color

Color Parsing and Manipulation Utilities

GTFS represents colors as 6-character hexadecimal strings without the # prefix (e.g., “FFFFFF” for white, “000000” for black). This module provides parsing, validation, and manipulation utilities.

Source: GTFS reference.md - Field Types

Values

black

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pub fn black() -> types.Color

Black color (#000000)

contrast_ratio

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pub fn contrast_ratio(
  color1: types.Color,
  color2: types.Color,
) -> Float

Calculate contrast ratio between two colors (1:1 to 21:1) WCAG AA requires 4.5:1 for normal text, 3:1 for large text

contrasting_text_color

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pub fn contrasting_text_color(
  background: types.Color,
) -> types.Color

Get a contrasting text color (black or white) for the given background

default_route_color

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pub fn default_route_color() -> types.Color

Default GTFS route color (white)

default_text_color

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pub fn default_text_color() -> types.Color

Default GTFS text color (black)

from_rgb

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pub fn from_rgb(
  red: Int,
  green: Int,
  blue: Int,
) -> Result(types.Color, String)

Create a Color from RGB values (0-255 each)

is_light

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pub fn is_light(color: types.Color) -> Bool

Determine if a color is “light” (useful for choosing text color) Returns True if the color is light (use dark text) Returns False if the color is dark (use light text)

luminance

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pub fn luminance(color: types.Color) -> Float

Calculate the perceived luminance of a color (0.0 to 1.0) Uses the relative luminance formula from WCAG

parse

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pub fn parse(value: String) -> Result(types.Color, String)

Parse a GTFS color string (6 hex characters without #) Examples: “FFFFFF” (white), “000000” (black), “FF5733” (orange)

parse_optional

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pub fn parse_optional(
  value: String,
) -> Result(option.Option(types.Color), String)

Parse an optional color string

to_css_string

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pub fn to_css_string(color: types.Color) -> String

Format a color with # prefix for CSS/HTML use

to_string

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pub fn to_string(color: types.Color) -> String

Format a color as a GTFS color string (6 hex characters, uppercase)

white

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pub fn white() -> types.Color

White color (#FFFFFF)