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<!-- Generated by pkgdown: do not edit by hand --><html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Image file output — renderImage • shiny</title><!-- jquery --><script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js" integrity="sha512-v2CJ7UaYy4JwqLDIrZUI/4hqeoQieOmAZNXBeQyjo21dadnwR+8ZaIJVT8EE2iyI61OV8e6M8PP2/4hpQINQ/g==" crossorigin="anonymous" referrerpolicy="no-referrer"></script><!-- Bootstrap --><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha256-bZLfwXAP04zRMK2BjiO8iu9pf4FbLqX6zitd+tIvLhE=" crossorigin="anonymous"><script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/js/bootstrap.min.js" integrity="sha256-nuL8/2cJ5NDSSwnKD8VqreErSWHtnEP9E7AySL+1ev4=" crossorigin="anonymous"></script><!-- bootstrap-toc --><link rel="stylesheet" href="../bootstrap-toc.css"><script src="../bootstrap-toc.js"></script><!-- Font Awesome icons --><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/all.min.css" integrity="sha256-mmgLkCYLUQbXn0B1SRqzHar6dCnv9oZFPEC1g1cwlkk=" crossorigin="anonymous"><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/v4-shims.min.css" integrity="sha256-wZjR52fzng1pJHwx4aV2AO3yyTOXrcDW7jBpJtTwVxw=" crossorigin="anonymous"><!-- clipboard.js --><script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.6/clipboard.min.js" integrity="sha256-inc5kl9MA1hkeYUt+EC3BhlIgyp/2jDIyBLS6k3UxPI=" crossorigin="anonymous"></script><!-- headroom.js --><script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/headroom.min.js" integrity="sha256-AsUX4SJE1+yuDu5+mAVzJbuYNPHj/WroHuZ8Ir/CkE0=" crossorigin="anonymous"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/jQuery.headroom.min.js" integrity="sha256-ZX/yNShbjqsohH1k95liqY9Gd8uOiE1S4vZc+9KQ1K4=" crossorigin="anonymous"></script><!-- pkgdown --><link href="../pkgdown.css" rel="stylesheet"><script src="../pkgdown.js"></script><meta property="og:title" content="Image file output — renderImage"><meta property="og:description" content="Renders a reactive image that is suitable for assigning to an output
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<h1>Image file output</h1>
<small class="dont-index">Source: <a href="https://github.com/rstudio/shiny/blob/main/R/shinywrappers.R" class="external-link"><code>R/shinywrappers.R</code></a></small>
<div class="hidden name"><code>renderImage.Rd</code></div>
</div>
<div class="ref-description">
<p>Renders a reactive image that is suitable for assigning to an <code>output</code>
slot.</p>
</div>
<div id="ref-usage">
<div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">renderImage</span><span class="op">(</span></span>
<span> <span class="va">expr</span>,</span>
<span> env <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/sys.parent.html" class="external-link">parent.frame</a></span><span class="op">(</span><span class="op">)</span>,</span>
<span> quoted <span class="op">=</span> <span class="cn">FALSE</span>,</span>
<span> <span class="va">deleteFile</span>,</span>
<span> outputArgs <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/list.html" class="external-link">list</a></span><span class="op">(</span><span class="op">)</span></span>
<span><span class="op">)</span></span></code></pre></div>
</div>
<div id="arguments">
<h2>Arguments</h2>
<dl><dt id="arg-expr">expr<a class="anchor" aria-label="anchor" href="#arg-expr"></a></dt>
<dd><p>An expression that returns a list.</p></dd>
<dt id="arg-env">env<a class="anchor" aria-label="anchor" href="#arg-env"></a></dt>
<dd><p>The parent environment for the reactive expression. By default,
this is the calling environment, the same as when defining an ordinary
non-reactive expression. If <code>expr</code> is a quosure and <code>quoted</code> is <code>TRUE</code>,
then <code>env</code> is ignored.</p></dd>
<dt id="arg-quoted">quoted<a class="anchor" aria-label="anchor" href="#arg-quoted"></a></dt>
<dd><p>If it is <code>TRUE</code>, then the <code><a href="https://rdrr.io/r/base/substitute.html" class="external-link">quote()</a></code>ed value of <code>expr</code>
will be used when <code>expr</code> is evaluated. If <code>expr</code> is a quosure and you
would like to use its expression as a value for <code>expr</code>, then you must set
<code>quoted</code> to <code>TRUE</code>.</p></dd>
<dt id="arg-deletefile">deleteFile<a class="anchor" aria-label="anchor" href="#arg-deletefile"></a></dt>
<dd><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></dd>
<dt id="arg-outputargs">outputArgs<a class="anchor" aria-label="anchor" href="#arg-outputargs"></a></dt>
<dd><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></dd>
</dl></div>
<div id="details">
<h2>Details</h2>
<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>
</div>
<div id="see-also">
<h2>See also</h2>
<div class="dont-index">
<ul><li><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></li>
<li><p>Use <code><a href="outputOptions.html">outputOptions()</a></code> to set general output options for an image output.</p></li>
</ul></div>
</div>
<div id="ref-examples">
<h2>Examples</h2>
<div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="co">## Only run examples in interactive R sessions</span></span></span>
<span class="r-in"><span><span class="kw">if</span> <span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/interactive.html" class="external-link">interactive</a></span><span class="op">(</span><span class="op">)</span><span class="op">)</span> <span class="op">{</span></span></span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/base/options.html" class="external-link">options</a></span><span class="op">(</span>device.ask.default <span class="op">=</span> <span class="cn">FALSE</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="va">ui</span> <span class="op">&lt;-</span> <span class="fu"><a href="fluidPage.html">fluidPage</a></span><span class="op">(</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="sliderInput.html">sliderInput</a></span><span class="op">(</span><span class="st">"n"</span>, <span class="st">"Number of observations"</span>, <span class="fl">2</span>, <span class="fl">1000</span>, <span class="fl">500</span><span class="op">)</span>,</span></span>
<span class="r-in"><span> <span class="fu"><a href="plotOutput.html">plotOutput</a></span><span class="op">(</span><span class="st">"plot1"</span><span class="op">)</span>,</span></span>
<span class="r-in"><span> <span class="fu"><a href="plotOutput.html">plotOutput</a></span><span class="op">(</span><span class="st">"plot2"</span><span class="op">)</span>,</span></span>
<span class="r-in"><span> <span class="fu"><a href="plotOutput.html">plotOutput</a></span><span class="op">(</span><span class="st">"plot3"</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="va">server</span> <span class="op">&lt;-</span> <span class="kw">function</span><span class="op">(</span><span class="va">input</span>, <span class="va">output</span>, <span class="va">session</span><span class="op">)</span> <span class="op">{</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># A plot of fixed size</span></span></span>
<span class="r-in"><span> <span class="va">output</span><span class="op">$</span><span class="va">plot1</span> <span class="op">&lt;-</span> <span class="fu">renderImage</span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="co"># A temp file to save the output. It will be deleted after renderImage</span></span></span>
<span class="r-in"><span> <span class="co"># sends it, because deleteFile=TRUE.</span></span></span>
<span class="r-in"><span> <span class="va">outfile</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/tempfile.html" class="external-link">tempfile</a></span><span class="op">(</span>fileext<span class="op">=</span><span class="st">'.png'</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># Generate a png</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/grDevices/png.html" class="external-link">png</a></span><span class="op">(</span><span class="va">outfile</span>, width<span class="op">=</span><span class="fl">400</span>, height<span class="op">=</span><span class="fl">400</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/graphics/hist.html" class="external-link">hist</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/stats/Normal.html" class="external-link">rnorm</a></span><span class="op">(</span><span class="va">input</span><span class="op">$</span><span class="va">n</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/grDevices/dev.html" class="external-link">dev.off</a></span><span class="op">(</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># Return a list</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/list.html" class="external-link">list</a></span><span class="op">(</span>src <span class="op">=</span> <span class="va">outfile</span>,</span></span>
<span class="r-in"><span> alt <span class="op">=</span> <span class="st">"This is alternate text"</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="op">}</span>, deleteFile <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># A dynamically-sized plot</span></span></span>
<span class="r-in"><span> <span class="va">output</span><span class="op">$</span><span class="va">plot2</span> <span class="op">&lt;-</span> <span class="fu">renderImage</span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="co"># Read plot2's width and height. These are reactive values, so this</span></span></span>
<span class="r-in"><span> <span class="co"># expression will re-run whenever these values change.</span></span></span>
<span class="r-in"><span> <span class="va">width</span> <span class="op">&lt;-</span> <span class="va">session</span><span class="op">$</span><span class="va">clientData</span><span class="op">$</span><span class="va">output_plot2_width</span></span></span>
<span class="r-in"><span> <span class="va">height</span> <span class="op">&lt;-</span> <span class="va">session</span><span class="op">$</span><span class="va">clientData</span><span class="op">$</span><span class="va">output_plot2_height</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># A temp file to save the output.</span></span></span>
<span class="r-in"><span> <span class="va">outfile</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/tempfile.html" class="external-link">tempfile</a></span><span class="op">(</span>fileext<span class="op">=</span><span class="st">'.png'</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/grDevices/png.html" class="external-link">png</a></span><span class="op">(</span><span class="va">outfile</span>, width<span class="op">=</span><span class="va">width</span>, height<span class="op">=</span><span class="va">height</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/graphics/hist.html" class="external-link">hist</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/stats/Normal.html" class="external-link">rnorm</a></span><span class="op">(</span><span class="va">input</span><span class="op">$</span><span class="va">n</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/grDevices/dev.html" class="external-link">dev.off</a></span><span class="op">(</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># Return a list containing the filename</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/list.html" class="external-link">list</a></span><span class="op">(</span>src <span class="op">=</span> <span class="va">outfile</span>,</span></span>
<span class="r-in"><span> width <span class="op">=</span> <span class="va">width</span>,</span></span>
<span class="r-in"><span> height <span class="op">=</span> <span class="va">height</span>,</span></span>
<span class="r-in"><span> alt <span class="op">=</span> <span class="st">"This is alternate text"</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="op">}</span>, deleteFile <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># Send a pre-rendered image, and don't delete the image after sending it</span></span></span>
<span class="r-in"><span> <span class="co"># NOTE: For this example to work, it would require files in a subdirectory</span></span></span>
<span class="r-in"><span> <span class="co"># named images/</span></span></span>
<span class="r-in"><span> <span class="va">output</span><span class="op">$</span><span class="va">plot3</span> <span class="op">&lt;-</span> <span class="fu">renderImage</span><span class="op">(</span><span class="op">{</span></span></span>
<span class="r-in"><span> <span class="co"># When input$n is 1, filename is ./images/image1.jpeg</span></span></span>
<span class="r-in"><span> <span class="va">filename</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/normalizePath.html" class="external-link">normalizePath</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/file.path.html" class="external-link">file.path</a></span><span class="op">(</span><span class="st">'./images'</span>,</span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/paste.html" class="external-link">paste</a></span><span class="op">(</span><span class="st">'image'</span>, <span class="va">input</span><span class="op">$</span><span class="va">n</span>, <span class="st">'.jpeg'</span>, sep<span class="op">=</span><span class="st">''</span><span class="op">)</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span> <span class="co"># Return a list containing the filename</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/base/list.html" class="external-link">list</a></span><span class="op">(</span>src <span class="op">=</span> <span class="va">filename</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="op">}</span>, deleteFile <span class="op">=</span> <span class="cn">FALSE</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="op">}</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="fu"><a href="shinyApp.html">shinyApp</a></span><span class="op">(</span><span class="va">ui</span>, <span class="va">server</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="op">}</span></span></span>
</code></pre></div>
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