RGraph is a JavaScript charts library based on HTML5 SVG and canvas. RGraph is mature (over 15 years old) and has a wealth of features making it an ideal choice to show charts on your website.

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Get the latest version of RGraph (version 6.17) from the download page. There's also older versions available, minified files and links to cdnjs.com hosted libraries.

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RGraph can be used for free under the GPL or if that doesn't suit your situation there's an inexpensive (£99) commercial license available.

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The save function

The save function saves the state of the canvas. It is most commonly used when using the clip function - so that you can save the state of the canvas, clip it, do some drawing whilst the canvas is clipped and then restore the canvas to as it was before the canvas was clipped, allowing you to draw freely again.

An example of the save function can be found in the page explaining the clip function .

What is saved by the save function?

The following settings are saved by the save function (and also are subsequently restored when you call restore):

An example

Here the canvas is first saved, then clipped to a small rectangle (but not stroked or filled). Then a bigger rectangle is drawn - though because the canvas is clipped the only thing that is seen is the clipped area. Then, using the restore function, the canvas is returned to the state it was in before it was clipped.

This demonstrates how the canvas state can be saved and then subsequently restored.

    window.onload = function ()
        var canvas  = document.getElementById("cvs");
        var context = canvas.getContext('2d');