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<title>RGraph: HTML5 Javascript charts library - Retrieving a PNG of your graph</title>
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line = new RGraph.Line('cvs', [4,3,7,4,5,6,7,4,8,9]);
line.Set('chart.labels', ['Dez', 'Fliss','Geoff','Hoolio','John','Rich','Kev','Charles','Lou','Bob']);
line.Set('chart.hmargin', 5);
line.Set('chart.title', 'Retrieving a PNG of your chart (context menu)');
line.Set('chart.title.vpos', 0.5);
line.Set('chart.tickmarks', 'endcircle');
line.Set('chart.contextmenu', [
['Get PNG', RGraph.showPNG],
null,
['Cancel', function () {}]
]);
line.Set('chart.linewidth', 2);
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Retrieving a PNG of your chart
</div>
<h1>RGraph: <span>HTML5 Javascript charts library</span> - Retrieving a PNG of your chart</h1>
<script>
if (RGraph.isIE8()) {
document.write('<div style="background-color: #fee; border: 2px dashed red; padding: 5px"><b>Important</b><br /><br /> Internet Explorer 8 does not natively support the HTML5 canvas tag, so if you want to see the charts, you can either:<ul><li>Install <a href="http://code.google.com/chrome/chromeframe/">Google Chrome Frame</a></li><li>Use ExCanvas. This is provided in the RGraph Archive.</li><li>Use another browser entirely. Your choices are Firefox 3.5+, Chrome 2+, Safari 4+ or Opera 10.5+. </li></ul> <b>Note:</b> Internet Explorer 9 fully supports the canvas tag.</div>');
}
</script>
<style>
span#png_link {
position: absolute;
left: 535px;
top: 30px;
border: 1px black solid;
padding: 1px;
background-color: white;
cursor: pointer;
color: blue;
font-size: 10pt;
border: 2px solid gray;
border-radius: 5px;
font-weight: bold;
font-family: Arial;
}
</style>
<div style="position: relative">
<span id="png_link" onclick="RGraph.showPNG(document.getElementById('cvs'), event);">PNG</span>
<canvas id="cvs" width="600" height="250" style="float: left">[No canvas support]</canvas>
</div>
<p>
RGraph provides an easy way to get a PNG image of your chart. This allows you to
easily save the image locally to use in (for example) a document, spreadsheet or presentation.
</p>
<p>
Originally, the function was designed to be used with a context menu, so it is located in the <i>RGraph.common.context.js</i>.
Now though, you do not have to use the function with a context menu, and can instead pass in the canvas as the optional argument. There's an
example of its usage on the first <a href="../examples/radar.html">Radar example</a href>.
</p>
<br clear="all" />
<p>Include the context menu code:</p>
<pre class="code"><script src="../libraries/RGraph.common.context.js" ></script></pre>
<p>Add the context menu:</p>
<pre class="code">
myGraph.Set('chart.contextmenu', [
<span style="color: green">['Get PNG', RGraph.showPNG]</span>,
null,
['Cancel', function () {}]
]);</pre>
<h4>Using the function without a context menu</h4>
<p>
If you want to use the function with a piece of text (or an image) as the "link", optionally positioned over the canvas, you can pass
the canvas into the function as an argument, along with the event object.
</p>
<pre class="code">
<!-- This CSS positions the link over the top right of the canvas -->
<style>
span#png_link {
position: absolute;
left: 450px;
top: 30px;
border: 1px black solid;
padding: 1px;
background-color: #eee;
cursor: pointer;
}
</style>
<div style="position: relative">
<span id="png_link" <span style="color: green">onclick="RGraph.showPNG(myCanvas, event)"</span>>Get PNG</span>
<canvas id="cvs" width="600" height="250">[No canvas support]</canvas>
</div>
</pre>
<h4>Retrieving just the PNG URL</h4>
<p>
If you just want to get the PNG image URL - this can be done with the standard canvas function<i>.toDataUrl()</i>:
</p>
<pre class="code">var myUrl = myCanvas.toDataURL();</pre>
<p>
This gives you a data: URL which represents the canvas. Like <a href="javascript: location.href = line.canvas.toDataURL()">this</a>.
Because the URLs are very long there are some things that you should be aware of:
</p>
<ul>
<li>Google Chrome shows the image, but doesn't show the URL in the address bar</li>
<li>MSIE9 can show the image using the context menu API (top) method, but not the stand-alone image.</li>
</ul>
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