fix for issues/56

_examples/pie_chart/main.go

@@ -30,7 +30,26 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 	}
 }
 
+func drawChartRegression(res http.ResponseWriter, req *http.Request) {
+	pie := chart.PieChart{
+		Width:  512,
+		Height: 512,
+		Values: []chart.Value{
+			{Value: 5, Label: "Blue"},
+			{Value: 2, Label: "Two"},
+			{Value: 1, Label: "One"},
+		},
+	}
+
+	res.Header().Set("Content-Type", chart.ContentTypeSVG)
+	err := pie.Render(chart.SVG, res)
+	if err != nil {
+		fmt.Printf("Error rendering pie chart: %v\n", err)
+	}
+}
+
 func main() {
 	http.HandleFunc("/", drawChart)
+	http.HandleFunc("/reg", drawChartRegression)
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }

_examples/pie_chart/reg.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="512" height="512">
+<path  d="M 256 256
+L 507 256
+A 251 251 225.00 1 1 79 79
+L 256 256
+Z" style="stroke-width:5;stroke:rgba(255,255,255,1.0);fill:rgba(106,195,203,1.0)"/>
+<path  d="M 256 256
+L 79 79
+A 251 251 90.00 0 1 433 79
+L 256 256
+Z" style="stroke-width:5;stroke:rgba(255,255,255,1.0);fill:rgba(42,190,137,1.0)"/>
+<path  d="M 256 256
+L 433 79
+A 251 251 45.00 0 1 507 256
+L 256 256
+Z" style="stroke-width:5;stroke:rgba(255,255,255,1.0);fill:rgba(110,128,139,1.0)"/>
+</svg>

pie_chart.go

@@ -11,6 +11,7 @@ import (
 )
 
 const (
+	_pi  = math.Pi
 	_pi2 = math.Pi / 2.0
 	_pi4 = math.Pi / 4.0
 )

vector_renderer.go

@@ -107,7 +107,12 @@ func (vr *vectorRenderer) ArcTo(cx, cy int, rx, ry, startAngle, delta float64) {
 
 	dd := util.Math.RadiansToDegrees(delta)
 
-	vr.p = append(vr.p, fmt.Sprintf("A %d %d %0.2f 0 1 %d %d", int(rx), int(ry), dd, endx, endy))
+	largeArcFlag := 0
+	if delta > _pi {
+		largeArcFlag = 1
+	}
+
+	vr.p = append(vr.p, fmt.Sprintf("A %d %d %0.2f %d 1 %d %d", int(rx), int(ry), dd, largeArcFlag, endx, endy))
 }
 
 // Close closes a shape.