mix colors for hybrid recoding strategies

• define scripts/color.nu to manipulate RGB colors, especially mix two colors together
• compute the color of hybrid recoding strategies as a weighted sum of the two simple recoding strategies involved, e.g. if the strategy is "10% of the time recode 2 shards and 90% of the time recode 3", then the color of that curve will be 10% the color of the simple strategy recoding 2 shards and 90% the color of the other simple strategy recoding 3 shards
• make the hybrid curves transparent and dashed

example

scripts/color.nu

+export const WHITE = { r: 1.0, g: 1.0, b: 1.0 }
+export const BLACK = { r: 0.0, g: 0.0, b: 0.0 }
+export const RED = { r: 1.0, g: 0.0, b: 0.0 }
+export const GREEN = { r: 0.0, g: 1.0, b: 0.0 }
+export const BLUE = { r: 0.0, g: 0.0, b: 1.0 }
+
+def "error throw" [err: record<err: string, label: string, span: record<start: int, end: int>>] {
+    error make {
+        msg: $"(ansi red_bold)($err.err)(ansi reset)",
+        label: {
+            text: $err.label,
+            span: $err.span,
+        },
+    }
+}
+
+export def "color from-floats" [
+    r: float,
+    g: float,
+    b: float
+]: nothing -> record<r: float, g: float, b: float> {
+    if $r < 0.0 or $r > 1.0 {
+        error throw {
+            err: "invalid RGB channel",
+            label: $"should be between 0 and 1, found ($r)",
+            span: (metadata $r).span,
+        }
+    }
+    if $g < 0.0 or $g > 1.0 {
+        error throw {
+            err: "invalid RGB channel",
+            label: $"should be between 0 and 1, found ($g)",
+            span: (metadata $g).span,
+        }
+    }
+    if $b < 0.0 or $b > 1.0 {
+        error throw {
+            err: "invalid RGB channel",
+            label: $"should be between 0 and 1, found ($b)",
+            span: (metadata $b).span,
+        }
+    }
+
+    { r: $r, g: $g, b: $b }
+}
+
+export def "color from-ints" [
+    r: int,
+    g: int,
+    b: int
+]: nothing -> record<r: float, g: float, b: float> {
+    if $r < 0 or $r > 255 {
+        error throw {
+            err: "invalid RGB channel",
+            label: $"should be between 0 and 255, found ($r)",
+            span: (metadata $r).span,
+        }
+    }
+    if $g < 0 or $g > 255 {
+        error throw {
+            err: "invalid RGB channel",
+            label: $"should be between 0 and 255, found ($g)",
+            span: (metadata $g).span,
+        }
+    }
+    if $b < 0 or $b > 255 {
+        error throw {
+            err: "invalid RGB channel",
+            label: $"should be between 0 and 255, found ($b)",
+            span: (metadata $b).span,
+        }
+    }
+
+    { r: ($r / 255 | into float), g: ($g / 255 | into float), b: ($b / 255 | into float) }
+}
+
+def try-string-to-int []: string -> int {
+    try {
+        $"0x($in)" | into int
+    } catch {
+        get debug | parse --regex 'CantConvert { to_type: "(?<to>.*)", from_type: "(?<from>.*)", span: Span { (?<span>.*) }, help: Some\("(?<help>.*)"\) }' | into record | error make --unspanned { msg: ($in.help | str replace --all '\"' '"') }
+    }
+}
+
+export def "color from-string" [s: string]: nothing -> record<r: float, g: float, b: float> {
+    let res = $s
+        | parse --regex '^0x(?<r>..)(?<g>..)(?<b>..)$'
+        | into record
+
+    if $res == {} {
+        error throw {
+            err: "invalid HEX color format",
+            label: $"format should be '0xRRGGBB', found ($s)",
+            span: (metadata $s).span,
+        }
+    }
+
+    {
+        r: ($res.r | try-string-to-int | $in / 255),
+        g: ($res.g | try-string-to-int | $in / 255),
+        b: ($res.b | try-string-to-int | $in / 255),
+    }
+}
+
+export def "color mix" [
+    c1: record<r: float, g: float, b: float>,
+    c2: record<r: float, g: float, b: float>,
+    c: float,
+]: nothing -> record<r: float, g: float, b: float> {
+    {
+        r: ($c * $c1.r + (1 - $c) * $c2.r),
+        g: ($c * $c1.g + (1 - $c) * $c2.g),
+        b: ($c * $c1.b + (1 - $c) * $c2.b),
+    }
+}
+
+def float-to-u8-hex []: float -> string {
+    $in * 255
+        | math round --precision 0
+        | into int
+        | fmt
+        | get lowerhex
+        | parse "0x{n}"
+        | into record
+        | get n
+        | into string
+        | fill --alignment "right" --character '0' --width 2
+}
+
+export def "color to-hex" []: record<r: float, g: float, b: float> -> string {
+    $"#($in.r | float-to-u8-hex)($in.g | float-to-u8-hex)($in.b | float-to-u8-hex)"
+}
+