将CSS Lch转换为RGB

L = L / 100
C = C / 100
H = H * (Math.PI / 180)

var X = C * Math.cos(H)
var Y = L
var Z = C * Math.sin(H)

var r = X * 3.2406 + Y * -1.5372 + Z * -0.4986
var g = X * -0.9689 + Y * 1.8758 + Z * 0.0415
var b = X * 0.0557 + Y * -0.2040 + Z * 1.0570

if (r > 0.0031308) {
  r = 1.055 * Math.pow(r, 1 / 2.4) - 0.055
} else {
  r = 12.92 * r
}

if (g > 0.0031308) {
  g = 1.055 * Math.pow(g, 1 / 2.4) - 0.055
} else {
  g = 12.92 * g
}

if (b > 0.0031308) {
  b = 1.055 * Math.pow(b, 1 / 2.4) - 0.055
} else {
  b = 12.92 * b
}

r = Math.max(0, Math.min(1, r))
g = Math.max(0, Math.min(1, g))
b = Math.max(0, Math.min(1, b))

r = Math.round(r * 255)
g = Math.round(g * 255)
b = Math.round(b * 255)