Get contrasting text colors for fills

Get appropriate high-contrast text colors for a vector of background colors. This function uses the W3C contrast ratio guidance (through the colorspace::contrast_ratio() function) to determine the contrast, and will raise an error if no high-enough contrast colors can be found.

Usage

choose_text_color(bg_color, text_colors = c("black", "white"), min_ratio = 4.5)

Arguments

bg_color

a vector of colors to be used as background colors

text_colors

a vector of options for text colors. Defaults to "black" and "white"

min_ratio

Minimum contrast ratio. By default this is set to 4.5, the WCAG recommendation for regular text.

Value

a vector of text colors the same length as bg_color.

Details

By default, this function uses black and white as the text color options, however custom text color options can be set with the text_colors argument.

Examples

library(ggplot2)

fills <- tntp_palette("top2_5")

diamonds |>
  dplyr::summarize(m = mean(price), .by = cut) |>
  ggplot(aes(cut, m, fill = cut)) +
  geom_col() +
  geom_text(aes(label = scales::dollar(m), color = cut), vjust = 1.5) +
  scale_fill_manual(values = fills, guide = "none") +
  scale_color_manual(values = choose_text_color(fills), guide = "none") +
  tntp_style(family = "sans")