R: Adjust Colors in One or More Directions Conveniently.

adjustcolor {grDevices} | R Documentation

## Adjust Colors in One or More Directions Conveniently.

### Description

Adjust or modify a vector of colors by “turning knobs” on one or more coordinates in (r,g,b,α) space, typically by up or down scaling them.

### Usage

    adjustcolor(col, alpha.f = 1, red.f = 1, green.f = 1, blue.f = 1,
                offset = c(0, 0, 0, 0),
                transform = diag(c(red.f, green.f, blue.f, alpha.f)))

### Arguments

`col` | vector of colors, in any format that col2rgb() accepts
`alpha.f` | factor modifying the opacity alpha; typically in [0,1]
`red.f, green.f, blue.f` | factors modifying the “red-”, “green-” or “blue-”ness of the colors, respectively.
`offset` |
`transform` |

### Value

a color vector of the same length as `col`, effectively the result of `rgb()`.

### See Also

`rgb`, `col2rgb`. For more sophisticated color constructions: `convertColor`

### Examples

    ## Illustrative examples :
    opal <- palette("default")
    stopifnot(identical(adjustcolor(1:8,       0.75),
                        adjustcolor(palette(), 0.75)))
    cbind(palette(), adjustcolor(1:8, 0.75))

    ##  alpha = 1/2 * previous alpha --> opaque colors
    x <- palette(adjustcolor(palette(), 0.5))

    sines <- outer(1:20, 1:4, function(x, y) sin(x / 20 * pi * y))
    matplot(sines, type = "b", pch = 21:23, col = 2:5, bg = 2:5,
            main = "Using an 'opaque ('translucent') color palette")

    x. <- adjustcolor(x, offset = c(0.5, 0.5, 0.5, 0), # <- "more white"
                      transform = diag(c(.7, .7, .7, 0.6)))
    cbind(x, x.)
    op <- par(bg = adjustcolor("goldenrod", offset = -rep(.4, 4)), xpd = NA)
    plot(0:9, 0:9, type = "n", axes = FALSE, xlab = "", ylab = "",
         main = "adjustcolor() -> translucent")
    text(1:8, labels = paste0(x,"++"), col = x., cex = 8)
    par(op)

    ## and

    (M <- cbind( rbind( matrix(1/3, 3, 3), 0), c(0, 0, 0, 1)))
    adjustcolor(x, transform = M)

    ## revert to previous palette: active
    palette(opal)

[Package grDevices version 3.1.2 Index]