Package 'Cairo'

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, 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) The PDF back-end supports following additional arguments: author, subject, creator, keywords, create.date and modify.date. If specified, all of the above must be single strings. The dates must be in PDF-defined format, you can use something like paste0("D:",gsub("[- :]","",.POSIXct(Sys.time(),"GMT"))),"Z") to convert from POSIXct to PDF format. In addition, the version argument (as documented in pdf) can be either a string or a scalar real number. However, the cairographics library only supports values 1.4 and 1.5. 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
fonts	see pdf, ignored, Cairo automatically detects and embeds fonts
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	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 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"))

---

Reports which output types are supported by this Cairo build

Description

Cairo.capabilities returns a logical vector describing the capabilities of this particular Cairo build.

Usage

Cairo.capabilities()

Details

The Cairo package provides multiple back-ends, such as images (PNG, JPEG, TIFF), vector graphics (PDF, PostScript, SVG) or displays (X11, Windows). However, not all systems support all back-ends. The Cairo.capabilities function returns a logical vector showing which capabilities are supported in this particular Cairo build.

Note that the capabilities depend both on the libraries available in the system as well as the compiled-in modules in cairo graphics.

See Also

Cairo

---

Capture contents of an image backend or a display list snapshot.

Description

Cairo.capture is essentially the same as dev.capture(native=TRUE) with the exception that it works where dev.capture doesn't such as onSave callbacks.

Cairo.snapshot is very similar to recordPlot except it also allows to retrieve the last snapshot.

Usage

Cairo.capture(device = dev.cur())
Cairo.snapshot(device = dev.cur(), last=FALSE)

Arguments

device	device number or an object of the class Cairo (as obtained from the Cairo function).
last	logical, if FALSE then a new snapshot is created (exactly the same as recordPlot()), if TRUE then the last known snapshot is retrieved, if NA then a snapshot is created first, but if the display list is empty last snapshot is retrieved instead.

Value

Cairo.capture: object of the class nativeRaster.

Cairo.snapshot: object of the class recordedplot.

Author(s)

Simon Urbanek

---

Cairo callbacks

Description

Cairo.onSave set the onSave callback which allows R code to be run when Cairo finalizes a page (either due to a new page being created or by the device being closed). The callback expects function(device, page) where device will be the device number and page is the currently finished page number (starting at 1).

Usage

Cairo.onSave(device = dev.cur(), onSave)

Arguments

device	device number or Cairo object (as returned by the Cairo function)
onSave	function that will replace the current callback or NULL to remove the current callback

Value

The old callback being replaced or NULL if there was none.

Note

The function onSave will be evaluated in the global environment and no error checking is done, so you must make sure to catch errors, otherwise the behavior is undefined (and may included crashing R or other bad things).

Author(s)

Simon Urbanek

See Also

Cairo

Examples

if (require(png, quietly=TRUE)) {
  dev <- Cairo(800, 600, type='raster')
  Cairo.onSave(dev, function(dev, page)
    .GlobalEnv$png <- writePNG(Cairo.capture(dev))
  )
  plot(1:10, col=2)
  dev.off()
  str(png)
}

---

Check for changes in the graphics state of Cairo devices.

Description

Cairo.serial returns an integer that is increased with every plotting operation on the device. This allows user code to determine whether any new content has been added to the device since it was last checked.

Usage

Cairo.serial(device = dev.cur())

Arguments

device

device number or an object of the class Cairo (as obtained from the Cairo function).

Value

Integer value.

Note

The integer value overflows to 0 at 2^31. Typically only equality should be checked and for such it is extremely unlikely that the state has changed yet the serial value is the same due to overflow.

Author(s)

Simon Urbanek

---

Find installed fonts with a fontconfig pattern

Description

CairoFontMatch searches for fonts based on a fontconfig pattern.

Usage

CairoFontMatch(fontpattern="Helvetica",sort=FALSE,verbose=FALSE)

Arguments

fontpattern	character; a fontconfig pattern.
sort	logical; if 'FALSE', display only the best matching font for the pattern. If 'TRUE', display a sorted list of best matching fonts.
verbose	logical; if 'FALSE', display the family, style, and file property for the pattern. if 'TRUE', display the canonical font pattern for each match.

Details

This function displays a list of one or more fonts matching the supplied fontconfig pattern. sort='FALSE' displays the font that Cairo will use for the supplied pattern, while sort='TRUE' displays a sorted list of best matching fonts. The simplest fontconfig pattern matching all installed fonts is ":". Here's what CairoFontMatch(":") displays on this system:

1. family: "Bitstream Vera Sans", style: "Roman", file: "/usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf"

verbose='FALSE' displays the font properties 'family', 'style', and 'file', while verbose='TRUE' will display the canonical font pattern, displaying all properties known for the font (output of CairoFontMatch(":",verbose=TRUE)):

1. family: "Bitstream Vera Sans", style: "Roman", file: "/usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf"
   "Bitstream Vera Sans-12:familylang=en:style=Roman:stylelang=en:slant=0:weight=80:width=100:pixelsize=12.5:foundry=bitstream:hintstyle=3:hinting=True:verticallayout=False:autohint=False:globaladvance=True:index=0:outline=True:scalable=True:dpi=75:rgba=1:scale=1:fontversion=131072:fontformat=TrueType:embeddedbitmap=True:decorative=False"

A simple approach to selecting a font starts with calling CairoFontMatch(":",sort=TRUE) to list all available fonts. Next, the user will choose a font from the list and call CairoFontMatch("FamilyName:style=PreferredStyle",sort=TRUE) substituting "FamilyName" and "PreferredStyle" with the desired values. If only one font is found, then the user has found the fontconfig pattern that will select the desired font. Otherwise, the user will call CairoFontMatch with verbose=TRUE to determine other properties to add to the pattern to attain the desired font, for instance the fontformat.

The following excerpt is from the fontconfig user's manual (http://fontconfig.org/) and better describes the fontconfig pattern definition:

"Fontconfig provides a textual representation for patterns that the library can both accept and generate. The representation is in three parts, first a list of family names, second a list of point sizes and finally a list of additional properties:

<families>-<point sizes>:<name1>=<values1>:<name2>=<values2>...

Values in a list are separated with commas. The name needn't include either families or point sizes; they can be elided. In addition, there are symbolic constants that simultaneously indicate both a name and a value. Here are some examples:

Font Pattern                    Meaning
----------------------------------------------------------
Times-12                        12 point Times Roman
Times-12:bold                   12 point Times Bold
Courier:italic                  Courier Italic in the default size
Monospace:matrix=1 .1 0 1       The users preferred monospace font
                                with artificial obliquing

The '\', '-', ':' and ',' characters in family names must be preceeded by a '\' character to avoid having them misinterpreted. Similarly, values containing '\', '=', '_', ':' and ',' must also have them preceeded by a '\' character. The '\' characters are stripped out of the family name and values as the font name is read."

Known issues

• This function is only available when the Cairo graphics library is configured with FreeType and FontConfig support.

See Also

CairoFonts, Cairo

---

Set the fonts used for all Cairo graphics devices.

Description

CairoFonts initializes the fonts used for Cairo graphics devices.

Usage

CairoFonts(
	regular="Helvetica:style=Regular",
	bold="Helvetica:style=Bold",
	italic="Helvetica:style=Italic",
	bolditalic="Helvetica:style=Bold Italic,BoldItalic",
	symbol="Symbol", usePUA=TRUE
)

Arguments

regular	character; fontconfig pattern for the 'plain text' font.
bold	character; fontconfig pattern for the 'bold face' font.
italic	character; fontconfig pattern for the 'italic' font.
bolditalic	character; fontconfig pattern for the 'bold italic' font.
symbol	character; fontconfig pattern for the 'symbol' font.
usePUA	logical; if FALSE then symbols are using regular Unicode code points (supported by regular fonts), otherwise Private Unicode Area (PUA) of symbols is used (typically better propulated by specialized symbol fonts). R 4.0.0 or higher is required for usePUA=FALSE.

Details

This function sets the fonts for Cairo graphics devices globally; previously opened Cairo graphics devices will also use these fonts. The argument names correspond to the five values of the graphical parameter 'font', i.e. regular is 1, bold is 2, italic is 3, etc.

For an explanation of fontconfig patterns, see CairoFontMatch.

Known issues

• This function is only available when the cairo graphics library is configured with FreeType and Fontcofig support.

• R math symbols are supported, but require a "Symbol" font with the Adobe Symbol Encoding unless usePUA=FALSE is used (available in R 4.0.0 or higher only).

See Also

CairoFontMatch, Cairo, par,

Examples

## Not run: 
#
# The following fontconfig patterns define the free truetype fonts 
# available in the debian package 'ttf-freefont'.
# 
# Freesans is very similar to Helvetica
CairoFonts(
	regular="FreeSans:style=Medium",
	bold="FreeSans:style=Bold",
	italic="FreeSans:style=Oblique",
	bolditalic="FreeSans:style=BoldOblique"
)

## End(Not run)

---