grid.raster {grid}R Documentation

Render a raster object

Description

Render a raster object (bitmap image) at the given location, size, and orientation.

Usage

grid.raster(image,
            x = unit(0.5, "npc"), y = unit(0.5, "npc"),
            width = NULL, height = NULL,
            just = "centre", hjust = NULL, vjust = NULL,
            interpolate = TRUE, default.units = "npc",
            name = NULL, gp = gpar(), vp = NULL)

rasterGrob(image,
           x = unit(0.5, "npc"), y = unit(0.5, "npc"),
           width = NULL, height = NULL,
           just = "centre", hjust = NULL, vjust = NULL,
           interpolate = TRUE, default.units = "npc",
           name = NULL, gp = gpar(), vp = NULL)

Arguments

image

Any R object that can be coerced to a raster object.

x

A numeric vector or unit object specifying x-location.

y

A numeric vector or unit object specifying y-location.

width

A numeric vector or unit object specifying width.

height

A numeric vector or unit object specifying height.

just

The justification of the rectangle relative to its (x, y) location. If there are two values, the first value specifies horizontal justification and the second value specifies vertical justification. Possible string values are: "left", "right", "centre", "center", "bottom", and "top". For numeric values, 0 means left alignment and 1 means right alignment.

hjust

A numeric vector specifying horizontal justification. If specified, overrides the just setting.

vjust

A numeric vector specifying vertical justification. If specified, overrides the just setting.

default.units

A string indicating the default units to use if x, y, width, or height are only given as numeric vectors.

name

A character identifier.

gp

An object of class gpar, typically the output from a call to the function gpar. This is basically a list of graphical parameter settings.

vp

A Grid viewport object (or NULL).

interpolate

A logical value indicating whether to linearly interpolate the image (the alternative is to use nearest-neighbour interpolation, which gives a more blocky result).

Details

Neither width nor height needs to be specified, in which case, the aspect ratio of the image is preserved. If both width and height are specified, it is likely that the image will be distorted.

Not all graphics devices are capable of rendering raster images and some may not be able to produce rotated images (i.e., if a raster object is rendered within a rotated viewport). See also the comments under rasterImage.

All graphical parameter settings in gp will be ignored, including alpha.

Value

A rastergrob grob.

Author(s)

Paul Murrell

See Also

as.raster.

dev.capabilities to see if it is supported.

Examples

redGradient <- matrix(hcl(0, 80, seq(50, 80, 10)),
                      nrow=4, ncol=5)
# interpolated
grid.newpage()
grid.raster(redGradient)
# blocky
grid.newpage()
grid.raster(redGradient, interpolate=FALSE)
# blocky and stretched
grid.newpage()
grid.raster(redGradient, interpolate=FALSE, height=unit(1, "npc"))

# The same raster drawn several times
grid.newpage()
grid.raster(0, x=1:3/4, y=1:3/4, w=.1, interp=FALSE)

[Package grid version 3.1.0 Index]