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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/shinywrappers.R
\name{renderImage}
\alias{renderImage}
\title{Image file output}
\usage{
renderImage(expr, env = parent.frame(), quoted = FALSE, deleteFile = TRUE,
outputArgs = list())
}
\arguments{
\item{expr}{An expression that returns a list.}
\item{env}{The environment in which to evaluate \code{expr}.}
\item{quoted}{Is \code{expr} a quoted expression (with \code{quote()})? This
is useful if you want to save an expression in a variable.}
\item{deleteFile}{Should the file in \code{func()$src} be deleted after
it is sent to the client browser? Generally speaking, if the image is a
temp file generated within \code{func}, then this should be \code{TRUE};
if the image is not a temp file, this should be \code{FALSE}.}
\item{outputArgs}{A list of arguments to be passed through to the implicit
call to \code{\link{imageOutput}} when \code{renderImage} is used in an
interactive R Markdown document.}
}
\description{
Renders a reactive image that is suitable for assigning to an \code{output}
slot.
}
\details{
The expression \code{expr} must return a list containing the attributes for
the \code{img} object on the client web page. For the image to display,
properly, the list must have at least one entry, \code{src}, which is the
path to the image file. It may also useful to have a \code{contentType}
entry specifying the MIME type of the image. If one is not provided,
\code{renderImage} will try to autodetect the type, based on the file
extension.
Other elements such as \code{width}, \code{height}, \code{class}, and
\code{alt}, can also be added to the list, and they will be used as
attributes in the \code{img} object.
The corresponding HTML output tag should be \code{div} or \code{img} and have
the CSS class name \code{shiny-image-output}.
}
\examples{
## Only run examples in interactive R sessions
if (interactive()) {
options(device.ask.default = FALSE)
ui <- fluidPage(
sliderInput("n", "Number of observations", 2, 1000, 500),
plotOutput("plot1"),
plotOutput("plot2"),
plotOutput("plot3")
)
server <- function(input, output, session) {
# A plot of fixed size
output$plot1 <- renderImage({
# A temp file to save the output. It will be deleted after renderImage
# sends it, because deleteFile=TRUE.
outfile <- tempfile(fileext='.png')
# Generate a png
png(outfile, width=400, height=400)
hist(rnorm(input$n))
dev.off()
# Return a list
list(src = outfile,
alt = "This is alternate text")
}, deleteFile = TRUE)
# A dynamically-sized plot
output$plot2 <- renderImage({
# Read plot2's width and height. These are reactive values, so this
# expression will re-run whenever these values change.
width <- session$clientData$output_plot2_width
height <- session$clientData$output_plot2_height
# A temp file to save the output.
outfile <- tempfile(fileext='.png')
png(outfile, width=width, height=height)
hist(rnorm(input$n))
dev.off()
# Return a list containing the filename
list(src = outfile,
width = width,
height = height,
alt = "This is alternate text")
}, deleteFile = TRUE)
# Send a pre-rendered image, and don't delete the image after sending it
# NOTE: For this example to work, it would require files in a subdirectory
# named images/
output$plot3 <- renderImage({
# When input$n is 1, filename is ./images/image1.jpeg
filename <- normalizePath(file.path('./images',
paste('image', input$n, '.jpeg', sep='')))
# Return a list containing the filename
list(src = filename)
}, deleteFile = FALSE)
}
shinyApp(ui, server)
}
}
\seealso{
For more details on how the images are generated, and how to control
the output, see \code{\link{plotPNG}}.
}
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