star example

examples/star.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"math"
+
+	"github.com/fogleman/dd"
+)
+
+type Point struct {
+	X, Y float64
+}
+
+func Polygon(n int, x, y, r float64) []Point {
+	result := make([]Point, n)
+	for i := 0; i < n; i++ {
+		a := float64(i)*2*math.Pi/float64(n) - math.Pi/2
+		result[i] = Point{x + r*math.Cos(a), y + r*math.Sin(a)}
+	}
+	return result
+}
+
+func main() {
+	points := Polygon(5, 512, 512, 400)
+	indexes := []int{0, 2, 4, 1, 3, 0}
+	dc := dd.NewContext(1024, 1024)
+	dc.SetSourceRGB(1, 1, 1)
+	dc.Paint()
+	for _, index := range indexes {
+		p := points[index]
+		dc.LineTo(p.X, p.Y)
+	}
+	dc.SetSourceRGBA(1, 0, 0, 0.5)
+	dc.SetFillRule(dd.FillRuleEvenOdd)
+	dc.FillPreserve()
+	dc.SetSourceRGB(0, 0, 0)
+	dc.SetLineWidth(8)
+	dc.Stroke()
+	dc.WriteToPNG("out.png")
+}