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