adds SliceStyle for pie chart.

README.md

@@ -31,13 +31,11 @@ Two axis:
 
 ![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/two_axis.png)
 
-Simple Moving Average:
+# Other Chart Types
 
-![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/ma_goog_ltm.png)
+Pie Chart:
 
-Bollinger Bounds:
-
-![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/spy_ltm_bbs.png)
+![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/pie_chart.png)
 
 # Code Examples
 

examples/pie_chart/main.go

@@ -10,6 +10,8 @@ import (
 
 func drawChart(res http.ResponseWriter, req *http.Request) {
 	pie := chart.PieChart{
+		Width:  512,
+		Height: 512,
 		Canvas: chart.Style{
 			FillColor: chart.ColorLightGray,
 		},

pie_chart.go

@@ -18,6 +18,7 @@ type PieChart struct {
 
 	Background Style
 	Canvas     Style
+	SliceStyle Style
 
 	Font        *truetype.Font
 	defaultFont *truetype.Font
@@ -214,14 +215,28 @@ func (pc PieChart) styleDefaultsPieChartValue() Style {
 }
 
 func (pc PieChart) stylePieChartValue(index int) Style {
-	return Style{
+	return pc.SliceStyle.InheritFrom(Style{
 		StrokeColor: ColorWhite,
 		StrokeWidth: 5.0,
 		FillColor:   GetAlternateColor(index),
-		FontSize:    24.0,
+		FontSize:    pc.getScaledFontSize(),
 		FontColor:   ColorWhite,
 		Font:        pc.GetFont(),
+	})
 }
+
+func (pc PieChart) getScaledFontSize() float64 {
+	effectiveDimension := MinInt(pc.GetWidth(), pc.GetHeight())
+	if effectiveDimension >= 2048 {
+		return 48.0
+	} else if effectiveDimension >= 1024 {
+		return 24.0
+	} else if effectiveDimension > 512 {
+		return 18.0
+	} else if effectiveDimension > 256 {
+		return 12.0
+	}
+	return 10.0
 }
 
 func (pc PieChart) styleDefaultsBackground() Style {