font

Documentation

Overview

Package font provides a simple interface to render fonts. An implementation is allowed to store glyphs in any form (pixmap, vector) but must return them rendered in alpha channel of image.Image.

Index

• Constants
• type Face
• type Magnifier
  • func Magnify(face Face, sx, sy int, mode byte) *Magnifier
  • func (p *Magnifier) Advance(r rune) int
  • func (p *Magnifier) Face() Face
  • func (p *Magnifier) Glyph(r rune) (img image.Image, origin image.Point, advance int)
  • func (p *Magnifier) Scale() (sx, sy int)
  • func (p *Magnifier) SetFace(face Face)
  • func (p *Magnifier) SetScale(sx, sy int)
  • func (p *Magnifier) Size() (height, ascent int)

Constants

const (
	// Nearest means nearest-neighbor scaling. Use if the pixelated look of the
	// scaled font is acceptable or desirable.
	Nearest = images.Nearest

	// Bilinear means bilinear interpolation. Use if the pixelated look of the
	// Nearest is undesirable.
	Bilinear = images.Bilinear
)

Scaling mode.

Types

type Face

type Face interface {
	// Size returns the font face height (interline spacing) and the ascent
	// (height above the baseline).
	Size() (height, ascent int)

	// Advance returns the glyph advance for the given rune. The advance
	// determines the x-distance on the baseline between the origin point of the
	// current character and the origin point of next character.
	Advance(r rune) int

	// Glyph returns the graphical representation of the given rune in the alpha
	// channel of returned image. The image is valid until the next Glyph call
	// which makes Face UNSAFE for concurrent use. The origin point is given in
	// the img coordinates, may be outside of the image bounds.
	Glyph(r rune) (img image.Image, origin image.Point, advance int)
}

Face converts an unicode codepoint (rune) to its graphical representation (glyph) in some font face. A font face represents a specific size, style and weight of a font.

The implementation of Face is allowed to be UNSAFE for concurrent use (see description of Glyph method). In such case a font repository should provide a way to request multiple independend Face instances that represents the same font face in the repository.

type Magnifier

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

Magnifier can wrap Face to scale it up at runtime by integer factor. It can be useful if the available fonts are too small for a display. Magnifier is UNSAFE for concurrent use. A goroutine should magnify the selected font face just before using it and should not share magnified faces with other goroutines.

func Magnify

func Magnify(face Face, sx, sy int, mode byte) *Magnifier

Magnify wraps face into Magnifier to scale it up by scale factor usind given scaling mode.

func (*Magnifier) Advance

func (p *Magnifier) Advance(r rune) int

Advance implements Face interface.

func (*Magnifier) Face

func (p *Magnifier) Face() Face

Face returns the base font face.

func (*Magnifier) Glyph

func (p *Magnifier) Glyph(r rune) (img image.Image, origin image.Point, advance int)

Glyph implements Face interface.

func (*Magnifier) Scale

func (p *Magnifier) Scale() (sx, sy int)

Scale returns current scaling factors.

func (*Magnifier) SetFace

func (p *Magnifier) SetFace(face Face)

SetFace sets the base font face.

func (*Magnifier) SetScale

func (p *Magnifier) SetScale(sx, sy int)

SetScale sets the scaling factor.

func (*Magnifier) Size

func (p *Magnifier) Size() (height, ascent int)

Size implements Face interface.