About
RGraph is a JavaScript charts library based on
HTML5 SVG and canvas. RGraph is mature (over 18 years
old) and has a wealth of features making it an ideal
choice to use for showing charts on your website.
Version 7.10 released
Version 7.10 (released in January 2026) is the
latest version of RGraph and contains various updates
to the code which you can see on
the changelog page. There's
also a big tidy up in terms of comments and a significant
change to the way that the internal code is referenced which
should lead to a performance improvement in effects and
animations.
New HTML datagrid
In the April 2025 (v6.21) release a new datagrid object
was added.
This makes it easy to add static or dynamic data
tables to your pages. It can be used whether you use the
canvas or SVG libraries or entirely standalone.
Download
Get the latest version of RGraph (version 7.10, 18th January 2026) from
the download page. You can read the changelog here. There's also older versions available,
minified files and links to cdnjs.com hosted libraries.
License
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.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
- The X coordinate at which to fetch data
- The Y coordinate at which to fetch data
- The width to fetch
- The height to fetch
An example
<script>
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);
}
</script>