Cairo

From Cairo v1.3-2 by Simon Urbanek

Create a new Cairo-based graphics device

Cairo initializes a new graphics device that uses the Cairo graphics library for rendering. The current implementation produces high-quality PNG, JPEG, TIFF bitmap files, high resolution PDF files with embedded fonts, SVG graphics and PostScript files. It also provides X11 and Windows interactive graphics devices. Unlike other devices it supports all graphics features including alpha blending, anti-aliasing etc.

CairoX11, CairoPNG, CairoPDF, CairoPS and CairoSVG are convenience wrappers of Cairo that take the same arguments as the corresponding device it replaces such as X11, png, pdf, etc.

Keywords: device

Usage

Cairo(width = 640, height = 480, file="", type="png", pointsize=12, 
      bg = "transparent", canvas = "white", units = "px", dpi = "auto",
      ...)
CairoX11(display=Sys.getenv("DISPLAY"), width = 7, height = 7,
         pointsize = 12, gamma = getOption("gamma"), bg = "transparent",
         canvas = "white", xpos = NA, ypos = NA)
CairoPNG(filename = "Rplot%03d.png", width = 480, height = 480,
         pointsize = 12, bg = "white",  res = NA, ...)
CairoJPEG(filename = "Rplot%03d.jpeg", width = 480, height = 480,
         pointsize = 12, quality = 75, bg = "white", res = NA, ...)
CairoTIFF(filename = "Rplot%03d.tiff", width = 480, height = 480,
         pointsize = 12, bg = "white", res = NA, ...)
CairoPDF(file = ifelse(onefile, "Rplots.pdf","Rplot%03d.pdf"),
         width = 6, height = 6, onefile = TRUE, family = "Helvetica",
         title = "R Graphics Output", fonts = NULL, version = "1.1",
         paper = "special", encoding, bg, fg, pointsize, pagecentre)
CairoWin(width = 7, height = 7, pointsize = 12,
         record = getOption("graphics.record"),
         rescale = c("R", "fit", "fixed"), xpinch, ypinch, bg =
         "transparent", canvas = "white", gamma = getOption("gamma"),
         xpos = NA, ypos = NA, buffered = getOption("windowsBuffered"),
         restoreConsole = FALSE)
CairoPS(file = ifelse(onefile, "Rplots.ps", "Rplot%03d.ps"),
        onefile = TRUE, family, title = "R Graphics Output", fonts = NULL,
        encoding, bg, fg, width, height, horizontal, pointsize, paper,
        pagecentre, print.it, command, colormodel)

Arguments

width: width of the plot area (also see units).
height: height of the plot area (also see units).
file: name of the file to be created or connection to write to. Only PDF, PS and PNG types support connections. For X11 type file specifies the display name. If NULL or "" a reasonable default will be chose wh
type: output type. This version of Cario supports "png", a 24 bit RGB image, and "png24", 24 bit RGB with 8 bit Alpha channel, "jpeg", "tiff" 24-bit bitmaps, "pdf" PDF-file with embedded fonts, "svg" SVG-file, "ps" PostScript-file, "x11" X11 intera
pointsize: initial text size (in points).
canvas: canvas color (must be opaque). The canvas is only used by devices that display graphics on a screen and the canvas is only visible only if bg is transparent.
bg: plot background color (can include alpha-component).
units: units for of the width and height specifications. In can be any of "px" (pixels), "in" (inches), "pt" (points), "cm" (centimeters) or "mm"
dpi: DPI used for the conversion of units to pixels. If set to "auto" the DPI resolution will be determined by the back-end.
...: additional backend specific parameters. All parameters listed below are defined by the other devices are are used by the wrappers to make it easier replace other devices by Cairo. They are described in detail in the
display: X11 display, see X11
gamma: gamma correction
xpos: see X11
ypos: see X11
filename: same as file in Cairo
res: see png, will be mapped to dpi for Cairo
quality: quality of the jpeg, see jpeg
onefile: logical: if true (the default) allow multiple figures in one file (see pdf). false is currently not supported by vector devices
family: font family, see pdf
title: see pdf (ignored)
fonts: see pdf, ignored, Cairo automatically detects and embeds fonts
version: PDF version, see pdf (ignored)
paper: see pdf (ignored, Cairo uses device dimensions)
encoding: see pdf (ignored, Cairo uses native enconding except for symbols)
fg: see pdf (ignored)
pagecentre: see pdf (ignored, Cairo uses device dimensions and thus it is irrelevant)

record: see windows (ignored)
rescale: see widnows (ignored)
xpinch: see windows (ignored)
ypinch: see windows (ignored)
buffered: see windows (ignored, Cairo always uses cache buffer)
restoreConsole: see windows (ignored)

record: Windows-specific, ignored on unix
rescale: Windows-specific, ignored on unix
xpinch: Windows-specific, ignored on unix
ypinch: Windows-specific, ignored on unix
buffered: Windows-specific, ignored on unix
restoreConsole: Windows-specific, ignored on unix

horizontal: see postscript (ignored)
print.it: see postscript (ignored)
command: see postscript (ignored)
colormodel: see postscript (ignored, Cairo always uses RGB or ARGB)

Value

The (invisible) return value is NULL if the device couldn't be created or a Cairo object if successful. The vaule of the object is the device number.

Known issues

The X11 backend is quite slow. The reason is the cairographics implementation of the backend, so we can't do much about it. It should be possible to drop cairographics' Xlib backend entirely and use image backend copied into an X11 window instead. We may try that in future releases.
TrueType (and OpenType) fonts are supported when this package is compiled against a cairo graphics library configured with FreeType and Fontconfig support. Therefore make sure have a cairo grpahics library with all bell and whistles to get a good result.
R math symbols are supported, but require a TrueType "Symbol" font accessible to Cairo under that name.

Examples

Cairo(800, 600, file="plot.png", type="png")
plot(rnorm(100),rnorm(100),col=2)
dev.off() # creates a file "plot.png" with the above plot

Documentation reproduced from package Cairo, version 1.3-2, License: GPL version 2

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