Package palette

Variables

var (
    // ErrOverflow is the error returned by ColorMaps when the specified
    // value is greater than the maximum value.
    ErrOverflow = errors.New("palette: specified value > maximum")

    // ErrUnderflow is the error returned by ColorMaps when the specified
    // value is less than the minimum value.
    ErrUnderflow = errors.New("palette: specified value < minimum")

    // ErrNaN is the error returned by ColorMaps when the specified
    // value is NaN.
    ErrNaN = errors.New("palette: specified value == NaN")
)

HSVAModel converts any color.Color to an HSVA color.

var HSVAModel = color.ModelFunc(hsvaModel)

type ColorMap ¶

A ColorMap maps scalar values to colors.

type ColorMap interface {
    // At returns the color associated with the given value.
    // If the value is not between Max() and Min(), an error is returned.
    At(float64) (color.Color, error)

    // Max returns the current maximum value of the ColorMap.
    Max() float64

    // SetMax sets the maximum value of the ColorMap.
    SetMax(float64)

    // Min returns the current minimum value of the ColorMap.
    Min() float64

    // SetMin sets the minimum value of the ColorMap.
    SetMin(float64)

    // Alpha returns the opacity value of the ColorMap.
    Alpha() float64

    // SetAlpha sets the opacity value of the ColorMap. Zero is transparent
    // and one is completely opaque. The default value of alpha should be
    // expected to be one. The function should be expected to panic
    // if alpha is not between zero and one.
    SetAlpha(float64)

    // Palette creates a Palette with the specified number of colors
    // from the ColorMap.
    Palette(colors int) Palette
}

func Reverse ¶

func Reverse(c ColorMap) ColorMap

Reverse reverses the direction of ColorMap c.

p := plot.New()
l := &plotter.ColorBar{ColorMap: moreland.Kindlmann()}
l2 := &plotter.ColorBar{ColorMap: palette.Reverse(moreland.Kindlmann())}
l.ColorMap.SetMin(0.5)
l.ColorMap.SetMax(2.5)
l2.ColorMap.SetMin(2.5)
l2.ColorMap.SetMax(4.5)

p.Add(l, l2)
p.HideY()
p.X.Padding = 0
p.Title.Text = "A ColorMap and its Reverse"

if err := p.Save(300, 48, "testdata/reverse.png"); err != nil {
    log.Panic(err)
}

p := plot.New()
thumbs := plotter.PaletteThumbnailers(palette.Reverse(moreland.Kindlmann()).Palette(10))
for i, t := range thumbs {
    p.Legend.Add(strconv.Itoa(i), t)
}
p.HideAxes()
p.X.Padding = 0
p.Y.Padding = 0

if err := p.Save(35, 120, "testdata/reverse_palette.png"); err != nil {
    log.Panic(err)
}

type DivergingColorMap ¶

DivergingColorMap maps scalar values to colors that diverge from a central value.

type DivergingColorMap interface {
    ColorMap

    // SetConvergePoint sets the value where the diverging colors
    // should meet. The default value should be expected to be
    // (Min() + Max()) / 2. It should be expected that calling either
    // SetMax() or SetMin() will set a new default value, so for a
    // custom convergence point this function should be called after
    // SetMax() and SetMin(). The function should be expected to panic
    // if the value is not between Min() and Max().
    SetConvergePoint(float64)

    // ConvergePoint returns the value where the diverging colors meet.
    ConvergePoint() float64
}

type DivergingPalette ¶

DivergingPalette is a collection of colors ordered into a palette with a critical class or break in the middle of the color range.

type DivergingPalette interface {
    Palette

    // CriticalIndex returns the indices of the lightest
    // (median) color or colors in the DivergingPalette.
    // The low and high index values will be equal when
    // there is a single median color.
    CriticalIndex() (low, high int)
}

func Radial ¶

func Radial(colors int, start, end Hue, alpha float64) DivergingPalette

Radial return a diverging palette across the specified range, through white and with the specified alpha.

type HSVA ¶

HSVA represents a Hue/Saturation/Value/Alpha color. H, S, V and A are valid within [0, 1].

type HSVA struct {
    H, S, V, A float64
}

func (HSVA) RGBA ¶

func (c HSVA) RGBA() (r, g, b, a uint32)

RGBA allows HSVAColor to satisfy the color.Color interface.

type Hue ¶

Hue represents a hue in HSV color space. Valid Hues are within [0, 1].

type Hue float64

const (
    Red Hue = Hue(iota) / 6
    Yellow
    Green
    Cyan
    Blue
    Magenta
)

func (Hue) Complement ¶

func (h Hue) Complement() Hue

Complement returns the complementary hue of a Hue.

type Palette ¶

Palette is a collection of colors ordered into a palette.

type Palette interface {
    Colors() []color.Color
}

func Heat ¶

func Heat(colors int, alpha float64) Palette

Heat returns a red to yellow palette with the specified number of colors and alpha.

func Rainbow ¶

func Rainbow(colors int, start, end Hue, sat, val, alpha float64) Palette

Rainbow returns a rainbow palette with the specified number of colors, saturation value and alpha, and hues in the specified range.

Subdirectories