Documentation

Overview

Package clip provides operations for clipping paint operations. Drawing outside the current clip area is ignored.

The current clip is initially the infinite set. An Op sets the clip to the intersection of the current clip and the clip area it represents. If you need to reset the current clip to its value before applying an Op, use op.StackOp.

General clipping areas are constructed with Path. Simpler special cases such as rectangular clip areas also exist as convenient constructors.

Index

Constants

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Variables

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Functions

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Types

type Circle

type Circle struct {
	Center f32.Point
	Radius float32
}

Circle represents the clip area of a circle.

func (Circle) Add

func (c Circle) Add(ops *op.Ops)

Add the circle clip.

func (Circle) Op

func (c Circle) Op(ops *op.Ops) Op

Op returns the op for the circle.

func (Circle) Path

func (c Circle) Path(ops *op.Ops) PathSpec

Path returns the PathSpec for the circle.

type Dash

type Dash struct {
	// contains filtered or unexported fields
}

Dash records dashes' lengths and phase for a stroked path.

func (*Dash) Begin

func (d *Dash) Begin(ops *op.Ops)

func (*Dash) Dash

func (d *Dash) Dash(length float32)

func (*Dash) End

func (d *Dash) End() DashSpec

func (*Dash) Phase

func (d *Dash) Phase(v float32)

type DashSpec

type DashSpec struct {
	// contains filtered or unexported fields
}

DashSpec describes a dashed pattern.

type Op

type Op struct {
	// contains filtered or unexported fields
}

Op represents a clip area. Op intersects the current clip area with itself.

func (Op) Add

func (p Op) Add(o *op.Ops)

type Outline

type Outline struct {
	Path PathSpec
}

Outline represents the area inside of a path, according to the non-zero winding rule.

func (Outline) Op

func (o Outline) Op() Op

Op returns a clip operation representing the outline.

type Path

type Path struct {
	// contains filtered or unexported fields
}

Path constructs a Op clip path described by lines and Bézier curves, where drawing outside the Path is discarded. The inside-ness of a pixel is determines by the non-zero winding rule, similar to the SVG rule of the same name.

Path generates no garbage and can be used for dynamic paths; path data is stored directly in the Ops list supplied to Begin.

func (*Path) Arc

func (p *Path) Arc(f1, f2 f32.Point, angle float32)

Arc adds an elliptical arc to the path. The implied ellipse is defined by its focus points f1 and f2. The arc starts in the current point and ends angle radians along the ellipse boundary. The sign of angle determines the direction; positive being counter-clockwise, negative clockwise.

func (*Path) Begin

func (p *Path) Begin(ops *op.Ops)

Begin the path, storing the path data and final Op into ops.

func (*Path) Close

func (p *Path) Close()

Close closes the path contour.

func (*Path) Cube

func (p *Path) Cube(ctrl0, ctrl1, to f32.Point)

Cube records a cubic Bézier from the pen through two control points ending in to.

func (*Path) CubeTo

func (p *Path) CubeTo(ctrl0, ctrl1, to f32.Point)

CubeTo records a cubic Bézier from the pen through two control points ending in to, with absolute coordinates.

func (*Path) End

func (p *Path) End() PathSpec

End returns a PathSpec ready to use in clipping operations.

func (*Path) Line

func (p *Path) Line(delta f32.Point)

Line moves the pen by the amount specified by delta, recording a line.

func (*Path) LineTo

func (p *Path) LineTo(to f32.Point)

LineTo moves the pen to the absolute point specified, recording a line.

func (*Path) Move

func (p *Path) Move(delta f32.Point)

Move moves the pen by the amount specified by delta.

func (*Path) MoveTo

func (p *Path) MoveTo(to f32.Point)

MoveTo moves the pen to the specified absolute coordinate.

func (*Path) Pos

func (p *Path) Pos() f32.Point

Pos returns the current pen position.

func (*Path) Quad

func (p *Path) Quad(ctrl, to f32.Point)

Quad records a quadratic Bézier from the pen to end with the control point ctrl.

func (*Path) QuadTo

func (p *Path) QuadTo(ctrl, to f32.Point)

QuadTo records a quadratic Bézier from the pen to end with the control point ctrl, with absolute coordinates.

type PathSpec

type PathSpec struct {
	// contains filtered or unexported fields
}

type RRect

type RRect struct {
	Rect f32.Rectangle
	// The corner radii.
	SE, SW, NW, NE float32
}

RRect represents the clip area of a rectangle with rounded corners.

Specify a square with corner radii equal to half the square size to construct a circular clip area.

func UniformRRect

func UniformRRect(rect f32.Rectangle, radius float32) RRect

UniformRRect returns an RRect with all corner radii set to the provided radius.

func (RRect) Add

func (rr RRect) Add(ops *op.Ops)

Add the rectangle clip.

func (RRect) Op

func (rr RRect) Op(ops *op.Ops) Op

Op returns the op for the rounded rectangle.

func (RRect) Path

func (rr RRect) Path(ops *op.Ops) PathSpec

Path returns the PathSpec for the rounded rectangle.

type Rect

type Rect image.Rectangle

Rect represents the clip area of a pixel-aligned rectangle.

func (Rect) Add

func (r Rect) Add(ops *op.Ops)

Add the clip operation.

func (Rect) Op

func (r Rect) Op() Op

Op returns the op for the rectangle.

type Stroke

type Stroke struct {
	Path  PathSpec
	Style StrokeStyle

	// Dashes specify the dashes of the stroke.
	// The empty value denotes no dashes.
	Dashes DashSpec
}

Stroke represents a stroked path.

func (Stroke) Op

func (s Stroke) Op() Op

Op returns a clip operation representing the stroke.

type StrokeCap

type StrokeCap uint8

StrokeCap describes the head or tail of a stroked path.

const (
	// RoundCap caps stroked paths with a round cap, joining the right-hand and
	// left-hand sides of a stroked path with a half disc of diameter the
	// stroked path's width.
	RoundCap StrokeCap = iota

	// FlatCap caps stroked paths with a flat cap, joining the right-hand
	// and left-hand sides of a stroked path with a straight line.
	FlatCap

	// SquareCap caps stroked paths with a square cap, joining the right-hand
	// and left-hand sides of a stroked path with a half square of length
	// the stroked path's width.
	SquareCap
)

type StrokeJoin

type StrokeJoin uint8

StrokeJoin describes how stroked paths are collated.

const (
	// RoundJoin joins path segments with a round segment.
	RoundJoin StrokeJoin = iota

	// BevelJoin joins path segments with sharp bevels.
	BevelJoin
)

type StrokeStyle

type StrokeStyle struct {
	Width float32 // Width of the stroked path.

	// Miter is the limit to apply to a miter joint.
	// The zero Miter disables the miter joint; setting Miter to +∞
	// unconditionally enables the miter joint.
	Miter float32
	Cap   StrokeCap  // Cap describes the head or tail of a stroked path.
	Join  StrokeJoin // Join describes how stroked paths are collated.
}

StrokeStyle describes how a path should be stroked.