@OPEN-KAPPA/COLORS
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    Class WcagAbstract

    Utilities for Web Content Accessibility Guidelines (WCAG) and APCA. Provides methods to check contrast ratios and readability.

    Index

    Constructors

    constructor

    Methods

    apcaContrast apcaFontRecommendations apcaRating contrast getBestContrastColor getMinFontSize isApcaReadable isDark isLight isReadable relativeLuminance

    Constructors

    Methods

    • Calculates the APCA (Advanced Perceptual Contrast Algorithm) value. Returns a value Lc between ~ -108 and +106.

      • Positive: Dark text on light background.
      • Negative: Light text on dark background.
      • APCA is perceptually more accurate than standard WCAG 2.1, accounting for polarity (light-on-dark vs dark-on-light).

      Parameters

      • background: Xyz

        The background.

      • text: Xyz

        The text.

      Returns number

      The score.

    • Returns font size requirements based on the APCA score. APCA couples contrast with font weight and size (unlike WCAG 2.1).

      Parameters

      • apcaScore: number

        The score.

      Returns FontRequirements

      The reequirements.

    • Get a human friendly string representing the score.

      Parameters

      • score: number

        The score.

      Returns string

      The string.

    • Computes the standard WCAG 2.1 contrast ratio. Formula: (L1 + 0.05) / (L2 + 0.05) Returns a value between 1.0 and 21.0.

      Parameters

      • c1: Xyz

        THe first color.

      • c2: Xyz

        The second color.

      Returns number

      The contrast.

    • Returns the color (c1 or c2) that provides the highest contrast against the background. Uses APCA by default for perceptual accuracy, but falls back to WCAG 2.1 if specified.

      Parameters

      • bg: Xyz

        The background color.

      • dark: Xyz

        The dark text option (usually Black).

      • light: Xyz

        The light text option (usually White).

      • algorithm: "APCA" | "WCAG" = "APCA"

        The algorithm to use ("APCA" or "WCAG").

      Returns Xyz

      The color with the best contrast.

    • Returns the minimum font size for a specific font weight.

      Parameters

      • apcaScore: number

        The calculated APCA score.

      • weight: ApcaWeight

        The font weight (200, 300, 400, 500, 600, 700, 900).

      Returns number

      The minimum size in pixels, or 999 if prohibited.

    • Check if the text is readable.

      Parameters

      • bg: Xyz

        The background.

      • text: Xyz

        The text.

      • fontSize: number

        The font size.

      • fontWeight: "normal" | "bold" = "normal"

        The font weight.

      Returns boolean

      True if readable.

    • Check if the text is dark.

      Parameters

      • color: Xyz

        The color.

      Returns boolean

      True if the color is dark.

    • Check if the text is light.

      Parameters

      • color: Xyz

        The color.

      Returns boolean

      True if the color is light.

    • Get the relative luminance.

      Parameters

      • color: Xyz

        The color.

      Returns number

      The luminance.

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