color maps

_examples/scatter/main.go

@@ -14,18 +14,19 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 		Series: []chart.Series{
 			chart.ContinuousSeries{
 				Style: chart.Style{
-					Show:        true,
+					Show:             true,
-					StrokeWidth: chart.Disabled,
+					StrokeWidth:      chart.Disabled,
-					DotWidth:    3,
+					DotWidthProvider: func(rx, ry, x, y float64) float64 { return 10 * (y / ry) },
+					DotColorProvider: chart.Vidris,
 				},
-				XValues: chart.Sequence.Random(8192, 1024),
+				XValues: chart.Sequence.Random(128, 1024),
-				YValues: chart.Sequence.Random(8192, 1024),
+				YValues: chart.Sequence.Random(128, 1024),
 			},
 		},
 	}
 
-	res.Header().Set("Content-Type", chart.ContentTypeSVG)
+	res.Header().Set("Content-Type", chart.ContentTypePNG)
-	err := graph.Render(chart.SVG, res)
+	err := graph.Render(chart.PNG, res)
 	if err != nil {
 		log.Println(err.Error())
 	}
@@ -49,8 +50,8 @@ func unit(res http.ResponseWriter, req *http.Request) {
 		},
 	}
 
-	res.Header().Set("Content-Type", chart.ContentTypeSVG)
+	res.Header().Set("Content-Type", chart.ContentTypePNG)
-	err := graph.Render(chart.SVG, res)
+	err := graph.Render(chart.PNG, res)
 	if err != nil {
 		log.Println(err.Error())
 	}

bar_chart.go

@@ -14,6 +14,8 @@ type BarChart struct {
 	Title      string
 	TitleStyle Style
 
+	ColorPalette ColorPalette
+
 	Width  int
 	Height int
 	DPI    float64
@@ -407,23 +409,23 @@ func (bc BarChart) getBackgroundStyle() Style {
 
 func (bc BarChart) styleDefaultsBackground() Style {
 	return Style{
-		FillColor:   DefaultBackgroundColor,
+		FillColor:   bc.GetColorPalette().BackgroundColor(),
-		StrokeColor: DefaultBackgroundStrokeColor,
+		StrokeColor: bc.GetColorPalette().BackgroundStrokeColor(),
 		StrokeWidth: DefaultStrokeWidth,
 	}
 }
 
 func (bc BarChart) styleDefaultsBar(index int) Style {
 	return Style{
-		StrokeColor: GetAlternateColor(index),
+		StrokeColor: bc.GetColorPalette().GetSeriesColor(index),
 		StrokeWidth: 3.0,
-		FillColor:   GetAlternateColor(index),
+		FillColor:   bc.GetColorPalette().GetSeriesColor(index),
 	}
 }
 
 func (bc BarChart) styleDefaultsTitle() Style {
 	return bc.TitleStyle.InheritFrom(Style{
-		FontColor:           DefaultTextColor,
+		FontColor:           bc.GetColorPalette().TextColor(),
 		Font:                bc.GetFont(),
 		FontSize:            bc.getTitleFontSize(),
 		TextHorizontalAlign: TextHorizontalAlignCenter,
@@ -448,10 +450,10 @@ func (bc BarChart) getTitleFontSize() float64 {
 
 func (bc BarChart) styleDefaultsAxes() Style {
 	return Style{
-		StrokeColor:         DefaultAxisColor,
+		StrokeColor:         bc.GetColorPalette().AxisStrokeColor(),
 		Font:                bc.GetFont(),
 		FontSize:            DefaultAxisFontSize,
-		FontColor:           DefaultAxisColor,
+		FontColor:           bc.GetColorPalette().TextColor(),
 		TextHorizontalAlign: TextHorizontalAlignCenter,
 		TextVerticalAlign:   TextVerticalAlignTop,
 		TextWrap:            TextWrapWord,
@@ -463,3 +465,11 @@ func (bc BarChart) styleDefaultsElements() Style {
 		Font: bc.GetFont(),
 	}
 }
+
+// GetColorPalette returns the color palette for the chart.
+func (bc BarChart) GetColorPalette() ColorPalette {
+	if bc.ColorPalette != nil {
+		return bc.ColorPalette
+	}
+	return AlternateColorPalette
+}

chart.go

@@ -14,6 +14,8 @@ type Chart struct {
 	Title      string
 	TitleStyle Style
 
+	ColorPalette ColorPalette
+
 	Width  int
 	Height int
 	DPI    float64
@@ -490,7 +492,7 @@ func (c Chart) drawSeries(r Renderer, canvasBox Box, xrange, yrange, yrangeAlt R
 func (c Chart) drawTitle(r Renderer) {
 	if len(c.Title) > 0 && c.TitleStyle.Show {
 		r.SetFont(c.TitleStyle.GetFont(c.GetFont()))
-		r.SetFontColor(c.TitleStyle.GetFontColor(DefaultTextColor))
+		r.SetFontColor(c.TitleStyle.GetFontColor(c.GetColorPalette().TextColor()))
 		titleFontSize := c.TitleStyle.GetFontSize(DefaultTitleFontSize)
 		r.SetFontSize(titleFontSize)
 
@@ -508,25 +510,24 @@ func (c Chart) drawTitle(r Renderer) {
 
 func (c Chart) styleDefaultsBackground() Style {
 	return Style{
-		FillColor:   DefaultBackgroundColor,
+		FillColor:   c.GetColorPalette().BackgroundColor(),
-		StrokeColor: DefaultBackgroundStrokeColor,
+		StrokeColor: c.GetColorPalette().BackgroundStrokeColor(),
 		StrokeWidth: DefaultBackgroundStrokeWidth,
 	}
 }
 
 func (c Chart) styleDefaultsCanvas() Style {
 	return Style{
-		FillColor:   DefaultCanvasColor,
+		FillColor:   c.GetColorPalette().CanvasColor(),
-		StrokeColor: DefaultCanvasStrokeColor,
+		StrokeColor: c.GetColorPalette().CanvasStrokeColor(),
 		StrokeWidth: DefaultCanvasStrokeWidth,
 	}
 }
 
 func (c Chart) styleDefaultsSeries(seriesIndex int) Style {
-	strokeColor := GetDefaultColor(seriesIndex)
 	return Style{
-		DotColor:    strokeColor,
+		DotColor:    c.GetColorPalette().GetSeriesColor(seriesIndex),
-		StrokeColor: strokeColor,
+		StrokeColor: c.GetColorPalette().GetSeriesColor(seriesIndex),
 		StrokeWidth: DefaultSeriesLineWidth,
 		Font:        c.GetFont(),
 		FontSize:    DefaultFontSize,
@@ -536,9 +537,9 @@ func (c Chart) styleDefaultsSeries(seriesIndex int) Style {
 func (c Chart) styleDefaultsAxes() Style {
 	return Style{
 		Font:        c.GetFont(),
-		FontColor:   DefaultAxisColor,
+		FontColor:   c.GetColorPalette().TextColor(),
 		FontSize:    DefaultAxisFontSize,
-		StrokeColor: DefaultAxisColor,
+		StrokeColor: c.GetColorPalette().AxisStrokeColor(),
 		StrokeWidth: DefaultAxisLineWidth,
 	}
 }
@@ -549,6 +550,14 @@ func (c Chart) styleDefaultsElements() Style {
 	}
 }
 
+// GetColorPalette returns the color palette for the chart.
+func (c Chart) GetColorPalette() ColorPalette {
+	if c.ColorPalette != nil {
+		return c.ColorPalette
+	}
+	return DefaultColorPalette
+}
+
 // Box returns the chart bounds as a box.
 func (c Chart) Box() Box {
 	dpr := c.Background.Padding.GetRight(DefaultBackgroundPadding.Right)

colors.go

@@ -0,0 +1,184 @@
+package chart
+
+import "github.com/wcharczuk/go-chart/drawing"
+
+var (
+	// ColorWhite is white.
+	ColorWhite = drawing.Color{R: 255, G: 255, B: 255, A: 255}
+	// ColorBlue is the basic theme blue color.
+	ColorBlue = drawing.Color{R: 0, G: 116, B: 217, A: 255}
+	// ColorCyan is the basic theme cyan color.
+	ColorCyan = drawing.Color{R: 0, G: 217, B: 210, A: 255}
+	// ColorGreen is the basic theme green color.
+	ColorGreen = drawing.Color{R: 0, G: 217, B: 101, A: 255}
+	// ColorRed is the basic theme red color.
+	ColorRed = drawing.Color{R: 217, G: 0, B: 116, A: 255}
+	// ColorOrange is the basic theme orange color.
+	ColorOrange = drawing.Color{R: 217, G: 101, B: 0, A: 255}
+	// ColorYellow is the basic theme yellow color.
+	ColorYellow = drawing.Color{R: 217, G: 210, B: 0, A: 255}
+	// ColorBlack is the basic theme black color.
+	ColorBlack = drawing.Color{R: 51, G: 51, B: 51, A: 255}
+	// ColorLightGray is the basic theme light gray color.
+	ColorLightGray = drawing.Color{R: 239, G: 239, B: 239, A: 255}
+
+	// ColorAlternateBlue is a alternate theme color.
+	ColorAlternateBlue = drawing.Color{R: 106, G: 195, B: 203, A: 255}
+	// ColorAlternateGreen is a alternate theme color.
+	ColorAlternateGreen = drawing.Color{R: 42, G: 190, B: 137, A: 255}
+	// ColorAlternateGray is a alternate theme color.
+	ColorAlternateGray = drawing.Color{R: 110, G: 128, B: 139, A: 255}
+	// ColorAlternateYellow is a alternate theme color.
+	ColorAlternateYellow = drawing.Color{R: 240, G: 174, B: 90, A: 255}
+	// ColorAlternateLightGray is a alternate theme color.
+	ColorAlternateLightGray = drawing.Color{R: 187, G: 190, B: 191, A: 255}
+
+	// ColorTransparent is a transparent (alpha zero) color.
+	ColorTransparent = drawing.Color{R: 1, G: 1, B: 1, A: 0}
+)
+
+var (
+	// DefaultBackgroundColor is the default chart background color.
+	// It is equivalent to css color:white.
+	DefaultBackgroundColor = ColorWhite
+	// DefaultBackgroundStrokeColor is the default chart border color.
+	// It is equivalent to color:white.
+	DefaultBackgroundStrokeColor = ColorWhite
+	// DefaultCanvasColor is the default chart canvas color.
+	// It is equivalent to css color:white.
+	DefaultCanvasColor = ColorWhite
+	// DefaultCanvasStrokeColor is the default chart canvas stroke color.
+	// It is equivalent to css color:white.
+	DefaultCanvasStrokeColor = ColorWhite
+	// DefaultTextColor is the default chart text color.
+	// It is equivalent to #333333.
+	DefaultTextColor = ColorBlack
+	// DefaultAxisColor is the default chart axis line color.
+	// It is equivalent to #333333.
+	DefaultAxisColor = ColorBlack
+	// DefaultStrokeColor is the default chart border color.
+	// It is equivalent to #efefef.
+	DefaultStrokeColor = ColorLightGray
+	// DefaultFillColor is the default fill color.
+	// It is equivalent to #0074d9.
+	DefaultFillColor = ColorBlue
+	// DefaultAnnotationFillColor is the default annotation background color.
+	DefaultAnnotationFillColor = ColorWhite
+	// DefaultGridLineColor is the default grid line color.
+	DefaultGridLineColor = ColorLightGray
+)
+
+var (
+	// DefaultColors are a couple default series colors.
+	DefaultColors = []drawing.Color{
+		ColorBlue,
+		ColorGreen,
+		ColorRed,
+		ColorCyan,
+		ColorOrange,
+	}
+
+	// DefaultAlternateColors are a couple alternate colors.
+	DefaultAlternateColors = []drawing.Color{
+		ColorAlternateBlue,
+		ColorAlternateGreen,
+		ColorAlternateGray,
+		ColorAlternateYellow,
+		ColorBlue,
+		ColorGreen,
+		ColorRed,
+		ColorCyan,
+		ColorOrange,
+	}
+)
+
+// GetDefaultColor returns a color from the default list by index.
+// NOTE: the index will wrap around (using a modulo).
+func GetDefaultColor(index int) drawing.Color {
+	finalIndex := index % len(DefaultColors)
+	return DefaultColors[finalIndex]
+}
+
+// GetAlternateColor returns a color from the default list by index.
+// NOTE: the index will wrap around (using a modulo).
+func GetAlternateColor(index int) drawing.Color {
+	finalIndex := index % len(DefaultAlternateColors)
+	return DefaultAlternateColors[finalIndex]
+}
+
+// ColorPalette is a set of colors that.
+type ColorPalette interface {
+	BackgroundColor() drawing.Color
+	BackgroundStrokeColor() drawing.Color
+	CanvasColor() drawing.Color
+	CanvasStrokeColor() drawing.Color
+	AxisStrokeColor() drawing.Color
+	TextColor() drawing.Color
+	GetSeriesColor(index int) drawing.Color
+}
+
+// DefaultColorPalette represents the default palatte.
+var DefaultColorPalette defaultColorPalette
+
+type defaultColorPalette struct{}
+
+func (dp defaultColorPalette) BackgroundColor() drawing.Color {
+	return DefaultBackgroundColor
+}
+
+func (dp defaultColorPalette) BackgroundStrokeColor() drawing.Color {
+	return DefaultBackgroundStrokeColor
+}
+
+func (dp defaultColorPalette) CanvasColor() drawing.Color {
+	return DefaultCanvasColor
+}
+
+func (dp defaultColorPalette) CanvasStrokeColor() drawing.Color {
+	return DefaultCanvasStrokeColor
+}
+
+func (dp defaultColorPalette) AxisStrokeColor() drawing.Color {
+	return DefaultAxisColor
+}
+
+func (dp defaultColorPalette) TextColor() drawing.Color {
+	return DefaultTextColor
+}
+
+func (dp defaultColorPalette) GetSeriesColor(index int) drawing.Color {
+	return GetDefaultColor(index)
+}
+
+// AlternateColorPalette represents the default palatte.
+var AlternateColorPalette alternateColorPalette
+
+type alternateColorPalette struct{}
+
+func (ap alternateColorPalette) BackgroundColor() drawing.Color {
+	return DefaultBackgroundColor
+}
+
+func (ap alternateColorPalette) BackgroundStrokeColor() drawing.Color {
+	return DefaultBackgroundStrokeColor
+}
+
+func (ap alternateColorPalette) CanvasColor() drawing.Color {
+	return DefaultCanvasColor
+}
+
+func (ap alternateColorPalette) CanvasStrokeColor() drawing.Color {
+	return DefaultCanvasStrokeColor
+}
+
+func (ap alternateColorPalette) AxisStrokeColor() drawing.Color {
+	return DefaultAxisColor
+}
+
+func (ap alternateColorPalette) TextColor() drawing.Color {
+	return DefaultTextColor
+}
+
+func (ap alternateColorPalette) GetSeriesColor(index int) drawing.Color {
+	return GetAlternateColor(index)
+}

defaults.go

@@ -1,12 +1,5 @@
 package chart
 
-import (
-	"sync"
-
-	"github.com/golang/freetype/truetype"
-	"github.com/wcharczuk/go-chart/drawing"
-)
-
 const (
 	// DefaultChartHeight is the default chart height.
 	DefaultChartHeight = 400
@@ -82,96 +75,6 @@ const (
 	DefaultBarWidth = 50
 )
 
-var (
-	// ColorWhite is white.
-	ColorWhite = drawing.Color{R: 255, G: 255, B: 255, A: 255}
-	// ColorBlue is the basic theme blue color.
-	ColorBlue = drawing.Color{R: 0, G: 116, B: 217, A: 255}
-	// ColorCyan is the basic theme cyan color.
-	ColorCyan = drawing.Color{R: 0, G: 217, B: 210, A: 255}
-	// ColorGreen is the basic theme green color.
-	ColorGreen = drawing.Color{R: 0, G: 217, B: 101, A: 255}
-	// ColorRed is the basic theme red color.
-	ColorRed = drawing.Color{R: 217, G: 0, B: 116, A: 255}
-	// ColorOrange is the basic theme orange color.
-	ColorOrange = drawing.Color{R: 217, G: 101, B: 0, A: 255}
-	// ColorYellow is the basic theme yellow color.
-	ColorYellow = drawing.Color{R: 217, G: 210, B: 0, A: 255}
-	// ColorBlack is the basic theme black color.
-	ColorBlack = drawing.Color{R: 51, G: 51, B: 51, A: 255}
-	// ColorLightGray is the basic theme light gray color.
-	ColorLightGray = drawing.Color{R: 239, G: 239, B: 239, A: 255}
-
-	// ColorAlternateBlue is a alternate theme color.
-	ColorAlternateBlue = drawing.Color{R: 106, G: 195, B: 203, A: 255}
-	// ColorAlternateGreen is a alternate theme color.
-	ColorAlternateGreen = drawing.Color{R: 42, G: 190, B: 137, A: 255}
-	// ColorAlternateGray is a alternate theme color.
-	ColorAlternateGray = drawing.Color{R: 110, G: 128, B: 139, A: 255}
-	// ColorAlternateYellow is a alternate theme color.
-	ColorAlternateYellow = drawing.Color{R: 240, G: 174, B: 90, A: 255}
-	// ColorAlternateLightGray is a alternate theme color.
-	ColorAlternateLightGray = drawing.Color{R: 187, G: 190, B: 191, A: 255}
-
-	// ColorTransparent is a transparent (alpha zero) color.
-	ColorTransparent = drawing.Color{R: 1, G: 1, B: 1, A: 0}
-)
-
-var (
-	// DefaultBackgroundColor is the default chart background color.
-	// It is equivalent to css color:white.
-	DefaultBackgroundColor = ColorWhite
-	// DefaultBackgroundStrokeColor is the default chart border color.
-	// It is equivalent to color:white.
-	DefaultBackgroundStrokeColor = ColorWhite
-	// DefaultCanvasColor is the default chart canvas color.
-	// It is equivalent to css color:white.
-	DefaultCanvasColor = ColorWhite
-	// DefaultCanvasStrokeColor is the default chart canvas stroke color.
-	// It is equivalent to css color:white.
-	DefaultCanvasStrokeColor = ColorWhite
-	// DefaultTextColor is the default chart text color.
-	// It is equivalent to #333333.
-	DefaultTextColor = ColorBlack
-	// DefaultAxisColor is the default chart axis line color.
-	// It is equivalent to #333333.
-	DefaultAxisColor = ColorBlack
-	// DefaultStrokeColor is the default chart border color.
-	// It is equivalent to #efefef.
-	DefaultStrokeColor = ColorLightGray
-	// DefaultFillColor is the default fill color.
-	// It is equivalent to #0074d9.
-	DefaultFillColor = ColorBlue
-	// DefaultAnnotationFillColor is the default annotation background color.
-	DefaultAnnotationFillColor = ColorWhite
-	// DefaultGridLineColor is the default grid line color.
-	DefaultGridLineColor = ColorLightGray
-)
-
-var (
-	// DefaultColors are a couple default series colors.
-	DefaultColors = []drawing.Color{
-		ColorBlue,
-		ColorGreen,
-		ColorRed,
-		ColorCyan,
-		ColorOrange,
-	}
-
-	// DefaultAlternateColors are a couple alternate colors.
-	DefaultAlternateColors = []drawing.Color{
-		ColorAlternateBlue,
-		ColorAlternateGreen,
-		ColorAlternateGray,
-		ColorAlternateYellow,
-		ColorBlue,
-		ColorGreen,
-		ColorRed,
-		ColorCyan,
-		ColorOrange,
-	}
-)
-
 var (
 	// DashArrayDots is a dash array that represents '....' style stroke dashes.
 	DashArrayDots = []int{1, 1}
@@ -183,20 +86,6 @@ var (
 	DashArrayDashesLarge = []int{10, 10}
 )
 
-// GetDefaultColor returns a color from the default list by index.
-// NOTE: the index will wrap around (using a modulo).
-func GetDefaultColor(index int) drawing.Color {
-	finalIndex := index % len(DefaultColors)
-	return DefaultColors[finalIndex]
-}
-
-// GetAlternateColor returns a color from the default list by index.
-// NOTE: the index will wrap around (using a modulo).
-func GetAlternateColor(index int) drawing.Color {
-	finalIndex := index % len(DefaultAlternateColors)
-	return DefaultAlternateColors[finalIndex]
-}
-
 var (
 	// DefaultAnnotationPadding is the padding around an annotation.
 	DefaultAnnotationPadding = Box{Top: 5, Left: 5, Right: 5, Bottom: 5}
@@ -205,27 +94,6 @@ var (
 	DefaultBackgroundPadding = Box{Top: 5, Left: 5, Right: 5, Bottom: 5}
 )
 
-var (
-	_defaultFontLock sync.Mutex
-	_defaultFont     *truetype.Font
-)
-
-// GetDefaultFont returns the default font (Roboto-Medium).
-func GetDefaultFont() (*truetype.Font, error) {
-	if _defaultFont == nil {
-		_defaultFontLock.Lock()
-		defer _defaultFontLock.Unlock()
-		if _defaultFont == nil {
-			font, err := truetype.Parse(roboto)
-			if err != nil {
-				return nil, err
-			}
-			_defaultFont = font
-		}
-	}
-	return _defaultFont, nil
-}
-
 const (
 	// ContentTypePNG is the png mime type.
 	ContentTypePNG = "image/png"

draw.go

@@ -56,15 +56,26 @@ func (d draw) LineSeries(r Renderer, canvasBox Box, xrange, yrange Range, style
 	}
 
 	if style.ShouldDrawDot() {
-		dotWidth := style.GetDotWidth()
+		defaultDotWidth := style.GetDotWidth()
 
 		style.GetDotOptions().WriteDrawingOptionsToRenderer(r)
-
 		for i := 0; i < vs.Len(); i++ {
 			vx, vy = vs.GetValue(i)
 			x = cl + xrange.Translate(vx)
 			y = cb - yrange.Translate(vy)
 
+			dotWidth := defaultDotWidth
+			if style.DotWidthProvider != nil {
+				dotWidth = style.DotWidthProvider(xrange.GetDelta(), yrange.GetDelta(), vx, vy)
+			}
+
+			if style.DotColorProvider != nil {
+				dotColor := style.DotColorProvider(xrange.GetDelta(), yrange.GetDelta(), vx, vy)
+
+				r.SetFillColor(dotColor)
+				r.SetStrokeColor(dotColor)
+			}
+
 			r.Circle(dotWidth, x, y)
 			r.FillStroke()
 		}

font.go

@@ -0,0 +1,28 @@
+package chart
+
+import (
+	"sync"
+
+	"github.com/golang/freetype/truetype"
+)
+
+var (
+	_defaultFontLock sync.Mutex
+	_defaultFont     *truetype.Font
+)
+
+// GetDefaultFont returns the default font (Roboto-Medium).
+func GetDefaultFont() (*truetype.Font, error) {
+	if _defaultFont == nil {
+		_defaultFontLock.Lock()
+		defer _defaultFontLock.Unlock()
+		if _defaultFont == nil {
+			font, err := truetype.Parse(roboto)
+			if err != nil {
+				return nil, err
+			}
+			_defaultFont = font
+		}
+	}
+	return _defaultFont, nil
+}

pie_chart.go

@@ -13,6 +13,8 @@ type PieChart struct {
 	Title      string
 	TitleStyle Style
 
+	ColorPalette ColorPalette
+
 	Width  int
 	Height int
 	DPI    float64
@@ -195,17 +197,17 @@ func (pc PieChart) getCanvasStyle() Style {
 
 func (pc PieChart) styleDefaultsCanvas() Style {
 	return Style{
-		FillColor:   DefaultCanvasColor,
+		FillColor:   pc.GetColorPalette().CanvasColor(),
-		StrokeColor: DefaultCanvasStrokeColor,
+		StrokeColor: pc.GetColorPalette().CanvasStrokeColor(),
 		StrokeWidth: DefaultStrokeWidth,
 	}
 }
 
 func (pc PieChart) styleDefaultsPieChartValue() Style {
 	return Style{
-		StrokeColor: ColorWhite,
+		StrokeColor: pc.GetColorPalette().TextColor(),
 		StrokeWidth: 5.0,
-		FillColor:   ColorWhite,
+		FillColor:   pc.GetColorPalette().TextColor(),
 	}
 }
 
@@ -213,9 +215,9 @@ func (pc PieChart) stylePieChartValue(index int) Style {
 	return pc.SliceStyle.InheritFrom(Style{
 		StrokeColor: ColorWhite,
 		StrokeWidth: 5.0,
-		FillColor:   GetAlternateColor(index),
+		FillColor:   pc.GetColorPalette().GetSeriesColor(index),
 		FontSize:    pc.getScaledFontSize(),
-		FontColor:   ColorWhite,
+		FontColor:   pc.GetColorPalette().TextColor(),
 		Font:        pc.GetFont(),
 	})
 }
@@ -236,8 +238,8 @@ func (pc PieChart) getScaledFontSize() float64 {
 
 func (pc PieChart) styleDefaultsBackground() Style {
 	return Style{
-		FillColor:   DefaultBackgroundColor,
+		FillColor:   pc.GetColorPalette().BackgroundColor(),
-		StrokeColor: DefaultBackgroundStrokeColor,
+		StrokeColor: pc.GetColorPalette().BackgroundStrokeColor(),
 		StrokeWidth: DefaultStrokeWidth,
 	}
 }
@@ -250,7 +252,7 @@ func (pc PieChart) styleDefaultsElements() Style {
 
 func (pc PieChart) styleDefaultsTitle() Style {
 	return pc.TitleStyle.InheritFrom(Style{
-		FontColor:           ColorWhite,
+		FontColor:           pc.GetColorPalette().TextColor(),
 		Font:                pc.GetFont(),
 		FontSize:            pc.getTitleFontSize(),
 		TextHorizontalAlign: TextHorizontalAlignCenter,
@@ -273,6 +275,14 @@ func (pc PieChart) getTitleFontSize() float64 {
 	return 10
 }
 
+// GetColorPalette returns the color palette for the chart.
+func (pc PieChart) GetColorPalette() ColorPalette {
+	if pc.ColorPalette != nil {
+		return pc.ColorPalette
+	}
+	return AlternateColorPalette
+}
+
 // Box returns the chart bounds as a box.
 func (pc PieChart) Box() Box {
 	dpr := pc.Background.Padding.GetRight(DefaultBackgroundPadding.Right)

style.go

@@ -45,6 +45,9 @@ type Style struct {
 	DotColor drawing.Color
 	DotWidth float64
 
+	DotWidthProvider SizeProvider
+	DotColorProvider ColorProvider
+
 	FillColor drawing.Color
 
 	FontSize  float64
@@ -355,6 +358,9 @@ func (s Style) InheritFrom(defaults Style) (final Style) {
 	final.DotColor = s.GetDotColor(defaults.DotColor)
 	final.DotWidth = s.GetDotWidth(defaults.DotWidth)
 
+	final.DotWidthProvider = s.DotWidthProvider
+	final.DotColorProvider = s.DotColorProvider
+
 	final.FillColor = s.GetFillColor(defaults.FillColor)
 	final.FontColor = s.GetFontColor(defaults.FontColor)
 	final.FontSize = s.GetFontSize(defaults.FontSize)
@@ -426,7 +432,7 @@ func (s Style) ShouldDrawStroke() bool {
 
 // ShouldDrawDot tells drawing functions if they should draw the dot.
 func (s Style) ShouldDrawDot() bool {
-	return !s.DotColor.IsZero() && s.DotWidth > 0
+	return (!s.DotColor.IsZero() && s.DotWidth > 0) || s.DotColorProvider != nil || s.DotWidthProvider != nil
 }
 
 // ShouldDrawFill tells drawing functions if they should draw the stroke.

value_provider.go

@@ -1,5 +1,7 @@
 package chart
 
+import "github.com/wcharczuk/go-chart/drawing"
+
 // ValueProvider is a type that produces values.
 type ValueProvider interface {
 	Len() int
@@ -33,3 +35,9 @@ type FullBoundedValueProvider interface {
 	BoundedValueProvider
 	BoundedLastValueProvider
 }
+
+// SizeProvider is a provider for integer size.
+type SizeProvider func(rx, ry, x, y float64) float64
+
+// ColorProvider is a provider for dot size.
+type ColorProvider func(rx, ry, x, y float64) drawing.Color

vidris.go

@@ -0,0 +1,272 @@
+package chart
+
+import "github.com/wcharczuk/go-chart/drawing"
+
+func colorFromValues(r, g, b float64) drawing.Color {
+	return drawing.Color{R: uint8(r * 256), G: uint8(g * 256), B: uint8(b * 256), A: 255}
+}
+
+var vidrisColors = [256]drawing.Color{
+	colorFromValues(0.26700401, 0.00487433, 0.32941519),
+	colorFromValues(0.26851048, 0.00960483, 0.33542652),
+	colorFromValues(0.26994384, 0.01462494, 0.34137895),
+	colorFromValues(0.27130489, 0.01994186, 0.34726862),
+	colorFromValues(0.27259384, 0.02556309, 0.35309303),
+	colorFromValues(0.27380934, 0.03149748, 0.35885256),
+	colorFromValues(0.27495242, 0.03775181, 0.36454323),
+	colorFromValues(0.27602238, 0.04416723, 0.37016418),
+	colorFromValues(0.2770184, 0.05034437, 0.37571452),
+	colorFromValues(0.27794143, 0.05632444, 0.38119074),
+	colorFromValues(0.27879067, 0.06214536, 0.38659204),
+	colorFromValues(0.2795655, 0.06783587, 0.39191723),
+	colorFromValues(0.28026658, 0.07341724, 0.39716349),
+	colorFromValues(0.28089358, 0.07890703, 0.40232944),
+	colorFromValues(0.28144581, 0.0843197, 0.40741404),
+	colorFromValues(0.28192358, 0.08966622, 0.41241521),
+	colorFromValues(0.28232739, 0.09495545, 0.41733086),
+	colorFromValues(0.28265633, 0.10019576, 0.42216032),
+	colorFromValues(0.28291049, 0.10539345, 0.42690202),
+	colorFromValues(0.28309095, 0.11055307, 0.43155375),
+	colorFromValues(0.28319704, 0.11567966, 0.43611482),
+	colorFromValues(0.28322882, 0.12077701, 0.44058404),
+	colorFromValues(0.28318684, 0.12584799, 0.44496),
+	colorFromValues(0.283072, 0.13089477, 0.44924127),
+	colorFromValues(0.28288389, 0.13592005, 0.45342734),
+	colorFromValues(0.28262297, 0.14092556, 0.45751726),
+	colorFromValues(0.28229037, 0.14591233, 0.46150995),
+	colorFromValues(0.28188676, 0.15088147, 0.46540474),
+	colorFromValues(0.28141228, 0.15583425, 0.46920128),
+	colorFromValues(0.28086773, 0.16077132, 0.47289909),
+	colorFromValues(0.28025468, 0.16569272, 0.47649762),
+	colorFromValues(0.27957399, 0.17059884, 0.47999675),
+	colorFromValues(0.27882618, 0.1754902, 0.48339654),
+	colorFromValues(0.27801236, 0.18036684, 0.48669702),
+	colorFromValues(0.27713437, 0.18522836, 0.48989831),
+	colorFromValues(0.27619376, 0.19007447, 0.49300074),
+	colorFromValues(0.27519116, 0.1949054, 0.49600488),
+	colorFromValues(0.27412802, 0.19972086, 0.49891131),
+	colorFromValues(0.27300596, 0.20452049, 0.50172076),
+	colorFromValues(0.27182812, 0.20930306, 0.50443413),
+	colorFromValues(0.27059473, 0.21406899, 0.50705243),
+	colorFromValues(0.26930756, 0.21881782, 0.50957678),
+	colorFromValues(0.26796846, 0.22354911, 0.5120084),
+	colorFromValues(0.26657984, 0.2282621, 0.5143487),
+	colorFromValues(0.2651445, 0.23295593, 0.5165993),
+	colorFromValues(0.2636632, 0.23763078, 0.51876163),
+	colorFromValues(0.26213801, 0.24228619, 0.52083736),
+	colorFromValues(0.26057103, 0.2469217, 0.52282822),
+	colorFromValues(0.25896451, 0.25153685, 0.52473609),
+	colorFromValues(0.25732244, 0.2561304, 0.52656332),
+	colorFromValues(0.25564519, 0.26070284, 0.52831152),
+	colorFromValues(0.25393498, 0.26525384, 0.52998273),
+	colorFromValues(0.25219404, 0.26978306, 0.53157905),
+	colorFromValues(0.25042462, 0.27429024, 0.53310261),
+	colorFromValues(0.24862899, 0.27877509, 0.53455561),
+	colorFromValues(0.2468114, 0.28323662, 0.53594093),
+	colorFromValues(0.24497208, 0.28767547, 0.53726018),
+	colorFromValues(0.24311324, 0.29209154, 0.53851561),
+	colorFromValues(0.24123708, 0.29648471, 0.53970946),
+	colorFromValues(0.23934575, 0.30085494, 0.54084398),
+	colorFromValues(0.23744138, 0.30520222, 0.5419214),
+	colorFromValues(0.23552606, 0.30952657, 0.54294396),
+	colorFromValues(0.23360277, 0.31382773, 0.54391424),
+	colorFromValues(0.2316735, 0.3181058, 0.54483444),
+	colorFromValues(0.22973926, 0.32236127, 0.54570633),
+	colorFromValues(0.22780192, 0.32659432, 0.546532),
+	colorFromValues(0.2258633, 0.33080515, 0.54731353),
+	colorFromValues(0.22392515, 0.334994, 0.54805291),
+	colorFromValues(0.22198915, 0.33916114, 0.54875211),
+	colorFromValues(0.22005691, 0.34330688, 0.54941304),
+	colorFromValues(0.21812995, 0.34743154, 0.55003755),
+	colorFromValues(0.21620971, 0.35153548, 0.55062743),
+	colorFromValues(0.21429757, 0.35561907, 0.5511844),
+	colorFromValues(0.21239477, 0.35968273, 0.55171011),
+	colorFromValues(0.2105031, 0.36372671, 0.55220646),
+	colorFromValues(0.20862342, 0.36775151, 0.55267486),
+	colorFromValues(0.20675628, 0.37175775, 0.55311653),
+	colorFromValues(0.20490257, 0.37574589, 0.55353282),
+	colorFromValues(0.20306309, 0.37971644, 0.55392505),
+	colorFromValues(0.20123854, 0.38366989, 0.55429441),
+	colorFromValues(0.1994295, 0.38760678, 0.55464205),
+	colorFromValues(0.1976365, 0.39152762, 0.55496905),
+	colorFromValues(0.19585993, 0.39543297, 0.55527637),
+	colorFromValues(0.19410009, 0.39932336, 0.55556494),
+	colorFromValues(0.19235719, 0.40319934, 0.55583559),
+	colorFromValues(0.19063135, 0.40706148, 0.55608907),
+	colorFromValues(0.18892259, 0.41091033, 0.55632606),
+	colorFromValues(0.18723083, 0.41474645, 0.55654717),
+	colorFromValues(0.18555593, 0.4185704, 0.55675292),
+	colorFromValues(0.18389763, 0.42238275, 0.55694377),
+	colorFromValues(0.18225561, 0.42618405, 0.5571201),
+	colorFromValues(0.18062949, 0.42997486, 0.55728221),
+	colorFromValues(0.17901879, 0.43375572, 0.55743035),
+	colorFromValues(0.17742298, 0.4375272, 0.55756466),
+	colorFromValues(0.17584148, 0.44128981, 0.55768526),
+	colorFromValues(0.17427363, 0.4450441, 0.55779216),
+	colorFromValues(0.17271876, 0.4487906, 0.55788532),
+	colorFromValues(0.17117615, 0.4525298, 0.55796464),
+	colorFromValues(0.16964573, 0.45626209, 0.55803034),
+	colorFromValues(0.16812641, 0.45998802, 0.55808199),
+	colorFromValues(0.1666171, 0.46370813, 0.55811913),
+	colorFromValues(0.16511703, 0.4674229, 0.55814141),
+	colorFromValues(0.16362543, 0.47113278, 0.55814842),
+	colorFromValues(0.16214155, 0.47483821, 0.55813967),
+	colorFromValues(0.16066467, 0.47853961, 0.55811466),
+	colorFromValues(0.15919413, 0.4822374, 0.5580728),
+	colorFromValues(0.15772933, 0.48593197, 0.55801347),
+	colorFromValues(0.15626973, 0.4896237, 0.557936),
+	colorFromValues(0.15481488, 0.49331293, 0.55783967),
+	colorFromValues(0.15336445, 0.49700003, 0.55772371),
+	colorFromValues(0.1519182, 0.50068529, 0.55758733),
+	colorFromValues(0.15047605, 0.50436904, 0.55742968),
+	colorFromValues(0.14903918, 0.50805136, 0.5572505),
+	colorFromValues(0.14760731, 0.51173263, 0.55704861),
+	colorFromValues(0.14618026, 0.51541316, 0.55682271),
+	colorFromValues(0.14475863, 0.51909319, 0.55657181),
+	colorFromValues(0.14334327, 0.52277292, 0.55629491),
+	colorFromValues(0.14193527, 0.52645254, 0.55599097),
+	colorFromValues(0.14053599, 0.53013219, 0.55565893),
+	colorFromValues(0.13914708, 0.53381201, 0.55529773),
+	colorFromValues(0.13777048, 0.53749213, 0.55490625),
+	colorFromValues(0.1364085, 0.54117264, 0.55448339),
+	colorFromValues(0.13506561, 0.54485335, 0.55402906),
+	colorFromValues(0.13374299, 0.54853458, 0.55354108),
+	colorFromValues(0.13244401, 0.55221637, 0.55301828),
+	colorFromValues(0.13117249, 0.55589872, 0.55245948),
+	colorFromValues(0.1299327, 0.55958162, 0.55186354),
+	colorFromValues(0.12872938, 0.56326503, 0.55122927),
+	colorFromValues(0.12756771, 0.56694891, 0.55055551),
+	colorFromValues(0.12645338, 0.57063316, 0.5498411),
+	colorFromValues(0.12539383, 0.57431754, 0.54908564),
+	colorFromValues(0.12439474, 0.57800205, 0.5482874),
+	colorFromValues(0.12346281, 0.58168661, 0.54744498),
+	colorFromValues(0.12260562, 0.58537105, 0.54655722),
+	colorFromValues(0.12183122, 0.58905521, 0.54562298),
+	colorFromValues(0.12114807, 0.59273889, 0.54464114),
+	colorFromValues(0.12056501, 0.59642187, 0.54361058),
+	colorFromValues(0.12009154, 0.60010387, 0.54253043),
+	colorFromValues(0.11973756, 0.60378459, 0.54139999),
+	colorFromValues(0.11951163, 0.60746388, 0.54021751),
+	colorFromValues(0.11942341, 0.61114146, 0.53898192),
+	colorFromValues(0.11948255, 0.61481702, 0.53769219),
+	colorFromValues(0.11969858, 0.61849025, 0.53634733),
+	colorFromValues(0.12008079, 0.62216081, 0.53494633),
+	colorFromValues(0.12063824, 0.62582833, 0.53348834),
+	colorFromValues(0.12137972, 0.62949242, 0.53197275),
+	colorFromValues(0.12231244, 0.63315277, 0.53039808),
+	colorFromValues(0.12344358, 0.63680899, 0.52876343),
+	colorFromValues(0.12477953, 0.64046069, 0.52706792),
+	colorFromValues(0.12632581, 0.64410744, 0.52531069),
+	colorFromValues(0.12808703, 0.64774881, 0.52349092),
+	colorFromValues(0.13006688, 0.65138436, 0.52160791),
+	colorFromValues(0.13226797, 0.65501363, 0.51966086),
+	colorFromValues(0.13469183, 0.65863619, 0.5176488),
+	colorFromValues(0.13733921, 0.66225157, 0.51557101),
+	colorFromValues(0.14020991, 0.66585927, 0.5134268),
+	colorFromValues(0.14330291, 0.66945881, 0.51121549),
+	colorFromValues(0.1466164, 0.67304968, 0.50893644),
+	colorFromValues(0.15014782, 0.67663139, 0.5065889),
+	colorFromValues(0.15389405, 0.68020343, 0.50417217),
+	colorFromValues(0.15785146, 0.68376525, 0.50168574),
+	colorFromValues(0.16201598, 0.68731632, 0.49912906),
+	colorFromValues(0.1663832, 0.69085611, 0.49650163),
+	colorFromValues(0.1709484, 0.69438405, 0.49380294),
+	colorFromValues(0.17570671, 0.6978996, 0.49103252),
+	colorFromValues(0.18065314, 0.70140222, 0.48818938),
+	colorFromValues(0.18578266, 0.70489133, 0.48527326),
+	colorFromValues(0.19109018, 0.70836635, 0.48228395),
+	colorFromValues(0.19657063, 0.71182668, 0.47922108),
+	colorFromValues(0.20221902, 0.71527175, 0.47608431),
+	colorFromValues(0.20803045, 0.71870095, 0.4728733),
+	colorFromValues(0.21400015, 0.72211371, 0.46958774),
+	colorFromValues(0.22012381, 0.72550945, 0.46622638),
+	colorFromValues(0.2263969, 0.72888753, 0.46278934),
+	colorFromValues(0.23281498, 0.73224735, 0.45927675),
+	colorFromValues(0.2393739, 0.73558828, 0.45568838),
+	colorFromValues(0.24606968, 0.73890972, 0.45202405),
+	colorFromValues(0.25289851, 0.74221104, 0.44828355),
+	colorFromValues(0.25985676, 0.74549162, 0.44446673),
+	colorFromValues(0.26694127, 0.74875084, 0.44057284),
+	colorFromValues(0.27414922, 0.75198807, 0.4366009),
+	colorFromValues(0.28147681, 0.75520266, 0.43255207),
+	colorFromValues(0.28892102, 0.75839399, 0.42842626),
+	colorFromValues(0.29647899, 0.76156142, 0.42422341),
+	colorFromValues(0.30414796, 0.76470433, 0.41994346),
+	colorFromValues(0.31192534, 0.76782207, 0.41558638),
+	colorFromValues(0.3198086, 0.77091403, 0.41115215),
+	colorFromValues(0.3277958, 0.77397953, 0.40664011),
+	colorFromValues(0.33588539, 0.7770179, 0.40204917),
+	colorFromValues(0.34407411, 0.78002855, 0.39738103),
+	colorFromValues(0.35235985, 0.78301086, 0.39263579),
+	colorFromValues(0.36074053, 0.78596419, 0.38781353),
+	colorFromValues(0.3692142, 0.78888793, 0.38291438),
+	colorFromValues(0.37777892, 0.79178146, 0.3779385),
+	colorFromValues(0.38643282, 0.79464415, 0.37288606),
+	colorFromValues(0.39517408, 0.79747541, 0.36775726),
+	colorFromValues(0.40400101, 0.80027461, 0.36255223),
+	colorFromValues(0.4129135, 0.80304099, 0.35726893),
+	colorFromValues(0.42190813, 0.80577412, 0.35191009),
+	colorFromValues(0.43098317, 0.80847343, 0.34647607),
+	colorFromValues(0.44013691, 0.81113836, 0.3409673),
+	colorFromValues(0.44936763, 0.81376835, 0.33538426),
+	colorFromValues(0.45867362, 0.81636288, 0.32972749),
+	colorFromValues(0.46805314, 0.81892143, 0.32399761),
+	colorFromValues(0.47750446, 0.82144351, 0.31819529),
+	colorFromValues(0.4870258, 0.82392862, 0.31232133),
+	colorFromValues(0.49661536, 0.82637633, 0.30637661),
+	colorFromValues(0.5062713, 0.82878621, 0.30036211),
+	colorFromValues(0.51599182, 0.83115784, 0.29427888),
+	colorFromValues(0.52577622, 0.83349064, 0.2881265),
+	colorFromValues(0.5356211, 0.83578452, 0.28190832),
+	colorFromValues(0.5455244, 0.83803918, 0.27562602),
+	colorFromValues(0.55548397, 0.84025437, 0.26928147),
+	colorFromValues(0.5654976, 0.8424299, 0.26287683),
+	colorFromValues(0.57556297, 0.84456561, 0.25641457),
+	colorFromValues(0.58567772, 0.84666139, 0.24989748),
+	colorFromValues(0.59583934, 0.84871722, 0.24332878),
+	colorFromValues(0.60604528, 0.8507331, 0.23671214),
+	colorFromValues(0.61629283, 0.85270912, 0.23005179),
+	colorFromValues(0.62657923, 0.85464543, 0.22335258),
+	colorFromValues(0.63690157, 0.85654226, 0.21662012),
+	colorFromValues(0.64725685, 0.85839991, 0.20986086),
+	colorFromValues(0.65764197, 0.86021878, 0.20308229),
+	colorFromValues(0.66805369, 0.86199932, 0.19629307),
+	colorFromValues(0.67848868, 0.86374211, 0.18950326),
+	colorFromValues(0.68894351, 0.86544779, 0.18272455),
+	colorFromValues(0.69941463, 0.86711711, 0.17597055),
+	colorFromValues(0.70989842, 0.86875092, 0.16925712),
+	colorFromValues(0.72039115, 0.87035015, 0.16260273),
+	colorFromValues(0.73088902, 0.87191584, 0.15602894),
+	colorFromValues(0.74138803, 0.87344918, 0.14956101),
+	colorFromValues(0.75188414, 0.87495143, 0.14322828),
+	colorFromValues(0.76237342, 0.87642392, 0.13706449),
+	colorFromValues(0.77285183, 0.87786808, 0.13110864),
+	colorFromValues(0.78331535, 0.87928545, 0.12540538),
+	colorFromValues(0.79375994, 0.88067763, 0.12000532),
+	colorFromValues(0.80418159, 0.88204632, 0.11496505),
+	colorFromValues(0.81457634, 0.88339329, 0.11034678),
+	colorFromValues(0.82494028, 0.88472036, 0.10621724),
+	colorFromValues(0.83526959, 0.88602943, 0.1026459),
+	colorFromValues(0.84556056, 0.88732243, 0.09970219),
+	colorFromValues(0.8558096, 0.88860134, 0.09745186),
+	colorFromValues(0.86601325, 0.88986815, 0.09595277),
+	colorFromValues(0.87616824, 0.89112487, 0.09525046),
+	colorFromValues(0.88627146, 0.89237353, 0.09537439),
+	colorFromValues(0.89632002, 0.89361614, 0.09633538),
+	colorFromValues(0.90631121, 0.89485467, 0.09812496),
+	colorFromValues(0.91624212, 0.89609127, 0.1007168),
+	colorFromValues(0.92610579, 0.89732977, 0.10407067),
+	colorFromValues(0.93590444, 0.8985704, 0.10813094),
+	colorFromValues(0.94563626, 0.899815, 0.11283773),
+	colorFromValues(0.95529972, 0.90106534, 0.11812832),
+	colorFromValues(0.96489353, 0.90232311, 0.12394051),
+	colorFromValues(0.97441665, 0.90358991, 0.13021494),
+	colorFromValues(0.98386829, 0.90486726, 0.13689671),
+	colorFromValues(0.99324789, 0.90615657, 0.1439362),
+}
+
+// Vidris creates a vidris color map provider.
+func Vidris(rx, ry, x, y float64) drawing.Color {
+	index := uint8((y / ry) * 256)
+	return vidrisColors[index]
+}