70 lines
1.6 KiB
Go
70 lines
1.6 KiB
Go
// Copyright 2010 The draw2d Authors. All rights reserved.
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// created: 21/11/2010 by Laurent Le Goff
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package curve
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import (
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"math"
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"code.google.com/p/freetype-go/freetype/raster"
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)
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// TraceArc trace an arc using a LineBuilder
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func TraceArc(t LineBuilder, x, y, rx, ry, start, angle, scale float64) (lastX, lastY float64) {
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end := start + angle
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clockWise := true
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if angle < 0 {
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clockWise = false
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}
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ra := (math.Abs(rx) + math.Abs(ry)) / 2
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da := math.Acos(ra/(ra+0.125/scale)) * 2
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//normalize
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if !clockWise {
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da = -da
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}
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angle = start + da
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var curX, curY float64
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for {
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if (angle < end-da/4) != clockWise {
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curX = x + math.Cos(end)*rx
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curY = y + math.Sin(end)*ry
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return curX, curY
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}
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curX = x + math.Cos(angle)*rx
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curY = y + math.Sin(angle)*ry
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angle += da
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t.LineTo(curX, curY)
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}
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return curX, curY
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}
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// TraceArc trace an arc using a Freetype
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func TraceArcFt(adder raster.Adder, x, y, rx, ry, start, angle, scale float64) raster.Point {
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end := start + angle
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clockWise := true
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if angle < 0 {
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clockWise = false
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}
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ra := (math.Abs(rx) + math.Abs(ry)) / 2
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da := math.Acos(ra/(ra+0.125/scale)) * 2
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//normalize
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if !clockWise {
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da = -da
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}
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angle = start + da
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var curX, curY float64
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for {
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if (angle < end-da/4) != clockWise {
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curX = x + math.Cos(end)*rx
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curY = y + math.Sin(end)*ry
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return raster.Point{raster.Fix32(curX * 256), raster.Fix32(curY * 256)}
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}
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curX = x + math.Cos(angle)*rx
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curY = y + math.Sin(angle)*ry
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angle += da
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adder.Add1(raster.Point{raster.Fix32(curX * 256), raster.Fix32(curY * 256)})
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}
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return raster.Point{raster.Fix32(curX * 256), raster.Fix32(curY * 256)}
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}
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