go-color/parse.go at master · dominikh/go-color

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package color

import (

"regexp"

"strconv"

)

var reColor = regexp.MustCompile(`^color\(` +

`([a-zA-Z0-9-]+) ` +

`((?:[+-]?\d+|[+-]?\d*\.\d+(?:[eE][+-]?\d+)?)%?) ` +

`((?:[+-]?\d+|[+-]?\d*\.\d+(?:[eE][+-]?\d+)?)%?)` +

`(?: / ((?:[+-]?\d+|[+-]?\d*\.\d+(?:[eE][+-]?\d+)?)%?))?\);?$`)

// Parse parses colors in the CSS 'color()' format. The double dash for

// non-standard color spaces is optional.

func Parse(s string) (Color, bool) {

m := reColor.FindStringSubmatch(s)

if m == nil {

return Color{}, false

}

space := m[1]

x := m[2]

y := m[3]

z := m[4]

a := m[5]

if space == "xyz" {

space = "xyz-d65"

}

cs, ok := LookupSpace(space)

if !ok {

return Make(SRGB, 0, 0, 0, 1), false

}

var values [4]float64

parseValue := func(idx int, s string) bool {

if idx == 3 && len(s) == 0 {

values[3] = 1

return true

}

if s[len(s)-1] == '%' {

f, err := strconv.ParseFloat(s[:len(s)-1], 64)

if err != nil {

// Even inputs that pass the regex can get here, e.g. because of

// absurdly large values.

return false

}

if f < 0 {

f = 0

}

if f > 100 {

f = 100

}

f /= 100

if idx == 3 {

values[3] = f

} else {

rng := cs.Coords[idx].RefRange

values[idx] = lerp(rng[0], rng[1], f)

}

} else {

f, err := strconv.ParseFloat(s, 64)

if err != nil {

// Even inputs that pass the regex can get here, e.g. because of

// absurdly large values.

return false

}

if idx == 3 {

if f < 0 {

f = 0

}

if f > 1 {

f = 1

}

values[idx] = f

}

return true

}

parseValue(0, x)

parseValue(1, y)

parseValue(2, z)

parseValue(3, a)

return Make(cs, values[0], values[1], values[2], values[3]), true

}

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