update_alpha: Update colour and/or pattern transparency

In gridpattern: 'grid' Pattern Grobs

Update colour and/or pattern transparency

Description

update_alpha() modifies the transparency of colours and/or patterns.

Usage

update_alpha(fill, alpha)

Arguments

fill	A fill colour given as a character or integer vector, or as a (list of) ⁠<GridPattern>⁠ object(s) and/or colour(s).
alpha	A transparency value between 0 (transparent) and 1 (opaque), parallel to fill.

Details

• This is a fork of pattern utilities mainly added to {ggplot2} by Teun van den Brand.

• update_alpha() does not depend on {ggplot2} or {scales}.

• Like ggplot2::fill_alpha() but unlike scales::alpha() it also attempts to set the transparency of ⁠<GridPattern>⁠ objects.

• Unlike ggplot2::fill_alpha() it will work on a list of length one containing a vector of color strings.

Value

A character vector of colours or list of ⁠<GridPattern>⁠ objects.

Usage in other packages

To avoid taking a dependency on gridpattern you may copy the source of update_alpha() into your own package under the permissive MIT license. Either use usethis::use_standalone("trevorld/gridpattern", "standalone-update_alpha.R") or copy the file update_alpha.R into your R directory and add grDevices, grid, and rlang to the Imports of your DESCRIPTION file.

Examples

# Typical color input
update_alpha("red", 0.5)

# Pattern input
if (getRversion() >= "4.2" && requireNamespace("grid", quietly = TRUE)) {
  update_alpha(list(grid::linearGradient()), 0.5)
}

gridpattern documentation built on April 3, 2025, 11:28 p.m.