libgo/go/image/geom.go

   1 // Copyright 2010 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package image
   6
   7 import (
   8         "strconv"
   9 )
  10
  11 // A Point is an X, Y coordinate pair. The axes increase right and down.
  12 type Point struct {
  13         X, Y int
  14 }
  15
  16 // String returns a string representation of p like "(3,4)".
  17 func (p Point) String() string {
  18         return "(" + strconv.Itoa(p.X) + "," + strconv.Itoa(p.Y) + ")"
  19 }
  20
  21 // Add returns the vector p+q.
  22 func (p Point) Add(q Point) Point {
  23         return Point{p.X + q.X, p.Y + q.Y}
  24 }
  25
  26 // Sub returns the vector p-q.
  27 func (p Point) Sub(q Point) Point {
  28         return Point{p.X - q.X, p.Y - q.Y}
  29 }
  30
  31 // Mul returns the vector p*k.
  32 func (p Point) Mul(k int) Point {
  33         return Point{p.X * k, p.Y * k}
  34 }
  35
  36 // Div returns the vector p/k.
  37 func (p Point) Div(k int) Point {
  38         return Point{p.X / k, p.Y / k}
  39 }
  40
  41 // Mod returns the point q in r such that p.X-q.X is a multiple of r's width
  42 // and p.Y-q.Y is a multiple of r's height.
  43 func (p Point) Mod(r Rectangle) Point {
  44         w, h := r.Dx(), r.Dy()
  45         p = p.Sub(r.Min)
  46         p.X = p.X % w
  47         if p.X < 0 {
  48                 p.X += w
  49         }
  50         p.Y = p.Y % h
  51         if p.Y < 0 {
  52                 p.Y += h
  53         }
  54         return p.Add(r.Min)
  55 }
  56
  57 // Eq returns whether p and q are equal.
  58 func (p Point) Eq(q Point) bool {
  59         return p.X == q.X && p.Y == q.Y
  60 }
  61
  62 // ZP is the zero Point.
  63 var ZP Point
  64
  65 // Pt is shorthand for Point{X, Y}.
  66 func Pt(X, Y int) Point {
  67         return Point{X, Y}
  68 }
  69
  70 // A Rectangle contains the points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y.
  71 // It is well-formed if Min.X <= Max.X and likewise for Y. Points are always
  72 // well-formed. A rectangle's methods always return well-formed outputs for
  73 // well-formed inputs.
  74 type Rectangle struct {
  75         Min, Max Point
  76 }
  77
  78 // String returns a string representation of r like "(3,4)-(6,5)".
  79 func (r Rectangle) String() string {
  80         return r.Min.String() + "-" + r.Max.String()
  81 }
  82
  83 // Dx returns r's width.
  84 func (r Rectangle) Dx() int {
  85         return r.Max.X - r.Min.X
  86 }
  87
  88 // Dy returns r's height.
  89 func (r Rectangle) Dy() int {
  90         return r.Max.Y - r.Min.Y
  91 }
  92
  93 // Size returns r's width and height.
  94 func (r Rectangle) Size() Point {
  95         return Point{
  96                 r.Max.X - r.Min.X,
  97                 r.Max.Y - r.Min.Y,
  98         }
  99 }
 100
 101 // Add returns the rectangle r translated by p.
 102 func (r Rectangle) Add(p Point) Rectangle {
 103         return Rectangle{
 104                 Point{r.Min.X + p.X, r.Min.Y + p.Y},
 105                 Point{r.Max.X + p.X, r.Max.Y + p.Y},
 106         }
 107 }
 108
 109 // Add returns the rectangle r translated by -p.
 110 func (r Rectangle) Sub(p Point) Rectangle {
 111         return Rectangle{
 112                 Point{r.Min.X - p.X, r.Min.Y - p.Y},
 113                 Point{r.Max.X - p.X, r.Max.Y - p.Y},
 114         }
 115 }
 116
 117 // Inset returns the rectangle r inset by n, which may be negative. If either
 118 // of r's dimensions is less than 2*n then an empty rectangle near the center
 119 // of r will be returned.
 120 func (r Rectangle) Inset(n int) Rectangle {
 121         if r.Dx() < 2*n {
 122                 r.Min.X = (r.Min.X + r.Max.X) / 2
 123                 r.Max.X = r.Min.X
 124         } else {
 125                 r.Min.X += n
 126                 r.Max.X -= n
 127         }
 128         if r.Dy() < 2*n {
 129                 r.Min.Y = (r.Min.Y + r.Max.Y) / 2
 130                 r.Max.Y = r.Min.Y
 131         } else {
 132                 r.Min.Y += n
 133                 r.Max.Y -= n
 134         }
 135         return r
 136 }
 137
 138 // Intersect returns the largest rectangle contained by both r and s. If the
 139 // two rectangles do not overlap then the zero rectangle will be returned.
 140 func (r Rectangle) Intersect(s Rectangle) Rectangle {
 141         if r.Min.X < s.Min.X {
 142                 r.Min.X = s.Min.X
 143         }
 144         if r.Min.Y < s.Min.Y {
 145                 r.Min.Y = s.Min.Y
 146         }
 147         if r.Max.X > s.Max.X {
 148                 r.Max.X = s.Max.X
 149         }
 150         if r.Max.Y > s.Max.Y {
 151                 r.Max.Y = s.Max.Y
 152         }
 153         if r.Min.X > r.Max.X || r.Min.Y > r.Max.Y {
 154                 return ZR
 155         }
 156         return r
 157 }
 158
 159 // Union returns the smallest rectangle that contains both r and s.
 160 func (r Rectangle) Union(s Rectangle) Rectangle {
 161         if r.Min.X > s.Min.X {
 162                 r.Min.X = s.Min.X
 163         }
 164         if r.Min.Y > s.Min.Y {
 165                 r.Min.Y = s.Min.Y
 166         }
 167         if r.Max.X < s.Max.X {
 168                 r.Max.X = s.Max.X
 169         }
 170         if r.Max.Y < s.Max.Y {
 171                 r.Max.Y = s.Max.Y
 172         }
 173         return r
 174 }
 175
 176 // Empty returns whether the rectangle contains no points.
 177 func (r Rectangle) Empty() bool {
 178         return r.Min.X >= r.Max.X || r.Min.Y >= r.Max.Y
 179 }
 180
 181 // Eq returns whether r and s are equal.
 182 func (r Rectangle) Eq(s Rectangle) bool {
 183         return r.Min.X == s.Min.X && r.Min.Y == s.Min.Y &&
 184                 r.Max.X == s.Max.X && r.Max.Y == s.Max.Y
 185 }
 186
 187 // Overlaps returns whether r and s have a non-empty intersection.
 188 func (r Rectangle) Overlaps(s Rectangle) bool {
 189         return r.Min.X < s.Max.X && s.Min.X < r.Max.X &&
 190                 r.Min.Y < s.Max.Y && s.Min.Y < r.Max.Y
 191 }
 192
 193 // Contains returns whether r contains p.
 194 func (r Rectangle) Contains(p Point) bool {
 195         return p.X >= r.Min.X && p.X < r.Max.X &&
 196                 p.Y >= r.Min.Y && p.Y < r.Max.Y
 197 }
 198
 199 // Canon returns the canonical version of r. The returned rectangle has minimum
 200 // and maximum coordinates swapped if necessary so that it is well-formed.
 201 func (r Rectangle) Canon() Rectangle {
 202         if r.Max.X < r.Min.X {
 203                 r.Min.X, r.Max.X = r.Max.X, r.Min.X
 204         }
 205         if r.Max.Y < r.Min.Y {
 206                 r.Min.Y, r.Max.Y = r.Max.Y, r.Min.Y
 207         }
 208         return r
 209 }
 210
 211 // ZR is the zero Rectangle.
 212 var ZR Rectangle
 213
 214 // Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}.
 215 func Rect(x0, y0, x1, y1 int) Rectangle {
 216         if x0 > x1 {
 217                 x0, x1 = x1, x0
 218         }
 219         if y0 > y1 {
 220                 y0, y1 = y1, y0
 221         }
 222         return Rectangle{Point{x0, y0}, Point{x1, y1}}
 223 }