- Creating and editing contours
- Contours Inspector
- Contextual menu
Contours are visual descriptions of glyph shapes using bezier curves.
Bezier curves were introduced into type design in the 1980s as two competing flavors, PostScript (Adobe) and TrueType (Microsoft/Apple). The PostScript format used cubic bezier curves, while the TrueType used quadratic ones. The formats evolved and were merged into the OpenType format, but the distiction remains between OpenType-CFF (cubic) and OpenType-TTF (quadratic) fonts.
The Ikarus format which existed before that was based on circle segments.
Contours can be made of line and curve segments.
- Line segments
- are made of two on-curve points
- Curve segments
- are made of two on-curve points and off-curve points
Contours can be open or closed. Open contours are allowed in UFO, but not in OpenType.
Cubic and quadratic beziers
RoboFont uses cubic bezier curves by default. This is the type of contours which is most familiar to designers, since it’s used by vector design applications. Cubic beziers are part of Adobe’s PostScript page description language, and are used by OpenType-CFF fonts.
Since version 4.0, RoboFont offers full support for quadratic bezier curves. This allows for a finer control over outlines meant to be exported as TrueType fonts.
Bezier points can be smooth or unsmooth.
- smooth point
- segments are continuous
- unsmooth point
- segments are at an angle
Point smoothness can be toggled on / off by double clicking the point.
Smooth points retain continuity between segments when its handles are moved.
The angle of handle is locked to the angle of the opposing line segment of or to the angle of the handle of the oppposing curve segment.
Points are represented by different icons depending on their smoothness and the type of segments they connect:
- Unsmooth connection between line and curve segments, or two line segments
- Smooth connection between line segment and curve segment
- Circle without stroke
- Unsmooth connection between two curve segments, handles can move independently
- Circle with black stroke
- Smooth connection between two curve segments
- Connected control points
- Quadratic bezier control point. Quadratic beziers allow for an infinite amount of control points
- Control points only connected to anchor
- Cubic bezier control points. Cubic beziers only allow for two control points, each one connected to an anchor
Creating and editing contours
It’s also possible to draw inside a glyph with code – see this example.
Contour and point properties can be edited in the Points section of the Inspector.
The contextual menu can be opened with a right-click using the Editing Tool. A different set of options is displayed depending on the context:
Contour selection actions
|Reverse Contours||Reverse selected contours.|
|Remove Overlap||Remove overlaps in the selected contours.|
|Add Extreme Points||Add extreme points to the selected contours.|
|Labels||Add labels to the selected points.|
Single point actions
|Break Contour||Breaks contour at the selected point.|
|Set Start Point||Set the selected point as starting point.|