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colors.go
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colors.go
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package giocanvas
import (
"image/color"
"math"
"strconv"
"strings"
)
// colornames maps SVG color names to RGB triples.
var colornames = map[string]color.NRGBA{
"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},
"darkgrey": {169, 169, 169, 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},
"darkslategrey": {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},
"dimgrey": {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},
"grey": {128, 128, 128, 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},
"lightgray": {211, 211, 211, 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},
"lightslategrey": {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},
"slategrey": {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},
}
// cc converts a color string to number
func cc(s string) uint8 {
v, err := strconv.Atoi(s)
if err != nil {
return 0
}
return uint8(v)
}
// hc converts a hex color string to number
func hc(s string) uint8 {
v, err := strconv.ParseInt(s, 16, 32)
if err != nil {
return 0
}
return uint8(v)
}
// ColorLookup returns a color.RGBA corresponding to the named color or
// "rgb(r)", "rgb(r,b)", "rgb(r,g,b), "rgb(r,g,b,a)",
// "#rr", "#rrgg", "#rrggbb", "#rrggbbaa" string.
// "hsv(hue,sat,value)"
// On error, return black.
func ColorLookup(s string) color.NRGBA {
c, ok := colornames[s]
if ok {
return c
}
black := color.NRGBA{0, 0, 0, 255}
ls := len(s)
// rgb(...)
if strings.HasPrefix(s, "rgb(") && strings.HasSuffix(s, ")") && ls > 5 {
c.R, c.G, c.B, c.A = 0, 0, 0, 255
v := strings.Split(s[4:ls-1], ",")
switch len(v) {
case 1:
c.R = cc(v[0])
return c
case 2:
c.R = cc(v[0])
c.G = cc(v[1])
return c
case 3:
c.R = cc(v[0])
c.G = cc(v[1])
c.B = cc(v[2])
return c
case 4:
c.R = cc(v[0])
c.G = cc(v[1])
c.B = cc(v[2])
c.A = cc(v[3])
return c
default:
return black
}
}
// hsv(h,s,v) or hsv(h,s,v,a); h=0-360, s, v=0-100, a=0-100
if strings.HasPrefix(s, "hsv(") && strings.HasSuffix(s, ")") && ls > 5 {
v := strings.Split(s[4:ls-1], ",")
switch len(v) {
case 3:
hue, _ := strconv.ParseFloat(v[0], 64)
sat, _ := strconv.ParseFloat(v[1], 64)
value, _ := strconv.ParseFloat(v[2], 64)
c.R, c.G, c.B = hsv2rgb(hue, sat, value)
c.A = 255
return c
case 4:
hue, _ := strconv.ParseFloat(v[0], 64)
sat, _ := strconv.ParseFloat(v[1], 64)
value, _ := strconv.ParseFloat(v[2], 64)
a := cc(v[3])
if a > 100 {
a = 100
}
c.R, c.G, c.B = hsv2rgb(hue, sat, value)
c.A = uint8((float64(a) / 100.0) * 255.0)
return c
default:
return black
}
}
// #rrggbb
if strings.HasPrefix(s, "#") && (ls >= 3) {
c.R, c.G, c.B, c.A = 0, 0, 0, 255
switch ls {
case 3:
c.R = hc(s[1:3])
case 5:
c.R = hc(s[1:3])
c.G = hc(s[3:5])
case 7:
c.R = hc(s[1:3])
c.G = hc(s[3:5])
c.B = hc(s[5:7])
case 9:
c.R = hc(s[1:3])
c.G = hc(s[3:5])
c.B = hc(s[5:7])
c.A = hc(s[7:9])
default:
return black
}
return c
}
return black
}
// hsv2rgb converts hsv(h (0-360), s (0-100), v (0-100)) to rgb
// reference: https://en.wikipedia.org/wiki/HSL_and_HSV#HSV_to_RGB
func hsv2rgb(h, s, v float64) (uint8, uint8, uint8) {
s /= 100
v /= 100
if s > 1 || v > 1 {
return 0, 0, 0
}
h = math.Mod(h, 360)
c := v * s
section := h / 60
x := c * (1 - math.Abs(math.Mod(section, 2)-1))
var r, g, b float64
switch {
case section >= 0 && section <= 1:
r = c
g = x
b = 0
case section > 1 && section <= 2:
r = x
g = c
b = 0
case section > 2 && section <= 3:
r = 0
g = c
b = x
case section > 3 && section <= 4:
r = 0
g = x
b = c
case section > 4 && section <= 5:
r = x
g = 0
b = c
case section > 5 && section <= 6:
r = c
g = 0
b = x
default:
return 0, 0, 0
}
m := v - c
r += m
g += m
b += m
return uint8(r * 255), uint8(g * 255), uint8(b * 255)
}