diff options
Diffstat (limited to 'vendor/github.com/golang/freetype/raster/geom.go')
| -rw-r--r-- | vendor/github.com/golang/freetype/raster/geom.go | 245 |
1 files changed, 245 insertions, 0 deletions
diff --git a/vendor/github.com/golang/freetype/raster/geom.go b/vendor/github.com/golang/freetype/raster/geom.go new file mode 100644 index 000000000..f3696ea98 --- /dev/null +++ b/vendor/github.com/golang/freetype/raster/geom.go @@ -0,0 +1,245 @@ +// Copyright 2010 The Freetype-Go Authors. All rights reserved. +// Use of this source code is governed by your choice of either the +// FreeType License or the GNU General Public License version 2 (or +// any later version), both of which can be found in the LICENSE file. + +package raster + +import ( + "fmt" + "math" + + "golang.org/x/image/math/fixed" +) + +// maxAbs returns the maximum of abs(a) and abs(b). +func maxAbs(a, b fixed.Int26_6) fixed.Int26_6 { + if a < 0 { + a = -a + } + if b < 0 { + b = -b + } + if a < b { + return b + } + return a +} + +// pNeg returns the vector -p, or equivalently p rotated by 180 degrees. +func pNeg(p fixed.Point26_6) fixed.Point26_6 { + return fixed.Point26_6{-p.X, -p.Y} +} + +// pDot returns the dot product p·q. +func pDot(p fixed.Point26_6, q fixed.Point26_6) fixed.Int52_12 { + px, py := int64(p.X), int64(p.Y) + qx, qy := int64(q.X), int64(q.Y) + return fixed.Int52_12(px*qx + py*qy) +} + +// pLen returns the length of the vector p. +func pLen(p fixed.Point26_6) fixed.Int26_6 { + // TODO(nigeltao): use fixed point math. + x := float64(p.X) + y := float64(p.Y) + return fixed.Int26_6(math.Sqrt(x*x + y*y)) +} + +// pNorm returns the vector p normalized to the given length, or zero if p is +// degenerate. +func pNorm(p fixed.Point26_6, length fixed.Int26_6) fixed.Point26_6 { + d := pLen(p) + if d == 0 { + return fixed.Point26_6{} + } + s, t := int64(length), int64(d) + x := int64(p.X) * s / t + y := int64(p.Y) * s / t + return fixed.Point26_6{fixed.Int26_6(x), fixed.Int26_6(y)} +} + +// pRot45CW returns the vector p rotated clockwise by 45 degrees. +// +// Note that the Y-axis grows downwards, so {1, 0}.Rot45CW is {1/√2, 1/√2}. +func pRot45CW(p fixed.Point26_6) fixed.Point26_6 { + // 181/256 is approximately 1/√2, or sin(π/4). + px, py := int64(p.X), int64(p.Y) + qx := (+px - py) * 181 / 256 + qy := (+px + py) * 181 / 256 + return fixed.Point26_6{fixed.Int26_6(qx), fixed.Int26_6(qy)} +} + +// pRot90CW returns the vector p rotated clockwise by 90 degrees. +// +// Note that the Y-axis grows downwards, so {1, 0}.Rot90CW is {0, 1}. +func pRot90CW(p fixed.Point26_6) fixed.Point26_6 { + return fixed.Point26_6{-p.Y, p.X} +} + +// pRot135CW returns the vector p rotated clockwise by 135 degrees. +// +// Note that the Y-axis grows downwards, so {1, 0}.Rot135CW is {-1/√2, 1/√2}. +func pRot135CW(p fixed.Point26_6) fixed.Point26_6 { + // 181/256 is approximately 1/√2, or sin(π/4). + px, py := int64(p.X), int64(p.Y) + qx := (-px - py) * 181 / 256 + qy := (+px - py) * 181 / 256 + return fixed.Point26_6{fixed.Int26_6(qx), fixed.Int26_6(qy)} +} + +// pRot45CCW returns the vector p rotated counter-clockwise by 45 degrees. +// +// Note that the Y-axis grows downwards, so {1, 0}.Rot45CCW is {1/√2, -1/√2}. +func pRot45CCW(p fixed.Point26_6) fixed.Point26_6 { + // 181/256 is approximately 1/√2, or sin(π/4). + px, py := int64(p.X), int64(p.Y) + qx := (+px + py) * 181 / 256 + qy := (-px + py) * 181 / 256 + return fixed.Point26_6{fixed.Int26_6(qx), fixed.Int26_6(qy)} +} + +// pRot90CCW returns the vector p rotated counter-clockwise by 90 degrees. +// +// Note that the Y-axis grows downwards, so {1, 0}.Rot90CCW is {0, -1}. +func pRot90CCW(p fixed.Point26_6) fixed.Point26_6 { + return fixed.Point26_6{p.Y, -p.X} +} + +// pRot135CCW returns the vector p rotated counter-clockwise by 135 degrees. +// +// Note that the Y-axis grows downwards, so {1, 0}.Rot135CCW is {-1/√2, -1/√2}. +func pRot135CCW(p fixed.Point26_6) fixed.Point26_6 { + // 181/256 is approximately 1/√2, or sin(π/4). + px, py := int64(p.X), int64(p.Y) + qx := (-px + py) * 181 / 256 + qy := (-px - py) * 181 / 256 + return fixed.Point26_6{fixed.Int26_6(qx), fixed.Int26_6(qy)} +} + +// An Adder accumulates points on a curve. +type Adder interface { + // Start starts a new curve at the given point. + Start(a fixed.Point26_6) + // Add1 adds a linear segment to the current curve. + Add1(b fixed.Point26_6) + // Add2 adds a quadratic segment to the current curve. + Add2(b, c fixed.Point26_6) + // Add3 adds a cubic segment to the current curve. + Add3(b, c, d fixed.Point26_6) +} + +// A Path is a sequence of curves, and a curve is a start point followed by a +// sequence of linear, quadratic or cubic segments. +type Path []fixed.Int26_6 + +// String returns a human-readable representation of a Path. +func (p Path) String() string { + s := "" + for i := 0; i < len(p); { + if i != 0 { + s += " " + } + switch p[i] { + case 0: + s += "S0" + fmt.Sprint([]fixed.Int26_6(p[i+1:i+3])) + i += 4 + case 1: + s += "A1" + fmt.Sprint([]fixed.Int26_6(p[i+1:i+3])) + i += 4 + case 2: + s += "A2" + fmt.Sprint([]fixed.Int26_6(p[i+1:i+5])) + i += 6 + case 3: + s += "A3" + fmt.Sprint([]fixed.Int26_6(p[i+1:i+7])) + i += 8 + default: + panic("freetype/raster: bad path") + } + } + return s +} + +// Clear cancels any previous calls to p.Start or p.AddXxx. +func (p *Path) Clear() { + *p = (*p)[:0] +} + +// Start starts a new curve at the given point. +func (p *Path) Start(a fixed.Point26_6) { + *p = append(*p, 0, a.X, a.Y, 0) +} + +// Add1 adds a linear segment to the current curve. +func (p *Path) Add1(b fixed.Point26_6) { + *p = append(*p, 1, b.X, b.Y, 1) +} + +// Add2 adds a quadratic segment to the current curve. +func (p *Path) Add2(b, c fixed.Point26_6) { + *p = append(*p, 2, b.X, b.Y, c.X, c.Y, 2) +} + +// Add3 adds a cubic segment to the current curve. +func (p *Path) Add3(b, c, d fixed.Point26_6) { + *p = append(*p, 3, b.X, b.Y, c.X, c.Y, d.X, d.Y, 3) +} + +// AddPath adds the Path q to p. +func (p *Path) AddPath(q Path) { + *p = append(*p, q...) +} + +// AddStroke adds a stroked Path. +func (p *Path) AddStroke(q Path, width fixed.Int26_6, cr Capper, jr Joiner) { + Stroke(p, q, width, cr, jr) +} + +// firstPoint returns the first point in a non-empty Path. +func (p Path) firstPoint() fixed.Point26_6 { + return fixed.Point26_6{p[1], p[2]} +} + +// lastPoint returns the last point in a non-empty Path. +func (p Path) lastPoint() fixed.Point26_6 { + return fixed.Point26_6{p[len(p)-3], p[len(p)-2]} +} + +// addPathReversed adds q reversed to p. +// For example, if q consists of a linear segment from A to B followed by a +// quadratic segment from B to C to D, then the values of q looks like: +// index: 01234567890123 +// value: 0AA01BB12CCDD2 +// So, when adding q backwards to p, we want to Add2(C, B) followed by Add1(A). +func addPathReversed(p Adder, q Path) { + if len(q) == 0 { + return + } + i := len(q) - 1 + for { + switch q[i] { + case 0: + return + case 1: + i -= 4 + p.Add1( + fixed.Point26_6{q[i-2], q[i-1]}, + ) + case 2: + i -= 6 + p.Add2( + fixed.Point26_6{q[i+2], q[i+3]}, + fixed.Point26_6{q[i-2], q[i-1]}, + ) + case 3: + i -= 8 + p.Add3( + fixed.Point26_6{q[i+4], q[i+5]}, + fixed.Point26_6{q[i+2], q[i+3]}, + fixed.Point26_6{q[i-2], q[i-1]}, + ) + default: + panic("freetype/raster: bad path") + } + } +} |