From d25019851fc52ec911ab9cfeb75eab2ce0c38184 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Thu, 10 Sep 2020 18:16:10 +0200
Subject: [PATCH] Add string/color.RGBA to HexColor

---
 hexcolor.go | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 hexcolor.go

diff --git a/hexcolor.go b/hexcolor.go
new file mode 100644
index 0000000..f03f7ce
--- /dev/null
+++ b/hexcolor.go
@@ -0,0 +1,100 @@
+package go_hexcolor
+
+import (
+	"fmt"
+	"image/color"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// HexColor represents a single hex color
+type HexColor struct {
+	original string
+	hex      string
+}
+
+// The compiled regular expression used to test the validity of a color statement
+var (
+	hexDefault *regexp.Regexp
+	hexShort   *regexp.Regexp
+)
+
+// The raw regular expression string used for testing the validity
+const (
+	hexDefaultRaw string = `[0-9a-f]{6}`
+	hexShortRaw   string = `[0-9a-f]{3}`
+)
+
+func init() {
+	hexDefault = regexp.MustCompile("^" + hexDefaultRaw + "$")
+	hexShort = regexp.MustCompile("^" + hexShortRaw + "$")
+}
+
+// NewHexColor convert string into a HexColor
+func NewHexColor(hc string) (*HexColor, error) {
+	c := &HexColor{original: hc}
+	hc = strings.TrimLeft(strings.ToLower(hc), "#")
+
+	if hexDefault.MatchString(hc) {
+		c.hex = hc
+		return c, nil
+	}
+	if hexShort.MatchString(hc) {
+		c.hex = hc[:1] + hc[:1] + hc[1:][:1] + hc[1:][:1] + hc[2:] + hc[2:]
+		return c, nil
+	}
+
+	// handle named colors
+
+	return nil, fmt.Errorf("Malformed color: %s", hc)
+}
+
+// ToString return normalized hex code of color
+func (c *HexColor) ToString() string {
+	if c == nil {
+		return ""
+	}
+	return c.hex
+}
+
+// ToRGBA return RGBA color
+func (c *HexColor) ToRGBA() (*color.RGBA, error) {
+	if c == nil {
+		return nil, nil
+	}
+	rr, err := strconv.ParseUint(c.hex[:2], 16, 8)
+	if err != nil {
+		return nil, err
+	}
+	gg, err := strconv.ParseUint(c.hex[2:][:2], 16, 8)
+	if err != nil {
+		return nil, err
+	}
+	bb, err := strconv.ParseUint(c.hex[4:], 16, 8)
+	if err != nil {
+		return nil, err
+	}
+	return &color.RGBA{
+		R: uint8(rr),
+		G: uint8(gg),
+		B: uint8(bb),
+		A: 0xff,
+	}, nil
+}
+
+// ToHexColor convert RGBA to HexColor
+func ToHexColor(c *color.RGBA) *HexColor {
+	toS := func(i uint8) string {
+		h := fmt.Sprintf("%x", i)
+		if len(h) == 1 {
+			h = "0" + h
+		}
+		return h
+	}
+
+	return &HexColor{
+		original: fmt.Sprintf("%v", c),
+		hex:      toS(c.R) + toS(c.G) + toS(c.B),
+	}
+}