service/vendor/github.com/xuri/excelize/v2/hsl.go

140 lines
3.6 KiB
Go

// Copyright (c) 2012 Rodrigo Moraes. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package excelize
import (
"image/color"
"math"
)
// HSLModel converts any color.Color to a HSL color.
var HSLModel = color.ModelFunc(hslModel)
// HSL represents a cylindrical coordinate of points in an RGB color model.
//
// Values are in the range 0 to 1.
type HSL struct {
H, S, L float64
}
// RGBA returns the alpha-premultiplied red, green, blue and alpha values
// for the HSL.
func (c HSL) RGBA() (uint32, uint32, uint32, uint32) {
r, g, b := HSLToRGB(c.H, c.S, c.L)
return uint32(r) * 0x101, uint32(g) * 0x101, uint32(b) * 0x101, 0xffff
}
// hslModel converts a color.Color to HSL.
func hslModel(c color.Color) color.Color {
if _, ok := c.(HSL); ok {
return c
}
r, g, b, _ := c.RGBA()
h, s, l := RGBToHSL(uint8(r>>8), uint8(g>>8), uint8(b>>8))
return HSL{h, s, l}
}
// RGBToHSL converts an RGB triple to an HSL triple.
func RGBToHSL(r, g, b uint8) (h, s, l float64) {
fR := float64(r) / 255
fG := float64(g) / 255
fB := float64(b) / 255
max := math.Max(math.Max(fR, fG), fB)
min := math.Min(math.Min(fR, fG), fB)
l = (max + min) / 2
if max == min {
// Achromatic.
h, s = 0, 0
} else {
// Chromatic.
d := max - min
if l > 0.5 {
s = d / (2.0 - max - min)
} else {
s = d / (max + min)
}
switch max {
case fR:
h = (fG - fB) / d
if fG < fB {
h += 6
}
case fG:
h = (fB-fR)/d + 2
case fB:
h = (fR-fG)/d + 4
}
h /= 6
}
return
}
// HSLToRGB converts an HSL triple to an RGB triple.
func HSLToRGB(h, s, l float64) (r, g, b uint8) {
var fR, fG, fB float64
if s == 0 {
fR, fG, fB = l, l, l
} else {
var q float64
if l < 0.5 {
q = l * (1 + s)
} else {
q = l + s - s*l
}
p := 2*l - q
fR = hueToRGB(p, q, h+1.0/3)
fG = hueToRGB(p, q, h)
fB = hueToRGB(p, q, h-1.0/3)
}
r = uint8((fR * 255) + 0.5)
g = uint8((fG * 255) + 0.5)
b = uint8((fB * 255) + 0.5)
return
}
// hueToRGB is a helper function for HSLToRGB.
func hueToRGB(p, q, t float64) float64 {
if t < 0 {
t++
}
if t > 1 {
t--
}
if t < 1.0/6 {
return p + (q-p)*6*t
}
if t < 0.5 {
return q
}
if t < 2.0/3 {
return p + (q-p)*(2.0/3-t)*6
}
return p
}