EVOLUTION-MANAGER

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<table width="100%" summary="page for renderImage {shiny}"><tr><td>renderImage {shiny}</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Image file output</h2>

<h3>Description</h3>

<p>Renders a reactive image that is suitable for assigning to an <code>output</code>
slot.
</p>

<h3>Usage</h3>

<pre>
renderImage(
  expr,
  env = parent.frame(),
  quoted = FALSE,
  deleteFile,
  outputArgs = list()
)
</pre>

<h3>Arguments</h3>

<table summary="R argblock">
<tr valign="top"><td><code>expr</code></td>
<td>
<p>An expression that returns a list.</p>
</td></tr>
<tr valign="top"><td><code>env</code></td>
<td>
<p>The environment in which to evaluate <code>expr</code>.</p>
</td></tr>
<tr valign="top"><td><code>quoted</code></td>
<td>
<p>Is <code>expr</code> a quoted expression (with <code>quote()</code>)? This
is useful if you want to save an expression in a variable.</p>
</td></tr>
<tr valign="top"><td><code>deleteFile</code></td>
<td>
<p>Should the file in <code>func()$src</code> be deleted after
it is sent to the client browser? Generally speaking, if the image is a
temp file generated within <code>func</code>, then this should be <code>TRUE</code>;
if the image is not a temp file, this should be <code>FALSE</code>. (For backward
compatibility reasons, if this argument is missing, a warning will be
emitted, and if the file is in the temp directory it will be deleted. In
the future, this warning will become an error.)</p>
</td></tr>
<tr valign="top"><td><code>outputArgs</code></td>
<td>
<p>A list of arguments to be passed through to the implicit
call to <code><a href="plotOutput.html">imageOutput()</a></code> when <code>renderImage</code> is used in an
interactive R Markdown document.</p>
</td></tr>
</table>

<h3>Details</h3>

<p>The expression <code>expr</code> must return a list containing the attributes for
the <code>img</code> object on the client web page. For the image to display,
properly, the list must have at least one entry, <code>src</code>, which is the
path to the image file. It may also useful to have a <code>contentType</code>
entry specifying the MIME type of the image. If one is not provided,
<code>renderImage</code> will try to autodetect the type, based on the file
extension.
</p>
<p>Other elements such as <code>width</code>, <code>height</code>, <code>class</code>, and
<code>alt</code>, can also be added to the list, and they will be used as
attributes in the <code>img</code> object.
</p>
<p>The corresponding HTML output tag should be <code>div</code> or <code>img</code> and have
the CSS class name <code>shiny-image-output</code>.
</p>

<p>For more details on how the images are generated, and how to control
the output, see <code><a href="plotPNG.html">plotPNG()</a></code>.
</p>

<h3>Examples</h3>

<pre>
## Only run examples in interactive R sessions
if (interactive()) {
options(device.ask.default = FALSE)

ui &lt;- fluidPage(
  sliderInput("n", "Number of observations", 2, 1000, 500),
  plotOutput("plot1"),
  plotOutput("plot2"),
  plotOutput("plot3")
)

server &lt;- function(input, output, session) {

# A plot of fixed size
  output$plot1 &lt;- renderImage({
    # A temp file to save the output. It will be deleted after renderImage
    # sends it, because deleteFile=TRUE.
    outfile &lt;- 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$plot2 &lt;- renderImage({
    # Read plot2's width and height. These are reactive values, so this
    # expression will re-run whenever these values change.
    width  &lt;- session$clientData$output_plot2_width
    height &lt;- session$clientData$output_plot2_height

# A temp file to save the output.
    outfile &lt;- 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$plot3 &lt;- renderImage({
    # When input$n is 1, filename is ./images/image1.jpeg
    filename &lt;- normalizePath(file.path('./images',
                              paste('image', input$n, '.jpeg', sep='')))

# Return a list containing the filename
    list(src = filename)
  }, deleteFile = FALSE)
}

shinyApp(ui, server)
}
</pre>

<hr /><div style="text-align: center;">[Package <em>shiny</em> version 1.5.0 <a href="00Index.html">Index</a>]</div>
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