need to flesh out this test more.

.travis.yml

@@ -6,6 +6,7 @@ go:
 sudo: false
 
 before:
+  - go get -u github.com/blendlabs/go-assert
   - go get ./...
 
 script:

annotation_series.go

@@ -2,18 +2,12 @@ package chart
 
 import "math"
 
-// Annotation is a label on the chart.
-type Annotation struct {
-	X, Y  float64
-	Label string
-}
-
 // AnnotationSeries is a series of labels on the chart.
 type AnnotationSeries struct {
 	Name        string
 	Style       Style
 	YAxis       YAxisType
-	Annotations []Annotation
+	Annotations []Value2
 }
 
 // GetName returns the name of the time series.
@@ -31,6 +25,17 @@ func (as AnnotationSeries) GetYAxis() YAxisType {
 	return as.YAxis
 }
 
+func (as AnnotationSeries) annotationStyleDefaults(defaults Style) Style {
+	return Style{
+		Font:        defaults.Font,
+		FillColor:   DefaultAnnotationFillColor,
+		FontSize:    DefaultAnnotationFontSize,
+		StrokeColor: defaults.StrokeColor,
+		StrokeWidth: defaults.StrokeWidth,
+		Padding:     DefaultAnnotationPadding,
+	}
+}
+
 // Measure returns a bounds box of the series.
 func (as AnnotationSeries) Measure(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) Box {
 	box := Box{
@@ -40,17 +45,11 @@ func (as AnnotationSeries) Measure(r Renderer, canvasBox Box, xrange, yrange Ran
 		Bottom: 0,
 	}
 	if as.Style.IsZero() || as.Style.Show {
-		style := as.Style.InheritFrom(Style{
+		seriesStyle := as.Style.InheritFrom(as.annotationStyleDefaults(defaults))
-			Font:        defaults.Font,
-			FillColor:   DefaultAnnotationFillColor,
-			FontSize:    DefaultAnnotationFontSize,
-			StrokeColor: defaults.StrokeColor,
-			StrokeWidth: defaults.StrokeWidth,
-			Padding:     DefaultAnnotationPadding,
-		})
 		for _, a := range as.Annotations {
-			lx := canvasBox.Left + xrange.Translate(a.X)
+			style := a.Style.InheritFrom(seriesStyle)
-			ly := canvasBox.Bottom - yrange.Translate(a.Y)
+			lx := canvasBox.Left + xrange.Translate(a.XValue)
+			ly := canvasBox.Bottom - yrange.Translate(a.YValue)
 			ab := MeasureAnnotation(r, canvasBox, style, lx, ly, a.Label)
 			box.Top = MinInt(box.Top, ab.Top)
 			box.Left = MinInt(box.Left, ab.Left)
@@ -64,18 +63,11 @@ func (as AnnotationSeries) Measure(r Renderer, canvasBox Box, xrange, yrange Ran
 // Render draws the series.
 func (as AnnotationSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
 	if as.Style.IsZero() || as.Style.Show {
-		style := as.Style.InheritFrom(Style{
+		seriesStyle := as.Style.InheritFrom(as.annotationStyleDefaults(defaults))
-			Font:        defaults.Font,
-			FontColor:   DefaultTextColor,
-			FillColor:   DefaultAnnotationFillColor,
-			FontSize:    DefaultAnnotationFontSize,
-			StrokeColor: defaults.StrokeColor,
-			StrokeWidth: defaults.StrokeWidth,
-			Padding:     DefaultAnnotationPadding,
-		})
 		for _, a := range as.Annotations {
-			lx := canvasBox.Left + xrange.Translate(a.X)
+			style := a.Style.InheritFrom(seriesStyle)
-			ly := canvasBox.Bottom - yrange.Translate(a.Y)
+			lx := canvasBox.Left + xrange.Translate(a.XValue)
+			ly := canvasBox.Bottom - yrange.Translate(a.YValue)
 			DrawAnnotation(r, canvasBox, style, lx, ly, a.Label)
 		}
 	}

annotation_series_test.go

@@ -15,11 +15,11 @@ func TestAnnotationSeriesMeasure(t *testing.T) {
 		Style: Style{
 			Show: true,
 		},
-		Annotations: []Annotation{
+		Annotations: []Value2{
-			{X: 1.0, Y: 1.0, Label: "1.0"},
+			{XValue: 1.0, YValue: 1.0, Label: "1.0"},
-			{X: 2.0, Y: 2.0, Label: "2.0"},
+			{XValue: 2.0, YValue: 2.0, Label: "2.0"},
-			{X: 3.0, Y: 3.0, Label: "3.0"},
+			{XValue: 3.0, YValue: 3.0, Label: "3.0"},
-			{X: 4.0, Y: 4.0, Label: "4.0"},
+			{XValue: 4.0, YValue: 4.0, Label: "4.0"},
 		},
 	}
 
@@ -68,11 +68,11 @@ func TestAnnotationSeriesRender(t *testing.T) {
 			FillColor:   drawing.ColorWhite,
 			StrokeColor: drawing.ColorBlack,
 		},
-		Annotations: []Annotation{
+		Annotations: []Value2{
-			{X: 1.0, Y: 1.0, Label: "1.0"},
+			{XValue: 1.0, YValue: 1.0, Label: "1.0"},
-			{X: 2.0, Y: 2.0, Label: "2.0"},
+			{XValue: 2.0, YValue: 2.0, Label: "2.0"},
-			{X: 3.0, Y: 3.0, Label: "3.0"},
+			{XValue: 3.0, YValue: 3.0, Label: "3.0"},
-			{X: 4.0, Y: 4.0, Label: "4.0"},
+			{XValue: 4.0, YValue: 4.0, Label: "4.0"},
 		},
 	}
 

examples/pie_chart/main.go

@@ -13,14 +13,14 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 		Canvas: chart.Style{
 			FillColor: chart.ColorLightGray,
 		},
-		Values: []chart.PieChartValue{
+		Values: []chart.Value{
-			{Value: 0.2, Label: "Blue"},
+			{Value: 10, Label: "Blue"},
-			{Value: 0.2, Label: "Green"},
+			{Value: 9, Label: "Green"},
-			{Value: 0.2, Label: "Gray"},
+			{Value: 8, Label: "Gray"},
-			{Value: 0.1, Label: "Orange"},
+			{Value: 7, Label: "Orange"},
-			{Value: 0.1, Label: "HEANG"},
+			{Value: 6, Label: "HEANG"},
-			{Value: 0.1, Label: "??"},
+			{Value: 5, Label: "??"},
-			{Value: 0.1, Label: "!!"},
+			{Value: 2, Label: "!!"},
 		},
 	}
 

pie_chart.go

@@ -7,13 +7,6 @@ import (
 	"github.com/golang/freetype/truetype"
 )
 
-// PieChartValue is a slice of a pie-chart.
-type PieChartValue struct {
-	Style Style
-	Label string
-	Value float64
-}
-
 // PieChart is a chart that draws sections of a circle based on percentages.
 type PieChart struct {
 	Title      string
@@ -29,7 +22,7 @@ type PieChart struct {
 	Font        *truetype.Font
 	defaultFont *truetype.Font
 
-	Values   []PieChartValue
+	Values   []Value
 	Elements []Renderable
 }
 
@@ -94,11 +87,8 @@ func (pc PieChart) Render(rp RendererProvider, w io.Writer) error {
 	pc.drawBackground(r)
 	pc.drawCanvas(r, canvasBox)
 
-	valuesWithPlaceholder, err := pc.finalizeValues(pc.Values)
+	finalValues := pc.finalizeValues(pc.Values)
-	if err != nil {
+	pc.drawSlices(r, canvasBox, finalValues)
-		return err
-	}
-	pc.drawSlices(r, canvasBox, valuesWithPlaceholder)
 	pc.drawTitle(r)
 	for _, a := range pc.Elements {
 		a(r, canvasBox, pc.styleDefaultsElements())
@@ -137,7 +127,7 @@ func (pc PieChart) drawTitle(r Renderer) {
 	}
 }
 
-func (pc PieChart) drawSlices(r Renderer, canvasBox Box, values []PieChartValue) {
+func (pc PieChart) drawSlices(r Renderer, canvasBox Box, values []Value) {
 	cx, cy := canvasBox.Center()
 	diameter := MinInt(canvasBox.Width(), canvasBox.Height())
 	radius := float64(diameter >> 1)
@@ -172,6 +162,7 @@ func (pc PieChart) drawSlices(r Renderer, canvasBox Box, values []PieChartValue)
 
 			tb := r.MeasureText(v.Label)
 			lx = lx - (tb.Width() >> 1)
+			ly = ly + (tb.Height() >> 1)
 
 			r.Text(v.Label, lx, ly)
 		}
@@ -179,22 +170,8 @@ func (pc PieChart) drawSlices(r Renderer, canvasBox Box, values []PieChartValue)
 	}
 }
 
-func (pc PieChart) finalizeValues(values []PieChartValue) ([]PieChartValue, error) {
+func (pc PieChart) finalizeValues(values []Value) []Value {
-	var total float64
+	return Values(values).Normalize()
-	for _, v := range values {
-		total += v.Value
-		if total > 1.0 {
-			return nil, errors.New("Values total exceeded 1.0; please normalize pie chart values to [0,1.0)")
-		}
-	}
-	remainder := 1.0 - total
-	if RoundDown(remainder, 0.0001) > 0 {
-		return append(values, PieChartValue{
-			Style: pc.styleDefaultsPieChartValue(),
-			Value: remainder,
-		}), nil
-	}
-	return values, nil
 }
 
 func (pc PieChart) getDefaultCanvasBox() Box {

pie_chart_test.go

@@ -0,0 +1,31 @@
+package chart
+
+import (
+	"bytes"
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestPieChart(t *testing.T) {
+	assert := assert.New(t)
+
+	pie := PieChart{
+		Canvas: Style{
+			FillColor: ColorLightGray,
+		},
+		Values: []Value{
+			{Value: 10, Label: "Blue"},
+			{Value: 9, Label: "Green"},
+			{Value: 8, Label: "Gray"},
+			{Value: 7, Label: "Orange"},
+			{Value: 6, Label: "HEANG"},
+			{Value: 5, Label: "??"},
+			{Value: 2, Label: "!!"},
+		},
+	}
+
+	b := bytes.NewBuffer([]byte{})
+	pie.Render(PNG, b)
+	assert.NotZero(b.Len())
+}

util.go

@@ -176,6 +176,24 @@ func SeqRand(samples int, scale float64) []float64 {
 	return values
 }
 
+// Sum sums a set of values.
+func Sum(values ...float64) float64 {
+	var total float64
+	for _, v := range values {
+		total += v
+	}
+	return total
+}
+
+// SumInt sums a set of values.
+func SumInt(values ...int) int {
+	var total int
+	for _, v := range values {
+		total += v
+	}
+	return total
+}
+
 // SeqDays generates a sequence of timestamps by day, from -days to today.
 func SeqDays(days int) []time.Time {
 	var values []time.Time

value.go

@@ -0,0 +1,46 @@
+package chart
+
+// Value is a chart value.
+type Value struct {
+	Style Style
+	Label string
+	Value float64
+}
+
+// Values is an array of Value.
+type Values []Value
+
+// Values returns the values.
+func (vs Values) Values() []float64 {
+	values := make([]float64, len(vs))
+	for index, v := range vs {
+		values[index] = v.Value
+	}
+	return values
+}
+
+// ValuesNormalized returns normalized values.
+func (vs Values) ValuesNormalized() []float64 {
+	return Normalize(vs.Values()...)
+}
+
+// Normalize returns the values normalized.
+func (vs Values) Normalize() []Value {
+	output := make([]Value, len(vs))
+	total := Sum(vs.Values()...)
+	for index, v := range vs {
+		output[index] = Value{
+			Style: v.Style,
+			Label: v.Label,
+			Value: (v.Value / total),
+		}
+	}
+	return output
+}
+
+// Value2 is a two axis value.
+type Value2 struct {
+	Style          Style
+	Label          string
+	XValue, YValue float64
+}