.net Powerful JavaScript charts
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 use for showing charts on your website.

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Get the latest version of RGraph (version 6.18, 1st June 2024) from the download page. You can read the changelog here. There's also older versions available, minified files and links to 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 (£129) commercial license available.

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The getImageData function

The getImageData function allows to retrieve an ImageData object from your canvas. This allows you to manipulate it as you wish and then you can add it back onto the canvas with the putImageData function (reference page for the putImageData function). You can pass it the X/Y/W/H that you want to fetch as arguments.

Arguments to the function

An example

    window.onload = function ()
        var canvas = document.getElementById('cvs');
        var context = canvas.getContext('2d');
        // Fetches image data from the canvas
        var imgData = context.getImageData(0,0,600,250);

See also