feat: pie chart render function

pie_chart.go

@@ -0,0 +1,111 @@
+// MIT License
+
+// Copyright (c) 2022 Tree Xie
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package charts
+
+import (
+	"math"
+
+	"github.com/wcharczuk/go-chart/v2"
+)
+
+const defaultRadiusPercent = 0.4
+
+func getPieStyle(theme *Theme, index int) chart.Style {
+	seriesColor := theme.GetSeriesColor(index)
+	return chart.Style{
+		StrokeColor: seriesColor,
+		StrokeWidth: 1,
+		FillColor:   seriesColor,
+	}
+
+}
+
+func pieChartRender(opt ChartOption, result *basicRenderResult) (*Draw, error) {
+	d, err := NewDraw(DrawOption{
+		Parent: result.d,
+	}, PaddingOption(chart.Box{
+		Top: result.titleBox.Height(),
+	}))
+	if err != nil {
+		return nil, err
+	}
+
+	values := make([]float64, len(opt.SeriesList))
+	total := float64(0)
+	for index, series := range opt.SeriesList {
+		value := float64(0)
+		for _, item := range series.Data {
+			value += item.Value
+		}
+		values[index] = value
+		total += value
+	}
+	r := d.Render
+	theme := NewTheme(opt.Theme)
+
+	box := d.Box
+	cx := box.Width() >> 1
+	cy := box.Height() >> 1
+
+	diameter := chart.MinInt(box.Width(), box.Height())
+	radius := float64(diameter) * defaultRadiusPercent
+	labelRadius := radius + 20
+
+	if len(values) == 1 {
+		getPieStyle(theme, 0).WriteToRenderer(r)
+		d.moveTo(cx, cy)
+		d.circle(radius, cx, cy)
+	} else {
+		currentValue := float64(0)
+		for index, v := range values {
+			getPieStyle(theme, index).WriteToRenderer(r)
+			d.moveTo(cx, cy)
+			start := chart.PercentToRadians(currentValue/total) - math.Pi/2
+			currentValue += v
+			delta := chart.PercentToRadians(v / total)
+			d.arcTo(cx, cy, radius, radius, start, delta)
+			d.lineTo(cx, cy)
+			r.Close()
+			r.FillStroke()
+
+			// label的角度为饼块中间
+			angle := start + delta/2
+			startx := cx + int(radius*math.Cos(angle))
+			starty := cy + int(radius*math.Sin(angle))
+
+			endx := cx + int(labelRadius*math.Cos(angle))
+			endy := cy + int(labelRadius*math.Sin(angle))
+			d.moveTo(startx, starty)
+			d.lineTo(endx, endy)
+			offset := 30
+			if endx < cx {
+				offset *= -1
+			}
+			d.moveTo(endx, endy)
+			d.lineTo(endx+offset, endy)
+			r.Stroke()
+			// TODO label show
+		}
+	}
+	return result.d, nil
+}