feat: support fill area of line chart

.gitignore

@@ -17,3 +17,4 @@
 *.svg
 tmp
 NotoSansSC.ttf
+.vscode

chart_option.go

@@ -66,6 +66,8 @@ type ChartOption struct {
 	SymbolShow *bool
 	// The stroke width of line chart
 	LineStrokeWidth float64
+	// Fill the area of line chart
+	FillArea bool
 	// The child charts
 	Children []ChartOption
 }

charts.go

@@ -381,6 +381,7 @@ func Render(opt ChartOption, opts ...OptionFunc) (*Painter, error) {
 				XAxis:       opt.XAxis,
 				SymbolShow:  opt.SymbolShow,
 				StrokeWidth: opt.LineStrokeWidth,
+				FillArea:    opt.FillArea,
 			}).render(renderResult, lineSeriesList)
 			return err
 		})

examples/area_line_chart/main.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/vicanso/go-charts/v2"
+)
+
+func writeFile(buf []byte) error {
+	tmpPath := "./tmp"
+	err := os.MkdirAll(tmpPath, 0700)
+	if err != nil {
+		return err
+	}
+
+	file := filepath.Join(tmpPath, "area-line-chart.png")
+	err = ioutil.WriteFile(file, buf, 0600)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func main() {
+	values := [][]float64{
+		{
+			120,
+			132,
+			101,
+			134,
+			90,
+			230,
+			210,
+		},
+	}
+	p, err := charts.LineRender(
+		values,
+		charts.TitleTextOptionFunc("Line"),
+		charts.XAxisDataOptionFunc([]string{
+			"Mon",
+			"Tue",
+			"Wed",
+			"Thu",
+			"Fri",
+			"Sat",
+			"Sun",
+		}),
+		charts.LegendLabelsOptionFunc([]string{
+			"Email",
+		}, "50"),
+		func(opt *charts.ChartOption) {
+			opt.Legend.Padding = charts.Box{
+				Top:    5,
+				Bottom: 10,
+			}
+			opt.FillArea = true
+		},
+	)
+
+	if err != nil {
+		panic(err)
+	}
+
+	buf, err := p.Bytes()
+	if err != nil {
+		panic(err)
+	}
+	err = writeFile(buf)
+	if err != nil {
+		panic(err)
+	}
+}

examples/charts/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"fmt"
 	"net/http"
 	"strconv"
 
@@ -261,6 +262,35 @@ func indexHandler(w http.ResponseWriter, req *http.Request) {
 				},
 			},
 		},
+		{
+			Title: charts.TitleOption{
+				Text: "Line Area",
+			},
+			Legend: charts.NewLegendOption([]string{
+				"Email",
+			}),
+			XAxis: charts.NewXAxisOption([]string{
+				"Mon",
+				"Tue",
+				"Wed",
+				"Thu",
+				"Fri",
+				"Sat",
+				"Sun",
+			}),
+			SeriesList: []charts.Series{
+				charts.NewSeriesFromValues([]float64{
+					120,
+					132,
+					101,
+					134,
+					90,
+					230,
+					210,
+				}),
+			},
+			FillArea: true,
+		},
 		// 柱状图
 		{
 			Title: charts.TitleOption{
@@ -1935,5 +1965,6 @@ func echartsHandler(w http.ResponseWriter, req *http.Request) {
 func main() {
 	http.HandleFunc("/", indexHandler)
 	http.HandleFunc("/echarts", echartsHandler)
+	fmt.Println("http://127.0.0.1:3012/")
 	http.ListenAndServe(":3012", nil)
 }

line_chart.go

@@ -64,6 +64,8 @@ type LineChartOption struct {
 	SymbolShow *bool
 	// The stroke width of line
 	StrokeWidth float64
+	// Fill the area of line
+	FillArea bool
 	// background is filled
 	backgroundIsFilled bool
 }
@@ -109,7 +111,6 @@ func (l *lineChart) render(result *defaultRenderResult, seriesList SeriesList) (
 			StrokeWidth: strokeWidth,
 		}
 
-		seriesPainter.SetDrawingStyle(drawingStyle)
 		yRange := result.axisRanges[series.AxisIndex]
 		points := make([]Point, 0)
 		for i, item := range series.Data {
@@ -120,6 +121,25 @@ func (l *lineChart) render(result *defaultRenderResult, seriesList SeriesList) (
 			}
 			points = append(points, p)
 		}
+		// 如果需要填充区域
+		if opt.FillArea {
+			areaPoints := make([]Point, len(points))
+			copy(areaPoints, points)
+			bottomY := yRange.getRestHeight(yRange.min)
+			areaPoints = append(areaPoints, Point{
+				X: areaPoints[len(areaPoints)-1].X,
+				Y: bottomY,
+			}, Point{
+				X: areaPoints[0].X,
+				Y: bottomY,
+			}, areaPoints[0])
+			seriesPainter.SetDrawingStyle(Style{
+				FillColor: seriesColor.WithAlpha(200),
+			})
+			seriesPainter.FillArea(areaPoints)
+		}
+		seriesPainter.SetDrawingStyle(drawingStyle)
+
 		// 画线
 		seriesPainter.LineStroke(points)