencil to obtain a rubbing, then scan the result, load it into a vector editor and recreate the outlines with Bezier curves.
    – r3mainer
    Mar 7, 2022 at 9:56
  • @r3mainer tried parchment paper + pencil: i.imgur.com/fIx2dHL.jpg Does crayon really work better?
    – Tomblarom
    Mar 7, 2022 at 10:04
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    You could even use a piece of acetate/clear film wrapped around the cylinder then trace the lettering. Remove the acetate, lay flat, scan, and import into a vector image editor, and use the Bézier tool to redraw the letters, or type letters, reposition, scale/transform as necessary, then delete the raster image after you have finished.
    – Billy Kerr
    Mar 7, 2022 at 15:25

1 Answer 1

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Of course, the dimensions of the cylinder are important for this to work, but one setup that could potentially fix the perspective errors is:

Print on an adhesive material two rulers and paste them on the upper and lower end of the cylinder. Let's say the ruler has 1 mm references.

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Now have vertical printed cardboard for your vertical reference.

enter image description here

Use the longest focal length you can afford. Let's say a 300mm lens. PUt the camera the further away you can to reduce perspective.

enter image description here

Now you could use a very slow turntable to rotate it. Make it turn several times so you can align the center of rotation with the center of the cylinder the best you can.

enter image description here

If you can use an intervalometer, not a video, you have a high-resolution image.

Now you have good reliable references to stitch the segments... probably by hand. Use transparent layers so you can align the segments.

Cross-reference the overall dimensions using some other measuring method, like the thin paper.

Probably this is too much tech for the project tho...

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  • Nope, that's great. Thanks for your input! Going to do this! - Not too technical ;)
    – Tomblarom
    Mar 7, 2022 at 10:29

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