| png {grDevices} | R Documentation |
Graphics devices for JPEG, PNG or TIFF format bitmap files.
bmp(filename = "Rplot%03d.bmp",
width = 480, height = 480, units = "px",
pointsize = 12, bg = "white", res = NA, ...,
type = c("cairo", "Xlib", "quartz"), antialias)
jpeg(filename = "Rplot%03d.jpeg",
width = 480, height = 480, units = "px",
pointsize = 12, quality = 75, bg = "white", res = NA, ...,
type = c("cairo", "Xlib", "quartz"), antialias)
png(filename = "Rplot%03d.png",
width = 480, height = 480, units = "px",
pointsize = 12, bg = "white", res = NA, ...,
type = c("cairo", "Xlib", "cairo1", "quartz"), antialias)
tiff(filename = "Rplot%03d.tiff",
width = 480, height = 480, units = "px", pointsize = 12,
compression = c("none", "rle", "lzw", "jpeg", "zip"),
bg = "white", res = NA, ...,
type = c("cairo", "Xlib", "quartz"), antialias)
filename |
the name of the output file.
The page number is substituted if a C integer format is included in
the character string, as in the default. (The result must be less
than |
width |
the width of the device. |
height |
the height of the device. |
units |
The units in which |
pointsize |
the default pointsize of plotted text, interpreted as
big points (1/72 inch) at |
bg |
the initial background colour: can be overridden by setting par("bg"). |
quality |
the ‘quality’ of the JPEG image, as a percentage. Smaller values will give more compression but also more degradation of the image. |
compression |
the type of compression to be used. |
res |
The nominal resolution in dpi which will be recorded in the
bitmap file, if a positive integer. Also used for |
... |
for |
type |
character string, one of |
antialias |
for |
Plots in PNG and JPEG format can easily be converted to many other
bitmap formats, and both can be displayed in modern web
browsers. The PNG format is lossless and is best for line
diagrams and blocks of colour. The JPEG format is lossy,
but may be useful for image plots, for example. BMP is a standard
format on Windows. TIFF is a meta-format: the default format written
by tiff is lossless and stores RGB (and alpha where
appropriate) values uncompressed—such files are widely accepted,
which is their main virtue over PNG.
png supports transparent backgrounds: use bg =
"transparent". Not all PNG viewers render files with transparency
correctly. When transparency is in use in the type = "Xlib"
variant a very light grey is used as the background and so appear as
transparent if used in the plot. This allows opaque white to be used,
as in the example. The type = "cairo" and type =
"cairo1" variants allows semi-transparent colours, including on a
transparent or semi-transparent background.
tiff(type = "cairo") supports semi-transparent colours,
including on a transparent or semi-transparent background.
R can be compiled without support for each of these devices: this
will be reported if you attempt to use them on a system where they are
not supported. For type = "Xlib" they may not be usable unless
the X11 display is available to the owner of the R process.
type = "cairo" requires cairo 1.2 or later. type =
"quartz" uses the quartz device and so is only
available where that is (on some Mac OS X) builds. It is at present
experimental.
By default no resolution is recorded in the file. Viewers will often assume a nominal resolution of 72dpi when none is recorded. As resolutions in PNG files are recorded in pixels/metre, the reported dpi value will be changed slightly.
For graphics parameters that make use of dimensions in inches
(including font sizes in points) the resolution used is res (or
72dpi if unset).
png will use a palette if there are less than 256 colours on
the page, and record a 24-bit RGB file otherwise (or a 32-bit RGBA
file if type = "cairo" and non-opaque colours are used).
png(type = "cairo1") uses cairo directly to output the file –
the resolution is not recorded and the PNG format used is chosen by
cairo (and undocumented – it is currently 32-bit RGBA, that is with
an alpha channel whether used or not). It is included for use on
platforms with cairo 1.0 (where type = "cairo" is not available).
A plot device is opened: nothing is returned to the R interpreter.
Note that by default the width and height are in pixels
not inches. A warning will be issued if both are less than 20.
If you plot more than one page on one of these devices and do not
include something like %d for the sequence number in
file, the file will contain the last page plotted.
This section describes the implementation of the conventions for graphics devices set out in the “R Internals Manual”.
The default device size is in pixels.
Font sizes are in big points interpreted at res dpi.
The default font family is Helvetica.
Line widths in 1/96 inch, minimum one pixel for type =
"Xlib", 0.01 for type = "cairo".
For type = "Xlib" circle radii are in pixels with
minimum one.
Colours are interpreted by the viewing application.
For type = "quartz" see the help for quartz.
For type = "Xlib" these devices are based on the X11
device. The colour model used will be that set up by
X11.options at the time the first Xlib-based devices was opened
(or the first after all such devices have been closed).
Guido Masarotto and Brian Ripley
Devices, dev.print
capabilities to see if these devices are
supported by this build of R, and if type = "cairo" is supported.
bitmap provides an alternative way to generate PNG and
JPEG plots that does not depend on accessing the X11 display but does
depend on having GhostScript installed. (Devices GDD in
CRAN package GDD and CairoJPEG / CairoPNG in CRAN
package Cairo are further alternatives using several other
additional pieces of software.)
## these examples will work only if the devices are available
## and either cairo or an X11 display is available.
## copy current plot to a (large) PNG file
## Not run: dev.print(png, file="myplot.png", width=1024, height=768)
png(file="myplot.png", bg="transparent")
plot(1:10)
rect(1, 5, 3, 7, col="white")
dev.off()
## will make myplot1.jpeg and myplot2.jpeg
jpeg(file="myplot%d.jpeg")
example(rect)
dev.off()