Tracing a Bitmap image.

Post questions on how to use or achieve an effect in Inkscape.
Jonboy
Posts: 22
Joined: Wed Jun 06, 2018 5:21 am

Tracing a Bitmap image.

Postby Jonboy » Sun Jul 08, 2018 9:14 pm

I am learning how to trace a Bitmap image of a horse silhouette with as much detail as possible for a CNC laser cutting machine.

I have established that the image that i want to trace is very small approximately 10 mm x 10 mm and i want the image to be 120 mm x 120 mm so i was thinking the best way to get as much detail as possible for CNC laser cutting is as follows:

1. Upload the image onto Autocad and scale the image to the size i want and "Save As".

2. Open the saved file in Inkscape and trace the image.

3. After tracing the image move the original image to the left of the traced image and manually trace any missed details using Bezier.

4. After the tracing is complete save as a DXF for laser cutting.

If i am going in the wrong way of this process please let me know any help would be much appreciated!!

Jonboy.

theozh
Posts: 431
Joined: Fri Mar 23, 2012 6:30 pm

Re: Tracing a Bitmap image.

Postby theozh » Sun Jul 08, 2018 10:35 pm

Hi Jonboy,
some comments/questions:
- what is the size of the bitmap image (not in mm, but in pixels)?
- why do you think you need AutoCAD? If you have it, it's nice, but you can also scale bitmap images with Inkscape.
- what format do you "save as" your file in AutoCAD and re-import it in Inkscape?
Maybe you can show the original bitmap image? Then we could see where there might be difficulties.
Win7/64, Inkscape 0.92.2

Moini
Posts: 2769
Joined: Mon Oct 05, 2015 10:44 am

Re: Tracing a Bitmap image.

Postby Moini » Mon Jul 09, 2018 12:26 am

If you really need to scale a raster/bitmap image up (sometimes that's necessary for trace bitmap to pick up the details), I'd suggest using specialized software for this, e.g. Gimp (free + open source raster graphics editor). It even offers different algorithms for upscaling.

While Inkscape can scale bitmap images, its functionality is less sophisticated, and just changing the size on the canvas, before tracing, will not make a difference to the tracing algorithm, as it uses the image data, not how large it is displayed on the canvas, and scaling bitmaps in Inkscape does not change the image data.

In the Trace bitmap dialog, there are a couple of options in the third tab. Try if you can get more detail when you turn them off or tune them.
Something doesn't work? - Keeping an eye on the status bar can save you a lot of time!

Inkscape FAQ - Learning Resources - Website with tutorials (German and English)

Jonboy
Posts: 22
Joined: Wed Jun 06, 2018 5:21 am

Re: Tracing a Bitmap image.

Postby Jonboy » Mon Jul 09, 2018 4:47 am

Firstly, thanks for all the information / help that you have given me.

I have uploaded a similar the type of image that i would like to laser cut. Any help would be great.

Thanks,

jonboy.
Attachments
Horse.png
Horse.png (7.7 KiB) Viewed 409 times

theozh
Posts: 431
Joined: Fri Mar 23, 2012 6:30 pm

Re: Tracing a Bitmap image.

Postby theozh » Mon Jul 09, 2018 6:57 am

Your uploaded image has 183x275 pixels. A bit more pixels would be probably better.
But still, with Inkscape's trace bitmap you get nice results.
- copy/import your bitmap as is into Inkscape (no need for AutoCAD)
- play with the parameters (e.g. Brightness cutoff) in the trace bitmap dialog
- edit the paths if necessary
- scale your vectorized image to your final size
- export/"save a copy" your image as DXF

Horse_vector.png
Horse_vector.png (101.25 KiB) Viewed 396 times
Win7/64, Inkscape 0.92.2

Jonboy
Posts: 22
Joined: Wed Jun 06, 2018 5:21 am

Re: Tracing a Bitmap image.

Postby Jonboy » Mon Jul 09, 2018 5:01 pm

Thanks for the help!
At that stage you have shown is it ok to cut on the cnc laser cutter or does it have to be outlines only / no shaded areas?
This is all new to me.
Thanks Jonboy

theozh
Posts: 431
Joined: Fri Mar 23, 2012 6:30 pm

Re: Tracing a Bitmap image.

Postby theozh » Mon Jul 09, 2018 6:22 pm

In the SVG it doesn't matter. The exported DXF contains only outlines of the areas...
Win7/64, Inkscape 0.92.2

Jonboy
Posts: 22
Joined: Wed Jun 06, 2018 5:21 am

Re: Tracing a Bitmap image.

Postby Jonboy » Mon Jul 09, 2018 7:12 pm

Would I be right in thinking even though the image is shaded / filled once saved as DXF the cnc laser cutter will detect the paths to cut?
Thanks again be patient with me lol.

theozh
Posts: 431
Joined: Fri Mar 23, 2012 6:30 pm

Re: Tracing a Bitmap image.

Postby theozh » Mon Jul 09, 2018 7:35 pm

...as I said, the DXF file contains the outline of the areas, independent whether the areas are filled or not in Inkscape.
The CNC laser cutter software should be able to import DXF files or converting them to a format which it can understand.
Win7/64, Inkscape 0.92.2

Jonboy
Posts: 22
Joined: Wed Jun 06, 2018 5:21 am

Re: Tracing a Bitmap image.

Postby Jonboy » Tue Jul 10, 2018 4:57 am

Thanks everyone for your help much appreciated.

jonboy.


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