60 lines
1.5 KiB
Go
60 lines
1.5 KiB
Go
package color
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import "fmt"
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import "image/color"
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// FormatNRGBA formats an NRGBA value into a hex string.
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func FormatNRGBA (nrgba color.NRGBA) string {
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return fmt.Sprintf("%02X%02X%02X%02X", nrgba.R, nrgba.G, nrgba.B, nrgba.A)
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}
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// ParseNRGBA parses an NRGBA value from a hex string. It can be of the format:
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// - RGB
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// - RGBA
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// - RRGGBB
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// - RRGGBBAA
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// If none of these are specified, this function will return an opaque black
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// color. Hex digits may either be upper case or lower case.
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func ParseNRGBA (str string) color.NRGBA {
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runes := []rune(str)
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c := color.NRGBA { A: 255 }
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switch len(runes) {
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case 3:
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c.R = fillOctet(hexDigit(runes[0]))
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c.G = fillOctet(hexDigit(runes[1]))
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c.B = fillOctet(hexDigit(runes[2]))
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case 4:
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c.R = fillOctet(hexDigit(runes[0]))
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c.G = fillOctet(hexDigit(runes[1]))
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c.B = fillOctet(hexDigit(runes[2]))
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c.A = fillOctet(hexDigit(runes[3]))
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case 6:
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c.R = hexOctet(runes[0], runes[1])
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c.G = hexOctet(runes[2], runes[3])
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c.B = hexOctet(runes[4], runes[5])
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case 8:
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c.R = hexOctet(runes[0], runes[1])
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c.G = hexOctet(runes[2], runes[3])
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c.B = hexOctet(runes[4], runes[5])
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c.A = hexOctet(runes[6], runes[7])
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}
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return c
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}
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func hexDigit (r rune) uint8 {
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switch {
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case r >= '0' && r <= '9': return uint8(r - '0')
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case r >= 'A' && r <= 'F': return uint8(r - 'A') + 10
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case r >= 'a' && r <= 'f': return uint8(r - 'a') + 10
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default: return 0
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}
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}
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func fillOctet (low uint8) uint8 {
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return low << 4 | low
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}
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func hexOctet (high, low rune) uint8 {
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return hexDigit(high) << 4 | hexDigit(low)
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}
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