Extract Foreground from Background in FontForge

Extracting a foreground vector layer from a background reference image in FontForge is a standard workflow for converting scanned sketches or raster graphics into scalable font glyphs. This process requires importing your bitmap graphic into the glyph's background layer, running an autotrace tool to convert the pixel data into vector paths, and ensuring those outlines are placed onto the active foreground layer where they can be manipulated, spaced, and generated as final font outlines.

1. Configure an Autotrace Utility

FontForge relies on external tracing software to convert raster images into vector contours. Ensure you have either Potrace or AutoTrace installed on your operating system.

  • On Linux or macOS, install Potrace via your package manager (such as apt install potrace or brew install potrace).
  • On Windows, standard FontForge distributions typically bundle Potrace automatically.
  • In FontForge, go to File > Preferences > Apps and verify that the path to your autotrace program is configured properly.

2. Import the Image into the Background Layer

  1. Double-click the target glyph cell in the FontForge font view window to open the glyph edit window.
  2. Open the Layers palette by navigating to Window > Layers if it is not already visible.
  3. Select the Back radio button in the Layers palette to make the background layer active.
  4. Go to File > Import.
  5. Set the format dropdown to image files (such as PNG, BMP, or TIFF), choose your reference image, and click Import.
  6. Scale or position the image inside the glyph editor to fit the baseline, ascender, and descender metrics using the Transform tool or the pointer.

3. Trace the Background to the Foreground

Once the image is aligned:

  1. Switch your active layer back to the foreground by selecting Fore in the Layers palette.
  2. Navigate to the top menu and select Element > AutoTrace (or press Ctrl + Shift + T / Cmd + Shift + T).
  3. FontForge will pass the background bitmap to the tracing engine, process the pixel boundaries, and place the resulting vector curves directly onto your Fore (foreground) layer.

4. Alternative: Copying Vectors from Background to Foreground

If the traced vectors were generated directly on the background layer instead of the foreground:

  1. Select the Back layer in the Layers palette.
  2. Choose Edit > Select > Select All (Ctrl + A / Cmd + A) to grab all generated outlines.
  3. Choose Edit > Cut or Edit > Copy.
  4. Switch to the Fore layer in the Layers palette.
  5. Choose Edit > Paste to place the vector outlines directly into the foreground.

5. Clean Up and Correct Direction

  1. Go to Element > Correct Direction (Ctrl + Shift + D / Cmd + Shift + D) to fix the path directions for proper rendering of counter-spaces and solid shapes.
  2. Go to Element > Simplify > Simplify to reduce redundant nodes generated during the autotrace process.
  3. Inspect and adjust nodes manually using the Point tool to ensure smooth curves and standard typographic alignment.