From afb30dc1e6908d135a631a2dfc3f5d63023c8fe3 Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Wed, 6 Mar 2019 19:24:03 +0100
Subject: [PATCH] Added Sub on RectangleF{,32}. Added Invert on PointF{,32}.
 Changed formula of Center (PointF{,32}).

---
 pointf.go       |  5 +++++
 pointf32.go     |  5 +++++
 rectanglef.go   | 10 +++++++++-
 rectanglef32.go | 10 +++++++++-
 4 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/pointf.go b/pointf.go
index fc42698..c7b91b1 100644
--- a/pointf.go
+++ b/pointf.go
@@ -72,6 +72,11 @@ func (p PointF) InPolygon(q PolygonF) bool {
 	return c
 }
 
+// Invert changes the sign of the components.
+func (p PointF) Invert() PointF {
+	return PointF{-p.X, -p.Y}
+}
+
 // Sub subtracts q as a vector from p.
 func (p PointF) Sub(q PointF) PointF {
 	return PointF{p.X - q.X, p.Y - q.Y}
diff --git a/pointf32.go b/pointf32.go
index 24c39e9..d66e3a2 100644
--- a/pointf32.go
+++ b/pointf32.go
@@ -54,6 +54,11 @@ func (p PointF32) In(r RectangleF32) bool {
 	return true
 }
 
+// Invert changes the sign of the components.
+func (p PointF32) Invert() PointF32 {
+	return PointF32{-p.X, -p.Y}
+}
+
 // Sub subtracts q as a vector from p.
 func (p PointF32) Sub(q PointF32) PointF32 {
 	return PointF32{p.X - q.X, p.Y - q.Y}
diff --git a/rectanglef.go b/rectanglef.go
index 2bc003f..41b2248 100644
--- a/rectanglef.go
+++ b/rectanglef.go
@@ -27,7 +27,7 @@ func (r RectangleF) Add(p PointF) RectangleF {
 
 // Center returns the center of the rectangle.
 func (r RectangleF) Center() PointF {
-	return PointF{r.Min.X + .5*(r.Max.X-r.Min.X), r.Min.Y + .5*(r.Max.Y-r.Min.Y)}
+	return PointF{.5 * (r.Min.X + r.Max.X), .5 * (r.Min.Y + r.Max.Y)}
 }
 
 // Dx returns the width of r.
@@ -64,3 +64,11 @@ func (r RectangleF) Inset(n float64) RectangleF {
 func (r RectangleF) Size() PointF {
 	return PointF{r.Max.X - r.Min.X, r.Max.Y - r.Min.Y}
 }
+
+// Sub translates rectangle r in the opposite direction of point p.
+func (r RectangleF) Sub(p PointF) RectangleF {
+	return RectangleF{
+		PointF{r.Min.X - p.X, r.Min.Y - p.Y},
+		PointF{r.Max.X - p.X, r.Max.Y - p.Y},
+	}
+}
diff --git a/rectanglef32.go b/rectanglef32.go
index 698737c..fab729a 100644
--- a/rectanglef32.go
+++ b/rectanglef32.go
@@ -27,7 +27,7 @@ func (r RectangleF32) Add(p PointF32) RectangleF32 {
 
 // Center returns the center of the rectangle.
 func (r RectangleF32) Center() PointF32 {
-	return PointF32{r.Min.X + .5*(r.Max.X-r.Min.X), r.Min.Y + .5*(r.Max.Y-r.Min.Y)}
+	return PointF32{.5 * (r.Min.X + r.Max.X), .5 * (r.Min.Y + r.Max.Y)}
 }
 
 // Dx returns the width of r.
@@ -64,3 +64,11 @@ func (r RectangleF32) Inset(n float32) RectangleF32 {
 func (r RectangleF32) Size() PointF32 {
 	return PointF32{r.Max.X - r.Min.X, r.Max.Y - r.Min.Y}
 }
+
+// Sub translates rectangle r in the opposite direction of point p.
+func (r RectangleF32) Sub(p PointF32) RectangleF32 {
+	return RectangleF32{
+		PointF32{r.Min.X - p.X, r.Min.Y - p.Y},
+		PointF32{r.Max.X - p.X, r.Max.Y - p.Y},
+	}
+}