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// Copyright 2011 The Graphics-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 detect
import (
"image"
)
// projector allows projecting from a source Rectangle onto a target Rectangle.
type projector struct {
// rx, ry is the scaling factor.
rx, ry float64
// dx, dy is the translation factor.
dx, dy float64
// r is the clipping region of the target.
r image.Rectangle
}
// newProjector creates a Projector with source src and target dst.
func newProjector(dst image.Rectangle, src image.Rectangle) *projector {
return &projector{
rx: float64(dst.Dx()) / float64(src.Dx()),
ry: float64(dst.Dy()) / float64(src.Dy()),
dx: float64(dst.Min.X - src.Min.X),
dy: float64(dst.Min.Y - src.Min.Y),
r: dst,
}
}
// pt projects p from the source rectangle onto the target rectangle.
func (s *projector) pt(p image.Point) image.Point {
return image.Point{
clamp(s.rx*float64(p.X)+s.dx, s.r.Min.X, s.r.Max.X),
clamp(s.ry*float64(p.Y)+s.dy, s.r.Min.Y, s.r.Max.Y),
}
}
// rect projects r from the source rectangle onto the target rectangle.
func (s *projector) rect(r image.Rectangle) image.Rectangle {
return image.Rectangle{s.pt(r.Min), s.pt(r.Max)}
}
// clamp rounds and clamps o to the integer range [x0, x1].
func clamp(o float64, x0, x1 int) int {
x := int(o + 0.5)
if x < x0 {
return x0
}
if x > x1 {
return x1
}
return x
}
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