Adds the ability to draw an XY scatter plot. (#27)

* works more or less

* updating comment

* removing debugging printf

* adding output

* tweaks

* missed a couple series validations

* testing auto coloring

* updated output.png

* color tests etc.

* sanity check tests.

* should not use unkeyed fields anyway.

_examples/request_timings/main.go

@@ -23,7 +23,7 @@ func parseFloat64(str string) float64 {
 func readData() ([]time.Time, []float64) {
 	var xvalues []time.Time
 	var yvalues []float64
-	chart.File.ReadByLines("requests.csv", func(line string) {
+	err := chart.File.ReadByLines("requests.csv", func(line string) {
 		parts := strings.Split(line, ",")
 		year := parseInt(parts[0])
 		month := parseInt(parts[1])
@@ -33,6 +33,9 @@ func readData() ([]time.Time, []float64) {
 		xvalues = append(xvalues, time.Date(year, time.Month(month), day, hour, 0, 0, 0, time.UTC))
 		yvalues = append(yvalues, elapsedMillis)
 	})
+	if err != nil {
+		fmt.Println(err.Error())
+	}
 	return xvalues, yvalues
 }
 

_examples/scatter/main.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"log"
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+	graph := chart.Chart{
+		Series: []chart.Series{
+			chart.ContinuousSeries{
+				Style: chart.Style{
+					Show:        true,
+					StrokeWidth: chart.Disabled,
+					DotWidth:    3,
+				},
+				XValues: chart.Sequence.Random(32, 1024),
+				YValues: chart.Sequence.Random(32, 1024),
+			},
+			chart.ContinuousSeries{
+				Style: chart.Style{
+					Show:        true,
+					StrokeWidth: chart.Disabled,
+					DotWidth:    5,
+				},
+				XValues: chart.Sequence.Random(16, 1024),
+				YValues: chart.Sequence.Random(16, 1024),
+			},
+			chart.ContinuousSeries{
+				Style: chart.Style{
+					Show:        true,
+					StrokeWidth: chart.Disabled,
+					DotWidth:    7,
+				},
+				XValues: chart.Sequence.Random(8, 1024),
+				YValues: chart.Sequence.Random(8, 1024),
+			},
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	err := graph.Render(chart.PNG, res)
+	if err != nil {
+		log.Println(err.Error())
+	}
+
+}
+
+func unit(res http.ResponseWriter, req *http.Request) {
+	graph := chart.Chart{
+		Height: 50,
+		Width:  50,
+		Canvas: chart.Style{
+			Padding: chart.Box{IsSet: true},
+		},
+		Background: chart.Style{
+			Padding: chart.Box{IsSet: true},
+		},
+		Series: []chart.Series{
+			chart.ContinuousSeries{
+				XValues: chart.Sequence.Float64(0, 4, 1),
+				YValues: chart.Sequence.Float64(0, 4, 1),
+			},
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	err := graph.Render(chart.PNG, res)
+	if err != nil {
+		log.Println(err.Error())
+	}
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.HandleFunc("/unit", unit)
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}

box.go

@@ -5,16 +5,36 @@ import (
 	"math"
 )
 
+var (
+	// BoxZero is a preset box that represents an intentional zero value.
+	BoxZero = Box{IsSet: true}
+)
+
+// NewBox returns a new (set) box.
+func NewBox(top, left, right, bottom int) Box {
+	return Box{
+		IsSet:  true,
+		Top:    top,
+		Left:   left,
+		Right:  right,
+		Bottom: bottom,
+	}
+}
+
 // Box represents the main 4 dimensions of a box.
 type Box struct {
 	Top    int
 	Left   int
 	Right  int
 	Bottom int
+	IsSet  bool
 }
 
 // IsZero returns if the box is set or not.
 func (b Box) IsZero() bool {
+	if b.IsSet {
+		return false
+	}
 	return b.Top == 0 && b.Left == 0 && b.Right == 0 && b.Bottom == 0
 }
 
@@ -25,7 +45,7 @@ func (b Box) String() string {
 
 // GetTop returns a coalesced value with a default.
 func (b Box) GetTop(defaults ...int) int {
-	if b.Top == 0 {
+	if !b.IsSet && b.Top == 0 {
 		if len(defaults) > 0 {
 			return defaults[0]
 		}
@@ -36,7 +56,7 @@ func (b Box) GetTop(defaults ...int) int {
 
 // GetLeft returns a coalesced value with a default.
 func (b Box) GetLeft(defaults ...int) int {
-	if b.Left == 0 {
+	if !b.IsSet && b.Left == 0 {
 		if len(defaults) > 0 {
 			return defaults[0]
 		}
@@ -47,7 +67,7 @@ func (b Box) GetLeft(defaults ...int) int {
 
 // GetRight returns a coalesced value with a default.
 func (b Box) GetRight(defaults ...int) int {
-	if b.Right == 0 {
+	if !b.IsSet && b.Right == 0 {
 		if len(defaults) > 0 {
 			return defaults[0]
 		}
@@ -58,7 +78,7 @@ func (b Box) GetRight(defaults ...int) int {
 
 // GetBottom returns a coalesced value with a default.
 func (b Box) GetBottom(defaults ...int) int {
-	if b.Bottom == 0 {
+	if !b.IsSet && b.Bottom == 0 {
 		if len(defaults) > 0 {
 			return defaults[0]
 		}
@@ -91,6 +111,7 @@ func (b Box) Aspect() float64 {
 // Clone returns a new copy of the box.
 func (b Box) Clone() Box {
 	return Box{
+		IsSet:  b.IsSet,
 		Top:    b.Top,
 		Left:   b.Left,
 		Right:  b.Right,

box_test.go

@@ -109,17 +109,17 @@ func TestBoxConstrain(t *testing.T) {
 func TestBoxOuterConstrain(t *testing.T) {
 	assert := assert.New(t)
 
-	box := Box{0, 0, 100, 100}
-	canvas := Box{5, 5, 95, 95}
-	taller := Box{-10, 5, 50, 50}
+	box := NewBox(0, 0, 100, 100)
+	canvas := NewBox(5, 5, 95, 95)
+	taller := NewBox(-10, 5, 50, 50)
 
 	c := canvas.OuterConstrain(box, taller)
 	assert.Equal(15, c.Top, c.String())
 	assert.Equal(5, c.Left, c.String())
 	assert.Equal(95, c.Right, c.String())
 	assert.Equal(95, c.Bottom, c.String())
 
-	wider := Box{5, 5, 110, 50}
+	wider := NewBox(5, 5, 110, 50)
 	d := canvas.OuterConstrain(box, wider)
 	assert.Equal(5, d.Top, d.String())
 	assert.Equal(5, d.Left, d.String())

chart.go

@@ -141,8 +141,10 @@ func (c Chart) Render(rp RendererProvider, w io.Writer) error {
 
 func (c Chart) checkHasVisibleSeries() error {
 	hasVisibleSeries := false
+	var style Style
 	for _, s := range c.Series {
-		hasVisibleSeries = hasVisibleSeries || (s.GetStyle().IsZero() || s.GetStyle().Show)
+		style = s.GetStyle()
+		hasVisibleSeries = hasVisibleSeries || (style.IsZero() || style.Show)
 	}
 	if !hasVisibleSeries {
 		return fmt.Errorf("must have (1) visible series; make sure if you set a style, you set .Show = true")
@@ -511,6 +513,7 @@ func (c Chart) styleDefaultsCanvas() Style {
 func (c Chart) styleDefaultsSeries(seriesIndex int) Style {
 	strokeColor := GetDefaultColor(seriesIndex)
 	return Style{
+		DotColor:    strokeColor,
 		StrokeColor: strokeColor,
 		StrokeWidth: DefaultSeriesLineWidth,
 		Font:        c.GetFont(),

chart_test.go

@@ -2,6 +2,8 @@ package chart
 
 import (
 	"bytes"
+	"image"
+	"image/png"
 	"math"
 	"testing"
 	"time"
@@ -483,3 +485,91 @@ func TestChartCheckRangesWithRanges(t *testing.T) {
 	xr, yr, yra := c.getRanges()
 	assert.Nil(c.checkRanges(xr, yr, yra))
 }
+
+func at(i image.Image, x, y int) drawing.Color {
+	return drawing.ColorFromAlphaMixedRGBA(i.At(x, y).RGBA())
+}
+
+func TestChartE2ELine(t *testing.T) {
+	assert := assert.New(t)
+
+	c := Chart{
+		Height: 50,
+		Width:  50,
+		Canvas: Style{
+			Padding: Box{IsSet: true},
+		},
+		Background: Style{
+			Padding: Box{IsSet: true},
+		},
+		Series: []Series{
+			ContinuousSeries{
+				XValues: Sequence.Float64(0, 4, 1),
+				YValues: Sequence.Float64(0, 4, 1),
+			},
+		},
+	}
+
+	var buffer = &bytes.Buffer{}
+	err := c.Render(PNG, buffer)
+	assert.Nil(err)
+
+	// do color tests ...
+
+	i, err := png.Decode(buffer)
+	assert.Nil(err)
+
+	// test the bottom and top of the line
+	assert.Equal(drawing.ColorWhite, at(i, 0, 0))
+	assert.Equal(drawing.ColorWhite, at(i, 49, 49))
+
+	// test a line mid point
+	defaultSeriesColor := GetDefaultColor(0)
+	assert.Equal(defaultSeriesColor, at(i, 0, 49))
+	assert.Equal(defaultSeriesColor, at(i, 49, 0))
+	assert.Equal(drawing.ColorFromHex("bddbf6"), at(i, 24, 24))
+}
+
+func TestChartE2ELineWithFill(t *testing.T) {
+	assert := assert.New(t)
+
+	c := Chart{
+		Height: 50,
+		Width:  50,
+		Canvas: Style{
+			Padding: Box{IsSet: true},
+		},
+		Background: Style{
+			Padding: Box{IsSet: true},
+		},
+		Series: []Series{
+			ContinuousSeries{
+				Style: Style{
+					Show:        true,
+					StrokeColor: drawing.ColorBlue,
+					FillColor:   drawing.ColorRed,
+				},
+				XValues: Sequence.Float64(0, 4, 1),
+				YValues: Sequence.Float64(0, 4, 1),
+			},
+		},
+	}
+
+	var buffer = &bytes.Buffer{}
+	err := c.Render(PNG, buffer)
+	assert.Nil(err)
+
+	// do color tests ...
+
+	i, err := png.Decode(buffer)
+	assert.Nil(err)
+
+	// test the bottom and top of the line
+	assert.Equal(drawing.ColorWhite, at(i, 0, 0))
+	assert.Equal(drawing.ColorRed, at(i, 49, 49))
+
+	// test a line mid point
+	defaultSeriesColor := drawing.ColorBlue
+	assert.Equal(defaultSeriesColor, at(i, 0, 49))
+	assert.Equal(defaultSeriesColor, at(i, 49, 0))
+}

defaults.go

@@ -14,6 +14,8 @@ const (
 	DefaultChartWidth = 1024
 	// DefaultStrokeWidth is the default chart stroke width.
 	DefaultStrokeWidth = 0.0
+	// DefaultDotWidth is the default chart dot width.
+	DefaultDotWidth = 0.0
 	// DefaultSeriesLineWidth is the default line width.
 	DefaultSeriesLineWidth = 1.0
 	// DefaultAxisLineWidth is the line width of the axis lines.

draw.go

@@ -27,9 +27,8 @@ func (d draw) LineSeries(r Renderer, canvasBox Box, xrange, yrange Range, style
 	var vx, vy float64
 	var x, y int
 
-	fill := style.GetFillColor()
-	if !fill.IsZero() {
-		style.GetFillOptions().WriteToRenderer(r)
+	if style.ShouldDrawStroke() && style.ShouldDrawFill() {
+		style.GetFillOptions().WriteDrawingOptionsToRenderer(r)
 		r.MoveTo(x0, y0)
 		for i := 1; i < vs.Len(); i++ {
 			vx, vy = vs.GetValue(i)
@@ -43,16 +42,33 @@ func (d draw) LineSeries(r Renderer, canvasBox Box, xrange, yrange Range, style
 		r.Fill()
 	}
 
-	style.GetStrokeOptions().WriteToRenderer(r)
+	if style.ShouldDrawStroke() {
+		style.GetStrokeOptions().WriteDrawingOptionsToRenderer(r)
 
-	r.MoveTo(x0, y0)
-	for i := 1; i < vs.Len(); i++ {
-		vx, vy = vs.GetValue(i)
-		x = cl + xrange.Translate(vx)
-		y = cb - yrange.Translate(vy)
-		r.LineTo(x, y)
+		r.MoveTo(x0, y0)
+		for i := 1; i < vs.Len(); i++ {
+			vx, vy = vs.GetValue(i)
+			x = cl + xrange.Translate(vx)
+			y = cb - yrange.Translate(vy)
+			r.LineTo(x, y)
+		}
+		r.Stroke()
+	}
+
+	if style.ShouldDrawDot() {
+		dotWidth := style.GetDotWidth()
+
+		style.GetDotOptions().WriteDrawingOptionsToRenderer(r)
+
+		for i := 0; i < vs.Len(); i++ {
+			vx, vy = vs.GetValue(i)
+			x = cl + xrange.Translate(vx)
+			y = cb - yrange.Translate(vy)
+
+			r.Circle(dotWidth, x, y)
+			r.FillStroke()
+		}
 	}
-	r.Stroke()
 }
 
 // BoundedSeries draws a series that implements BoundedValueProvider.