example embedded png plots html outputter

plots.go

package main

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"log"
	"math/rand"
	"net/http"
	"time"

	"gonum.org/v1/plot"
	"gonum.org/v1/plot/plotter"
	"gonum.org/v1/plot/plotutil"
	"gonum.org/v1/plot/vg"
)

const template = `
<div>
  <p>Fake data for now</p>
  <img src="data:image/png;base64, %s" alt="phrase_search" />
</div>
`

func getGraph() string {
	// returns base64 encoded png string
	rand.Seed(time.Now().UTC().UnixNano())
	p, err := plot.New()
	if err != nil {
		panic(err)
	}

	p.Title.Text = "Some Bible Search"
	p.Y.Label.Text = "Count"
	p.X.Label.Text = "Matthew"

	err = plotutil.AddLinePoints(p,
		"ThatPhrase", randomPoints(15),
	)

	if err != nil {
		panic(err)
	}

	vgWid := 4 * vg.Inch
	vgHig := 4 * vg.Inch
	format := "png"

	stuff, err := p.WriterTo(vgWid, vgHig, format)
	if err != nil {
		println("Failed WriterTo")
		panic(err)
	}

	var buf bytes.Buffer
	stuff.WriteTo(&buf)

	////////////////////////////////
	// Write the html page	      //
	////////////////////////////////
	encodedPNG := base64.StdEncoding.EncodeToString(buf.Bytes())
	return fmt.Sprintf(template, encodedPNG)
}

// randomPoints returns some random x, y points.
func randomPoints(n int) plotter.XYs {
	pts := make(plotter.XYs, n)
	for i := range pts {
		fmt.Println("i: ", i)

		if i == 0 {
			pts[i].X = rand.Float64()
			fmt.Printf("pts[%d].X + rand.Float64 = %v\n", i, pts[i].X)
		} else {
			pts[i].X = pts[i-1].X + rand.Float64()
		}
		pts[i].Y = pts[i].X + 10*rand.Float64()
	}

	fmt.Printf("randomPoints.pts: %v\n", pts)
	return pts
}

func handler(w http.ResponseWriter, r *http.Request) {
	graph := getGraph()
	fmt.Fprintf(w, graph)
}

func main() {

	http.HandleFunc("/", handler)
	log.Fatal(http.ListenAndServe(":8080", nil))
}