John - I use Gimp and Inkscape to make a pattern from a photo. Steve Good has a video on some of the process, but basically:
- Open photo in Gimp
- Crop it to the interesting parts; move parts around to make a better layout.
- It usually helps to erase all the background around a subject so the subject controls the rest of the process rather than some background noise.
- Use Filters-Artistic-Photocopy to get a low contrast B/W version.
- I sometimes add Filters-Artistic-Cartoon (before or after Photocopy) to help highlight some of the lines in the photo.
- Save the photocopy from Gimp to disk.
- Open the photocopy in Inkscape.
- In Inkscape, click on the open image so it is surrounded by arrows.
- Use Path-Trace Bitmap to make a Vector Graphic (SVG) from the photocopy.
- Click once on the image, then click and drag to move the SVG out of the center box.
- If it is too light, click back on the photocopy then adjust the Bightness Cutoff - Threshold. Try .5, .6, .7, .8, .9 to see which gives the best SVG.
- Use Path-Simplify to see if the image gets cleaner, then Cntrl-Z if you don't like it.
- Move the original photocopy out of the center box and drag the best SVG into the center box.
- Save the SVG to disk as a .svg file.
- Open the .SVG in Gimp. Use the erase and draw tools to clean up and to add white bridges to connect islands.
- Set foreground color to black then do a fill with black to see if you missed any islands (they will stand out in white). Cntrl-Z to undo the fill, then fix the islands.
- Option - Set the Image-Mode to Indexed, then click on Black and White.
- You can save to disk (option - as a B/W GIF) and go back to Inkscape for another SVG conversion to smooth out your Gimp changes if you need to.
That's the general process. You can get artistic if the important lines (dimples, wrinkles, ears) did not survive the process. Hair may take some work to get right. You can also use Gimp to set the size of the canvass (remember to hit the Center button), or to Scale Image (make it bigger or smaller).
It's quicker than it sounds once you've done it once or twice.
If the photo was of a person looking to the right or left, I like to try to blacken the field in that direction to better highlight the face (see Steve Good's Einstein for a good example of that).
