rgb {grDevices} | R Documentation |
This function creates colors corresponding to the given
intensities (between 0 and max
) of the red, green and blue
primaries.
An alpha transparency value can also be specified
(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
.
rgb(red, green, blue, alpha, names = NULL, maxColorValue = 1)
red, blue, green, alpha |
numeric vectors with values in [0, M]
where M is maxColorValue . When this is 255 , the
red , blue , green , and alpha
values are coerced to integers in 0:255 and the result is
computed most efficiently. |
names |
character. The names for the resulting vector. |
maxColorValue |
number giving the maximum of the color values range, see above. |
The colors may be specified by passing a matrix or dataframe 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 only on the pdf
,
windows
and quartz
devices as well as
several third-party devices such as those in packages Cairo,
cairoDevice, JavaGD and RSvgDevice. On most of
these devices the actual alpha values used are multiples of 1/255.
Typically other graphics devices silently plot semi-transparent colors as fully transparent.
A character vector with elements of 7 or 9 characters, "#"
followed by the red, blue, green and optionally alpha values in
hexadecimal (after rescaling to 0 ... 255
).
col2rgb
for translating R colors to RGB vectors;
rainbow
, hsv
, hcl
,
gray
.
rgb(0,1,0) (u01 <- seq(0,1, length=11)) stopifnot(rgb(u01,u01,u01) == gray(u01)) reds <- rgb((0:15)/15, green=0, blue=0, names=paste("red",0:15,sep=".")) reds rgb(0, 0:12, 0, max = 255)# integer input ramp <- colorRamp(c("red", "white")) rgb( ramp(seq(0, 1, length = 5)), max = 255)