Server/internal/color/xy.go

package color

import (
	"github.com/lucasb-eyer/go-colorful"
	"math"
)

const eps = 0.0001
const epsSquare = eps * eps

type Gamut struct {
	Red   XY `json:"red"`
	Green XY `json:"green"`
	Blue  XY `json:"blue"`
}

func (cg *Gamut) side(x1, y1, x2, y2, x, y float64) float64 {
	return (y2-y1)*(x-x1) + (-x2+x1)*(y-y1)
}

func (cg *Gamut) naiveContains(color XY) bool {
	x, y := color.X, color.Y
	x1, y1 := cg.Red.X, cg.Red.Y
	x2, y2 := cg.Green.X, cg.Green.Y
	x3, y3 := cg.Blue.X, cg.Blue.Y

	checkSide1 := cg.side(x1, y1, x2, y2, x, y) < 0
	checkSide2 := cg.side(x2, y2, x3, y3, x, y) < 0
	checkSide3 := cg.side(x3, y3, x1, y1, x, y) < 0

	return checkSide1 && checkSide2 && checkSide3
}

func (cg *Gamut) getBounds() (xMin, xMax, yMin, yMax float64) {
	x1, y1 := cg.Red.X, cg.Red.Y
	x2, y2 := cg.Green.X, cg.Green.Y
	x3, y3 := cg.Blue.X, cg.Blue.Y

	xMin = math.Min(x1, math.Min(x2, x3)) - eps
	xMax = math.Max(x1, math.Max(x2, x3)) + eps
	yMin = math.Min(y1, math.Min(y2, y3)) - eps
	yMax = math.Max(y1, math.Max(y2, y3)) + eps

	return
}

func (cg *Gamut) isInBounds(color XY) bool {
	x, y := color.X, color.Y
	xMin, xMax, yMin, yMax := cg.getBounds()

	return !(x < xMin || xMax < x || y < yMin || yMax < y)
}

func (cg *Gamut) distanceSquarePointToSegment(x1, y1, x2, y2, x, y float64) float64 {
	sqLength1 := (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1)
	dotProduct := ((x-x1)*(x2-x1) + (y-y1)*(y2-y1)) / sqLength1
	if dotProduct < 0 {
		return (x-x1)*(x-x1) + (y-y1)*(y-y1)
	} else if dotProduct <= 1 {
		sqLength2 := (x1-x)*(x1-x) + (y1-y)*(y1-y)
		return sqLength2 - dotProduct*dotProduct*sqLength1
	} else {
		return (x-x2)*(x-x2) + (y-y2)*(y-y2)
	}
}

func (cg *Gamut) atTheEdge(color XY) bool {
	x, y := color.X, color.Y
	x1, y1 := cg.Red.X, cg.Red.Y
	x2, y2 := cg.Green.X, cg.Green.Y
	x3, y3 := cg.Blue.X, cg.Blue.Y

	if cg.distanceSquarePointToSegment(x1, y1, x2, y2, x, y) <= epsSquare {
		return true
	}
	if cg.distanceSquarePointToSegment(x2, y2, x3, y3, x, y) <= epsSquare {
		return true
	}
	if cg.distanceSquarePointToSegment(x3, y3, x1, y1, x, y) <= epsSquare {
		return true
	}

	return false
}

func (cg *Gamut) Contains(color XY) bool {
	if cg == nil {
		return true
	}

	return cg.isInBounds(color) && (cg.naiveContains(color) || cg.atTheEdge(color))
}

func (cg *Gamut) Conform(color XY) XY {
	if cg.Contains(color) {
		return color
	}

	var best *XY

	xMin, xMax, yMin, yMax := cg.getBounds()

	for x := xMin; x < xMax; x += 0.001 {
		for y := yMin; y < yMax; y += 0.001 {
			color2 := XY{X: x, Y: y}

			if cg.Contains(color2) {
				if best == nil || color.DistanceTo(color2) < color.DistanceTo(*best) {
					best = &color2
				}
			}
		}
	}

	if best == nil {
		centerX := (cg.Red.X + cg.Green.X + cg.Blue.X) / 3
		centerY := (cg.Red.Y + cg.Green.Y + cg.Blue.Y) / 3

		stepX := (centerX - color.X) / 5000
		stepY := (centerY - color.Y) / 5000

		for !cg.Contains(color) {
			color.X += stepX
			color.Y += stepY
		}

		return color
	}

	for x := best.X - 0.001; x < best.X+0.001; x += 0.0002 {
		for y := best.Y - 0.001; y < best.Y+0.001; y += 0.0002 {
			color2 := XY{X: x, Y: y}

			if cg.atTheEdge(color2) {
				if best == nil || color.DistanceTo(color2) < color.DistanceTo(*best) {
					best = &color2
				}
			}
		}
	}

	for x := best.X - 0.0001; x < best.X+0.0001; x += 0.00003 {
		for y := best.Y - 0.0001; y < best.Y+0.0001; y += 0.00003 {
			color2 := XY{X: x, Y: y}

			if cg.atTheEdge(color2) {
				if best == nil || color.DistanceTo(color2) < color.DistanceTo(*best) {
					best = &color2
				}
			}
		}
	}

	return *best
}

type XY struct {
	X float64 `json:"x"`
	Y float64 `json:"y"`
}

func (xy XY) ToRGB() RGB {
	h, s, _ := colorful.Xyy(xy.X, xy.Y, 0.5).Hsv()
	c := colorful.Hsv(h, s, 1)
	return RGB{Red: c.R, Green: c.G, Blue: c.B}
}

func (xy XY) ToHS() HueSat {
	h, s, _ := colorful.Xyy(xy.X, xy.Y, 0.5).Hsv()
	return HueSat{Hue: h, Sat: s}
}

func (xy XY) DistanceTo(other XY) float64 {
	return math.Sqrt(math.Pow(xy.X-other.X, 2) + math.Pow(xy.Y-other.Y, 2))
}

func (xy XY) Round() XY {
	return XY{
		X: math.Round(xy.X*10000) / 10000,
		Y: math.Round(xy.Y*10000) / 10000,
	}
}