Skip to contents

WCAG contrast ratio between two colours

Source: R/contrast.R
contrast_ratio.Rd

Compare the relative luminance of two colours using the Web Content Accessibility Guidelines. The ratio ranges from 1 for identical colours to 21 for black against white. The guidelines specify at least 4.5 for body text and 3 for large text and graphical objects.

Usage

contrast_ratio(colour, background = "white")

Arguments

colour, background

Colours, in any form col2rgb accepts. Vectors are recycled against each other.

Value

A numeric vector of contrast ratios.

Details

Embedded transparency is composited against the background. A transparent background is first composited over white.

See also

check_contrast(), which applies this to a whole plot.

Examples

contrast_ratio("black", "white")
#> [1] 21
contrast_ratio(c("grey20", "grey50", "grey80"), "white")
#> [1] 12.634654  4.004107  1.605929