| rgb {grDevices} | R Documentation |
RGB Color Specification
Description
This function creates colors corresponding to the given
intensities (between 0 and max) of the red, green and blue
primaries. The colour specification refers to the
standard sRGB colorspace (IEC standard 61966).
An alpha transparency value can also be specified (as an opacity, so
0 means fully transparent and max means opaque). If
alpha is not specified, an opaque colour is generated.
The names argument may be used to provide names for the
colors.
The values returned by these functions can be used with a
col= specification in graphics functions or in par.
Usage
rgb(red, green, blue, alpha, names = NULL, maxColorValue = 1)
Arguments
red, blue, green, alpha |
numeric vectors with values in |
names |
character vector. The names for the resulting vector. |
maxColorValue |
number giving the maximum of the color values range, see above. |
Details
The colors may be specified by passing a matrix or data frame as argument
red, and leaving blue and green missing.
In this case the first three columns of red are taken to be
the red, green and blue values.
Semi-transparent colors (0 < alpha < 1) are supported only on
some devices: at the time of writing on the pdf,
windows, quartz and X11(type = "cairo") devices and
associated bitmap devices (jpeg, png, bmp,
tiff and bitmap). They are supported by several
third-party devices such as those in packages Cairo,
cairoDevice and JavaGD. Only some of these
devices support semi-transparent backgrounds.
Most other graphics devices plot semi-transparent colors as fully transparent, usually with a warning when first encountered.
NA values are not allowed for any of red, blue,
green or alpha.
Value
A character vector with elements of 7 or 9 characters,
beginning with "#" followed by the red,
blue, green and optionally alpha values in hexadecimal (after
rescaling to 0 ... 255). The optional alpha values range
from 0 (fully transparent) to 255 (opaque).
R does not use ‘premultiplied alpha’.
See Also
col2rgb for translating R colors to RGB vectors;
rainbow, hsv, hcl,
gray.
Examples
rgb(0, 1, 0)
rgb((0:15)/15, green = 0, blue = 0, names = paste("red", 0:15, sep = "."))
rgb(0, 0:12, 0, maxColorValue = 255) # integer input
ramp <- colorRamp(c("red", "white"))
rgb( ramp(seq(0, 1, length.out = 5)), maxColorValue = 255)