bumped to 25.2.1 - new visuals tab - all functions in place - code cleanup has started

R/contrast_text.R

@@ -0,0 +1,51 @@
+#' @title Contrast Text Color
+#' @description Calculates the best contrast text color for a given
+#' background color.
+#' @param background A hex/named color value that represents the background.
+#' @param light_text A hex/named color value that represents the light text
+#' color.
+#' @param dark_text A hex/named color value that represents the dark text color.
+#' @param threshold A numeric value between 0 and 1 that is used to determine
+#' the luminance threshold of the background color for text color.
+#' @param method A character string that specifies the method for calculating
+#' the luminance. Three different methods are available:
+#' c("relative","perceived","perceived_2")
+#' @param ... parameter overflow. Ignored.
+#' @details
+#' This function aids in deciding the font color to print on a given background.
+#' The function is based on the example provided by teppo:
+#' https://stackoverflow.com/a/66669838/21019325.
+#' The different methods provided are based on the methods outlined in the
+#' StackOverflow thread:
+#' https://stackoverflow.com/questions/596216/formula-to-determine-perceived-brightness-of-rgb-color
+#' @return A character string that contains the best contrast text color.
+#' @examples
+#' contrast_text(c("#F2F2F2", "blue"))
+#'
+#' contrast_text(c("#F2F2F2", "blue"), method="relative")
+#' @export
+#'
+#' @importFrom grDevices col2rgb
+#'
+contrast_text <- function(background,
+                          light_text = 'white',
+                          dark_text = 'black',
+                          threshold = 0.5,
+                          method = "perceived_2",
+                          ...) {
+  if (method == "relative") {
+    luminance <-
+      c(c(.2126, .7152, .0722) %*% grDevices::col2rgb(background) / 255)
+  } else if (method == "perceived") {
+    luminance <-
+      c(c(.299, .587, .114) %*% grDevices::col2rgb(background) / 255)
+  } else if (method == "perceived_2") {
+    luminance <- c(sqrt(colSums((
+      c(.299, .587, .114) * grDevices::col2rgb(background)
+    ) ^ 2)) / 255)
+  }
+
+  ifelse(luminance < threshold,
+         light_text,
+         dark_text)
+}