pie_chart.go

package charts

import (
	"errors"
	"math"

	"github.com/golang/freetype/truetype"

	"github.com/go-analyze/charts/chartdraw"
)

type pieChart struct {
	p   *Painter
	opt *PieChartOption
}

type PieChartOption struct {
	// Theme specifies the colors used for the pie chart.
	Theme ColorPalette
	// Padding specifies the padding of pie chart.
	Padding Box
	// Font is the font used to render the chart.
	Font *truetype.Font
	// SeriesList provides the data series.
	SeriesList SeriesList
	// Title are options for rendering the title.
	Title TitleOption
	// Legend are options for the data legend.
	Legend LegendOption
	// backgroundIsFilled is set to true if the background is filled.
	backgroundIsFilled bool
}

// NewPieChart returns a pie chart renderer
func NewPieChart(p *Painter, opt PieChartOption) *pieChart {
	return &pieChart{
		p:   p,
		opt: &opt,
	}
}

type sector struct {
	value       float64
	percent     float64
	cx          int
	cy          int
	rx          float64
	ry          float64
	start       float64
	delta       float64
	offset      int
	quadrant    int
	lineStartX  int
	lineStartY  int
	lineBranchX int
	lineBranchY int
	lineEndX    int
	lineEndY    int
	showLabel   bool
	label       string
	series      Series
	color       Color
}

func NewSector(cx int, cy int, radius float64, labelRadius float64, value float64, currentValue float64, totalValue float64, labelLineLength int, label string, series Series, color Color) sector {
	s := sector{}
	s.value = value
	s.percent = value / totalValue
	s.cx = cx
	s.cy = cy
	s.rx = radius
	s.ry = radius
	p := (currentValue + value/2) / totalValue
	if p < 0.25 {
		s.quadrant = 1
	} else if p < 0.5 {
		s.quadrant = 4
	} else if p < 0.75 {
		s.quadrant = 3
	} else {
		s.quadrant = 2
	}
	s.start = chartdraw.PercentToRadians(currentValue/totalValue) - math.Pi/2
	s.delta = chartdraw.PercentToRadians(value / totalValue)
	angle := s.start + s.delta/2
	s.lineStartX = cx + int(radius*math.Cos(angle))
	s.lineStartY = cy + int(radius*math.Sin(angle))
	s.lineBranchX = cx + int(labelRadius*math.Cos(angle))
	s.lineBranchY = cy + int(labelRadius*math.Sin(angle))
	s.offset = labelLineLength
	if s.lineBranchX <= cx {
		s.offset *= -1
	}
	s.lineEndX = s.lineBranchX + s.offset
	s.lineEndY = s.lineBranchY
	s.series = series
	s.color = color
	s.showLabel = series.Label.Show
	s.label = NewPieLabelFormatter([]string{label}, series.Label.Formatter)(0, s.value, s.percent)
	return s
}

func (s *sector) calculateY(prevY int) int {
	for i := 0; i <= s.cy; i++ {
		if s.quadrant <= 2 {
			if (prevY - s.lineBranchY) > labelFontSize+5 {
				break
			}
			s.lineBranchY -= 1
		} else {
			if (s.lineBranchY - prevY) > labelFontSize+5 {
				break
			}
			s.lineBranchY += 1
		}
	}
	s.lineEndY = s.lineBranchY
	return s.lineBranchY
}

func (s *sector) calculateTextXY(textBox Box) (x int, y int) {
	textMargin := 3
	x = s.lineEndX + textMargin
	y = s.lineEndY + textBox.Height()>>1 - 1
	if s.offset < 0 {
		textWidth := textBox.Width()
		x = s.lineEndX - textWidth - textMargin
	}
	return
}

func (p *pieChart) render(result *defaultRenderResult, seriesList SeriesList) (Box, error) {
	opt := p.opt
	values := make([]float64, len(seriesList))
	total := float64(0)
	radiusValue := ""
	for index, series := range seriesList {
		if len(series.Radius) != 0 {
			radiusValue = series.Radius
		}
		value := float64(0)
		for _, item := range series.Data {
			value += item.Value
		}
		values[index] = value
		total += value
	}
	if total <= 0 {
		return BoxZero, errors.New("the sum value of pie chart should greater than 0")
	}
	seriesPainter := result.seriesPainter
	cx := seriesPainter.Width() >> 1
	cy := seriesPainter.Height() >> 1

	diameter := chartdraw.MinInt(seriesPainter.Width(), seriesPainter.Height())
	radius := getRadius(float64(diameter), radiusValue)

	labelLineWidth := 15
	if radius < 50 {
		labelLineWidth = 10
	}
	labelRadius := radius + float64(labelLineWidth)
	seriesNames := opt.Legend.Data
	if len(seriesNames) == 0 {
		seriesNames = seriesList.Names()
	}
	theme := opt.Theme

	currentValue := float64(0)

	var quadrant1, quadrant2, quadrant3, quadrant4 []sector
	for index, v := range values {
		series := seriesList[index]
		color := theme.GetSeriesColor(index)
		if index == len(values)-1 {
			if color == theme.GetSeriesColor(0) {
				color = theme.GetSeriesColor(1)
			}
		}
		s := NewSector(cx, cy, radius, labelRadius, v, currentValue, total, labelLineWidth, seriesNames[index], series, color)
		switch quadrant := s.quadrant; quadrant {
		case 1:
			quadrant1 = append([]sector{s}, quadrant1...)
		case 2:
			quadrant2 = append(quadrant2, s)
		case 3:
			quadrant3 = append([]sector{s}, quadrant3...)
		case 4:
			quadrant4 = append(quadrant4, s)
		}
		currentValue += v
	}
	sectors := append(quadrant1, quadrant4...)
	sectors = append(sectors, quadrant3...)
	sectors = append(sectors, quadrant2...)

	currentQuadrant := 0
	prevY := 0
	maxY := 0
	minY := 0
	for _, s := range sectors {
		seriesPainter.OverrideDrawingStyle(chartdraw.Style{
			StrokeWidth: 1,
			StrokeColor: s.color,
			FillColor:   s.color,
		})
		seriesPainter.MoveTo(s.cx, s.cy)
		seriesPainter.ArcTo(s.cx, s.cy, s.rx, s.ry, s.start, s.delta).LineTo(s.cx, s.cy).Close().FillStroke()
		if !s.showLabel {
			continue
		}
		if currentQuadrant != s.quadrant {
			currentQuadrant = s.quadrant
			if s.quadrant == 1 {
				minY = cy * 2
				maxY = 0
				prevY = cy * 2
			}
			if s.quadrant == 2 {
				prevY = minY
			}
			if s.quadrant == 3 {
				minY = cy * 2
				maxY = 0
				prevY = 0
			}
			if s.quadrant == 4 {
				prevY = maxY
			}
		}
		prevY = s.calculateY(prevY)
		if prevY > maxY {
			maxY = prevY
		}
		if prevY < minY {
			minY = prevY
		}
		seriesPainter.MoveTo(s.lineStartX, s.lineStartY)
		seriesPainter.LineTo(s.lineBranchX, s.lineBranchY)
		seriesPainter.MoveTo(s.lineBranchX, s.lineBranchY)
		seriesPainter.LineTo(s.lineEndX, s.lineEndY)
		seriesPainter.Stroke()
		textStyle := FontStyle{
			FontColor: theme.GetTextColor(),
			FontSize:  labelFontSize,
			Font:      opt.Font,
		}
		if !s.series.Label.FontStyle.FontColor.IsZero() {
			textStyle.FontColor = s.series.Label.FontStyle.FontColor
		}
		seriesPainter.OverrideFontStyle(textStyle)
		x, y := s.calculateTextXY(seriesPainter.MeasureText(s.label))
		seriesPainter.Text(s.label, x, y)
	}
	return p.p.box, nil
}

func (p *pieChart) Render() (Box, error) {
	opt := p.opt
	if opt.Theme == nil {
		opt.Theme = getPreferredTheme(p.p.theme)
	}

	renderResult, err := defaultRender(p.p, defaultRenderOption{
		Theme:      opt.Theme,
		Padding:    opt.Padding,
		SeriesList: opt.SeriesList,
		XAxis: XAxisOption{
			Show: False(),
		},
		YAxis: []YAxisOption{
			{
				Show: False(),
			},
		},
		Title:              opt.Title,
		Legend:             opt.Legend,
		backgroundIsFilled: opt.backgroundIsFilled,
	})
	if err != nil {
		return BoxZero, err
	}
	seriesList := opt.SeriesList.Filter(ChartTypePie)
	return p.render(renderResult, seriesList)
}