pie charts!

pie_chart.go

@@ -0,0 +1,284 @@
+package chart
+
+import (
+	"errors"
+	"io"
+	"math"
+
+	"github.com/golang/freetype/truetype"
+)
+
+// PieChartValue is a slice of a pie-chart.
+type PieChartValue struct {
+	Style Style
+	Label string
+	Value float64
+}
+
+// PieChart is a chart that draws sections of a circle based on percentages.
+type PieChart struct {
+	Title      string
+	TitleStyle Style
+
+	Width  int
+	Height int
+	DPI    float64
+
+	Background Style
+	Canvas     Style
+
+	Font        *truetype.Font
+	defaultFont *truetype.Font
+
+	Values   []PieChartValue
+	Elements []Renderable
+}
+
+// GetDPI returns the dpi for the chart.
+func (pc PieChart) GetDPI(defaults ...float64) float64 {
+	if pc.DPI == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultDPI
+	}
+	return pc.DPI
+}
+
+// GetFont returns the text font.
+func (pc PieChart) GetFont() *truetype.Font {
+	if pc.Font == nil {
+		return pc.defaultFont
+	}
+	return pc.Font
+}
+
+// GetWidth returns the chart width or the default value.
+func (pc PieChart) GetWidth() int {
+	if pc.Width == 0 {
+		return DefaultChartWidth
+	}
+	return pc.Width
+}
+
+// GetHeight returns the chart height or the default value.
+func (pc PieChart) GetHeight() int {
+	if pc.Height == 0 {
+		return DefaultChartWidth
+	}
+	return pc.Height
+}
+
+// Render renders the chart with the given renderer to the given io.Writer.
+func (pc PieChart) Render(rp RendererProvider, w io.Writer) error {
+	if len(pc.Values) == 0 {
+		return errors.New("Please provide at least one value.")
+	}
+
+	r, err := rp(pc.GetWidth(), pc.GetHeight())
+	if err != nil {
+		return err
+	}
+
+	if pc.Font == nil {
+		defaultFont, err := GetDefaultFont()
+		if err != nil {
+			return err
+		}
+		pc.defaultFont = defaultFont
+	}
+	r.SetDPI(pc.GetDPI(DefaultDPI))
+
+	canvasBox := pc.getDefaultCanvasBox()
+	canvasBox = pc.getCircleAdjustedCanvasBox(canvasBox)
+
+	pc.drawBackground(r)
+	pc.drawCanvas(r, canvasBox)
+
+	valuesWithPlaceholder, err := pc.finalizeValues(pc.Values)
+	if err != nil {
+		return err
+	}
+	pc.drawSlices(r, canvasBox, valuesWithPlaceholder)
+	pc.drawTitle(r)
+	for _, a := range pc.Elements {
+		a(r, canvasBox, pc.styleDefaultsElements())
+	}
+
+	return r.Save(w)
+}
+
+func (pc PieChart) drawBackground(r Renderer) {
+	DrawBox(r, Box{
+		Right:  pc.GetWidth(),
+		Bottom: pc.GetHeight(),
+	}, pc.getBackgroundStyle())
+}
+
+func (pc PieChart) drawCanvas(r Renderer, canvasBox Box) {
+	DrawBox(r, canvasBox, pc.getCanvasStyle())
+}
+
+func (pc PieChart) drawTitle(r Renderer) {
+	if len(pc.Title) > 0 && pc.TitleStyle.Show {
+		r.SetFont(pc.TitleStyle.GetFont(pc.GetFont()))
+		r.SetFontColor(pc.TitleStyle.GetFontColor(DefaultTextColor))
+		titleFontSize := pc.TitleStyle.GetFontSize(DefaultTitleFontSize)
+		r.SetFontSize(titleFontSize)
+
+		textBox := r.MeasureText(pc.Title)
+
+		textWidth := textBox.Width()
+		textHeight := textBox.Height()
+
+		titleX := (pc.GetWidth() >> 1) - (textWidth >> 1)
+		titleY := pc.TitleStyle.Padding.GetTop(DefaultTitleTop) + textHeight
+
+		r.Text(pc.Title, titleX, titleY)
+	}
+}
+
+func (pc PieChart) drawSlices(r Renderer, canvasBox Box, values []PieChartValue) {
+	cx, cy := canvasBox.Center()
+	diameter := MinInt(canvasBox.Width(), canvasBox.Height())
+	radius := float64(diameter >> 1)
+	radius2 := (radius * 2.0) / 3.0
+
+	var rads, delta, delta2, total float64
+	var lx, ly int
+	for index, v := range values {
+		v.Style.InheritFrom(pc.stylePieChartValue(index)).PersistToRenderer(r)
+		r.MoveTo(cx, cy)
+
+		rads = PercentToRadians(total)
+		delta = PercentToRadians(v.Value)
+
+		r.ArcTo(cx, cy, radius, radius, rads, delta)
+
+		r.LineTo(cx, cy)
+		r.Close()
+		r.FillStroke()
+		total = total + v.Value
+	}
+
+	total = 0
+	for index, v := range values {
+		v.Style.InheritFrom(pc.stylePieChartValue(index)).PersistToRenderer(r)
+		if len(v.Label) > 0 {
+			delta2 = RadianAdd(PercentToRadians(total+(v.Value/2.0)), _pi2)
+			lx = cx + int(radius2*math.Sin(delta2))
+			ly = cy - int(radius2*math.Cos(delta2))
+
+			tb := r.MeasureText(v.Label)
+			lx = lx - (tb.Width() >> 1)
+
+			r.Text(v.Label, lx, ly)
+		}
+		total = total + v.Value
+	}
+}
+
+func (pc PieChart) finalizeValues(values []PieChartValue) ([]PieChartValue, error) {
+	var total float64
+	for _, v := range values {
+		total += v.Value
+		if total > 1.0 {
+			return nil, errors.New("Values total exceeded 1.0; please normalize pie chart values to [0,1.0)")
+		}
+	}
+	remainder := 1.0 - total
+	if RoundDown(remainder, 0.0001) > 0 {
+		return append(values, PieChartValue{
+			Style: pc.styleDefaultsPieChartValue(),
+			Value: remainder,
+		}), nil
+	}
+	return values, nil
+}
+
+func (pc PieChart) getDefaultCanvasBox() Box {
+	return pc.Box()
+}
+
+func (pc PieChart) getCircleAdjustedCanvasBox(canvasBox Box) Box {
+	circleDiameter := MinInt(canvasBox.Width(), canvasBox.Height())
+
+	square := Box{
+		Right:  circleDiameter,
+		Bottom: circleDiameter,
+	}
+
+	return canvasBox.Fit(square)
+}
+
+func (pc PieChart) getBackgroundStyle() Style {
+	return pc.Background.InheritFrom(pc.styleDefaultsBackground())
+}
+
+func (pc PieChart) getCanvasStyle() Style {
+	return pc.Canvas.InheritFrom(pc.styleDefaultsCanvas())
+}
+
+func (pc PieChart) styleDefaultsCanvas() Style {
+	return Style{
+		FillColor:   DefaultCanvasColor,
+		StrokeColor: DefaultCanvasStrokeColor,
+		StrokeWidth: DefaultStrokeWidth,
+	}
+}
+
+func (pc PieChart) styleDefaultsPieChartValue() Style {
+	return Style{
+		StrokeColor: ColorWhite,
+		StrokeWidth: 5.0,
+		FillColor:   ColorWhite,
+	}
+}
+
+func (pc PieChart) stylePieChartValue(index int) Style {
+	return Style{
+		StrokeColor: ColorWhite,
+		StrokeWidth: 5.0,
+		FillColor:   GetDefaultPieChartValueColor(index),
+		FontSize:    24.0,
+		FontColor:   ColorWhite,
+		Font:        pc.GetFont(),
+	}
+}
+
+func (pc PieChart) styleDefaultsBackground() Style {
+	return Style{
+		FillColor:   DefaultBackgroundColor,
+		StrokeColor: DefaultBackgroundStrokeColor,
+		StrokeWidth: DefaultStrokeWidth,
+	}
+}
+
+func (pc PieChart) styleDefaultsSeries(seriesIndex int) Style {
+	strokeColor := GetDefaultSeriesStrokeColor(seriesIndex)
+	return Style{
+		StrokeColor: strokeColor,
+		StrokeWidth: DefaultStrokeWidth,
+		Font:        pc.GetFont(),
+		FontSize:    DefaultFontSize,
+	}
+}
+
+func (pc PieChart) styleDefaultsElements() Style {
+	return Style{
+		Font: pc.GetFont(),
+	}
+}
+
+// Box returns the chart bounds as a box.
+func (pc PieChart) Box() Box {
+	dpr := pc.Background.Padding.GetRight(DefaultBackgroundPadding.Right)
+	dpb := pc.Background.Padding.GetBottom(DefaultBackgroundPadding.Bottom)
+
+	return Box{
+		Top:    pc.Background.Padding.GetTop(DefaultBackgroundPadding.Top),
+		Left:   pc.Background.Padding.GetLeft(DefaultBackgroundPadding.Left),
+		Right:  pc.GetWidth() - dpr,
+		Bottom: pc.GetHeight() - dpb,
+	}
+}