About
RGraph is a JavaScript charts library based on
HTML5 SVG and canvas. RGraph is mature (over 17 years
old) and has a wealth of features making it an ideal
choice to use for showing charts on your website.
New datagrid in v6.21
In version 6.21 a new datagrid object has been 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 6.21, 10th April 2025) 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>