basics of stacked bar.

stacked_bar_chart.go

@@ -0,0 +1,209 @@
+package chart
+
+import (
+	"errors"
+	"io"
+
+	"github.com/golang/freetype/truetype"
+)
+
+// StackedBar is a bar within a StackedBarChart.
+type StackedBar struct {
+	Name   string
+	Width  int
+	Values []Value
+}
+
+// GetWidth returns the width of the bar.
+func (sb StackedBar) GetWidth() int {
+	if sb.Width == 0 {
+		return 20
+	}
+	return sb.Width
+}
+
+// StackedBarChart is a chart that draws sections of a bar based on percentages.
+type StackedBarChart struct {
+	Title      string
+	TitleStyle Style
+
+	Width  int
+	Height int
+	DPI    float64
+
+	Background Style
+	Canvas     Style
+
+	BarSpacing int
+
+	Font        *truetype.Font
+	defaultFont *truetype.Font
+
+	Bars     []StackedBar
+	Elements []Renderable
+}
+
+// GetDPI returns the dpi for the chart.
+func (sbc StackedBarChart) GetDPI(defaults ...float64) float64 {
+	if sbc.DPI == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultDPI
+	}
+	return sbc.DPI
+}
+
+// GetFont returns the text font.
+func (sbc StackedBarChart) GetFont() *truetype.Font {
+	if sbc.Font == nil {
+		return sbc.defaultFont
+	}
+	return sbc.Font
+}
+
+// GetWidth returns the chart width or the default value.
+func (sbc StackedBarChart) GetWidth() int {
+	if sbc.Width == 0 {
+		return DefaultChartWidth
+	}
+	return sbc.Width
+}
+
+// GetHeight returns the chart height or the default value.
+func (sbc StackedBarChart) GetHeight() int {
+	if sbc.Height == 0 {
+		return DefaultChartWidth
+	}
+	return sbc.Height
+}
+
+// GetBarSpacing returns the spacing between bars.
+func (sbc StackedBarChart) GetBarSpacing() int {
+	if sbc.BarSpacing == 0 {
+		return 100
+	}
+	return sbc.BarSpacing
+}
+
+// Render renders the chart with the given renderer to the given io.Writer.
+func (sbc StackedBarChart) Render(rp RendererProvider, w io.Writer) error {
+	if len(sbc.Bars) == 0 {
+		return errors.New("Please provide at least one bar.")
+	}
+
+	r, err := rp(sbc.GetWidth(), sbc.GetHeight())
+	if err != nil {
+		return err
+	}
+
+	if sbc.Font == nil {
+		defaultFont, err := GetDefaultFont()
+		if err != nil {
+			return err
+		}
+		sbc.defaultFont = defaultFont
+	}
+	r.SetDPI(sbc.GetDPI(DefaultDPI))
+
+	canvasBox := sbc.getAdjustedCanvasBox(sbc.getDefaultCanvasBox())
+	sbc.drawBars(r, canvasBox)
+
+	sbc.drawTitle(r)
+	for _, a := range sbc.Elements {
+		a(r, canvasBox, sbc.styleDefaultsElements())
+	}
+
+	return r.Save(w)
+}
+
+func (sbc StackedBarChart) drawBars(r Renderer, canvasBox Box) {
+	xoffset := canvasBox.Left
+	for _, bar := range sbc.Bars {
+		sbc.drawBar(r, canvasBox, xoffset, bar)
+		xoffset += sbc.GetBarSpacing()
+	}
+}
+
+func (sbc StackedBarChart) drawBar(r Renderer, canvasBox Box, xoffset int, bar StackedBar) int {
+	bxl := xoffset
+	bxr := xoffset + bar.GetWidth()
+
+	normalizedBarComponents := Values(bar.Values).Normalize()
+	yoffset := canvasBox.Top
+	for index, bv := range normalizedBarComponents {
+		barHeight := int(bv.Value * float64(canvasBox.Height()))
+		barBox := Box{Top: yoffset, Left: bxl, Right: bxr, Bottom: yoffset + barHeight}
+		DrawBox(r, barBox, bv.Style.InheritFrom(sbc.styleDefaultsStackedBarValue(index)))
+		yoffset += barHeight
+	}
+
+	return bxr
+}
+
+func (sbc StackedBarChart) drawTitle(r Renderer) {
+	if len(sbc.Title) > 0 && sbc.TitleStyle.Show {
+		r.SetFont(sbc.TitleStyle.GetFont(sbc.GetFont()))
+		r.SetFontColor(sbc.TitleStyle.GetFontColor(DefaultTextColor))
+		titleFontSize := sbc.TitleStyle.GetFontSize(DefaultTitleFontSize)
+		r.SetFontSize(titleFontSize)
+
+		textBox := r.MeasureText(sbc.Title)
+
+		textWidth := textBox.Width()
+		textHeight := textBox.Height()
+
+		titleX := (sbc.GetWidth() >> 1) - (textWidth >> 1)
+		titleY := sbc.TitleStyle.Padding.GetTop(DefaultTitleTop) + textHeight
+
+		r.Text(sbc.Title, titleX, titleY)
+	}
+}
+
+func (sbc StackedBarChart) getDefaultCanvasBox() Box {
+	return sbc.Box()
+}
+
+func (sbc StackedBarChart) getAdjustedCanvasBox(canvasBox Box) Box {
+	var totalWidth int
+	for index, bar := range sbc.Bars {
+		totalWidth += bar.GetWidth()
+		if index < len(sbc.Bars)-1 {
+			totalWidth += sbc.GetBarSpacing()
+		}
+	}
+
+	return canvasBox.OuterConstrain(sbc.Box(), Box{
+		Top:    canvasBox.Top,
+		Left:   canvasBox.Left,
+		Right:  canvasBox.Left + totalWidth,
+		Bottom: canvasBox.Bottom,
+	})
+}
+
+// Box returns the chart bounds as a box.
+func (sbc StackedBarChart) Box() Box {
+	dpr := sbc.Background.Padding.GetRight(DefaultBackgroundPadding.Right)
+	dpb := sbc.Background.Padding.GetBottom(DefaultBackgroundPadding.Bottom)
+
+	return Box{
+		Top:    sbc.Background.Padding.GetTop(DefaultBackgroundPadding.Top),
+		Left:   sbc.Background.Padding.GetLeft(DefaultBackgroundPadding.Left),
+		Right:  sbc.GetWidth() - dpr,
+		Bottom: sbc.GetHeight() - dpb,
+	}
+}
+
+func (sbc StackedBarChart) styleDefaultsStackedBarValue(index int) Style {
+	return Style{
+		StrokeColor: GetAlternateColor(index),
+		StrokeWidth: 3.0,
+		FillColor:   GetAlternateColor(index),
+	}
+}
+
+func (sbc StackedBarChart) styleDefaultsElements() Style {
+	return Style{
+		Font: sbc.GetFont(),
+	}
+}