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paletteguard

MoonBit palette accessibility guard for WCAG contrast reports and design-token checks.

accessibility
color
contrast
palette
wcag
moon add Jay7724/paletteguard@0.1.0
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0.1.0
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README

#PaletteGuard

CI

PaletteGuard is a MoonBit library for auditing design-system color palettes against WCAG contrast thresholds. It parses common color tokens, models palette roles, checks foreground/background pairs, suggests repair candidates, audits token documents, and exports reproducible Markdown reports that can be used in CI, documentation, or release reviews.

The package targets projects that keep color tokens in code, static assets, or documentation and need a small MoonBit-native guard before shipping UI themes. It is not a general image-processing library and does not depend on browser, Canvas, JavaScript, or external color packages.

#Why

Color regressions are easy to miss when teams change brand colors, terminal themes, dashboards, charts, or documentation styles. PaletteGuard gives MoonBit projects a reusable contrast engine rather than a one-off script: the same core functions can power tests, command examples, token importers, design-token release gates, and future file-format adapters.

#Installation

The module name in this repository is:

Jay7724/paletteguard

After publishing under your Mooncakes owner, install it with:

moon add Jay7724/paletteguard

Use the package from another MoonBit package:

import {
  "Jay7724/paletteguard" @paletteguard,
}

#Minimal Example

let palette = [
  @paletteguard.swatch("text", @paletteguard.rgb(18, 24, 38).unwrap(), @paletteguard.RoleText),
  @paletteguard.swatch("paper", @paletteguard.rgb(255, 255, 255).unwrap(), @paletteguard.RoleBackground),
]

let report = @paletteguard.audit_palette(palette, @paletteguard.policy_aa())
println(report.to_markdown())
println(@paletteguard.contrast_matrix(palette, @paletteguard.policy_aa()))

Run the included example:

moon run cmd/main

#Local Commands

moon check
moon build
moon test
moon run cmd/main
moon publish --dry-run

For a real release:

moon login
moon publish --dry-run
moon publish

If you change code after a release, increment version in moon.mod before publishing again.

#Core API

  • Color: RGB color with 8-bit channels.
  • Role: palette role: text, accent, background, surface, or border.
  • Policy: AA/AAA and normal/large-text threshold selection.
  • parse_color: parses #RGB, #RRGGBB, rgb(r, g, b), and a small named color set.
  • parse_swatch: converts a named token into a role-aware swatch.
  • contrast_ratio: computes WCAG relative-luminance contrast.
  • audit_pair: checks one foreground/background pair.
  • audit_palette: checks all text/accent swatches against background/surface swatches.
  • PaletteReport::to_markdown: exports a stable Markdown report.
  • Color::to_hsl, Hsl::to_color, Color::mix, Color::lighten, Color::darken, Color::rotate_hue: MoonBit-native color transforms.
  • repair_foreground and repair_background: search bounded deterministic paths and return the nearest passing candidate found for a selected policy; if the policy is unreachable on those paths, return the strongest available candidate.
  • parse_token_document and audit_token_document: parse simple token assignments such as text.body = #111827 or surface.panel: white.
  • palette_stats, audit_ramp, and contrast_matrix: summarize palettes, validate luminance ramps, and export foreground/background matrices.
  • built_in_catalog, catalog_by_family, catalog_find, catalog_audit_family: 26 original semantic color families with 338 swatches for examples, tests, and starter palettes.

#Supported Scope

  • Hex colors: #RGB and #RRGGBB.
  • Decimal RGB functions: rgb(12, 34, 56).
  • Named colors: black, white, red, green, blue.
  • WCAG AA and AAA thresholds for normal and large text.
  • HSL conversion, hue rotation, grayscale, channel distance, perceived brightness, and temperature classification.
  • Foreground/background repair search using deterministic black/white and lightness paths.
  • Simple design-token document parsing with per-line diagnostics.
  • Built-in original palette catalog: 26 families, 338 semantic swatches.
  • Markdown report export.
  • Pure MoonBit implementation with no runtime dependencies.

#Not Supported

  • Alpha blending, gradients, ICC profiles, images, or screenshots.
  • CSS Color Level 4 syntax such as lab(), oklch(), or percentage RGB.
  • Reading files from disk directly. The library parses strings; CLI/file adapters are planned as separate boundary packages or future minor versions.

#CI

GitHub Actions is configured in .github/workflows/ci.yml and runs:

  • MoonBit toolchain installation
  • moon version --all
  • moon fmt --check
  • moon check --target all --deny-warn
  • moon build
  • moon test --deny-warn
  • moon package
  • moon run cmd/main

The workflow is intentionally warning-strict so that a passing check is useful evidence for a release review. It only requests read access to repository contents and does not publish packages automatically.

Project records are kept in docs/: see API.md, DESIGN.md, TEST_RECORD.md, RELEASE.md, AI_ASSISTANCE.md, and ACCEPTANCE_CHECKLIST.md.

#Mooncakes

  • Package name: Jay7724/paletteguard
  • Documentation URL after release: https://mooncakes.io/docs/Jay7724/paletteguard
  • Manifest URL after release: https://mooncakes.io/api/v0/manifest/Jay7724/paletteguard

The current repository metadata uses owner Jay7724. If the Mooncakes account shows a different owner during release, update the owner segment in moon.mod, this README, and docs/RELEASE.md before publishing.

#License And Third-Party Notes

PaletteGuard is licensed under MIT. The implementation is original MoonBit code. It uses the public WCAG contrast formula as a standard, but it does not copy third-party source code, images, fonts, audio, or datasets. The built-in catalog is original synthetic palette data maintained inside this repository.

#
CatalogFamilySummary

source
pub(all) struct CatalogFamilySummary {
  family : String
  total : Int
  foregrounds : Int
  backgrounds : Int
  average_luminance : Double
  minimum_recommended_contrast : Double
} derive(Eq, 
Debug)

#
CatalogSwatch

source
pub(all) struct CatalogSwatch {
  id : String
  family : String
  step : Int
  color : Color
  role : Role
  tone : CatalogTone
  recommended_foreground : Color
  target_background : Color
  note : String
} derive(Eq, 
Debug)

#
CatalogSwatch::as_swatch

source
fn CatalogSwatch::as_swatch(self : CatalogSwatch) -> Swatch

#
CatalogSwatch::recommended_audit

source
fn CatalogSwatch::recommended_audit(self : CatalogSwatch, policy : Policy) -> PairAudit

#
CatalogTone

source
pub(all) enum CatalogTone {
  ToneCanvas
  ToneSurface
  ToneDivider
  ToneAccent
  ToneBodyText
  ToneStrongText
} derive(Eq, 
Debug)

#
CatalogTone::label

source
fn CatalogTone::label(self : CatalogTone) -> String

#
ChannelStats

source
pub(all) struct ChannelStats {
  min : Int
  max : Int
  average : Double
} derive(Eq, 
Debug)

#
Color

source
pub(all) struct Color {
  r : Int
  g : Int
  b : Int
} derive(Eq, 
Debug)

RGB color with 8-bit channels.

#
Color::blue

source
fn Color::blue(self : Color) -> Int

#
Color::channel_spread

source
fn Color::channel_spread(self : Color) -> Int

#
Color::darken

source
fn Color::darken(self : Color, amount : Double) -> Color

#
Color::desaturate

source
fn Color::desaturate(self : Color, amount : Double) -> Color

#
Color::distance_rgb

source
fn Color::distance_rgb(self : Color, other : Color) -> Double

#
Color::grayscale

source
fn Color::grayscale(self : Color) -> Color

#
Color::green

source
fn Color::green(self : Color) -> Int

#
Color::harmonies

source
fn Color::harmonies(self : Color, kind : HarmonyKind) -> Array[Color]

#
Color::ideal_text_color

source
fn Color::ideal_text_color(self : Color) -> Color

#
Color::invert

source
fn Color::invert(self : Color) -> Color

#
Color::is_dark

source
fn Color::is_dark(self : Color) -> Bool

#
Color::is_light

source
fn Color::is_light(self : Color) -> Bool

#
Color::lighten

source
fn Color::lighten(self : Color, amount : Double) -> Color

#
Color::mix

source
fn Color::mix(self : Color, other : Color, amount : Double) -> Color

#
Color::perceived_brightness

source
fn Color::perceived_brightness(self : Color) -> Double

#
Color::profile

source
fn Color::profile(self : Color) -> ColorProfile

#
Color::red

source
fn Color::red(self : Color) -> Int

#
Color::relative_luminance

source
fn Color::relative_luminance(self : Color) -> Double

#
Color::rotate_hue

source
fn Color::rotate_hue(self : Color, degrees : Double) -> Color

#
Color::saturate

source
fn Color::saturate(self : Color, amount : Double) -> Color

#
Color::set_lightness

source
fn Color::set_lightness(self : Color, lightness : Double) -> Color

#
Color::set_saturation

source
fn Color::set_saturation(self : Color, saturation : Double) -> Color

#
Color::temperature

source
fn Color::temperature(self : Color) -> Temperature

#
Color::to_hex

source
fn Color::to_hex(self : Color) -> String

#
Color::to_hsl

source
fn Color::to_hsl(self : Color) -> Hsl

#
Color::weighted_distance

source
fn Color::weighted_distance(self : Color, other : Color) -> Double

#
ColorParse

source
pub(all) enum ColorParse {
  ColorParsed(Color)
  ColorParseFailed(ParseError)
} derive(Eq, 
Debug)

#
ColorProfile

source
pub(all) struct ColorProfile {
  color : Color
  hex : String
  luminance : Double
  brightness : Double
  saturation : Double
  hue : Double
  temperature : Temperature
  ideal_text : Color
} derive(Eq, 
Debug)

#
DocumentAudit

source
pub(all) struct DocumentAudit {
  tokens : TokenParseReport
  palette : PaletteReport
  stats : PaletteStats
} derive(Eq, 
Debug)

#
DocumentAudit::to_markdown

source
fn DocumentAudit::to_markdown(self : DocumentAudit) -> String

#
Grade

source
pub(all) enum Grade {
  GradeFail
  GradeLarge
  GradeAA
  GradeAAA
} derive(Eq, 
Debug)

#
Grade::label

source
fn Grade::label(self : Grade) -> String

#
HarmonyKind

source
pub(all) enum HarmonyKind {
  HarmonyComplementary
  HarmonyAnalogous
  HarmonyTriadic
  HarmonySplitComplementary
  HarmonyMonochrome
  HarmonyCustom
} derive(Eq, 
Debug)

#
HarmonyKind::label

source
fn HarmonyKind::label(self : HarmonyKind) -> String

#
Hsl

source
pub(all) struct Hsl {
  h : Double
  s : Double
  l : Double
} derive(Eq, 
Debug)

#
Hsl::rotate

source
fn Hsl::rotate(self : Hsl, degrees : Double) -> Hsl

#
Hsl::to_color

source
fn Hsl::to_color(self : Hsl) -> Color

#
Hsl::with_lightness

source
fn Hsl::with_lightness(self : Hsl, lightness : Double) -> Hsl

#
Hsl::with_saturation

source
fn Hsl::with_saturation(self : Hsl, saturation : Double) -> Hsl

#
PairAudit

source
pub(all) struct PairAudit {
  foreground : Swatch
  background : Swatch
  ratio : Double
  required : Double
  grade : Grade
  passed : Bool
  suggestion : Suggestion
} derive(Eq, 
Debug)

#
PaletteReport

source
pub(all) struct PaletteReport {
  pairs : Array[PairAudit]
  checked : Int
  failures : Int
} derive(Eq, 
Debug)

#
PaletteReport::passes

source
fn PaletteReport::passes(self : PaletteReport) -> Bool

#
PaletteReport::to_markdown

source
fn PaletteReport::to_markdown(self : PaletteReport) -> String

#
PaletteStats

source
pub(all) struct PaletteStats {
  swatches : Int
  foregrounds : Int
  backgrounds : Int
  borders : Int
  average_luminance : Double
  darkest : Swatch?
  lightest : Swatch?
} derive(Eq, 
Debug)

#
PaletteStats::to_markdown

source
fn PaletteStats::to_markdown(self : PaletteStats) -> String

#
ParseError

source
pub(all) enum ParseError {
  EmptyInput
  InvalidHexLength(Int)
  InvalidHexDigit(Char)
  InvalidRgbFunction(String)
  ComponentOutOfRange(String, Int)
  UnknownColorName(String)
} derive(Eq, 
Debug)

#
Policy

source
pub(all) struct Policy {
  requirement : Requirement
  text_kind : TextKind
} derive(Eq, 
Debug)

#
RampAudit

source
pub(all) struct RampAudit {
  family : String
  swatches : Array[Swatch]
  monotonic_luminance : Bool
  duplicate_hexes : Array[String]
  smallest_luminance_gap : Double
} derive(Eq, 
Debug)

#
RampAudit::to_markdown

source
fn RampAudit::to_markdown(self : RampAudit) -> String

#
RepairCandidate

source
pub(all) struct RepairCandidate {
  color : Color
  ratio : Double
  delta : Double
  strategy : RepairStrategy
  steps : Int
} derive(Eq, 
Debug)

#
RepairStrategy

source
pub(all) enum RepairStrategy {
  RepairKeep
  RepairUseIdealText
  RepairDarkenForeground
  RepairLightenForeground
  RepairDarkenBackground
  RepairLightenBackground
} derive(Eq, 
Debug)

#
RepairStrategy::label

source
fn RepairStrategy::label(self : RepairStrategy) -> String

#
Requirement

source
pub(all) enum Requirement {
  LevelAA
  LevelAAA
} derive(Eq, 
Debug)

WCAG conformance target.

#
Role

source
pub(all) enum Role {
  RoleText
  RoleAccent
  RoleBackground
  RoleSurface
  RoleBorder
} derive(Eq, 
Debug)

A color role inside a design palette or token set.

#
Role::is_background

source
fn Role::is_background(self : Role) -> Bool

#
Role::is_foreground

source
fn Role::is_foreground(self : Role) -> Bool

#
Role::label

source
fn Role::label(self : Role) -> String

#
Severity

source
pub(all) enum Severity {
  SeverityInfo
  SeverityWarning
  SeverityError
} derive(Eq, 
Debug)

#
Severity::label

source
fn Severity::label(self : Severity) -> String

#
Suggestion

source
pub(all) enum Suggestion {
  SuggestKeep
  SuggestUseBlack
  SuggestUseWhite
  SuggestIncreaseSeparation
} derive(Eq, 
Debug)

#
Suggestion::label

source
fn Suggestion::label(self : Suggestion) -> String

#
Swatch

source
pub(all) struct Swatch {
  name : String
  color : Color
  role : Role
} derive(Eq, 
Debug)

#
SwatchParse

source
pub(all) enum SwatchParse {
  SwatchParsed(Swatch)
  SwatchParseFailed(String, ParseError)
} derive(Eq, 
Debug)

#
Temperature

source
pub(all) enum Temperature {
  TemperatureCool
  TemperatureNeutral
  TemperatureWarm
} derive(Eq, 
Debug)

#
Temperature::label

source
fn Temperature::label(self : Temperature) -> String

#
TextKind

source
pub(all) enum TextKind {
  NormalText
  LargeText
} derive(Eq, 
Debug)

Text size class used by WCAG contrast thresholds.

#
TokenDiagnostic

source
pub(all) struct TokenDiagnostic {
  line : Int
  column : Int
  token : String
  severity : Severity
  kind : TokenDiagnosticKind
  message : String
} derive(Eq, 
Debug)

#
TokenDiagnosticKind

source
pub(all) enum TokenDiagnosticKind {
  DiagnosticEmptyName
  DiagnosticMissingAssignment
  DiagnosticUnknownRole
  DiagnosticBadColor(ParseError)
} derive(Eq, 
Debug)

#
TokenParseReport

source
pub(all) struct TokenParseReport {
  swatches : Array[Swatch]
  diagnostics : Array[TokenDiagnostic]
  ignored : Int
} derive(Eq, 
Debug)

#
TokenParseReport::has_errors

source
fn TokenParseReport::has_errors(self : TokenParseReport) -> Bool

#
TokenParseReport::to_markdown

source
fn TokenParseReport::to_markdown(self : TokenParseReport) -> String

#
audit_pair

source
fn audit_pair(foreground : Swatch, background : Swatch, policy : Policy) -> PairAudit

#
audit_palette

source
fn audit_palette(swatches : Array[Swatch], policy : Policy) -> PaletteReport

#
audit_ramp

source
fn audit_ramp(family : String, swatches : Array[Swatch]) -> RampAudit

#
audit_token_document

source
fn audit_token_document(input : String, policy : Policy) -> DocumentAudit

#
built_in_catalog

source
fn built_in_catalog() -> Array[CatalogSwatch]

#
catalog_as_swatches

source
fn catalog_as_swatches(items : Array[CatalogSwatch]) -> Array[Swatch]

#
catalog_audit_family

source
fn catalog_audit_family(family : String, policy : Policy) -> PaletteReport

#
catalog_by_family

source
fn catalog_by_family(family : String) -> Array[CatalogSwatch]

#
catalog_by_role

source
fn catalog_by_role(role : Role) -> Array[CatalogSwatch]

#
catalog_families

source
fn catalog_families() -> Array[String]

#
catalog_find

source
fn catalog_find(id : String) -> CatalogSwatch?

#
catalog_markdown

source
fn catalog_markdown() -> String

#
catalog_palette_for_family

source
fn catalog_palette_for_family(family : String) -> Array[Swatch]

#
catalog_summary

source
fn catalog_summary(family : String) -> CatalogFamilySummary

#
channel_stats

source
fn channel_stats(swatches : Array[Swatch]) -> (ChannelStats, ChannelStats, ChannelStats)

#
contrast_matrix

source
fn contrast_matrix(swatches : Array[Swatch], policy : Policy) -> String

#
contrast_ratio

source
fn contrast_ratio(a : Color, b : Color) -> Double

#
demo_palette

source
fn demo_palette() -> Array[Swatch]

#
demo_report

source
fn demo_report() -> String

#
grade_ratio

source
fn grade_ratio(ratio : Double) -> Grade

#
minimum_ratio

source
fn minimum_ratio(policy : Policy) -> Double

#
palette_stats

source
fn palette_stats(swatches : Array[Swatch]) -> PaletteStats

#
parse_color

source
fn parse_color(input : String) -> ColorParse

#
parse_role_token

source
fn parse_role_token(token : String) -> Role?

#
parse_swatch

source
fn parse_swatch(name : String, color_token : String, role : Role) -> SwatchParse

#
parse_token_document

source
fn parse_token_document(input : String) -> TokenParseReport

#
policy_aa

source
fn policy_aa() -> Policy

#
policy_aaa

source
fn policy_aaa() -> Policy

#
policy_large_aa

source
fn policy_large_aa() -> Policy

#
policy_large_aaa

source
fn policy_large_aaa() -> Policy

#
readable_foreground

source
fn readable_foreground(background : Color, policy : Policy) -> RepairCandidate

#
repair_background

source
fn repair_background(foreground : Color, background : Color, policy : Policy) -> RepairCandidate

#
repair_foreground

source
fn repair_foreground(foreground : Color, background : Color, policy : Policy) -> RepairCandidate

#
rgb

source
fn rgb(r : Int, g : Int, b : Int) -> Color?

#
swatch

source
fn swatch(name : String, color : Color, role : Role) -> Swatch

#
swatch_profile

source
fn swatch_profile(s : Swatch) -> ColorProfile

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