R: Create a new Cairo-based graphics device

Cairo {Cairo} | R Documentation

## Create a new Cairo-based graphics device

### Description

`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. Use of the `Cairo` function is encouraged as it is more flexible than the wrappers.

### 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)
    CairoSVG(file = ifelse(onefile, "Rplots.svg", "Rplot%03d.svg"),
             width = 6, height = 6, onefile = TRUE, bg = "transparent",
             pointsize = 12, ...)
    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 chosen which is `"plot.type"` for file-oriented types and value of the `DISPLAY` environment variable for X11. For image types the file name can contain printf-style formatting expecting one integer parameter which is the page number, such as `"Rplot%03d.png"`. The page numbers start at one. The filename is expanded using `path.expand`.
`type` | output type. This version of Cario supports "png", "jpeg" and "tiff" bitmaps (png/tiff with transparent background), "pdf" PDF-file with embedded fonts, "svg" SVG-file, "ps" PostScript-file, "x11" X11 interactive window and "win" Windows graphics. A special type "raster" creates an image back-end that produces no actual output file but can be used in conjunction with any of `dev.capture()`, `grid.cap()` or `Cairo:::.image()` to create in-memory images. Depending on the support of various backends in cairo graphics some of the options may not be available for your system. See `Cairo.capabilities` function.
`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 or be transparent alltogether).
`units` | units for of the `width` and `height` specifications. It can be any of `"px"` (pixels), `"in"` (inches), `"pt"` (points), `"cm"` (centimeters) or `"mm"` (millimeters).
`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 (e.g. `quality` setting for JPEG (0..100), `compression` for TIFF (0,1=none, 5=LZW (default), 7=JPEG, 8=Adobe Deflate), `locator` for a custom locator function in image back-ends) 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 documentation corresponding to the device that is being replaced.
`display` | X11 display, see `X11`
`gamma` | gamma correction
`xpos` | see `X11`
`ypos` | see `X11`
`filename` | same as `file` in `Cairo`
`res` | resolution in ppi, see `png`, will override `dpi` in `Cairo` if set to anything other than `NA` or `NULL`. Note that cairographics does not support tagging PNG output files with DPI so the raster image will be produced with the dpi setting, but readers may render it at some default dpi setting.
`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 `windows` (ignored)
`xpinch` | see `windows` (ignored)
`ypinch` | see `windows` (ignored)
`buffered` | see `windows` (ignored, `Cairo` always uses cache buffer)
`restoreConsole` | see `windows` (ignored)

`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 graphics library with all bells and whistles to get a good result.

- R math symbols are supported, but require a TrueType "Symbol" font accessible to Cairo under that name.

### See Also

`CairoFonts`

### Examples

    # very simple KDE
    Cairo(600, 600, file="plot.png", type="png", bg="white")
    plot(rnorm(4000),rnorm(4000),col="#ff000018",pch=19,cex=2) # semi-transparent red
    dev.off() # creates a file "plot.png" with the above plot

    # you can use any Cairo backend and get the same result
    # vector, bitmap or on-screen
    CairoPDF("plot.pdf", 6, 6, bg="transparent")
    data(iris)
    attach(iris)
    plot(Petal.Length, rep(-0.03,length(Species)), xlim=c(1,7),
         ylim=c(0,1.7), xlab="Petal.Length", ylab="Density",
         pch=21, cex=1.5, col="#00000001", main = "Iris (yet again)",
         bg=c("#ff000020","#00ff0020","#0000ff20")[unclass(Species)])
    for (i in 1:3)
      polygon(density(Petal.Length[unclass(Species)==i],bw=0.2),
        col=c("#ff000040","#00ff0040","#0000ff40")[i])
    dev.off()

    ## remove the example files if not in an interactive session
    if (!interactive()) unlink(c("plot.png","plot.pdf"))

[Package Cairo version 1.5-12.2 Index]