How to Clean Up Jagged Vector Traces in FontForge

Autotracing bitmap images in FontForge often produces contours with excessive control points, uneven bezier handles, and jagged edges. This guide explains the best workflow to clean up these messy outlines, focusing on automated simplification, manual node reduction, handle harmonization, and contour correction to transform rough traces into smooth, professional font glyphs.

1. Apply Automatic Simplification

The fastest way to remove unnecessary nodes generated by autotracing is the Simplify command.

  1. Open the glyph in the Glyph Edit window and select all paths (Ctrl + A).
  2. Go to Element > Simplify > Simplify (or press Ctrl + Shift + M).
  3. For more aggressive cleanup, use Element > Simplify > Simplify More.

In the Simplify dialog, adjust the error tolerance (measured in font units). A higher tolerance removes more points but can distort sharp corners, while a lower tolerance preserves the original shape more strictly. Finding a balance removes the micro-steps typical of raster tracing without losing glyph details.

2. Remove Extraneous Points Manually

Autotracers often place multiple points along straight lines or around single curves where only two points are needed.

  • Select redundant points along smooth curves or flat stems and press Delete (or Backspace). FontForge will automatically attempt to reconnect the adjacent points with a smooth curve.
  • Use Point > Merge (Ctrl + M) to combine adjacent nodes that are excessively close together.
  • Strive to place points only at the local extrema (the highest, lowest, leftmost, and rightmost points of each curve) and at sharp inflection points.

3. Convert Points to the Correct Type

Jagged traces frequently misclassify curve nodes as corner nodes. To restore smooth curves:

  1. Select points along a continuous curve.
  2. Go to Point > Make Smooth to force the incoming and outgoing control handles to remain collinear (180 degrees apart).
  3. For transitions between a curve and a straight line, use Point > Make Tangent.
  4. Reserve Corner Points strictly for sharp vertices.

4. Harmonize Bezier Handles

Uneven handle lengths cause wobbles and flat spots in curves.

  1. Select the affected curved segments.
  2. Go to Element > Harmonize (or press Ctrl + Shift + H).
  3. FontForge balances the curvature and tension between paired control points, creating smooth transitions without shifting the physical positions of the on-curve nodes.

5. Remove Tiny Artifacts and Overlaps

Autotrace often captures speckles or creates self-intersecting loops:

  1. Delete tiny floating contours that represent background noise.
  2. Use Element > Overlap > Remove Overlap (Ctrl + Shift + O) to resolve any twisted or self-intersecting path segments.
  3. Finally, run Element > Correct Direction (Ctrl + Shift + D) to ensure all outer paths run counter-clockwise and internal cutouts (counters) run clockwise, preventing rendering errors in the final font file.