feat: initial release v0.3.0
- Support 9 chart types: line, bar, pie, scatter, bubble, donut, mixed, polar, radar - Multi-format output: ANSI, SVG, PNG, Markdown - Go + Fiber + gonum/plot - Docker support - Morandi color palette
This commit is contained in:
620
internal/renderer/svg.go
Normal file
620
internal/renderer/svg.go
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@@ -0,0 +1,620 @@
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package renderer
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import (
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"bytes"
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"fmt"
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"math"
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"github.com/picoclaw/chart/internal/types"
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"gonum.org/v1/plot"
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"gonum.org/v1/plot/plotter"
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"gonum.org/v1/plot/vg"
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"gonum.org/v1/plot/vg/draw"
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"gonum.org/v1/plot/vg/vgsvg"
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)
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type SVGRenderer struct {
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width vg.Length
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height vg.Length
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}
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func NewSVGRenderer() *SVGRenderer {
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return &SVGRenderer{
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width: 600,
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height: 400,
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}
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}
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func (r *SVGRenderer) Render(chart *types.Chart) ([]byte, error) {
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p := plot.New()
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if chart.Title != "" {
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p.Title.Text = chart.Title
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}
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p.X.Label.Text = ""
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p.Y.Label.Text = ""
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width := r.width
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height := r.height
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if chart.Data.Options != nil {
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if chart.Data.Options.Width > 0 {
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width = vg.Length(chart.Data.Options.Width)
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}
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if chart.Data.Options.Height > 0 {
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height = vg.Length(chart.Data.Options.Height)
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}
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}
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switch chart.Type {
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case types.ChartTypeLine:
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r.addLineChart(p, &chart.Data)
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case types.ChartTypeBar:
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r.addBarChart(p, &chart.Data)
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case types.ChartTypePie:
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return r.renderPieChart(chart, false)
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case types.ChartTypeScatter:
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r.addScatterChart(p, &chart.Data)
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case types.ChartTypeBubble:
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return r.renderBubbleChart(chart)
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case types.ChartTypeDonut:
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return r.renderPieChart(chart, true)
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case types.ChartTypeMixed:
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return r.renderMixedChart(chart)
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case types.ChartTypePolar:
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return r.renderPolarChart(chart)
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case types.ChartTypeRadar:
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return r.renderRadarChart(chart)
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default:
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r.addLineChart(p, &chart.Data)
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}
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var buf bytes.Buffer
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canvas := vgsvg.New(width, height)
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p.Draw(draw.New(canvas))
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_, err := canvas.WriteTo(&buf)
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if err != nil {
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return nil, fmt.Errorf("failed to write svg: %w", err)
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}
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return buf.Bytes(), nil
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}
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func (r *SVGRenderer) addLineChart(p *plot.Plot, data *types.ChartData) {
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for i, dataset := range data.Datasets {
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pts := make(plotter.XYs, len(dataset.Values))
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for j, v := range dataset.Values {
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pts[j].X = float64(j)
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pts[j].Y = v
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}
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line, err := plotter.NewLine(pts)
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if err != nil {
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continue
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}
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colorStr := getColor(i)
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if dataset.Color != "" {
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colorStr = dataset.Color
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}
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line.Color = parseColor(colorStr)
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p.Add(line)
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}
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if len(data.Labels) > 0 {
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p.NominalX(data.Labels...)
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}
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}
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func (r *SVGRenderer) addBarChart(p *plot.Plot, data *types.ChartData) {
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if len(data.Datasets) == 0 {
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return
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}
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dataset := data.Datasets[0]
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labels := data.Labels
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if len(labels) == 0 {
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labels = make([]string, len(dataset.Values))
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for i := range labels {
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labels[i] = fmt.Sprintf("%d", i)
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}
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}
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barChart, err := plotter.NewBarChart(plotter.Values(dataset.Values), vg.Points(20))
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if err != nil {
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return
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}
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barChart.Color = parseColor(getColor(0))
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if len(data.Datasets) > 0 && data.Datasets[0].Color != "" {
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barChart.Color = parseColor(data.Datasets[0].Color)
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}
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p.Add(barChart)
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p.NominalX(labels...)
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}
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func (r *SVGRenderer) renderPieChart(chart *types.Chart, isDonut bool) ([]byte, error) {
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if len(chart.Data.Datasets) == 0 || len(chart.Data.Datasets[0].Values) == 0 {
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return []byte{}, nil
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}
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dataset := chart.Data.Datasets[0]
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values := dataset.Values
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labels := chart.Data.Labels
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total := 0.0
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for _, v := range values {
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total += v
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}
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var sb bytes.Buffer
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sb.WriteString(`<?xml version="1.0" encoding="UTF-8"?>`)
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sb.WriteString(fmt.Sprintf("\n<svg width=\"%v\" height=\"%v\" xmlns=\"http://www.w3.org/2000/svg\">", int(r.width), int(r.height)))
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if chart.Title != "" {
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sb.WriteString(fmt.Sprintf("\n<text x=\"50%\" y=\"30\" text-anchor=\"middle\" font-size=\"16\" font-weight=\"bold\">%s</text>", escapeXML(chart.Title)))
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}
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cx, cy := float64(r.width)/2, float64(r.height)/2-20
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radius := math.Min(cx, cy) * 0.7
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innerRadius := radius * 0.5
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if !isDonut {
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innerRadius = 0
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}
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startAngle := -90.0
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legendY := float64(r.height) - 80
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for i, v := range values {
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label := fmt.Sprintf("Item %d", i+1)
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if i < len(labels) {
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label = labels[i]
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}
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percentage := v / total * 100
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angle := v / total * 360
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color := getColor(i)
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if i < len(dataset.Color) && dataset.Color != "" {
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color = dataset.Color
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}
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endAngle := startAngle + angle
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largeArc := 0
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if angle > 180 {
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largeArc = 1
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}
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if isDonut {
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x1 := cx + radius*math.Cos(startAngle*math.Pi/180)
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y1 := cy + radius*math.Sin(startAngle*math.Pi/180)
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x2 := cx + radius*math.Cos(endAngle*math.Pi/180)
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y2 := cy + radius*math.Sin(endAngle*math.Pi/180)
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x3 := cx + innerRadius*math.Cos(endAngle*math.Pi/180)
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y3 := cy + innerRadius*math.Sin(endAngle*math.Pi/180)
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x4 := cx + innerRadius*math.Cos(startAngle*math.Pi/180)
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y4 := cy + innerRadius*math.Sin(startAngle*math.Pi/180)
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path := fmt.Sprintf("M %f,%f L %f,%f A %f,%f 0 %d,1 %f,%f L %f,%f A %f,%f 0 %d,0 %f,%f Z",
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x4, y4, x1, y1, radius, radius, largeArc, x2, y2, x3, y3, innerRadius, innerRadius, largeArc, x4, y4)
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sb.WriteString(fmt.Sprintf("\n<path d=\"%s\" fill=\"%s\" stroke=\"white\" stroke-width=\"2\"/>", path, color))
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} else {
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x1 := cx + radius*math.Cos(startAngle*math.Pi/180)
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y1 := cy + radius*math.Sin(startAngle*math.Pi/180)
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x2 := cx + radius*math.Cos(endAngle*math.Pi/180)
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y2 := cy + radius*math.Sin(endAngle*math.Pi/180)
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path := fmt.Sprintf("M %f,%f L %f,%f A %f,%f 0 %d,1 %f,%f Z",
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cx, cy, x1, y1, radius, radius, largeArc, x2, y2)
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sb.WriteString(fmt.Sprintf("\n<path d=\"%s\" fill=\"%s\" stroke=\"white\" stroke-width=\"2\"/>", path, color))
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sb.WriteString(fmt.Sprintf("\n<text x=\"%f\" y=\"%f\" text-anchor=\"middle\" font-size=\"12\" fill=\"white\">%.1f%%</text>",
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cx+radius*0.5*math.Cos((startAngle+angle/2)*math.Pi/180),
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cy+radius*0.5*math.Sin((startAngle+angle/2)*math.Pi/180),
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percentage))
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}
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sb.WriteString(fmt.Sprintf("\n<rect x=\"%f\" y=\"%f\" width=\"15\" height=\"15\" fill=\"%s\"/>", 20, legendY+float64(i)*25, color))
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sb.WriteString(fmt.Sprintf("\n<text x=\"40\" y=\"%f\" font-size=\"12\">%s: %.2f (%.1f%%)</text>", legendY+float64(i)*25+12, escapeXML(label), v, percentage))
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startAngle = endAngle
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}
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sb.WriteString("\n</svg>")
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return sb.Bytes(), nil
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}
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func (r *SVGRenderer) addScatterChart(p *plot.Plot, data *types.ChartData) {
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for i, dataset := range data.Datasets {
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pts := make(plotter.XYs, len(dataset.Values))
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for j, v := range dataset.Values {
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pts[j].X = float64(j)
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pts[j].Y = v
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}
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scatter, err := plotter.NewScatter(pts)
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if err != nil {
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continue
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}
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colorStr := getColor(i)
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if dataset.Color != "" {
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colorStr = dataset.Color
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}
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scatter.Color = parseColor(colorStr)
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scatter.GlyphStyle.Radius = vg.Points(4)
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p.Add(scatter)
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}
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if len(data.Labels) > 0 {
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p.NominalX(data.Labels...)
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}
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}
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func escapeXML(s string) string {
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var result bytes.Buffer
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for _, c := range s {
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switch c {
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case '<':
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result.WriteString("<")
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case '>':
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result.WriteString(">")
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case '&':
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result.WriteString("&")
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case '"':
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result.WriteString(""")
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case '\'':
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result.WriteString("'")
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default:
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result.WriteRune(c)
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}
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}
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return result.String()
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}
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func (r *SVGRenderer) renderBubbleChart(chart *types.Chart) ([]byte, error) {
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if len(chart.Data.Datasets) == 0 {
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return []byte{}, nil
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}
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var sb bytes.Buffer
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sb.WriteString(`<?xml version="1.0" encoding="UTF-8"?>`)
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sb.WriteString(fmt.Sprintf("\n<svg width=\"%v\" height=\"%v\" xmlns=\"http://www.w3.org/2000/svg\">", int(r.width), int(r.height)))
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if chart.Title != "" {
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sb.WriteString(fmt.Sprintf("\n<text x=\"50%%\" y=\"30\" text-anchor=\"middle\" font-size=\"16\" font-weight=\"bold\">%s</text>", escapeXML(chart.Title)))
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}
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padding := 60.0
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chartWidth := float64(r.width) - 2*padding
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chartHeight := float64(r.height) - 2*padding
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maxValue := 0.0
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maxBubble := 0.0
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for _, dataset := range chart.Data.Datasets {
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for i, v := range dataset.Values {
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if v > maxValue {
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maxValue = v
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}
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if i < len(dataset.Values) && float64(i+1)*50 > maxBubble {
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maxBubble = float64(i+1) * 50
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}
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}
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}
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if maxValue == 0 {
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maxValue = 100
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}
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if maxBubble == 0 {
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maxBubble = 100
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}
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sb.WriteString(fmt.Sprintf("\n<rect x=\"%f\" y=\"%f\" width=\"%f\" height=\"%f\" fill=\"#f8f9fa\" stroke=\"#ddd\"/>", padding, padding, chartWidth, chartHeight))
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for i, dataset := range chart.Data.Datasets {
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color := getColor(i)
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if dataset.Color != "" {
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color = dataset.Color
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}
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for j, v := range dataset.Values {
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x := padding + (float64(j)/float64(len(dataset.Values)))*chartWidth
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y := padding + chartHeight - (v/maxValue)*chartHeight
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bubbleRadius := 10 + (v/maxValue)*30
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sb.WriteString(fmt.Sprintf("\n<circle cx=\"%f\" cy=\"%f\" r=\"%f\" fill=\"%s\" opacity=\"0.6\" stroke=\"%s\" stroke-width=\"2\"/>",
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x, y, bubbleRadius, color, color))
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sb.WriteString(fmt.Sprintf("\n<text x=\"%f\" y=\"%f\" text-anchor=\"middle\" font-size=\"10\" fill=\"#333\">%.0f</text>",
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x, y+4, v))
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}
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}
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labels := chart.Data.Labels
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if len(labels) > 0 {
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labelSpacing := chartWidth / float64(len(labels)-1)
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for i, label := range labels {
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x := padding + float64(i)*labelSpacing
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sb.WriteString(fmt.Sprintf("\n<text x=\"%f\" y=\"%f\" text-anchor=\"middle\" font-size=\"11\" fill=\"#666\">%s</text>",
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x, float64(r.height)-padding+20, escapeXML(label)))
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}
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}
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sb.WriteString("\n</svg>")
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return sb.Bytes(), nil
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}
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func (r *SVGRenderer) renderMixedChart(chart *types.Chart) ([]byte, error) {
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if len(chart.Data.Datasets) == 0 {
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return []byte{}, nil
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}
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p := plot.New()
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if chart.Title != "" {
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p.Title.Text = chart.Title
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}
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p.X.Label.Text = ""
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p.Y.Label.Text = ""
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padding := 60.0
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chartWidth := float64(r.width) - 2*padding
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chartHeight := float64(r.height) - 2*padding
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labels := chart.Data.Labels
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if len(labels) == 0 {
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labels = make([]string, len(chart.Data.Datasets[0].Values))
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for i := range labels {
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labels[i] = fmt.Sprintf("%d", i+1)
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}
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}
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maxValue := 0.0
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for _, dataset := range chart.Data.Datasets {
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for _, v := range dataset.Values {
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if v > maxValue {
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maxValue = v
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}
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}
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}
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if maxValue == 0 {
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maxValue = 100
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}
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var sb bytes.Buffer
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sb.WriteString(`<?xml version="1.0" encoding="UTF-8"?>`)
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sb.WriteString(fmt.Sprintf("\n<svg width=\"%v\" height=\"%v\" xmlns=\"http://www.w3.org/2000/svg\">", int(r.width), int(r.height)))
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if chart.Title != "" {
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sb.WriteString(fmt.Sprintf("\n<text x=\"50%%\" y=\"25\" text-anchor=\"middle\" font-size=\"16\" font-weight=\"bold\">%s</text>", escapeXML(chart.Title)))
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}
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sb.WriteString(fmt.Sprintf("\n<rect x=\"%f\" y=\"%f\" width=\"%f\" height=\"%f\" fill=\"#f8f9fa\" stroke=\"#ddd\"/>", padding, padding, chartWidth, chartHeight))
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barWidth := chartWidth / float64(len(labels)*len(chart.Data.Datasets)+len(chart.Data.Datasets))
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seriesWidth := barWidth * float64(len(labels))
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for i, dataset := range chart.Data.Datasets {
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color := getColor(i)
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if dataset.Color != "" {
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color = dataset.Color
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}
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isLine := i%2 == 1
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if isLine {
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points := ""
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for j, v := range dataset.Values {
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x := padding + float64(j)*seriesWidth + seriesWidth/2
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y := padding + chartHeight - (v/maxValue)*chartHeight
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points += fmt.Sprintf("%f,%f ", x, y)
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}
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sb.WriteString(fmt.Sprintf("\n<polyline points=\"%s\" fill=\"none\" stroke=\"%s\" stroke-width=\"3\"/>", points, color))
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for j, v := range dataset.Values {
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x := padding + float64(j)*seriesWidth + seriesWidth/2
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y := padding + chartHeight - (v/maxValue)*chartHeight
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sb.WriteString(fmt.Sprintf("\n<circle cx=\"%f\" cy=\"%f\" r=\"5\" fill=\"%s\"/>", x, y, color))
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}
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} else {
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for j, v := range dataset.Values {
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x := padding + float64(j)*seriesWidth + float64(i)*barWidth
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barHeight := (v / maxValue) * chartHeight
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y := padding + chartHeight - barHeight
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sb.WriteString(fmt.Sprintf("\n<rect x=\"%f\" y=\"%f\" width=\"%f\" height=\"%f\" fill=\"%s\"/>", x, y, barWidth*0.8, barHeight, color))
|
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}
|
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}
|
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}
|
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labelSpacing := chartWidth / float64(len(labels))
|
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for i, label := range labels {
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x := padding + float64(i)*labelSpacing + labelSpacing/2
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sb.WriteString(fmt.Sprintf("\n<text x=\"%f\" y=\"%f\" text-anchor=\"middle\" font-size=\"11\" fill=\"#666\">%s</text>",
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x, float64(r.height)-padding+20, escapeXML(label)))
|
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}
|
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sb.WriteString("\n</svg>")
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return sb.Bytes(), nil
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}
|
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func (r *SVGRenderer) renderPolarChart(chart *types.Chart) ([]byte, error) {
|
||||
if len(chart.Data.Datasets) == 0 || len(chart.Data.Datasets[0].Values) == 0 {
|
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return []byte{}, nil
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}
|
||||
|
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dataset := chart.Data.Datasets[0]
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values := dataset.Values
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labels := chart.Data.Labels
|
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maxValue := 0.0
|
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for _, v := range values {
|
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if v > maxValue {
|
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maxValue = v
|
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}
|
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}
|
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if maxValue == 0 {
|
||||
maxValue = 100
|
||||
}
|
||||
|
||||
var sb bytes.Buffer
|
||||
sb.WriteString(`<?xml version="1.0" encoding="UTF-8"?>`)
|
||||
sb.WriteString(fmt.Sprintf("\n<svg width=\"%v\" height=\"%v\" xmlns=\"http://www.w3.org/2000/svg\">", int(r.width), int(r.height)))
|
||||
|
||||
if chart.Title != "" {
|
||||
sb.WriteString(fmt.Sprintf("\n<text x=\"50%%\" y=\"25\" text-anchor=\"middle\" font-size=\"16\" font-weight=\"bold\">%s</text>", escapeXML(chart.Title)))
|
||||
}
|
||||
|
||||
cx, cy := float64(r.width)/2, float64(r.height)/2
|
||||
radius := math.Min(cx, cy) * 0.6
|
||||
|
||||
numCategories := len(values)
|
||||
angleStep := 360.0 / float64(numCategories)
|
||||
|
||||
for i := 1; i <= 4; i++ {
|
||||
rRing := radius * float64(i) / 4
|
||||
points := ""
|
||||
for j := 0; j <= numCategories; j++ {
|
||||
angle := -90 + float64(j)*angleStep
|
||||
x := cx + rRing*math.Cos(angle*math.Pi/180)
|
||||
y := cy + rRing*math.Sin(angle*math.Pi/180)
|
||||
points += fmt.Sprintf("%f,%f ", x, y)
|
||||
}
|
||||
sb.WriteString(fmt.Sprintf("\n<polygon points=\"%s\" fill=\"none\" stroke=\"#ddd\" stroke-width=\"1\"/>", points))
|
||||
}
|
||||
|
||||
nodes := ""
|
||||
for i, v := range values {
|
||||
angle := -90 + float64(i)*angleStep
|
||||
normalizedValue := v / maxValue
|
||||
x := cx + radius*normalizedValue*math.Cos(angle*math.Pi/180)
|
||||
y := cy + radius*normalizedValue*math.Sin(angle*math.Pi/180)
|
||||
nodes += fmt.Sprintf("%f,%f ", x, y)
|
||||
|
||||
labelRadius := radius + 25
|
||||
labelX := cx + labelRadius*math.Cos(angle*math.Pi/180)
|
||||
labelY := cy + labelRadius*math.Sin(angle*math.Pi/180)
|
||||
|
||||
label := fmt.Sprintf("Item %d", i+1)
|
||||
if i < len(labels) {
|
||||
label = labels[i]
|
||||
}
|
||||
|
||||
anchor := "middle"
|
||||
if math.Cos(angle*math.Pi/180) > 0.1 {
|
||||
anchor = "start"
|
||||
} else if math.Cos(angle*math.Pi/180) < -0.1 {
|
||||
anchor = "end"
|
||||
}
|
||||
|
||||
sb.WriteString(fmt.Sprintf("\n<text x=\"%f\" y=\"%f\" text-anchor=\"%s\" font-size=\"11\" fill=\"#666\">%s</text>",
|
||||
labelX, labelY+4, anchor, escapeXML(label)))
|
||||
}
|
||||
|
||||
color := getColor(0)
|
||||
if dataset.Color != "" {
|
||||
color = dataset.Color
|
||||
}
|
||||
sb.WriteString(fmt.Sprintf("\n<polygon points=\"%s\" fill=\"%s\" opacity=\"0.5\" stroke=\"%s\" stroke-width=\"2\"/>", nodes, color, color))
|
||||
|
||||
sb.WriteString("\n</svg>")
|
||||
return sb.Bytes(), nil
|
||||
}
|
||||
|
||||
func (r *SVGRenderer) renderRadarChart(chart *types.Chart) ([]byte, error) {
|
||||
if len(chart.Data.Datasets) == 0 || len(chart.Data.Datasets[0].Values) == 0 {
|
||||
return []byte{}, nil
|
||||
}
|
||||
|
||||
dataset := chart.Data.Datasets[0]
|
||||
values := dataset.Values
|
||||
labels := chart.Data.Labels
|
||||
|
||||
maxValue := 0.0
|
||||
for _, v := range values {
|
||||
if v > maxValue {
|
||||
maxValue = v
|
||||
}
|
||||
}
|
||||
if maxValue == 0 {
|
||||
maxValue = 100
|
||||
}
|
||||
|
||||
var sb bytes.Buffer
|
||||
sb.WriteString(`<?xml version="1.0" encoding="UTF-8"?>`)
|
||||
sb.WriteString(fmt.Sprintf("\n<svg width=\"%v\" height=\"%v\" xmlns=\"http://www.w3.org/2000/svg\">", int(r.width), int(r.height)))
|
||||
|
||||
if chart.Title != "" {
|
||||
sb.WriteString(fmt.Sprintf("\n<text x=\"50%%\" y=\"25\" text-anchor=\"middle\" font-size=\"16\" font-weight=\"bold\">%s</text>", escapeXML(chart.Title)))
|
||||
}
|
||||
|
||||
cx, cy := float64(r.width)/2, float64(r.height)/2
|
||||
radius := math.Min(cx, cy) * 0.5
|
||||
|
||||
numAxes := len(values)
|
||||
angleStep := 360.0 / float64(numAxes)
|
||||
|
||||
for level := 1; level <= 5; level++ {
|
||||
rLevel := radius * float64(level) / 5
|
||||
points := ""
|
||||
for i := 0; i <= numAxes; i++ {
|
||||
angle := -90 + float64(i)*angleStep
|
||||
x := cx + rLevel*math.Cos(angle*math.Pi/180)
|
||||
y := cy + rLevel*math.Sin(angle*math.Pi/180)
|
||||
points += fmt.Sprintf("%f,%f ", x, y)
|
||||
}
|
||||
sb.WriteString(fmt.Sprintf("\n<polygon points=\"%s\" fill=\"none\" stroke=\"#ddd\" stroke-width=\"1\"/>", points))
|
||||
}
|
||||
|
||||
for i := 0; i < len(values); i++ {
|
||||
angle := -90 + float64(i)*angleStep
|
||||
x := cx + radius*math.Cos(angle*math.Pi/180)
|
||||
y := cy + radius*math.Sin(angle*math.Pi/180)
|
||||
sb.WriteString(fmt.Sprintf("\n<line x1=\"%f\" y1=\"%f\" x2=\"%f\" y2=\"%f\" stroke=\"#ddd\" stroke-width=\"1\"/>", cx, cy, x, y))
|
||||
|
||||
labelRadius := radius + 20
|
||||
labelX := cx + labelRadius*math.Cos(angle*math.Pi/180)
|
||||
labelY := cy + labelRadius*math.Sin(angle*math.Pi/180)
|
||||
|
||||
label := fmt.Sprintf("Item %d", i+1)
|
||||
if i < len(labels) {
|
||||
label = labels[i]
|
||||
}
|
||||
|
||||
anchor := "middle"
|
||||
if math.Cos(angle*math.Pi/180) > 0.1 {
|
||||
anchor = "start"
|
||||
} else if math.Cos(angle*math.Pi/180) < -0.1 {
|
||||
anchor = "end"
|
||||
}
|
||||
|
||||
sb.WriteString(fmt.Sprintf("\n<text x=\"%f\" y=\"%f\" text-anchor=\"%s\" font-size=\"11\" fill=\"#666\">%s</text>",
|
||||
labelX, labelY+4, anchor, escapeXML(label)))
|
||||
}
|
||||
|
||||
nodes := ""
|
||||
for i, v := range values {
|
||||
angle := -90 + float64(i)*angleStep
|
||||
normalizedValue := v / maxValue
|
||||
x := cx + radius*normalizedValue*math.Cos(angle*math.Pi/180)
|
||||
y := cy + radius*normalizedValue*math.Sin(angle*math.Pi/180)
|
||||
nodes += fmt.Sprintf("%f,%f ", x, y)
|
||||
}
|
||||
|
||||
color := getColor(0)
|
||||
if dataset.Color != "" {
|
||||
color = dataset.Color
|
||||
}
|
||||
sb.WriteString(fmt.Sprintf("\n<polygon points=\"%s\" fill=\"%s\" opacity=\"0.3\" stroke=\"%s\" stroke-width=\"2\"/>", nodes, color, color))
|
||||
|
||||
for i, v := range values {
|
||||
angle := -90 + float64(i)*angleStep
|
||||
normalizedValue := v / maxValue
|
||||
x := cx + radius*normalizedValue*math.Cos(angle*math.Pi/180)
|
||||
y := cy + radius*normalizedValue*math.Sin(angle*math.Pi/180)
|
||||
sb.WriteString(fmt.Sprintf("\n<circle cx=\"%f\" cy=\"%f\" r=\"4\" fill=\"%s\"/>", x, y, color))
|
||||
}
|
||||
|
||||
sb.WriteString("\n</svg>")
|
||||
return sb.Bytes(), nil
|
||||
}
|
||||
Reference in New Issue
Block a user