Documentation
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Overview ¶
Package raster provides an anti-aliasing 2-D rasterizer.
It is part of the larger Freetype suite of font-related packages, but the raster package is not specific to font rasterization, and can be used standalone without any other Freetype package.
Rasterization is done by the same area/coverage accumulation algorithm as the Freetype "smooth" module, and the Anti-Grain Geometry library. A description of the area/coverage algorithm is at http://projects.tuxee.net/cl-vectors/section-the-cl-aa-algorithm
Index ¶
- func Stroke(p Adder, q Path, width fixed.Int26_6, cr Capper, jr Joiner)
- type Adder
- type AlphaOverPainter
- type AlphaSrcPainter
- type Capper
- type CapperFunc
- type GammaCorrectionPainter
- type Joiner
- type JoinerFunc
- type MonochromePainter
- type Painter
- type PainterFunc
- type Path
- func (p *Path) Add1(b fixed.Point26_6)
- func (p *Path) Add2(b, c fixed.Point26_6)
- func (p *Path) Add3(b, c, d fixed.Point26_6)
- func (p *Path) AddPath(q Path)
- func (p *Path) AddStroke(q Path, width fixed.Int26_6, cr Capper, jr Joiner)
- func (p *Path) Clear()
- func (p *Path) Start(a fixed.Point26_6)
- func (p Path) String() string
- type RGBAPainter
- type Rasterizer
- func (r *Rasterizer) Add1(b fixed.Point26_6)
- func (r *Rasterizer) Add2(b, c fixed.Point26_6)
- func (r *Rasterizer) Add3(b, c, d fixed.Point26_6)
- func (r *Rasterizer) AddPath(p Path)
- func (r *Rasterizer) AddStroke(q Path, width fixed.Int26_6, cr Capper, jr Joiner)
- func (r *Rasterizer) Clear()
- func (r *Rasterizer) Rasterize(p Painter)
- func (r *Rasterizer) SetBounds(width, height int)
- func (r *Rasterizer) Start(a fixed.Point26_6)
- type Span
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Adder ¶
type Adder interface {
// Start starts a new curve at the given point.
Start(a fixed.Point26_6)
// Add1 adds a linear segment to the current curve.
Add1(b fixed.Point26_6)
// Add2 adds a quadratic segment to the current curve.
Add2(b, c fixed.Point26_6)
// Add3 adds a cubic segment to the current curve.
Add3(b, c, d fixed.Point26_6)
}
An Adder accumulates points on a curve.
type AlphaOverPainter ¶
An AlphaOverPainter is a Painter that paints Spans onto a *image.Alpha using the Over Porter-Duff composition operator.
func NewAlphaOverPainter ¶
func NewAlphaOverPainter(m *image.Alpha) AlphaOverPainter
NewAlphaOverPainter creates a new AlphaOverPainter for the given image.
func (AlphaOverPainter) Paint ¶
func (r AlphaOverPainter) Paint(ss []Span, done bool)
Paint satisfies the Painter interface.
type AlphaSrcPainter ¶
An AlphaSrcPainter is a Painter that paints Spans onto a *image.Alpha using the Src Porter-Duff composition operator.
func NewAlphaSrcPainter ¶
func NewAlphaSrcPainter(m *image.Alpha) AlphaSrcPainter
NewAlphaSrcPainter creates a new AlphaSrcPainter for the given image.
func (AlphaSrcPainter) Paint ¶
func (r AlphaSrcPainter) Paint(ss []Span, done bool)
Paint satisfies the Painter interface.
type Capper ¶
type Capper interface {
// Cap adds a cap to p given a pivot point and the normal vector of a
// terminal segment. The normal's length is half of the stroke width.
Cap(p Adder, halfWidth fixed.Int26_6, pivot, n1 fixed.Point26_6)
}
A Capper signifies how to begin or end a stroked path.
var ButtCapper Capper = CapperFunc(buttCapper)
ButtCapper adds butt caps to a stroked path.
var RoundCapper Capper = CapperFunc(roundCapper)
RoundCapper adds round caps to a stroked path.
var SquareCapper Capper = CapperFunc(squareCapper)
SquareCapper adds square caps to a stroked path.
type CapperFunc ¶
The CapperFunc type adapts an ordinary function to be a Capper.
type GammaCorrectionPainter ¶
type GammaCorrectionPainter struct {
// Painter is the wrapped Painter.
Painter Painter
// contains filtered or unexported fields
}
A GammaCorrectionPainter wraps another Painter, performing gamma-correction on each Span's alpha value.
func NewGammaCorrectionPainter ¶
func NewGammaCorrectionPainter(p Painter, gamma float64) *GammaCorrectionPainter
NewGammaCorrectionPainter creates a new GammaCorrectionPainter that wraps the given Painter.
func (*GammaCorrectionPainter) Paint ¶
func (g *GammaCorrectionPainter) Paint(ss []Span, done bool)
Paint delegates to the wrapped Painter after performing gamma-correction on each Span.
func (*GammaCorrectionPainter) SetGamma ¶
func (g *GammaCorrectionPainter) SetGamma(gamma float64)
SetGamma sets the gamma value.
type Joiner ¶
type Joiner interface {
// Join adds a join to the two sides of a stroked path given a pivot
// point and the normal vectors of the trailing and leading segments.
// Both normals have length equal to half of the stroke width.
Join(lhs, rhs Adder, halfWidth fixed.Int26_6, pivot, n0, n1 fixed.Point26_6)
}
A Joiner signifies how to join interior nodes of a stroked path.
var BevelJoiner Joiner = JoinerFunc(bevelJoiner)
BevelJoiner adds bevel joins to a stroked path.
var RoundJoiner Joiner = JoinerFunc(roundJoiner)
RoundJoiner adds round joins to a stroked path.
type JoinerFunc ¶
The JoinerFunc type adapts an ordinary function to be a Joiner.
type MonochromePainter ¶
type MonochromePainter struct {
Painter Painter
// contains filtered or unexported fields
}
A MonochromePainter wraps another Painter, quantizing each Span's alpha to be either fully opaque or fully transparent.
func NewMonochromePainter ¶
func NewMonochromePainter(p Painter) *MonochromePainter
NewMonochromePainter creates a new MonochromePainter that wraps the given Painter.
func (*MonochromePainter) Paint ¶
func (m *MonochromePainter) Paint(ss []Span, done bool)
Paint delegates to the wrapped Painter after quantizing each Span's alpha value and merging adjacent fully opaque Spans.
type Painter ¶
A Painter knows how to paint a batch of Spans. Rasterization may involve Painting multiple batches, and done will be true for the final batch. The Spans' Y values are monotonically increasing during a rasterization. Paint may use all of ss as scratch space during the call.
type PainterFunc ¶
The PainterFunc type adapts an ordinary function to the Painter interface.
func (PainterFunc) Paint ¶
func (f PainterFunc) Paint(ss []Span, done bool)
Paint just delegates the call to f.
type Path ¶
A Path is a sequence of curves, and a curve is a start point followed by a sequence of linear, quadratic or cubic segments.
func (*Path) Clear ¶
func (p *Path) Clear()
Clear cancels any previous calls to p.Start or p.AddXxx.
type RGBAPainter ¶
type RGBAPainter struct {
// Image is the image to compose onto.
Image *image.RGBA
// Op is the Porter-Duff composition operator.
Op draw.Op
// contains filtered or unexported fields
}
An RGBAPainter is a Painter that paints Spans onto a *image.RGBA.
func NewRGBAPainter ¶
func NewRGBAPainter(m *image.RGBA) *RGBAPainter
NewRGBAPainter creates a new RGBAPainter for the given image.
func (*RGBAPainter) Paint ¶
func (r *RGBAPainter) Paint(ss []Span, done bool)
Paint satisfies the Painter interface.
func (*RGBAPainter) SetColor ¶
func (r *RGBAPainter) SetColor(c color.Color)
SetColor sets the color to paint the spans.
type Rasterizer ¶
type Rasterizer struct {
// If false, the default behavior is to use the even-odd winding fill
// rule during Rasterize.
UseNonZeroWinding bool
// An offset (in pixels) to the painted spans.
Dx, Dy int
// contains filtered or unexported fields
}
func NewRasterizer ¶
func NewRasterizer(width, height int) *Rasterizer
NewRasterizer creates a new Rasterizer with the given bounds.
func (*Rasterizer) Add1 ¶
func (r *Rasterizer) Add1(b fixed.Point26_6)
Add1 adds a linear segment to the current curve.
func (*Rasterizer) Add2 ¶
func (r *Rasterizer) Add2(b, c fixed.Point26_6)
Add2 adds a quadratic segment to the current curve.
func (*Rasterizer) Add3 ¶
func (r *Rasterizer) Add3(b, c, d fixed.Point26_6)
Add3 adds a cubic segment to the current curve.
func (*Rasterizer) Clear ¶
func (r *Rasterizer) Clear()
Clear cancels any previous calls to r.Start or r.AddXxx.
func (*Rasterizer) Rasterize ¶
func (r *Rasterizer) Rasterize(p Painter)
Rasterize converts r's accumulated curves into Spans for p. The Spans passed to p are non-overlapping, and sorted by Y and then X. They all have non-zero width (and 0 <= X0 < X1 <= r.width) and non-zero A, except for the final Span, which has Y, X0, X1 and A all equal to zero.
func (*Rasterizer) SetBounds ¶
func (r *Rasterizer) SetBounds(width, height int)
SetBounds sets the maximum width and height of the rasterized image and calls Clear. The width and height are in pixels, not fixed.Int26_6 units.
func (*Rasterizer) Start ¶
func (r *Rasterizer) Start(a fixed.Point26_6)
Start starts a new curve at the given point.
Source Files