Software for extruding 2d image into 3d model?

I am getting started with 3D printing and I often want the ability to extrude a 2d image into a 3d model. I have been using this tool from Shapeways, but I was wondering if there are other ways to do this. Thanks!

How to go from bitmap to STL. There are many ways to do this, but here is one way that
uses free and open source software. It's a little convoluted, but it's free and it works.
At least for me. Your mileage may vary.

There is a different way to do it on Tony Buser's blog here.

You will need:
Inkscape
Better Better DXF plugin for Inkscape
OpenSCAD

To install Better Better DXF,
Go to the page above and get b2_dxf_output.zip.
Go to your Inkscape/share/extensions directory.
Rename simpletransform.py if you want to keep it.
Extract b2_dxf_output.zip to Inkscape/share/extensions.

This comment is on the Better Better DXF page, and indeed I had to make this change to get it to work:
"I was getting errors using Ubuntu 8.10 and Inkscape 0.47–these were resolved by replacing xpath(path,inkex.NSS) with xpath(path,namespaces = inkex.NSS) in b2_dxf_outlines.py"

Now start Inkscape and...

File -> Import to import the bitmap image, say .bmp
Choose (embed) as the option

Path -> Trace Bitmap
You may have to try different settings here...

Select the path you created above, and drag it away from the original bitmap.

Path -> Break Apart

Object -> Fill and Stroke ... -> remove Fill (click the X), and turn on Stroke

You should now have outlines and "inlines" of your pattern.
Select and delete the pieces you don't want to keep, including original pattern.

Now you'll want to resize the page to your image:

File -> Document Properties -> Resize page to drawing or selection

Save it as a .svg just for good measure, in case you want to come back to it later.

Now save it as a dxf, choosing the "Better Better DXF Output" option.

Close Inkscape. Start OpenSCAD. In OpenSCAD, run these lines

linear_extrude(height = 10, convexity = 10)
import(file = "THE_NAME_OF_MY_FILE.dxf", layer = "Layer 1");

and you should get an extrusion of your dxf. It may not line up with the origin, so you may have to
look around for it, then move it where you want with the translate() command.

F6 and Design -> Export as STL to create an STL file.

If you want to use vanilla Inkscape without the extra plugin, I've written a tutorial here.

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-Nudel
Blog with RepRap Comic