56 lines
1.4 KiB
Go
56 lines
1.4 KiB
Go
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// Copyright 2011 The Graphics-Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package detect
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import (
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"image"
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)
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// projector allows projecting from a source Rectangle onto a target Rectangle.
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type projector struct {
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// rx, ry is the scaling factor.
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rx, ry float64
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// dx, dy is the translation factor.
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dx, dy float64
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// r is the clipping region of the target.
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r image.Rectangle
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}
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// newProjector creates a Projector with source src and target dst.
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func newProjector(dst image.Rectangle, src image.Rectangle) *projector {
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return &projector{
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rx: float64(dst.Dx()) / float64(src.Dx()),
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ry: float64(dst.Dy()) / float64(src.Dy()),
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dx: float64(dst.Min.X - src.Min.X),
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dy: float64(dst.Min.Y - src.Min.Y),
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r: dst,
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}
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}
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// pt projects p from the source rectangle onto the target rectangle.
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func (s *projector) pt(p image.Point) image.Point {
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return image.Point{
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clamp(s.rx*float64(p.X)+s.dx, s.r.Min.X, s.r.Max.X),
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clamp(s.ry*float64(p.Y)+s.dy, s.r.Min.Y, s.r.Max.Y),
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}
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}
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// rect projects r from the source rectangle onto the target rectangle.
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func (s *projector) rect(r image.Rectangle) image.Rectangle {
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return image.Rectangle{s.pt(r.Min), s.pt(r.Max)}
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}
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// clamp rounds and clamps o to the integer range [x0, x1].
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func clamp(o float64, x0, x1 int) int {
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x := int(o + 0.5)
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if x < x0 {
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return x0
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}
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if x > x1 {
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return x1
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}
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return x
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}
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