/draw2d/curve/cubic_float64.go
https://code.google.com/p/draw2d/ · Go · 67 lines · 50 code · 10 blank · 7 comment · 5 complexity · c4658af1fdc06d28f92e499ee81dce8c MD5 · raw file
- // Copyright 2010 The draw2d Authors. All rights reserved.
- // created: 17/05/2011 by Laurent Le Goff
- package curve
- import (
- "math"
- )
- const (
- CurveRecursionLimit = 32
- )
- // X1, Y1, X2, Y2, X3, Y3, X4, Y4 float64
- type CubicCurveFloat64 [8]float64
- type LineTracer interface {
- LineTo(x, y float64)
- }
- func (c *CubicCurveFloat64) Subdivide(c1, c2 *CubicCurveFloat64) (x23, y23 float64) {
- // Calculate all the mid-points of the line segments
- //----------------------
- c1[0], c1[1] = c[0], c[1]
- c2[6], c2[7] = c[6], c[7]
- c1[2] = (c[0] + c[2]) / 2
- c1[3] = (c[1] + c[3]) / 2
- x23 = (c[2] + c[4]) / 2
- y23 = (c[3] + c[5]) / 2
- c2[4] = (c[4] + c[6]) / 2
- c2[5] = (c[5] + c[7]) / 2
- c1[4] = (c1[2] + x23) / 2
- c1[5] = (c1[3] + y23) / 2
- c2[2] = (x23 + c2[4]) / 2
- c2[3] = (y23 + c2[5]) / 2
- c1[6] = (c1[4] + c2[2]) / 2
- c1[7] = (c1[5] + c2[3]) / 2
- c2[0], c2[1] = c1[6], c1[7]
- return
- }
- func (curve *CubicCurveFloat64) Segment(t LineTracer, flattening_threshold float64) {
- var curves [CurveRecursionLimit]CubicCurveFloat64
- curves[0] = *curve
- i := 0
- // current curve
- var c *CubicCurveFloat64
- var dx, dy, d2, d3 float64
- for i >= 0 {
- c = &curves[i]
- dx = c[6] - c[0]
- dy = c[7] - c[1]
- d2 = math.Abs(((c[2]-c[6])*dy - (c[3]-c[7])*dx))
- d3 = math.Abs(((c[4]-c[6])*dy - (c[5]-c[7])*dx))
- if (d2+d3)*(d2+d3) < flattening_threshold*(dx*dx+dy*dy) || i == len(curves)-1 {
- t.LineTo(c[6], c[7])
- i--
- } else {
- // second half of bezier go lower onto the stack
- c.Subdivide(&curves[i+1], &curves[i])
- i++
- }
- }
- }