68 lines
2.4 KiB
Go
68 lines
2.4 KiB
Go
package shape
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import (
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"math"
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"oss.terrastruct.com/d2/lib/geo"
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"oss.terrastruct.com/util-go/go2"
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)
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type shapeOval struct {
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*baseShape
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}
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func NewOval(box *geo.Box) Shape {
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shape := shapeOval{
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baseShape: &baseShape{
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Type: OVAL_TYPE,
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Box: box,
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},
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}
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shape.FullShape = go2.Pointer(Shape(shape))
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return shape
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}
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func (s shapeOval) GetInnerBox() *geo.Box {
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width := s.Box.Width
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height := s.Box.Height
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insideTL := s.GetInsidePlacement(width, height, 0)
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tl := s.Box.TopLeft.Copy()
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width -= 2 * (insideTL.X - tl.X)
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height -= 2 * (insideTL.Y - tl.Y)
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return geo.NewBox(&insideTL, width, height)
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}
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func (s shapeOval) GetDimensionsToFit(width, height, paddingX, paddingY float64) (float64, float64) {
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theta := math.Atan2(height, width)
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// add padding in direction of diagonal so there is padding distance between top left and border
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paddedWidth := width + paddingX*math.Cos(theta)
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paddedHeight := height + paddingY*math.Sin(theta)
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// see https://stackoverflow.com/questions/433371/ellipse-bounding-a-rectangle
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return math.Ceil(math.Sqrt2 * paddedWidth), math.Ceil(math.Sqrt2 * paddedHeight)
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}
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func (s shapeOval) GetInsidePlacement(width, height, padding float64) geo.Point {
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// showing the top left arc of the ellipse (drawn with '*')
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// ┌──────────────────* ┬
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// │ * │ │ry
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// │ *┌───────────┤ │ ┬
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// │ * │ │ │ │sin*r
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// │* │ │ │ │
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// *──────┴───────────┼ ┴ ┴
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// ├────────rx────────┤
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// ├───cos*r───┤
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rx := s.Box.Width / 2
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ry := s.Box.Height / 2
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theta := math.Atan2(ry, rx)
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sin := math.Sin(theta)
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cos := math.Cos(theta)
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// r is the ellipse radius on the line between node.TopLeft and the ellipse center
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// see https://math.stackexchange.com/questions/432902/how-to-get-the-radius-of-an-ellipse-at-a-specific-angle-by-knowing-its-semi-majo
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r := rx * ry / math.Sqrt(math.Pow(rx*sin, 2)+math.Pow(ry*cos, 2))
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// we want to offset r-padding/2 away from the center
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return *geo.NewPoint(s.Box.TopLeft.X+math.Ceil(rx-cos*(r-padding/2)), s.Box.TopLeft.Y+math.Ceil(ry-sin*(r-padding/2)))
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}
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func (s shapeOval) Perimeter() []geo.Intersectable {
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return []geo.Intersectable{geo.NewEllipse(s.Box.Center(), s.Box.Width/2, s.Box.Height/2)}
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}
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