Custom Shapes

Paint.NET's Shapes tool supports Custom Shapes as a form of declarative plugin - code is not involved! The object model is intentionally identical to WPF geometry, with only a few caveats, and is compatible with XAML files created for WPF as long as you change the namespace and wrap the geometry object in a SimpleGeometryShape element.

The object model for Custom Shapes is contained in the PaintDotNet.Shapes and PaintDotNet.UI.Media namespaces.

Links:

Installing Additional Plugins - Paint.NET Documentation
Plugins - Shapes section of the Paint.NET forum. Download custom shapes plugins.
How to make custom shapes tutorial by BoltBait
ShapeMaker plugin by The Dwarf Horde

Differences from WPF Geometry

The Geometry object model used for Custom Shapes is identical to WPF's Geometry object model, except for a few differences:

Added:

PolyCurveSegment
- This is a PathSegment that draws a curve going through each given point. Also known as a spline.
- These can be used within a PathGeometry, similar to PolyLineSegment or PolyBezierSegment.
FlattenedGeometry
- This is a declarative equivalent to the imperative Geometry.GetFlattenedPathGeometry (WPF) or IGeometry.Simplify (Direct2D) methods.
- It is primarily useful for increasing the tesellation resolution of curves that, for whatever reason, appear "too pointy". This happens when Direct2D does not use enough line segments to approximate a curve.
- You could also use this to reduce tessellation resolution, forcing a curve to appear "low-res" or "pointy." (use a value larger than 1 for the FlatteningTolerance property).
- This is used by the built-in Ellipse shape to improve its rendering quality (a very low flattening tolerance of 0.0001 is used).
OutlinedGeometry
- This is a declarative equivalent to the imperative Geometry.GetOutlinedPathGeometry (WPF) or IGeometry.Outline (Direct2D) methods.
WidenedGeometry
- This is a declarative equivalent to the imperative Geometry.GetWidenedPathGeometry (WPF) or IGeometry.Widen (Direct2D) methods.
- Widening is often referred to as "stroking." You can use this to create the 2-dimensional stroked outline of a 1-dimensional line or curve.

Removed:

StreamGeometry does not exist
- StreamGeometry is primarily used in code, not in XAML, and does not exist for Custom Shapes.
- You can, however, use Path Markup syntax to initialize any property of type Geometry.
- For example: <SimpleGeometryShape Geometry="F1 M 21,142 L 160,22 L 300,142 L 300,318 L 21,318 Z" />

Examples

There are two primary ways of expressing a custom shape. The first is with Path Markup syntax, and the other is with the Geometry object model.

Path Markup syntax example

This is an example of a coffee mug shape defined using Path Markup syntax, which is compatible with SVG path data syntax.

This example is from TechnoRobbo's shapes pack.

<ps:SimpleGeometryShape 
  xmlns="clr-namespace:PaintDotNet.UI.Media;assembly=PaintDotNet.Framework"
  xmlns:ps="clr-namespace:PaintDotNet.Shapes;assembly=PaintDotNet.Framework"                 
  DisplayName="Mug"
  Geometry="M 68,106 A 6.74,23.82,90,1,1,150.5,106 L 150.5,126 A 20.51,15.15,149.74,1,1,150.5,178.5 L 150.5,193.5 A 6.73,23.81,-90,1,1,68,193.5 L 68,106 M 73,106 A 4.03,20.96,89.29,1,1,145,105 A 6.8,24.52,-91.12,1,1,73,106 M 150.5,133.5 A 22.12,15.15,150.46,1,1,150.5,171 L 150.5,133.5 M 109,10.5 C 114.86,15.45,120,20.5,127,33,128.5,42.5,127.5,43,117.5,51,105.5,59.5,124.66,76.88,124,83.5,117,53.5,132,55.5,140.5,46,147.5,28,119.5,15,109,10.5 M 78,7 C 83.86,11.95,89,17,96,29.5,97.5,39,96.5,39.5,86.5,47.5,74.5,56,93.66,73.38,93,80,86,50,101,52,109.5,42.5,116.5,24.5,88.5,11.5,78,7" />

Coffee Mug

Geometry object model example

This is an example of a clock shape defined using the Geometry object model.