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271 lines
6.9 KiB
Go
271 lines
6.9 KiB
Go
package twin
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import (
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"fmt"
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"math"
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"github.com/alecthomas/chroma/v2"
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)
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// Create using NewColor16(), NewColor256 or NewColor24Bit(), or use
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// ColorDefault.
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type Color uint32
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type ColorCount uint8
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const (
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// Default foreground / background color
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ColorCountDefault ColorCount = iota
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// https://en.wikipedia.org/wiki/ANSI_escape_code#3-bit_and_4-bit
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//
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// Note that this type is only used for output, on input we store 3 bit
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// colors as 4 bit colors since they map to the same values.
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ColorCount8
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// https://en.wikipedia.org/wiki/ANSI_escape_code#3-bit_and_4-bit
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ColorCount16
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// https://en.wikipedia.org/wiki/ANSI_escape_code#8-bit
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ColorCount256
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// RGB: https://en.wikipedia.org/wiki/ANSI_escape_code#24-bit
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ColorCount24bit
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)
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type colorType uint8
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const (
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colorTypeForeground colorType = iota
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colorTypeBackground
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colorTypeUnderline
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)
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// Reset to default foreground / background color
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var ColorDefault = newColor(ColorCountDefault, 0)
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// From: https://en.wikipedia.org/wiki/ANSI_escape_code#3-bit_and_4-bit
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var colorNames16 = map[int]string{
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0: "0 black",
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1: "1 red",
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2: "2 green",
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3: "3 yellow (orange)",
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4: "4 blue",
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5: "5 magenta",
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6: "6 cyan",
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7: "7 white (light gray)",
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8: "8 bright black (dark gray)",
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9: "9 bright red",
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10: "10 bright green",
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11: "11 bright yellow",
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12: "12 bright blue",
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13: "13 bright magenta",
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14: "14 bright cyan",
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15: "15 bright white",
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}
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func newColor(colorCount ColorCount, value uint32) Color {
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return Color(value | (uint32(colorCount) << 24))
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}
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// Four bit colors as defined here:
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// https://en.wikipedia.org/wiki/ANSI_escape_code#3-bit_and_4-bit
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func NewColor16(colorNumber0to15 int) Color {
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return newColor(ColorCount16, uint32(colorNumber0to15))
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}
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func NewColor256(colorNumber uint8) Color {
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return newColor(ColorCount256, uint32(colorNumber))
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}
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func NewColor24Bit(red uint8, green uint8, blue uint8) Color {
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return newColor(ColorCount24bit, (uint32(red)<<16)+(uint32(green)<<8)+(uint32(blue)<<0))
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}
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func NewColorHex(rgb uint32) Color {
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return newColor(ColorCount24bit, rgb)
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}
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func (color Color) ColorCount() ColorCount {
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return ColorCount(color >> 24)
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}
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func (color Color) colorValue() uint32 {
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return uint32(color & 0xff_ff_ff)
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}
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// Render color into an ANSI string.
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//
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// Ref: https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_(Select_Graphic_Rendition)_parameters
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func (color Color) ansiString(cType colorType, terminalColorCount ColorCount) string {
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var typeMarker string
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if cType == colorTypeForeground {
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typeMarker = "3"
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} else if cType == colorTypeBackground {
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typeMarker = "4"
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} else if cType == colorTypeUnderline {
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typeMarker = "5"
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} else {
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panic(fmt.Errorf("unhandled color type %d", cType))
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}
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if color.ColorCount() == ColorCountDefault {
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return fmt.Sprint("\x1b[", typeMarker, "9m")
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}
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color = color.downsampleTo(terminalColorCount)
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// We never create any ColorCount8 colors, but we store them as
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// ColorCount16. So this if() statement will cover both.
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if color.ColorCount() == ColorCount16 {
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if cType == colorTypeUnderline {
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// Only 256 and 24 bit colors supported for underline color
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return ""
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}
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value := color.colorValue()
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if value < 8 {
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return fmt.Sprint("\x1b[", typeMarker, value, "m")
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} else if value <= 15 {
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typeMarker := "9"
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if cType == colorTypeBackground {
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typeMarker = "10"
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}
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return fmt.Sprint("\x1b[", typeMarker, value-8, "m")
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}
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panic(fmt.Errorf("unhandled color16 value %d", value))
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}
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if color.ColorCount() == ColorCount256 {
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value := color.colorValue()
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if value <= 255 {
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return fmt.Sprint("\x1b[", typeMarker, "8;5;", value, "m")
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}
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}
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if color.ColorCount() == ColorCount24bit {
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value := color.colorValue()
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red := (value & 0xff0000) >> 16
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green := (value & 0xff00) >> 8
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blue := value & 0xff
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return fmt.Sprint("\x1b[", typeMarker, "8;2;", red, ";", green, ";", blue, "m")
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}
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panic(fmt.Errorf("unhandled color type=%d %s", color.ColorCount(), color.String()))
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}
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func (color Color) String() string {
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switch color.ColorCount() {
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case ColorCountDefault:
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return "Default color"
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case ColorCount16:
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return colorNames16[int(color.colorValue())]
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case ColorCount256:
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if color.colorValue() < 16 {
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return colorNames16[int(color.colorValue())]
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}
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return fmt.Sprintf("#%02x", color.colorValue())
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case ColorCount24bit:
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return fmt.Sprintf("#%06x", color.colorValue())
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}
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panic(fmt.Errorf("unhandled color type %d", color.ColorCount()))
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}
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func (color Color) to24Bit() Color {
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if color.ColorCount() == ColorCount24bit {
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return color
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}
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if color.ColorCount() == ColorCount8 || color.ColorCount() == ColorCount16 || color.ColorCount() == ColorCount256 {
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r0, g0, b0 := color256ToRGB(uint8(color.colorValue()))
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return NewColor24Bit(r0, g0, b0)
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}
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panic(fmt.Errorf("unhandled color type %d", color.ColorCount()))
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}
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func (color Color) downsampleTo(terminalColorCount ColorCount) Color {
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if color.ColorCount() == ColorCountDefault || terminalColorCount == ColorCountDefault {
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panic(fmt.Errorf("downsampling to or from default color not supported, %s -> %#v", color.String(), terminalColorCount))
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}
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if color.ColorCount() <= terminalColorCount {
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// Already low enough
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return color
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}
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target := color.to24Bit()
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// Find the closest match in the terminal color palette
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var scanFirst int
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var scanLast int
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switch terminalColorCount {
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case ColorCount8:
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scanFirst = 0
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scanLast = 7
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case ColorCount16:
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scanFirst = 0
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scanLast = 15
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case ColorCount256:
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// Colors 0-15 can be customized by the user, so we skip them and use
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// only the well defined ones
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scanFirst = 16
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scanLast = 255
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default:
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panic(fmt.Errorf("unhandled terminal color count %#v", terminalColorCount))
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}
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// Iterate over the scan range and find the best matching index
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bestMatch := 0
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bestDistance := math.MaxFloat64
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for i := scanFirst; i <= scanLast; i++ {
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r, g, b := color256ToRGB(uint8(i))
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candidate := NewColor24Bit(r, g, b)
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distance := target.Distance(candidate)
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if distance < bestDistance {
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bestDistance = distance
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bestMatch = i
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}
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}
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if bestMatch <= 15 {
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return NewColor16(bestMatch)
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}
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return NewColor256(uint8(bestMatch))
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}
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// Wrapper for Chroma's color distance function.
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//
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// That one says it uses this formula: https://www.compuphase.com/cmetric.htm
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//
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// The result from this function has been scaled to 0.0-1.0, where 1.0 is the
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// distance between black and white.
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func (color Color) Distance(other Color) float64 {
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if color.ColorCount() != ColorCount24bit {
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panic(fmt.Errorf("contrast only supported for 24 bit colors, got %s vs %s", color.String(), other.String()))
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}
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baseColor := chroma.NewColour(
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uint8(color.colorValue()>>16&0xff),
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uint8(color.colorValue()>>8&0xff),
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uint8(color.colorValue()&0xff),
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)
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otherColor := chroma.NewColour(
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uint8(other.colorValue()>>16&0xff),
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uint8(other.colorValue()>>8&0xff),
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uint8(other.colorValue()&0xff),
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)
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// Magic constant comes from testing
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maxDistance := 764.8333151739665
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return baseColor.Distance(otherColor) / maxDistance
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}
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