moved annotation to separate file. Now does Y scale too.

internal/gopow/annotater.go

@@ -0,0 +1,170 @@
+package gopow
+
+import (
+	"image"
+	"math"
+	"time"
+
+	"code.google.com/p/freetype-go/freetype"
+	log "github.com/Sirupsen/logrus"
+	"github.com/dustin/go-humanize"
+
+	"github.com/dhogborg/rtl-gopow/internal/resources"
+)
+
+// font configuration
+const (
+	dpi      float64 = 72
+	fontfile string  = "resources/fonts/luxisr.ttf"
+	hinting  string  = "none"
+	size     float64 = 18
+)
+
+type Annotator struct {
+	image *image.RGBA
+	table *TableComplex
+
+	context *freetype.Context
+}
+
+func NewAnnotator(img *image.RGBA, table *TableComplex) (*Annotator, error) {
+
+	a := &Annotator{
+		image: img,
+		table: table,
+	}
+
+	err := a.init()
+	if err != nil {
+		return nil, err
+	}
+
+	return a, nil
+
+}
+
+func (a *Annotator) init() error {
+
+	// load the font
+	fontBytes, err := resources.Asset(fontfile)
+	if err != nil {
+		return err
+	}
+
+	font, err := freetype.ParseFont(fontBytes)
+	if err != nil {
+		return err
+	}
+
+	// Initialize the context.
+	fg := image.White
+
+	a.context = freetype.NewContext()
+	a.context.SetDPI(dpi)
+	a.context.SetFont(font)
+	a.context.SetFontSize(size)
+
+	a.context.SetClip(a.image.Bounds())
+	a.context.SetDst(a.image)
+	a.context.SetSrc(fg)
+
+	switch hinting {
+	default:
+		a.context.SetHinting(freetype.NoHinting)
+	case "full":
+		a.context.SetHinting(freetype.FullHinting)
+	}
+
+	return nil
+}
+
+func (a *Annotator) DrawXScale() error {
+
+	log.WithFields(log.Fields{
+		"hzLow":  a.table.HzLow,
+		"hzHigh": a.table.HzHigh,
+	}).Debug("annotate X scale")
+
+	// how many samples?
+	count := int(math.Floor(float64(a.table.Bins) / float64(500)))
+
+	log.WithFields(log.Fields{
+		"labels": count,
+	}).Debug("annotate X scale")
+
+	hzPerLabel := float64(a.table.HzHigh-a.table.HzLow) / float64(count)
+	pxPerLabel := int(math.Floor(float64(a.table.Bins) / float64(count)))
+
+	for si := 0; si < count; si++ {
+
+		hz := a.table.HzLow + (float64(si) * hzPerLabel)
+		px := si * pxPerLabel
+
+		str := humanize.SI(hz, "Hz")
+
+		// draw a guideline on the exact frequency
+		for i := 0; i < 50; i++ {
+			a.image.Set(px, i, image.White)
+		}
+
+		// draw the text
+		pt := freetype.Pt(px+10, 30)
+		_, _ = a.context.DrawString(str, pt)
+
+	}
+
+	return nil
+}
+
+func (a *Annotator) DrawYScale() error {
+
+	log.WithFields(log.Fields{
+		"timestart": a.table.TimeStart.String(),
+		"timeend":   a.table.TimeEnd.String(),
+	}).Debug("annotate Y scale")
+
+	start, end := a.table.TimeStart, a.table.TimeEnd
+
+	// how many samples?
+	count := int(math.Floor(float64(a.table.Integrations) / float64(100)))
+
+	uStart := start.Unix()
+	uEnd := end.Unix()
+
+	secsPerLabel := int(math.Floor(float64(uEnd-uStart) / float64(count)))
+	pxPerLabel := int(math.Floor(float64(a.table.Integrations) / float64(count)))
+
+	log.WithFields(log.Fields{
+		"labels":       count,
+		"secsPerLabel": secsPerLabel,
+		"pxPerLabel":   pxPerLabel,
+	}).Debug("annotate Y scale")
+
+	for si := 0; si < count; si++ {
+
+		secs := time.Duration(secsPerLabel * si * int(time.Second))
+		px := si * pxPerLabel
+
+		var str string = ""
+
+		if si == 0 {
+			str = start.String()
+		} else {
+			point := start.Add(secs)
+			str = point.Format("15:04:05")
+		}
+
+		// draw a guideline on the exact time
+		for i := 0; i < 75; i++ {
+			a.image.Set(i, px, image.White)
+		}
+
+		// draw the text, 3 px margin to the line
+		pt := freetype.Pt(3, px-3)
+		_, _ = a.context.DrawString(str, pt)
+
+	}
+
+	return nil
+
+}