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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package imageutil implements some image utility functions.
package imageutil
import (
"image"
)
// TODO: move Border into the standard library's package image?
// Border returns four rectangles that together contain those points between r
// and r.Inset(inset). Visually:
//
// 00000000
// 00000000
// 11....22
// 11....22
// 11....22
// 33333333
// 33333333
//
// The inset may be negative, in which case the points will be outside r.
//
// Some of the returned rectangles may be empty. None of the returned
// rectangles will overlap.
func Border(r image.Rectangle, inset int) [4]image.Rectangle {
if inset == 0 {
return [4]image.Rectangle{}
}
if r.Dx() <= 2*inset || r.Dy() <= 2*inset {
return [4]image.Rectangle{r}
}
x := [4]int{
r.Min.X,
r.Min.X + inset,
r.Max.X - inset,
r.Max.X,
}
y := [4]int{
r.Min.Y,
r.Min.Y + inset,
r.Max.Y - inset,
r.Max.Y,
}
if inset < 0 {
x[0], x[1] = x[1], x[0]
x[2], x[3] = x[3], x[2]
y[0], y[1] = y[1], y[0]
y[2], y[3] = y[3], y[2]
}
// The top and bottom sections are responsible for filling the corners.
// The top and bottom sections go from x[0] to x[3], across the y's.
// The left and right sections go from y[1] to y[2], across the x's.
return [4]image.Rectangle{{
// Top section.
Min: image.Point{
X: x[0],
Y: y[0],
},
Max: image.Point{
X: x[3],
Y: y[1],
},
}, {
// Left section.
Min: image.Point{
X: x[0],
Y: y[1],
},
Max: image.Point{
X: x[1],
Y: y[2],
},
}, {
// Right section.
Min: image.Point{
X: x[2],
Y: y[1],
},
Max: image.Point{
X: x[3],
Y: y[2],
},
}, {
// Bottom section.
Min: image.Point{
X: x[0],
Y: y[2],
},
Max: image.Point{
X: x[3],
Y: y[3],
},
}}
}
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