Commits
Diff
package color
import (
"fmt"
ic "image/color"
"strconv"
"strings"
)
// ParseRGBA parses a CSS color string and returns an RGBA color
func ParseRGBA(color string) (ic.RGBA, error) {
color = strings.TrimSpace(strings.ToLower(color))
// Named color
if namedColor, ok := namedColors[color]; ok {
return namedColor, nil
}
// Hex color format: #RRGGBB or #RRGGBBAA
if strings.HasPrefix(color, "#") {
hexValue := strings.TrimPrefix(color, "#")
// Check if it's a three-letter hex code and expand it to six-letter hex code
if len(hexValue) == 3 {
hexValue = fmt.Sprintf("%c%c%c%c%c%c",
hexValue[0], hexValue[0],
hexValue[1], hexValue[1],
hexValue[2], hexValue[2])
}
rgb, err := strconv.ParseUint(hexValue, 16, 32)
if err != nil {
return ic.RGBA{}, fmt.Errorf("Invalid hex code")
}
// Check if it's #RRGGBB or #RRGGBBAA
alpha := uint8(255)
if len(hexValue) == 8 {
alpha = uint8(rgb >> 24)
}
return ic.RGBA{uint8(rgb >> 16), uint8((rgb >> 8) & 0xFF), uint8(rgb & 0xFF), alpha}, nil
}
// RGB or RGBA color format: rgb(255, 0, 0) or rgba(255, 0, 0, 0.5)
if strings.HasPrefix(color, "rgb(") && strings.HasSuffix(color, ")") {
return parseRGB(color)
} else if strings.HasPrefix(color, "rgba(") && strings.HasSuffix(color, ")") {
return parseRGBA(color)
}
// HSL or HSLA color format: hsl(0, 100%, 50%) or hsla(0, 100%, 50%, 0.5)
if strings.HasPrefix(color, "hsl(") && strings.HasSuffix(color, ")") {
return parseHSL(color)
} else if strings.HasPrefix(color, "hsla(") && strings.HasSuffix(color, ")") {
return parseHSLA(color)
}
return ic.RGBA{}, fmt.Errorf("Unable to parse color")
}
func parseRGB(rgb string) (ic.RGBA, error) {
rgbValues := strings.TrimSuffix(strings.TrimPrefix(rgb, "rgb("), ")")
rgbParts := strings.Split(rgbValues, ",")
if len(rgbParts) != 3 {
return ic.RGBA{}, fmt.Errorf("Not enough values to parse RGB")
}
r, err := strconv.Atoi(strings.TrimSpace(rgbParts[0]))
if err != nil {
return ic.RGBA{}, err
}
g, err := strconv.Atoi(strings.TrimSpace(rgbParts[1]))
if err != nil {
return ic.RGBA{}, err
}
b, err := strconv.Atoi(strings.TrimSpace(rgbParts[2]))
if err != nil {
return ic.RGBA{}, err
}
return ic.RGBA{uint8(r), uint8(g), uint8(b), 255}, nil
}
func parseRGBA(rgba string) (ic.RGBA, error) {
rgbaValues := strings.TrimSuffix(strings.TrimPrefix(rgba, "rgba("), ")")
rgbaParts := strings.Split(rgbaValues, ",")
if len(rgbaParts) != 4 {
return ic.RGBA{}, fmt.Errorf("Not enough values to parse RGBA")
}
r, err := strconv.Atoi(strings.TrimSpace(rgbaParts[0]))
if err != nil {
return ic.RGBA{}, err
}
g, err := strconv.Atoi(strings.TrimSpace(rgbaParts[1]))
if err != nil {
return ic.RGBA{}, err
}
b, err := strconv.Atoi(strings.TrimSpace(rgbaParts[2]))
if err != nil {
return ic.RGBA{}, err
}
alpha, err := strconv.ParseFloat(strings.TrimSpace(rgbaParts[3]), 64)
if err != nil {
return ic.RGBA{}, err
}
return ic.RGBA{uint8(r), uint8(g), uint8(b), uint8(alpha * 255)}, nil
}
func parseHSL(hsl string) (ic.RGBA, error) {
hslValues := strings.TrimSuffix(strings.TrimPrefix(hsl, "hsl("), ")")
hslParts := strings.Split(hslValues, ",")
if len(hslParts) != 3 {
return ic.RGBA{}, fmt.Errorf("Not enough values to parse HSL")
}
h, err := strconv.Atoi(strings.TrimSpace(hslParts[0]))
if err != nil {
return ic.RGBA{}, err
}
s, err := strconv.Atoi(strings.TrimSpace(strings.TrimSuffix(hslParts[1], "%")))
if err != nil {
return ic.RGBA{}, err
}
l, err := strconv.Atoi(strings.TrimSpace(strings.TrimSuffix(hslParts[2], "%")))
if err != nil {
return ic.RGBA{}, err
}
return hslToRGB(uint16(h), float64(s)/100, float64(l)/100)
}
func parseHSLA(hsla string) (ic.RGBA, error) {
hslaValues := strings.TrimSuffix(strings.TrimPrefix(hsla, "hsla("), ")")
hslaParts := strings.Split(hslaValues, ",")
if len(hslaParts) != 4 {
return ic.RGBA{}, fmt.Errorf("Not enough values to parse HSLA")
}
h, err := strconv.Atoi(strings.TrimSpace(hslaParts[0]))
if err != nil {
return ic.RGBA{}, err
}
s, err := strconv.Atoi(strings.TrimSpace(strings.TrimSuffix(hslaParts[1], "%")))
if err != nil {
return ic.RGBA{}, err
}
l, err := strconv.Atoi(strings.TrimSpace(strings.TrimSuffix(hslaParts[2], "%")))
if err != nil {
return ic.RGBA{}, err
}
alpha, err := strconv.ParseFloat(strings.TrimSpace(hslaParts[3]), 64)
if err != nil {
return ic.RGBA{}, err
}
return hslToRGB(uint16(h), float64(s)/100, float64(l)/100, alpha)
}
func hslToRGB(hue uint16, saturation, lightness float64, alpha ...float64) (ic.RGBA, error) {
var r, g, b float64
if saturation == 0 {
r = lightness
g = lightness
b = lightness
} else {
var q float64
if lightness < 0.5 {
q = lightness * (1 + saturation)
} else {
q = lightness + saturation - (lightness * saturation)
}
p := 2*lightness - q
h := float64(hue) / 360
// Convert hue to RGB
var tc [3]float64
tc[0] = h + 1/3
tc[1] = h
tc[2] = h - 1/3
for i := 0; i < 3; i++ {
if tc[i] < 0 {
tc[i] += 1
} else if tc[i] > 1 {
tc[i] -= 1
}
if tc[i] < 1/6 {
tc[i] = p + (q-p)*6*tc[i]
} else if tc[i] < 1/2 {
tc[i] = q
} else if tc[i] < 2/3 {
tc[i] = p + (q-p)*6*(2/3-tc[i])
} else {
tc[i] = p
}
}
r, g, b = tc[0], tc[1], tc[2]
}
// Scale to 0-255
r *= 255
g *= 255
b *= 255
var alphaValue uint8 = 255
if len(alpha) > 0 {
alphaValue = uint8(alpha[0] * 255)
}
return ic.RGBA{uint8(r), uint8(g), uint8(b), alphaValue}, nil
}
var namedColors = map[string]ic.RGBA{
"aliceblue": {240, 248, 255, 255},
"antiquewhite": {250, 235, 215, 255},
"aqua": {0, 255, 255, 255},
"aquamarine": {127, 255, 212, 255},
"azure": {240, 255, 255, 255},
"beige": {245, 245, 220, 255},
"bisque": {255, 228, 196, 255},
"black": {0, 0, 0, 255},
"blanchedalmond": {255, 235, 205, 255},
"blue": {0, 0, 255, 255},
"blueviolet": {138, 43, 226, 255},
"brown": {165, 42, 42, 255},
"burlywood": {222, 184, 135, 255},
"cadetblue": {95, 158, 160, 255},
"chartreuse": {127, 255, 0, 255},
"chocolate": {210, 105, 30, 255},
"coral": {255, 127, 80, 255},
"cornflowerblue": {100, 149, 237, 255},
"cornsilk": {255, 248, 220, 255},
"crimson": {220, 20, 60, 255},
"cyan": {0, 255, 255, 255},
"darkblue": {0, 0, 139, 255},
"darkcyan": {0, 139, 139, 255},
"darkgoldenrod": {184, 134, 11, 255},
"darkgray": {169, 169, 169, 255},
"darkgreen": {0, 100, 0, 255},
"darkkhaki": {189, 183, 107, 255},
"darkmagenta": {139, 0, 139, 255},
"darkolivegreen": {85, 107, 47, 255},
"darkorange": {255, 140, 0, 255},
"darkorchid": {153, 50, 204, 255},
"darkred": {139, 0, 0, 255},
"darksalmon": {233, 150, 122, 255},
"darkseagreen": {143, 188, 143, 255},
"darkslateblue": {72, 61, 139, 255},
"darkslategray": {47, 79, 79, 255},
"darkturquoise": {0, 206, 209, 255},
"darkviolet": {148, 0, 211, 255},
"deeppink": {255, 20, 147, 255},
"deepskyblue": {0, 191, 255, 255},
"dimgray": {105, 105, 105, 255},
"dodgerblue": {30, 144, 255, 255},
"firebrick": {178, 34, 34, 255},
"floralwhite": {255, 250, 240, 255},
"forestgreen": {34, 139, 34, 255},
"fuchsia": {255, 0, 255, 255},
"gainsboro": {220, 220, 220, 255},
"ghostwhite": {248, 248, 255, 255},
"gold": {255, 215, 0, 255},
"goldenrod": {218, 165, 32, 255},
"gray": {128, 128, 128, 255},
"green": {0, 128, 0, 255},
"greenyellow": {173, 255, 47, 255},
"honeydew": {240, 255, 240, 255},
"hotpink": {255, 105, 180, 255},
"indianred": {205, 92, 92, 255},
"indigo": {75, 0, 130, 255},
"ivory": {255, 255, 240, 255},
"khaki": {240, 230, 140, 255},
"lavender": {230, 230, 250, 255},
"lavenderblush": {255, 240, 245, 255},
"lawngreen": {124, 252, 0, 255},
"lemonchiffon": {255, 250, 205, 255},
"lightblue": {173, 216, 230, 255},
"lightcoral": {240, 128, 128, 255},
"lightcyan": {224, 255, 255, 255},
"lightgoldenrodyellow": {250, 250, 210, 255},
"lightgreen": {144, 238, 144, 255},
"lightgrey": {211, 211, 211, 255},
"lightpink": {255, 182, 193, 255},
"lightsalmon": {255, 160, 122, 255},
"lightseagreen": {32, 178, 170, 255},
"lightskyblue": {135, 206, 250, 255},
"lightslategray": {119, 136, 153, 255},
"lightsteelblue": {176, 196, 222, 255},
"lightyellow": {255, 255, 224, 255},
"lime": {0, 255, 0, 255},
"limegreen": {50, 205, 50, 255},
"linen": {250, 240, 230, 255},
"magenta": {255, 0, 255, 255},
"maroon": {128, 0, 0, 255},
"mediumaquamarine": {102, 205, 170, 255},
"mediumblue": {0, 0, 205, 255},
"mediumorchid": {186, 85, 211, 255},
"mediumpurple": {147, 112, 219, 255},
"mediumseagreen": {60, 179, 113, 255},
"mediumslateblue": {123, 104, 238, 255},
"mediumspringgreen": {0, 250, 154, 255},
"mediumturquoise": {72, 209, 204, 255},
"mediumvioletred": {199, 21, 133, 255},
"midnightblue": {25, 25, 112, 255},
"mintcream": {245, 255, 250, 255},
"mistyrose": {255, 228, 225, 255},
"moccasin": {255, 228, 181, 255},
"navajowhite": {255, 222, 173, 255},
"navy": {0, 0, 128, 255},
"oldlace": {253, 245, 230, 255},
"olive": {128, 128, 0, 255},
"olivedrab": {107, 142, 35, 255},
"orange": {255, 165, 0, 255},
"orangered": {255, 69, 0, 255},
"orchid": {218, 112, 214, 255},
"palegoldenrod": {238, 232, 170, 255},
"palegreen": {152, 251, 152, 255},
"paleturquoise": {175, 238, 238, 255},
"palevioletred": {219, 112, 147, 255},
"papayawhip": {255, 239, 213, 255},
"peachpuff": {255, 218, 185, 255},
"peru": {205, 133, 63, 255},
"pink": {255, 192, 203, 255},
"plum": {221, 160, 221, 255},
"powderblue": {176, 224, 230, 255},
"purple": {128, 0, 128, 255},
"red": {255, 0, 0, 255},
"rosybrown": {188, 143, 143, 255},
"royalblue": {65, 105, 225, 255},
"saddlebrown": {139, 69, 19, 255},
"salmon": {250, 128, 114, 255},
"sandybrown": {244, 164, 96, 255},
"seagreen": {46, 139, 87, 255},
"seashell": {255, 245, 238, 255},
"sienna": {160, 82, 45, 255},
"silver": {192, 192, 192, 255},
"skyblue": {135, 206, 235, 255},
"slateblue": {106, 90, 205, 255},
"slategray": {112, 128, 144, 255},
"snow": {255, 250, 250, 255},
"springgreen": {0, 255, 127, 255},
"steelblue": {70, 130, 180, 255},
"tan": {210, 180, 140, 255},
"teal": {0, 128, 128, 255},
"thistle": {216, 191, 216, 255},
"tomato": {255, 99, 71, 255},
"turquoise": {64, 224, 208, 255},
"violet": {238, 130, 238, 255},
"wheat": {245, 222, 179, 255},
"white": {255, 255, 255, 255},
"whitesmoke": {245, 245, 245, 255},
"yellow": {255, 255, 0, 255},
"yellowgreen": {154, 205, 50, 255},
}
func Color(color string) (ic.RGBA, error) {
if color == "" {
color = "rgba(0,0,0,1)"
}
// Parse the background color and return the result
return ParseRGBA(color)
}
