Create curve package with a test bench

draw2d/curve/Makefile

@@ -0,0 +1,7 @@
+include $(GOROOT)/src/Make.inc
+
+TARG=draw2d.googlecode.com/hg/draw2d/curve
+GOFILES=\
+	curve_float64.go\
+
+include $(GOROOT)/src/Make.pkg

draw2d/curve/curve_float64.go

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+// Copyright 2010 The draw2d Authors. All rights reserved.
+// created: 17/05/2011 by Laurent Le Goff
+package curve
+
+import (
+	"math"
+)
+
+var (
+	m_distance_tolerance float64 = 0.25
+)
+
+type CubicCurveFloat64 struct {
+	x1, y1, x2, y2, x3, y3, x4, y4 float64
+	segments                       []float64
+}
+
+func NewCubicCurveFloat64(x1, y1, x2, y2, x3, y3, x4, y4 float64) (*CubicCurveFloat64){
+	return &CubicCurveFloat64{x1, y1, x2, y2, x3, y3, x4, y4, make([]float64, 0, 2)}
+}
+
+func (c *CubicCurveFloat64) addPoint(x, y float64) {
+	c.segments = append(c.segments, x, y)
+}
+
+func (c *CubicCurveFloat64) Subdivide() (c1, c2 *CubicCurveFloat64) {
+	// Calculate all the mid-points of the line segments
+	//----------------------
+	x12 := (c.x1 + c.x2) / 2
+	y12 := (c.y1 + c.y2) / 2
+	x23 := (c.x2 + c.x3) / 2
+	y23 := (c.y2 + c.y3) / 2
+	x34 := (c.x3 + c.x4) / 2
+	y34 := (c.y3 + c.y4) / 2
+	x123 := (x12 + x23) / 2
+	y123 := (y12 + y23) / 2
+	x234 := (x23 + x34) / 2
+	y234 := (y23 + y34) / 2
+	x1234 := (x123 + x234) / 2
+	y1234 := (y123 + y234) / 2
+	c1 = &CubicCurveFloat64{c.x1, c.y1, x12, y12, x123, y123, x1234, y1234, c.segments}
+	c2 = &CubicCurveFloat64{x1234, y1234, x234, y234, x34, y34, c.x4, c.y4, c.segments}
+	return
+}
+
+func (c *CubicCurveFloat64) SegmentCasteljau() []float64{
+	// reinit segments
+	c.segments = make([]float64, 0, 2)
+	c.addPoint(c.x1, c.y1)
+	c.segmentCasteljauRec()
+	c.addPoint(c.x4, c.y4)
+	return c.segments
+}
+
+func (c *CubicCurveFloat64) segmentCasteljauRec() {
+
+	c1, c2 := c.Subdivide()
+
+	// Try to approximate the full cubic curve by a single straight line
+	//------------------
+	dx := c.x4 - c.x1
+	dy := c.y4 - c.y1
+
+	d2 := math.Fabs(((c.x2-c.x4)*dy - (c.y2-c.y4)*dx))
+	d3 := math.Fabs(((c.x3-c.x4)*dy - (c.y3-c.y4)*dx))
+
+	if (d2+d3)*(d2+d3) < m_distance_tolerance*(dx*dx+dy*dy) {
+		c.addPoint(c2.x1, c2.y1)
+		return
+	} else {
+		// Continue subdivision
+		//----------------------
+		c1.segmentCasteljauRec()
+		c2.segments = c1.segments 
+		c2.segmentCasteljauRec()
+		c.segments = c2.segments 
+	}
+}

draw2d/curve/curve_test.go

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+package curve
+
+import (
+	"testing"
+	"log"
+)
+
+
+var (
+
+	cf64Test1 = NewCubicCurveFloat64(0, 0, 20000, 0, 0, 20000, 20000, 20000)
+)
+
+func BenchmarkCubicCurveCasteljauFloat64(b *testing.B) {
+	var s []float64
+	for i := 0; i < b.N; i++ {
+        s = cf64Test1.SegmentCasteljau()
+    }
+	log.Printf("Num of points: %d\n", len(s));
+}