Determine the equivalent opaque RGB color for a given partially transparent RGB color against a background of any color.
ColToOpaque(col, alpha = NULL, bg = NULL)An named vector with the hexcodes of the opaque colors.
the color as hex value (use converters below if it's not available). col and alpha are recycled.
the alpha channel, if left to NULL the alpha channels of the colors are used
the background color to be used to calculate against (default is "white")
Andri Signorell <andri@signorell.net>
Reducing the opacity against a white background is a good way to find usable lighter and less saturated tints of a base color. For doing so, we sometimes need to get the equivalent opaque color for the transparent color.
ColToHex, DecToHex, RgbToHex
cols <- c(SetAlpha("limegreen", 0.4), ColToOpaque(ColToHex("limegreen"), 0.4), "limegreen")
barplot(c(1, 1.2, 1.3), col=cols, panel.first=abline(h=0.4, lwd=10, col="grey35"))
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