font

package
Version: v2.0.0+incompatible Latest Latest
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Published: Feb 13, 2016 License: AGPL-3.0, Apache-2.0 Imports: 4 Imported by: 0

Documentation

Overview

Package font defines an interface for font faces, for drawing text on an image.

Other packages provide font face implementations. For example, a truetype package would provide one based on .ttf font files.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Drawer

type Drawer struct {
	// Dst is the destination image.
	Dst draw.Image
	// Src is the source image.
	Src image.Image
	// Face provides the glyph mask images.
	Face Face
	// Dot is the baseline location to draw the next glyph. The majority of the
	// affected pixels will be above and to the right of the dot, but some may
	// be below or to the left. For example, drawing a 'j' in an italic face
	// may affect pixels below and to the left of the dot.
	Dot fixed.Point26_6
}

Drawer draws text on a destination image.

A Drawer is not safe for concurrent use by multiple goroutines, since its Face is not.

func (*Drawer) DrawString

func (d *Drawer) DrawString(s string)

DrawString draws s at the dot and advances the dot's location.

func (*Drawer) MeasureString

func (d *Drawer) MeasureString(s string) (advance fixed.Int26_6)

MeasureString returns how far dot would advance by drawing s.

type Face

type Face interface {
	io.Closer

	// Glyph returns the draw.DrawMask parameters (dr, mask, maskp) to draw r's
	// glyph at the sub-pixel destination location dot, and that glyph's
	// advance width.
	//
	// It returns !ok if the face does not contain a glyph for r.
	//
	// The contents of the mask image returned by one Glyph call may change
	// after the next Glyph call. Callers that want to cache the mask must make
	// a copy.
	Glyph(dot fixed.Point26_6, r rune) (
		dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool)

	// GlyphBounds returns the bounding box of r's glyph, drawn at a dot equal
	// to the origin, and that glyph's advance width.
	//
	// It returns !ok if the face does not contain a glyph for r.
	//
	// The glyph's ascent and descent equal -bounds.Min.Y and +bounds.Max.Y. A
	// visual depiction of what these metrics are is at
	// https://developer.apple.com/library/mac/documentation/TextFonts/Conceptual/CocoaTextArchitecture/Art/glyph_metrics_2x.png
	GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool)

	// GlyphAdvance returns the advance width of r's glyph.
	//
	// It returns !ok if the face does not contain a glyph for r.
	GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool)

	// Kern returns the horizontal adjustment for the kerning pair (r0, r1). A
	// positive kern means to move the glyphs further apart.
	Kern(r0, r1 rune) fixed.Int26_6
}

Face is a font face. Its glyphs are often derived from a font file, such as "Comic_Sans_MS.ttf", but a face has a specific size, style, weight and hinting. For example, the 12pt and 18pt versions of Comic Sans are two different faces, even if derived from the same font file.

A Face is not safe for concurrent use by multiple goroutines, as its methods may re-use implementation-specific caches and mask image buffers.

To create a Face, look to other packages that implement specific font file formats.

type Hinting

type Hinting int

Hinting selects how to quantize a vector font's glyph nodes.

Not all fonts support hinting.

const (
	HintingNone Hinting = iota
	HintingVertical
	HintingFull
)

type Stretch

type Stretch int

Stretch selects a normal, condensed, or expanded face.

Not all fonts support stretches.

const (
	StretchUltraCondensed Stretch = -4
	StretchExtraCondensed Stretch = -3
	StretchCondensed      Stretch = -2
	StretchSemiCondensed  Stretch = -1
	StretchNormal         Stretch = +0
	StretchSemiExpanded   Stretch = +1
	StretchExpanded       Stretch = +2
	StretchExtraExpanded  Stretch = +3
	StretchUltraExpanded  Stretch = +4
)

type Style

type Style int

Style selects a normal, italic, or oblique face.

Not all fonts support styles.

const (
	StyleNormal Style = iota
	StyleItalic
	StyleOblique
)

type Weight

type Weight int

Weight selects a normal, light or bold face.

Not all fonts support weights.

const (
	WeightThin       Weight = 100
	WeightExtraLight Weight = 200
	WeightLight      Weight = 300
	WeightNormal     Weight = 400
	WeightMedium     Weight = 500
	WeightSemiBold   Weight = 600
	WeightBold       Weight = 700
	WeightExtraBold  Weight = 800
	WeightBlack      Weight = 900
)

Source Files

Directories

Path Synopsis
Package basicfont provides fixed-size font faces.
Package basicfont provides fixed-size font faces.
Package plan9font implements font faces for the Plan 9 font and subfont file formats.
Package plan9font implements font faces for the Plan 9 font and subfont file formats.

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