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50 lines
2.0 KiB
R
50 lines
2.0 KiB
R
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#' @title Contrast Text Color
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#' @description Calculates the best contrast text color for a given background color.
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#' @param background A hex/named color value that represents the background.
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#' @param light_text A hex/named color value that represents the light text color.
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#' @param dark_text A hex/named color value that represents the dark text color.
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#' @param threshold A numeric value between 0 and 1 that is used to determine
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#' the luminance threshold of the background color for text color.
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#' @param method A character string that specifies the method for calculating
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#' the luminance. Three different methods are available:
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#' c("relative","perceived","perceived_2")
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#' @details
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#' This function aids in deciding the font color to print on a given background.
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#' The function is based on the example provided by teppo:
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#' https://stackoverflow.com/a/66669838/21019325.
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#' The different methods provided are based on the methods outlined in the
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#' StackOverflow thread: https://stackoverflow.com/questions/596216/formula-to-determine-perceived-brightness-of-rgb-color
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#' @return A character string that contains the best contrast text color.
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#' @examples
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#' contrast_text(c("#F2F2F2", "blue"))
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#'
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#' contrast_text(c("#F2F2F2", "blue"), method="relative")
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#' @export
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#'
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#' @importFrom grDevices col2rgb
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#'
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contrast_text <- function(background,
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light_text = 'white',
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dark_text = 'black',
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threshold = 0.5,
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method = "perceived_2") {
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if (method == "relative") {
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luminance <- c(c(.2126, .7152, .0722) %*% grDevices::col2rgb(background) / 255)
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} else if (method == "perceived") {
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luminance <- c(c(.299, .587, .114) %*% grDevices::col2rgb(background) / 255)
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} else if (method == "perceived_2") {
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luminance <- c(sqrt(colSums((
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c(.299, .587, .114) * grDevices::col2rgb(background)
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) ^ 2)) / 255)
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}
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ifelse(
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luminance < threshold,
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light_text,
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dark_text
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)
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}
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