How to convert a bitmap into an embroiderable file with free tools.

<p>
Find an image you'd like to work with. Here's an Imperial Penguin
from
<a href="http://caro.officialpsds.com/Darth-Vader-Penguin-PSD45192.html">submitter SoUnique</a>:

<p>
<img src="original.png">

<p>
Open it in gimp, select Image -&gt; Mode -&gt; indexed,
select "Generate optimum palette",
and try different small values for "Maximum number of colors".
More colors means more fine detail and more thread changes;
so start as simple as you can while making an interesting image.
Here's our image brought down to 5 colors:

<p>
<img src="indexed-5.png">

<p>
Bring up inkscape, and paste the indexed raster image in.
Select it, and click Path -&gt; Trace Bitmap.

<p>
In the Mode tab, in the Multiple Scans group, select "Colors",
set Scans to the number of colors you used when making the image
indexed in Gimp.
Unselect "stack scans", so that the colors end up non-overlapping.
Select "remove background" to eliminate the rectangular border.
Click OK, and you've got a vector version of your image:

<p>
<img src="traced.png">

<p>
Here are the vector layers, separated:

<p>
<img src="traced-exploded.png">

<p>
(Past this point, I did some cheating not recorded here: I colored the
white parts of the image red in Gimp, so that "remove background" would
eliminate the border, while still generating a layer for the white
foreground elements. Then, in inkscape, I recolored the red traced layer
white.)

<p>
Spread the layers out. I've turned the white layer olive so I can see
it; obviously, the finished color will be whatever thread I put in the
embroidery machine. :v)

<p>
<img src="spread.png">

<p>
At this point, you'll need to have my half-baked embroidery extension
installed.

<p>
For each layer, select the layer path, invoke Path -&gt; Break Apart,
then invoke Object -&gt; Group. Then invoke Extensions -&gt; Embroider
to generate stitching paths.
As you generate each path, copy off the embroider-output.exp file
into a file named for the color layer.

<p>
It's not quite this easy, since my embroidery code (and the comptuational
geometry library it calls) isn't as robust as I'd like it to be. I had to
hand-tune the geometry a bit to make it simple enough to pass through the
embroider script without exploding. Helpful tips:
<ul>
<li>Use Path outset/inset to remove anomalous structures on paths;
sometimes that's enough.
<li>Path Simplify can help, too, but it changes
the boundaries more noticeably.
<li>Paths with lots of holes (like the black layer in the center above)
have a really tough time. You can Break Apart and Union to get rid of the
holes, and let the layers above just lay thread down on top of this layer's
stitching. I'm sorry that you've got to use embroidery thread to make
up for algorithmic failure!
<li>My code can handle holes, as long as they're simple. In the yellow layer,
it was enough to break apart the path, then select pairs of inner and outer
paths, and Path Exclude to punch the hole back through the outer path.
</ul>

<p>Ultimately, you want to convert all the paths in one step, to ensure
that all the colors end up in a single file, with a common origin, so
you don't have to align them at embroidery time.

<p>
Convert the .exp file to your machine's format using TrueSizer.