Add another line chart example, this one showing more use of the Painter

This example disables most of the default rendering (Y-Axis, legend), and instead renders the labels manually on the Painter.

Author: jentfoo

examples/README.md

@@ -14,6 +14,7 @@ Examples are our primary method for demonstrating the starting point our use and
 * [line_chart-1](./line_chart-1) - Basic line chart with some simple styling changes and a demonstration of `null` values.
 * [line_chart-2](./line_chart-2) - The above example line chart re-demonstrated using the Painter API.
 * [line_chart-3](./line_chart-3) - Line chart with dense data and more custom styling configured.
+* [line_chart-4](./line_chart-4) - Line chart with dense data and most default rendering disabled, instead rendering labels manually on the Painter.
 * [line_chart-area](./line_chart-area) - Example line chart with the area below the line shaded.
 * [multiple_charts-1](./multiple_charts-1) - Example of manually building a painter so that you can render 4 charts on the same image.
 * [multiple_charts-2](./multiple_charts-2) - Combining two charts together by writting one chart over the other.

examples/line_chart-4/main.go

@@ -0,0 +1,207 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+
+	"github.com/go-analyze/charts"
+	"github.com/go-analyze/charts/chartdraw/drawing"
+)
+
+/*
+Another line chart example with large data point counts, and use of gaps. This helps demonstrate additional
+configuration and styling, and notably includes custom drawing directly on the Painter.
+
+The data shown here is an example of comparing the f-stop across multiple Canon lens options.
+*/
+
+const startMM = 60
+const endMM = 510
+
+var lensDefinitions = map[string]string{
+	"70-200mm f/2.8":           "70f2.8,201f-", // use a string encoding to define the f/stop point changes
+	"70-200mm f/2.8 + 1.4x TC": "98f4,281f-",
+	"70-200mm f/2.8 + 2x TC":   "140f5.6,401f-",
+	"100-500mm f/4.5-7.1":      "100f4.5,151f5,254f5.6,363f6.3,472f7.1,501f-",
+	//"200-800mm f/6.3-9":        "200f6.3,268f7.1,455f8,637f9,801f-",
+}
+
+func writeFile(buf []byte) error {
+	tmpPath := "./tmp"
+	if err := os.MkdirAll(tmpPath, 0700); err != nil {
+		return err
+	}
+
+	file := filepath.Join(tmpPath, "line-chart-4.png")
+	return os.WriteFile(file, buf, 0600)
+}
+
+func main() {
+	values, xAxisLabels, labels, err := populateData()
+	if err != nil {
+		panic(err)
+	}
+
+	opt := charts.LineChartOption{}
+	opt.Theme = charts.GetTheme(charts.ThemeAnt)
+	opt.Padding = charts.Box{
+		Top:    20,
+		Left:   20,
+		Right:  20,
+		Bottom: 10,
+	}
+	opt.SeriesList = charts.NewSeriesListDataFromValues(values, charts.ChartTypeLine)
+	opt.Title.Text = "Canon RF Zoom Lenses"
+	opt.Title.Offset = charts.OffsetCenter
+	opt.Title.FontStyle.FontSize = 16
+
+	opt.XAxis.Data = xAxisLabels
+	opt.XAxis.Unit = 40
+	opt.XAxis.LabelCount = 10
+	opt.XAxis.BoundaryGap = charts.True()
+	opt.XAxis.FontStyle = charts.FontStyle{
+		FontSize: 6.0,
+	}
+	opt.YAxis = []charts.YAxisOption{
+		{
+			Show:          charts.False(), // disabling in favor of manually printed y-values
+			Min:           charts.FloatPointer(1.4),
+			Max:           charts.FloatPointer(8.0),
+			LabelCount:    4,
+			SpineLineShow: charts.True(),
+			FontStyle: charts.FontStyle{
+				FontSize: 8.0,
+			},
+		},
+	}
+	opt.Legend.Show = charts.False()
+	opt.SymbolShow = charts.False()
+	opt.StrokeWidth = 1.5
+
+	p, err := charts.NewPainter(charts.PainterOptions{
+		OutputFormat: charts.ChartOutputPNG,
+		// positions drawn below depend on the canvas size set here
+		Width:  600,
+		Height: 400,
+	})
+	if err != nil {
+		panic(err)
+	}
+	if _, err = charts.NewLineChart(p, opt).Render(); err != nil {
+		panic(err)
+	}
+
+	// Custom drawing directly on the Painter
+	fontStyle := charts.FontStyle{
+		FontSize:  12,
+		FontColor: drawing.ColorBlack,
+		Font:      charts.GetDefaultFont(),
+	}
+	p.SetFontStyle(fontStyle)
+	//p.TextRotation("f/stop", 10, 170, chartdraw.DegreesToRadians(90))
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(0)
+	p.SetFontStyle(fontStyle)
+	p.Text(labels[0], 420, 84)
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(1)
+	p.SetFontStyle(fontStyle)
+	p.Text(labels[1], 45, 284)
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(2)
+	p.SetFontStyle(fontStyle)
+	p.Text(labels[2], 140, 230)
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(3)
+	p.SetFontStyle(fontStyle)
+	p.Text(labels[3], 160, 155)
+
+	fontStyle.FontSize = 8
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(0)
+	p.SetFontStyle(fontStyle)
+	p.Text("f/4.5", 42, 220)
+	p.Text("f/5.0", 105, 196)
+	p.Text("f/6.3", 370, 137)
+	p.Text("f/7.1", 570, 100)
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(1)
+	p.SetFontStyle(fontStyle)
+	p.Text("f/2.8", 5, 298)
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(2)
+	p.SetFontStyle(fontStyle)
+	p.Text("f/4.0", 40, 244)
+
+	fontStyle.FontColor = opt.Theme.GetSeriesColor(3)
+	p.SetFontStyle(fontStyle)
+	p.Text("f/5.6", 92, 168)
+
+	if buf, err := p.Bytes(); err != nil {
+		panic(err)
+	} else if err = writeFile(buf); err != nil {
+		panic(err)
+	}
+}
+
+func populateData() (values [][]float64, xAxisLabels []string, labels []string, err error) {
+	for k, _ := range lensDefinitions {
+		labels = append(labels, k)
+	}
+	sort.Slice(labels, func(i, j int) bool {
+		return labels[i] < labels[j]
+	})
+
+	for i := startMM; i <= endMM; i++ {
+		xAxisLabels = append(xAxisLabels, fmt.Sprintf("%vmm", i))
+	}
+
+	for _, lens := range labels {
+		parts := strings.Split(lensDefinitions[lens], ",")
+		count := (endMM - startMM) + 1
+		lensValues := make([]float64, count)
+		currentFValue := charts.GetNullValue()
+		// for code simplicity we assume startMM is strictly BEFORE the first lens, this allows us to set null
+		// values until the start point (which will be loaded on the first run of the loop)
+		nextPartIndex := 0
+		nextMM := startMM
+		nextFStop := currentFValue
+		for i := 0; i < count; i++ {
+			if i+startMM == nextMM {
+				currentFValue = nextFStop
+				if nextPartIndex < len(parts) {
+					nextFStop, nextMM, err = parseFStopMM(parts[nextPartIndex])
+					nextPartIndex++
+					if err != nil {
+						return
+					}
+				} else {
+					nextFStop = charts.GetNullValue()
+				}
+			}
+			lensValues[i] = currentFValue
+		}
+		values = append(values, lensValues)
+	}
+
+	return
+}
+
+func parseFStopMM(str string) (float64, int, error) {
+	parts := strings.Split(str, "f")
+	if len(parts) != 2 {
+		return 0, 0, fmt.Errorf("invalid lens spec str: '%s'", str)
+	}
+	mm, err := strconv.Atoi(parts[0])
+	if err != nil {
+		return 0, 0, err
+	}
+	if parts[1] == "-" {
+		return charts.GetNullValue(), mm, nil
+	}
+	fstop, err := strconv.ParseFloat(parts[1], 64)
+	return fstop, mm, err
+}