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fcf963639e
This version of Cairo properly uses the res argument, so it works with resolutions higher than 72.
50 lines
2.1 KiB
R
50 lines
2.1 KiB
R
#' Run a plotting function and save the output as a PNG
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#'
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#' This function returns the name of the PNG file that it generates. In
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#' essence, it calls \code{png()}, then \code{func()}, then \code{dev.off()}.
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#' So \code{func} must be a function that will generate a plot when used this
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#' way.
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#'
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#' For output, it will try to use the following devices, in this order:
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#' quartz (via \code{\link[grDevices]{png}}), then \code{\link[Cairo]{CairoPNG}},
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#' and finally \code{\link[grDevices]{png}}. This is in order of quality of
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#' output. Notably, plain \code{png} output on Linux and Windows may not
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#' antialias some point shapes, resulting in poor quality output.
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#'
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#' In some cases, \code{Cairo()} provides output that looks worse than
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#' \code{png()}. To disable Cairo output for an app, use
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#' \code{options(shiny.usecairo=FALSE)}.
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#'
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#' @param func A function that generates a plot.
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#' @param filename The name of the output file. Defaults to a temp file with
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#' extension \code{.png}.
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#' @param width Width in pixels.
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#' @param height Height in pixels.
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#' @param res Resolution in pixels per inch. This value is passed to
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#' \code{\link{png}}. Note that this affects the resolution of PNG rendering in
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#' R; it won't change the actual ppi of the browser.
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#' @param ... Arguments to be passed through to \code{\link[grDevices]{png}}.
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#' These can be used to set the width, height, background color, etc.
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#'
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#' @export
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plotPNG <- function(func, filename=tempfile(fileext='.png'),
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width=400, height=400, res=72, ...) {
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# If quartz is available, use png() (which will default to quartz).
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# Otherwise, if the Cairo package is installed, use CairoPNG().
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# Finally, if neither quartz nor Cairo, use png().
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if (capabilities("aqua")) {
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pngfun <- png
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} else if (getOption('shiny.usecairo', TRUE) &&
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nchar(system.file(package = "Cairo"))) {
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pngfun <- Cairo::CairoPNG
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} else {
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pngfun <- png
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}
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pngfun(filename=filename, width=width, height=height, res=res, ...)
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dv <- dev.cur()
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tryCatch(shinyCallingHandlers(func()), finally = dev.off(dv))
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filename
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}
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