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math/fixed: add rectangle types and the R function.

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Change-Id: Ibb3785bcd57f13c7b6f1dc37526f65e44b4ac695
Reviewed-on: https://go-review.googlesource.com/13823
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Nigel Tao 2015-08-24 10:24:01 +10:00
parent d9c0088098
commit 8ab1ac6834
1 changed files with 51 additions and 2 deletions
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53
math/fixed/fixed.go
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@ -13,7 +13,7 @@ import (
// I returns the integer value i as an Int26_6. // I returns the integer value i as an Int26_6.
// //
// For example, the integer value 2 is the Int26_6 128. // For example, passing the integer value 2 yields Int26_6(128).
func I(i int) Int26_6 { func I(i int) Int26_6 {
return Int26_6(i << 6) return Int26_6(i << 6)
} }
@ -67,12 +67,14 @@ func (x Int52_12) String() string {
// P returns the integer values x and y as a Point26_6. // P returns the integer values x and y as a Point26_6.
// //
// For example, the integer value pair (2, -3) is the Point26_6 (128, -192). // For example, passing the integer values (2, -3) yields Point26_6{128, -192}.
func P(x, y int) Point26_6 { func P(x, y int) Point26_6 {
return Point26_6{Int26_6(x << 6), Int26_6(y << 6)} return Point26_6{Int26_6(x << 6), Int26_6(y << 6)}
} }
// Point26_6 is a 26.6 fixed-point coordinate pair. // Point26_6 is a 26.6 fixed-point coordinate pair.
//
// It is analogous to the image.Point type in the standard library.
type Point26_6 struct { type Point26_6 struct {
X, Y Int26_6 X, Y Int26_6
} }
@ -98,6 +100,8 @@ func (p Point26_6) Div(k Int26_6) Point26_6 {
} }
// Point52_12 is a 52.12 fixed-point coordinate pair. // Point52_12 is a 52.12 fixed-point coordinate pair.
//
// It is analogous to the image.Point type in the standard library.
type Point52_12 struct { type Point52_12 struct {
X, Y Int52_12 X, Y Int52_12
} }
@ -121,3 +125,48 @@ func (p Point52_12) Mul(k Int52_12) Point52_12 {
func (p Point52_12) Div(k Int52_12) Point52_12 { func (p Point52_12) Div(k Int52_12) Point52_12 {
return Point52_12{p.X * 4096 / k, p.Y * 4096 / k} return Point52_12{p.X * 4096 / k, p.Y * 4096 / k}
} }
// R returns the integer values minX, minY, maxX, maxY as a Rectangle26_6.
//
// For example, passing the integer values (0, 1, 2, 3) yields
// Rectangle26_6{Point26_6{0, 64}, Point26_6{128, 192}}.
//
// Like the image.Rect function in the standard library, the returned rectangle
// has minimum and maximum coordinates swapped if necessary so that it is
// well-formed.
func R(minX, minY, maxX, maxY int) Rectangle26_6 {
if minX > maxX {
minX, maxX = maxX, minX
}
if minY > maxY {
minY, maxY = maxY, minY
}
return Rectangle26_6{
Point26_6{
Int26_6(minX << 6),
Int26_6(minY << 6),
},
Point26_6{
Int26_6(maxX << 6),
Int26_6(maxY << 6),
},
}
}
// Rectangle26_6 is a 26.6 fixed-point coordinate rectangle. The Min bound is
// inclusive and the Max bound is exclusive. It is well-formed if Min.X <=
// Max.X and likewise for Y.
//
// It is analogous to the image.Rectangle type in the standard library.
type Rectangle26_6 struct {
Min, Max Point26_6
}
// Rectangle52_12 is a 52.12 fixed-point coordinate rectangle. The Min bound is
// inclusive and the Max bound is exclusive. It is well-formed if Min.X <=
// Max.X and likewise for Y.
//
// It is analogous to the image.Rectangle type in the standard library.
type Rectangle52_12 struct {
Min, Max Point52_12
}