From d6468fc114217678e8bc8b4324fd6185794e0182 Mon Sep 17 00:00:00 2001
From: xuri <xuri.me@gmail.com>
Date: Sat, 7 Jul 2018 15:59:48 +0800
Subject: - Initialize theme support; - RGBA, HSL color convert has been added;
 - go test updated

---
 hsl.go | 141 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 hsl.go

(limited to 'hsl.go')

diff --git a/hsl.go b/hsl.go
new file mode 100644
index 0000000..bd868b1
--- /dev/null
+++ b/hsl.go
@@ -0,0 +1,141 @@
+/*
+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 a 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 a 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
+}
-- 
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