Representation¶

Overview¶

SketchKit uses a unified representation for sketches, making it easy to work with various datasets.
All sketches are converted into the Sketch standard format, which provides a structured way to access paths, curves and points.

Core Concepts¶

A Sketch is composed of several levels of hierarchy, which contains a list of Paths.
A Path contains a list of Curves.
And each Curve is a cubic bezier curve with start and end vertices and two control points.
A Vertex is a point with many other drawing attributes than naive Point (which only has x,y position.)

Sketch¶

The top-level object representing a full sketch.
Contains multiple paths.

Path¶

A sequence of one or more curves that form a continuous stroke.
e.g. A single hand-drawn line

Curve¶

A cubic Bézier curve connecting two vertices.
e.g. cutting a path into multiple parts, each part represents a curve
Defined by:
- Start Vertex
- End Vertex
- Control Point 1
- Control Point 2

Vertex¶

A specialized point with additional drawing attributes.
Attributes include:
- pressure: pen pressure at this point
- thickness: stroke width at this point
- Other style information
e.g. every curve’s start and end points are vertices.

Point¶

The most basic element in a sketch.
Stores the 2D position (x, y) of a point.
e.g. mostly serve as control points for cubic Bézier curves, defining the curve’s shape.

Visualization¶

The structure can be visualized as follows:

Sketch
  - Path
    - Curve
      - Start Vertex
      - End Vertex
      - Control Point 1
      - Control Point 2
    - Curve
    ...
  - Path
  ...