318 lines
7.3 KiB
Go
318 lines
7.3 KiB
Go
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// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package image
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import (
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"image/color"
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"math/bits"
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"strconv"
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)
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// A Point is an X, Y coordinate pair. The axes increase right and down.
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type Point struct {
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X, Y int
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}
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// String returns a string representation of p like "(3,4)".
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func (p Point) String() string {
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return "(" + strconv.Itoa(p.X) + "," + strconv.Itoa(p.Y) + ")"
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}
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// Add returns the vector p+q.
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func (p Point) Add(q Point) Point {
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return Point{p.X + q.X, p.Y + q.Y}
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}
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// Sub returns the vector p-q.
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func (p Point) Sub(q Point) Point {
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return Point{p.X - q.X, p.Y - q.Y}
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}
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// Mul returns the vector p*k.
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func (p Point) Mul(k int) Point {
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return Point{p.X * k, p.Y * k}
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}
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// Div returns the vector p/k.
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func (p Point) Div(k int) Point {
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return Point{p.X / k, p.Y / k}
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}
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// In reports whether p is in r.
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func (p Point) In(r Rectangle) bool {
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return r.Min.X <= p.X && p.X < r.Max.X &&
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r.Min.Y <= p.Y && p.Y < r.Max.Y
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}
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// Mod returns the point q in r such that p.X-q.X is a multiple of r's width
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// and p.Y-q.Y is a multiple of r's height.
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func (p Point) Mod(r Rectangle) Point {
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w, h := r.Dx(), r.Dy()
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p = p.Sub(r.Min)
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p.X = p.X % w
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if p.X < 0 {
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p.X += w
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}
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p.Y = p.Y % h
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if p.Y < 0 {
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p.Y += h
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}
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return p.Add(r.Min)
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}
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// Eq reports whether p and q are equal.
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func (p Point) Eq(q Point) bool {
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return p == q
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}
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// ZP is the zero Point.
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//
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// Deprecated: Use a literal image.Point{} instead.
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var ZP Point
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// Pt is shorthand for Point{X, Y}.
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func Pt(X, Y int) Point {
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return Point{X, Y}
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}
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// A Rectangle contains the points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y.
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// It is well-formed if Min.X <= Max.X and likewise for Y. Points are always
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// well-formed. A rectangle's methods always return well-formed outputs for
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// well-formed inputs.
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//
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// A Rectangle is also an Image whose bounds are the rectangle itself. At
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// returns color.Opaque for points in the rectangle and color.Transparent
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// otherwise.
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type Rectangle struct {
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Min, Max Point
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}
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// String returns a string representation of r like "(3,4)-(6,5)".
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func (r Rectangle) String() string {
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return r.Min.String() + "-" + r.Max.String()
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}
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// Dx returns r's width.
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func (r Rectangle) Dx() int {
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return r.Max.X - r.Min.X
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}
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// Dy returns r's height.
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func (r Rectangle) Dy() int {
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return r.Max.Y - r.Min.Y
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}
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// Size returns r's width and height.
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func (r Rectangle) Size() Point {
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return Point{
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r.Max.X - r.Min.X,
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r.Max.Y - r.Min.Y,
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}
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}
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// Add returns the rectangle r translated by p.
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func (r Rectangle) Add(p Point) Rectangle {
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return Rectangle{
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Point{r.Min.X + p.X, r.Min.Y + p.Y},
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Point{r.Max.X + p.X, r.Max.Y + p.Y},
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}
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}
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// Sub returns the rectangle r translated by -p.
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func (r Rectangle) Sub(p Point) Rectangle {
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return Rectangle{
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Point{r.Min.X - p.X, r.Min.Y - p.Y},
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Point{r.Max.X - p.X, r.Max.Y - p.Y},
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}
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}
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// Inset returns the rectangle r inset by n, which may be negative. If either
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// of r's dimensions is less than 2*n then an empty rectangle near the center
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// of r will be returned.
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func (r Rectangle) Inset(n int) Rectangle {
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if r.Dx() < 2*n {
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r.Min.X = (r.Min.X + r.Max.X) / 2
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r.Max.X = r.Min.X
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} else {
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r.Min.X += n
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r.Max.X -= n
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}
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if r.Dy() < 2*n {
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r.Min.Y = (r.Min.Y + r.Max.Y) / 2
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r.Max.Y = r.Min.Y
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} else {
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r.Min.Y += n
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r.Max.Y -= n
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}
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return r
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}
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// Intersect returns the largest rectangle contained by both r and s. If the
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// two rectangles do not overlap then the zero rectangle will be returned.
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func (r Rectangle) Intersect(s Rectangle) Rectangle {
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if r.Min.X < s.Min.X {
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r.Min.X = s.Min.X
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}
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if r.Min.Y < s.Min.Y {
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r.Min.Y = s.Min.Y
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}
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if r.Max.X > s.Max.X {
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r.Max.X = s.Max.X
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}
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if r.Max.Y > s.Max.Y {
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r.Max.Y = s.Max.Y
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}
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// Letting r0 and s0 be the values of r and s at the time that the method
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// is called, this next line is equivalent to:
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//
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// if max(r0.Min.X, s0.Min.X) >= min(r0.Max.X, s0.Max.X) || likewiseForY { etc }
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if r.Empty() {
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return ZR
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}
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return r
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}
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// Union returns the smallest rectangle that contains both r and s.
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func (r Rectangle) Union(s Rectangle) Rectangle {
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if r.Empty() {
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return s
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}
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if s.Empty() {
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return r
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}
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if r.Min.X > s.Min.X {
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r.Min.X = s.Min.X
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}
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if r.Min.Y > s.Min.Y {
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r.Min.Y = s.Min.Y
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}
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if r.Max.X < s.Max.X {
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r.Max.X = s.Max.X
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}
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if r.Max.Y < s.Max.Y {
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r.Max.Y = s.Max.Y
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}
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return r
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}
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// Empty reports whether the rectangle contains no points.
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func (r Rectangle) Empty() bool {
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return r.Min.X >= r.Max.X || r.Min.Y >= r.Max.Y
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}
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// Eq reports whether r and s contain the same set of points. All empty
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// rectangles are considered equal.
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func (r Rectangle) Eq(s Rectangle) bool {
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return r == s || r.Empty() && s.Empty()
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}
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// Overlaps reports whether r and s have a non-empty intersection.
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func (r Rectangle) Overlaps(s Rectangle) bool {
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return !r.Empty() && !s.Empty() &&
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r.Min.X < s.Max.X && s.Min.X < r.Max.X &&
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r.Min.Y < s.Max.Y && s.Min.Y < r.Max.Y
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}
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// In reports whether every point in r is in s.
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func (r Rectangle) In(s Rectangle) bool {
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if r.Empty() {
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return true
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}
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// Note that r.Max is an exclusive bound for r, so that r.In(s)
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// does not require that r.Max.In(s).
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return s.Min.X <= r.Min.X && r.Max.X <= s.Max.X &&
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s.Min.Y <= r.Min.Y && r.Max.Y <= s.Max.Y
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}
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// Canon returns the canonical version of r. The returned rectangle has minimum
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// and maximum coordinates swapped if necessary so that it is well-formed.
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func (r Rectangle) Canon() Rectangle {
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if r.Max.X < r.Min.X {
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r.Min.X, r.Max.X = r.Max.X, r.Min.X
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}
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if r.Max.Y < r.Min.Y {
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r.Min.Y, r.Max.Y = r.Max.Y, r.Min.Y
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}
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return r
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}
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// At implements the Image interface.
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func (r Rectangle) At(x, y int) color.Color {
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if (Point{x, y}).In(r) {
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return color.Opaque
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}
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return color.Transparent
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}
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// RGBA64At implements the RGBA64Image interface.
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func (r Rectangle) RGBA64At(x, y int) color.RGBA64 {
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if (Point{x, y}).In(r) {
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return color.RGBA64{0xffff, 0xffff, 0xffff, 0xffff}
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}
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return color.RGBA64{}
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}
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// Bounds implements the Image interface.
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func (r Rectangle) Bounds() Rectangle {
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return r
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}
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// ColorModel implements the Image interface.
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func (r Rectangle) ColorModel() color.Model {
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return color.Alpha16Model
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}
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// ZR is the zero Rectangle.
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//
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// Deprecated: Use a literal image.Rectangle{} instead.
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var ZR Rectangle
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// Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}. The returned
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// rectangle has minimum and maximum coordinates swapped if necessary so that
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// it is well-formed.
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func Rect(x0, y0, x1, y1 int) Rectangle {
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if x0 > x1 {
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x0, x1 = x1, x0
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}
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if y0 > y1 {
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y0, y1 = y1, y0
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}
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return Rectangle{Point{x0, y0}, Point{x1, y1}}
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}
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// mul3NonNeg returns (x * y * z), unless at least one argument is negative or
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// if the computation overflows the int type, in which case it returns -1.
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func mul3NonNeg(x int, y int, z int) int {
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if (x < 0) || (y < 0) || (z < 0) {
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return -1
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}
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hi, lo := bits.Mul64(uint64(x), uint64(y))
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if hi != 0 {
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return -1
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}
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hi, lo = bits.Mul64(lo, uint64(z))
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if hi != 0 {
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return -1
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}
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a := int(lo)
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if (a < 0) || (uint64(a) != lo) {
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return -1
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}
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return a
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}
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// add2NonNeg returns (x + y), unless at least one argument is negative or if
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// the computation overflows the int type, in which case it returns -1.
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func add2NonNeg(x int, y int) int {
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if (x < 0) || (y < 0) {
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return -1
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}
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a := x + y
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if a < 0 {
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return -1
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}
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return a
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}
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