| png {grDevices} | R Documentation |
Graphics devices for BMP, JPEG, PNG and TIFF format bitmap files.
bmp(filename = "Rplot%03d.bmp", width = 480, height = 480,
units = "px", pointsize = 12, bg = "white", res = NA,
restoreConsole = TRUE)
jpeg(filename = "Rplot%03d.jpg", width = 480, height = 480,
units = "px", pointsize = 12, quality = 75, bg = "white",
res = NA, restoreConsole = TRUE)
png(filename = "Rplot%03d.png", width = 480, height = 480,
units = "px", pointsize = 12, bg = "white", res = NA,
restoreConsole = TRUE)
tiff(filename = "Rplot%03d.tif", width = 480, height = 480,
units = "px", pointsize = 12,
compression = c("none", "rle", "lzw", "jpeg", "zip"),
bg = "white", res = NA,
restoreConsole = TRUE)
filename |
the name of the output file, up to 511 characters. The
page number is substituted if a C integer format is included in the
character string, as in the default, and tilde-expansion is
performed (see |
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 units other than the default. If not specified, taken as 72 dpi to set the size of text and line widths. |
restoreConsole |
See the ‘Details’ section of
|
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. The BMP format is
standard on Windows, and supported by most viewers elsewhere.
TIFF is a meta-format: the default format written by tiff is lossless
and stores RGB values uncompressed—such files are widely accepted,
which is their main virtue over PNG.
Windows imposes limits on the size of bitmaps: these are not
documented in the SDK and may depend on the version of Windows.
It seems that width and height are each limited to
2^{15}-1.
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,
res dpi (default 72) is assumed.
Both bmp and png will use a palette if there are less
than 256 colours on the page, and record a 24-bit RGB file otherwise.
png supports transparent backgrounds on 16-bit (‘High
Color’) or better screens: use bg = "transparent". There is
also support for semi-transparent colours of lines, fills and text.
However, as there is only partial support for transparency in the
graphics toolkit used, if there is a transparent background
semi-transparent colours are painted onto a slightly off-white
background and hence the pixels are opague.
Not all PNG viewers render files with transparency correctly.
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 Arial.
Line widths are a multiple of 1/96 inch (interpreted at
res dpi), with a minimum of one pixel.
The minimum radius of a circle is 1 pixel.
Colours are interpreted by the viewing application.
These devices effectively plot on a hidden screen and then copy the image to the required format. This means that they have the same colour handling as the actual screen device, and work best if that is set to a 24-bit or 32-bit colour mode.
Devices, dev.print
bitmap provides an alternative way to generate PNG,
JPEG and other types of bitmap plots. Devices GDD in
CRAN package GDD and CairoJPEG / CairoPNG in CRAN
package Cairo are further alternatives.
## 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()
jpeg(file="myplot.jpeg")
example(rect)
dev.off()
## End(Not run)