Class ContourMeasure

Namespace

Egami.Drawing

Assembly

Egami.Drawing.dll

One measured contour of a PathMeasure. Distances run from 0 at the contour's start to Length at its end; distances outside are clamped to them, as in Skia.

public sealed class ContourMeasure

Inheritance

object

ContourMeasure

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Examples

// Measure a path: its length, and a point and direction at any distance, curves included.
Path route = new PathBuilder().MoveTo(10, 90).CubicTo(60, 0, 140, 160, 190, 60).ToPath();
PathMeasure measure = new(route);
ContourMeasure contour = measure.Contours[0];
Vector2 halfway = contour.GetPosition(contour.Length / 2);
Vector2 heading = contour.GetTangent(contour.Length / 2);

// An arrowhead placed at the end, turned along the path, and the middle third as a path of its own (still a cubic).
Path arrow = Path.Polygon([new(-6, -4), new(0, 0), new(-6, 4)]).Transform(contour.GetMatrix(contour.Length));
Path middle = contour.GetSegment(contour.Length / 3, 2 * contour.Length / 3);

Properties

IsClosed

Gets a value indicating whether the contour is closed, so its end meets its start.

public bool IsClosed { get; }

Property Value

bool

Length

Gets the contour's length.

public float Length { get; }

Property Value

float

Methods

AddSegment(PathBuilder, float, float, bool)

Adds the piece between two distances to a builder, as GetSegment(float, float) describes.

public void AddSegment(PathBuilder builder, float start, float end, bool startWithMove = true)

Parameters

builder PathBuilder

The builder.

start float

Where the piece starts; clamped to the contour.

end float

Where the piece ends; clamped to the contour.

startWithMove bool

Whether the piece starts a new contour; otherwise a line joins it to the builder's current point, to chain pieces into one contour.

GetMatrix(float)

Returns the transform that puts a shape on the contour at a distance: its x axis along the direction of travel and its origin at the point, so a shape drawn along +x follows the path.

public Matrix3x2 GetMatrix(float distance)

Parameters

distance float

The distance from the start, clamped to the contour.

Returns

Matrix3x2

A rotation and translation.

GetPosition(float)

Returns the point at a distance along the contour.

public Vector2 GetPosition(float distance)

Parameters

distance float

The distance from the start, clamped to the contour.

Returns

Vector2

The point.

GetSegment(float, float)

Returns the piece of the contour between two distances, as a path of one open contour that keeps the contour's lines, quadratics and cubics: curves cut at the ends are split exactly, so the piece exports as cleanly as the whole. The whole of a closed contour comes back closed.

public Path GetSegment(float start, float end)

Parameters

start float

Where the piece starts; clamped to the contour.

end float

Where the piece ends; clamped to the contour.

Returns

Path

The piece, or an empty path when end is not after start.

GetTangent(float)

Returns the direction of travel at a distance along the contour, as a unit vector.

public Vector2 GetTangent(float distance)

Parameters

distance float

The distance from the start, clamped to the contour.

Returns

Vector2

The direction; where a curve's direction is undefined (a cusp), the limit from inside the curve.