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103 lines
3.1 KiB
R
103 lines
3.1 KiB
R
\name{renderImage}
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\alias{renderImage}
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\title{Image file output}
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\usage{
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renderImage(expr, env = parent.frame(), quoted = FALSE,
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deleteFile = TRUE)
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}
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\arguments{
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\item{expr}{An expression that returns a list.}
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\item{env}{The environment in which to evaluate
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\code{expr}.}
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\item{quoted}{Is \code{expr} a quoted expression (with
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\code{quote()})? This is useful if you want to save an
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expression in a variable.}
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\item{deleteFile}{Should the file in \code{func()$src} be
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deleted after it is sent to the client browser? Genrrally
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speaking, if the image is a temp file generated within
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\code{func}, then this should be \code{TRUE}; if the
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image is not a temp file, this should be \code{FALSE}.}
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}
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\description{
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Renders a reactive image that is suitable for assigning
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to an \code{output} slot.
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}
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\details{
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The expression \code{expr} must return a list containing
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the attributes for the \code{img} object on the client
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web page. For the image to display, properly, the list
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must have at least one entry, \code{src}, which is the
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path to the image file. It may also useful to have a
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\code{contentType} entry specifying the MIME type of the
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image. If one is not provided, \code{renderImage} will
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try to autodetect the type, based on the file extension.
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Other elements such as \code{width}, \code{height},
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\code{class}, and \code{alt}, can also be added to the
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list, and they will be used as attributes in the
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\code{img} object.
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The corresponding HTML output tag should be \code{div} or
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\code{img} and have the CSS class name
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\code{shiny-image-output}.
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}
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\examples{
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\dontrun{
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shinyServer(function(input, output, clientData) {
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# A plot of fixed size
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output$plot1 <- renderImage({
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# A temp file to save the output. It will be deleted after renderImage
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# sends it, because deleteFile=TRUE.
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outfile <- tempfile(fileext='.png')
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# Generate a png
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png(outfile, width=400, height=400)
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hist(rnorm(input$n))
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dev.off()
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# Return a list
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list(src = outfile,
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alt = "This is alternate text")
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}, deleteFile = TRUE)
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# A dynamically-sized plot
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output$plot2 <- renderImage({
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# Read plot2's width and height. These are reactive values, so this
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# expression will re-run whenever these values change.
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width <- clientData$output_plot2_width
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height <- clientData$output_plot2_height
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# A temp file to save the output.
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outfile <- tempfile(fileext='.png')
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png(outfile, width=width, height=height)
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hist(rnorm(input$obs))
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dev.off()
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# Return a list containing the filename
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list(src = outfile,
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width = width,
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height = height,
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alt = "This is alternate text")
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}, deleteFile = TRUE)
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# Send a pre-rendered image, and don't delete the image after sending it
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output$plot3 <- renderImage({
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# When input$n is 1, filename is ./images/image1.jpeg
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filename <- normalizePath(file.path('./images',
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paste('image', input$n, '.jpeg', sep='')))
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# Return a list containing the filename
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list(src = filename)
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}, deleteFile = FALSE)
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})
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}
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}
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