adjust_transparency {colorspace} | R Documentation |
Add, remove, or modify alpha transparency of a vector of colors.
adjust_transparency(col, alpha = TRUE)
col |
vector of R colors. Can be any of the three kinds of R colors,
i.e., either a color name (an element of
|
alpha |
either a new numeric alpha transparency value or logical (to add/remove alpha)
or |
Alpha transparency is useful for making colors semi-transparent, e.g., for overlaying different elements in graphics. An alpha value of 0 (or 00 in hex strings) corresponds to fully transparent and an alpha value of 1 (or FF in hex strings) corresponds to fully opaque. If a color hex string in R does not provide an explicit alpha transparency, the color is assumed to be fully opaque.
The adjust_transparency
function can be used to adjust the alpha transparency
of a set of colors. It always returns a hex color specification. This hex color
can have the alpha transparency added/removed/modified depending on the
specification of alpha
:
alpha = NULL
: Returns a hex vector with alpha transparency only if needed.
Thus, it keeps the alpha transparency for the colors (if any) but only if
different from opaque.
alpha = TRUE
: Returns a hex vector with alpha transparency
for all colors, using opaque (FF) as the default if missing.
alpha = FALSE
: Returns a hex vector without alpha transparency for
all colors (even if the original colors had non-opaque alpha).
alpha
numeric: Returns a hex vector with alpha transparency for
all colors set to the alpha
argument (recycled if necessary).
A character vector with hexadecimal color strings with alpha transparency
corresponding to alpha
argument.
Zeileis A, Fisher JC, Hornik K, Ihaka R, McWhite CD, Murrell P, Stauffer R, Wilke CO (2020). “ccolorspace: A Toolbox for Manipulating and Assessing Colors and Palettes.” Journal of Statistical Software, 96(1), 1–49. doi: 10.18637/jss.v096.i01
## modify transparency of a color (in different formats) adjust_transparency("black", alpha = c(0, 0.5, 1)) ## name adjust_transparency("#000000", alpha = c(0, 0.5, 1)) ## hex string adjust_transparency(1, alpha = c(0, 0.5, 1)) ## palette() integer ## three shades of gray (in different formats: ## name/opaque, hex/opaque, hex/semi-transparent) x <- c("gray", "#BEBEBE", "#BEBEBE80") ## adjust transparency adjust_transparency(x, alpha = NULL) ## only if necessary adjust_transparency(x, alpha = TRUE) ## add adjust_transparency(x, alpha = FALSE) ## remove adjust_transparency(x, alpha = 0.8) ## modify