56 lines
1.4 KiB
Go
56 lines
1.4 KiB
Go
// 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
|
|
}
|