Added RectangleF32.

Added ZeroPtF32.
Added Center methods for rectangles.

pointf32.go

@@ -5,6 +5,9 @@ type PointF32 struct {
 	X, Y float32
 }
 
+// ZeroPtF32 is initialized on (0, 0).
+var ZeroPtF32 = PointF32{X: 0, Y: 0}
+
 // PtF32 is a shorthand function to create a point.
 func PtF32(x, y float32) PointF32 {
 	return PointF32{x, y}

rectanglef.go

@@ -55,6 +55,11 @@ func (r RectangleF) Dy() float64 {
 	return r.Max.Y - r.Min.Y
 }
 
+// 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)}
+}
+
 // Size returns the size of the rectangle.
 func (r RectangleF) Size() PointF {
 	return PointF{r.Max.X - r.Min.X, r.Max.Y - r.Min.Y}

rectanglef32.go

@@ -0,0 +1,66 @@
+package geom
+
+// RectangleF32 is defined by two points, the minimum and maximum (floating point).
+// Tries to use the same interface as the image. Rectangle but uses float32 instead of int.
+type RectangleF32 struct {
+	Min, Max PointF32
+}
+
+// RectF32 is a shorthand function to create a rectangle.
+func RectF32(x0, y0, x1, y1 float32) RectangleF32 {
+	if x0 > x1 {
+		x0, x1 = x1, x0
+	}
+	if y0 > y1 {
+		y0, y1 = y1, y0
+	}
+	return RectangleF32{PtF32(x0, y0), PtF32(x1, y1)}
+}
+
+// Add translates rectangle r by point p.
+func (r RectangleF32) Add(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},
+	}
+}
+
+// Inset returns the rectangle r inset by n. The resulting rectangle will never have
+// a negative size.
+func (r RectangleF32) Inset(n float32) RectangleF32 {
+	if r.Dx() < 2*n {
+		r.Min.X = (r.Min.X + r.Max.X) / 2
+		r.Max.X = r.Min.X
+	} else {
+		r.Min.X += n
+		r.Max.X -= n
+	}
+	if r.Dy() < 2*n {
+		r.Min.Y = (r.Min.Y + r.Max.Y) / 2
+		r.Max.Y = r.Min.Y
+	} else {
+		r.Min.Y += n
+		r.Max.Y -= n
+	}
+	return r
+}
+
+// Dx returns the width of r.
+func (r RectangleF32) Dx() float32 {
+	return r.Max.X - r.Min.X
+}
+
+// Dy returns the height of r.
+func (r RectangleF32) Dy() float32 {
+	return r.Max.Y - r.Min.Y
+}
+
+// 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)}
+}
+
+// Size returns the size of the rectangle.
+func (r RectangleF32) Size() PointF32 {
+	return PointF32{r.Max.X - r.Min.X, r.Max.Y - r.Min.Y}
+}