Package text

Constants

Position specifies the text position.

const (
    PosLeft   = -1
    PosBottom = -1
    PosCenter = 0
    PosTop    = +1
    PosRight  = +1
)

type Handler ¶

Handler parses, formats and renders text.

type Handler interface {
    // Cache returns the cache of fonts used by the text handler.
    Cache() *font.Cache

    // Extents returns the Extents of a font.
    Extents(fnt font.Font) font.Extents

    // Lines splits a given block of text into separate lines.
    Lines(txt string) []string

    // Box returns the bounding box of the given non-multiline text where:
    //  - width is the horizontal space from the origin.
    //  - height is the vertical space above the baseline.
    //  - depth is the vertical space below the baseline, a positive number.
    Box(txt string, fnt font.Font) (width, height, depth vg.Length)

    // Draw renders the given text with the provided style and position
    // on the canvas.
    Draw(c vg.Canvas, txt string, sty Style, pt vg.Point)
}

type Latex ¶

Latex parses, formats and renders LaTeX.

type Latex struct {
    // Fonts is the cache of font faces used by this text handler.
    Fonts *font.Cache

    // DPI is the dot-per-inch controlling the font resolution used by LaTeX.
    // If zero, the resolution defaults to 72.
    DPI float64
}

fonts := font.NewCache(liberation.Collection())
plot.DefaultTextHandler = text.Latex{
    Fonts: fonts,
}

p := plot.New()
p.Title.Text = `$f(x) = \sqrt{\alpha x \Gamma}$`
p.X.Label.Text = `$\frac{\sqrt{x}}{2\pi\Gamma\gamma}$`
p.Y.Label.Text = `$\beta$`

p.X.Min = -1
p.X.Max = +1
p.Y.Min = -1
p.Y.Max = +1

labels, err := plotter.NewLabels(plotter.XYLabels{
    XYs: []plotter.XY{
        {X: +0.0, Y: +0.0},
        {X: -0.9, Y: -0.9},
        {X: +0.6, Y: +0.0},
        {X: +0.5, Y: -0.9},
    },
    Labels: []string{
        `$\frac{\sqrt{x}}{2\pi\Gamma\gamma}$`,
        `$LaTeX$`,
        "plain",
        `$\frac{\sqrt{x}}{2\beta}$`,
    },
})
if err != nil {
    log.Fatalf("could not create labels: %+v", err)
}
labels.TextStyle[0].Font.Size = 24
labels.TextStyle[0].Color = color.RGBA{B: 255, A: 255}
labels.TextStyle[0].XAlign = draw.XCenter
labels.TextStyle[0].YAlign = draw.YCenter

labels.TextStyle[1].Font.Size = 24
labels.TextStyle[1].Color = color.RGBA{R: 255, A: 255}
labels.TextStyle[1].Rotation = math.Pi / 4

labels.TextStyle[2].Font.Size = 24
labels.TextStyle[2].Rotation = math.Pi / 4
labels.TextStyle[2].YAlign = draw.YCenter
labels.TextStyle[2].Handler = &text.Plain{Fonts: fonts}

labels.TextStyle[3].Font.Size = 24
labels.TextStyle[3].Rotation = math.Pi / 2

p.Add(labels)
p.Add(plotter.NewGlyphBoxes())
p.Add(plotter.NewGrid())

err = p.Save(10*vg.Centimeter, 5*vg.Centimeter, "testdata/latex.png")
if err != nil {
    log.Fatalf("could not save plot: %+v", err)
}

func (Latex) Box ¶

func (hdlr Latex) Box(txt string, fnt font.Font) (width, height, depth vg.Length)

Box returns the bounding box of the given non-multiline text where:

• width is the horizontal space from the origin.
• height is the vertical space above the baseline.
• depth is the vertical space below the baseline, a positive number.

func (Latex) Cache ¶

func (hdlr Latex) Cache() *font.Cache

Cache returns the cache of fonts used by the text handler.

func (Latex) Draw ¶

func (hdlr Latex) Draw(c vg.Canvas, txt string, sty Style, pt vg.Point)

Draw renders the given text with the provided style and position on the canvas.

func (Latex) Extents ¶

func (hdlr Latex) Extents(fnt font.Font) font.Extents

Extents returns the Extents of a font.

func (Latex) Lines ¶

func (hdlr Latex) Lines(txt string) []string

Lines splits a given block of text into separate lines.

type Plain ¶

Plain is a text/plain handler.

type Plain struct {
    Fonts *font.Cache
}

func (Plain) Box ¶

func (hdlr Plain) Box(txt string, fnt font.Font) (width, height, depth vg.Length)

Box returns the bounding box of the given non-multiline text where:

• width is the horizontal space from the origin.
• height is the vertical space above the baseline.
• depth is the vertical space below the baseline, a positive number.

func (Plain) Cache ¶

func (hdlr Plain) Cache() *font.Cache

Cache returns the cache of fonts used by the text handler.

func (Plain) Draw ¶

func (hdlr Plain) Draw(c vg.Canvas, txt string, sty Style, pt vg.Point)

Draw renders the given text with the provided style and position on the canvas.

func (Plain) Extents ¶

func (hdlr Plain) Extents(fnt font.Font) font.Extents

Extents returns the Extents of a font.

func (Plain) Lines ¶

func (hdlr Plain) Lines(txt string) []string

Lines splits a given block of text into separate lines.

type Style ¶

Style describes what text will look like.

type Style struct {
    // Color is the text color.
    Color color.Color

    // Font is the font description.
    Font font.Font

    // Rotation is the text rotation in radians, performed around the axis
    // defined by XAlign and YAlign.
    Rotation float64

    // XAlign and YAlign specify the alignment of the text.
    XAlign XAlignment
    YAlign YAlignment

    // Handler parses and formats text according to a given
    // dialect (Markdown, LaTeX, plain, ...)
    // The default is a plain text handler.
    Handler Handler
}

func (Style) FontExtents ¶

func (s Style) FontExtents() font.Extents

FontExtents returns the extents of this Style's font.

func (Style) Height ¶

func (s Style) Height(txt string) vg.Length

Height returns the height of the text when using the given font before any text rotation is applied.

func (Style) Rectangle ¶

func (s Style) Rectangle(txt string) vg.Rectangle

Rectangle returns a rectangle giving the bounds of this text assuming that it is drawn at (0, 0).

func (Style) Width ¶

func (s Style) Width(txt string) (max vg.Length)

Width returns the width of lines of text when using the given font before any text rotation is applied.

type XAlignment ¶

XAlignment specifies text alignment in the X direction. Three preset options are available, but an arbitrary alignment can also be specified using XAlignment(desired number).

type XAlignment float64

const (
    // XLeft aligns the left edge of the text with the specified location.
    XLeft XAlignment = 0
    // XCenter aligns the horizontal center of the text with the specified location.
    XCenter XAlignment = -0.5
    // XRight aligns the right edge of the text with the specified location.
    XRight XAlignment = -1
)

type YAlignment ¶

YAlignment specifies text alignment in the Y direction. Three preset options are available, but an arbitrary alignment can also be specified using YAlignment(desired number).

type YAlignment float64

const (
    // YTop aligns the top of of the text with the specified location.
    YTop YAlignment = -1
    // YCenter aligns the vertical center of the text with the specified location.
    YCenter YAlignment = -0.5
    // YBottom aligns the bottom of the text with the specified location.
    YBottom YAlignment = 0
)