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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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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Get the latest version of RGraph (version 6.16) from the download page. There's also older versions available, minified files and links to cdnjs.com hosted libraries.

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The clip function

The clip function can be used when you want to restrict any drawing to a particular area of the canvas. You draw a path without stroking or filling it, call the clip function and then any further drawing will be restricted to that area. There is (currently) no resetClip function so you need to save the state of the canvas before you clip it and then restore it when you're finished - as the example shows.

In the latest canvas specification you can also give the function a Path2D object to clip to which specifies the clipping area. This isn't implemented in most browsers yet though.

Arguments to the function

An example

    window.onload = function ()
        var canvas  = document.getElementById("cvs");
        var context = canvas.getContext('2d');
            // Because the canvas is currently clipped only part of the rectangle is drawn on the canvas