About RGraph and me

About the RGraph software

RGraph is a modern JavaScript based charts and graphs library for modern websites. It aims to be the best Open Source charting library you can get your hands on and with the number of different types of chart having grown to 50-60, using both HTML5 canvas and SVG, RGraph has a wide appeal and can represent many types of data quickly and efficiently.

RGraph is totally free to use, being available under the MIT license. You don't even have send me a Christmas card (it would be nice though...)! Any donations are appreciated - (you can find more on the donations page).

RGraph is suitable for all websites with charts being rendered using JavaScript, SVG and canvas. The size of the JavaScript files and the code to make a chart is small and can be further reduced with minification and compression and so offers significant speed boosts to websites.

With Google putting an ever-increasing emphasis on page speed and it affecting search ranking now using a Javascript based charts library can offer tangible benefits for your website and your bottom line!

About the author

You can read about me on this page.

About the SVG and canvas tags

<CANVAS> and <SVG>are new HTML tags which are part of the HTML5 standard. Canvas allows bitmap drawing which is controlled using JavaScript (ie you draw on the <canvas> using JavaScript), and is what the canvas based RGraph libraries use to draw the charts. You could liken it to a piece of paper which is part of your page, on to which you can draw. Because you use JavaScript to draw on the canvas it becomes part of your page and allows interaction very easily. SVG on the other hand has a DOM just like the HTML document and each element (lines, circles rectangles etc) can be referenced directly like HTML elements can in your document.

The <canvas> tag uses a "fire and forget" drawing methodology - there is no DOM that's maintained, so if you want to alter something you'll probably (but not necessarily) have to redraw the entire canvas. The lack of a DOM means that canvas is fast to draw on and very responsive - important when you're providing interactive or animated charts to your users.

SVG uses a drawing methodology that is similar to your HTML page - where each element is an object in a DOM that can be referenced. When you update the properties of these objects the scene is converted to a bitmap and displayed automatically for you.

Other uses for the <svg> and <canvas> include providing a control panel to your users and using it to create games. You should note though that when it comes to accessibility then a more traditional HTML based interface that uses <canvas> for certain elements and SVG for others may be preferable.

History of the tags

The canvas tag was originally introduced by Apple in 2004 for use in Mac OS X WebKit to power dashboard applications and their Safari web browser. Since then it has been adopted by Mozilla and Opera and now the W3C has adopted it in the upcoming HTML5 specification. It's now supported by all modern web browsers including modern versions of MSIE (starting from version 9).

The SVG tag is is a bit like canvas but instead of being a bitmap drawing surface it's vector based and has a structure more like a HTML document.

SVG is XML based, an open standard and has been in development by the W3C since 1999. All modern browsers have some degree of support for SVG. It's currently at version 1.1 with version 2 on its way which will use CSS integration more.

Here's an example of both tags:

CANVAS

<canvas width="200" height="120" id="cvs" style="border: 1px solid gray"></canvas>

<script>
    // Get hold of references to the canvas tag and the 2D drawing context
    canvas  = document.getElementById('cvs');
    context = canvas.getContext('2d');
    
    // Draw the read square
    context.beginPath();
    context.rect(10,10,50,50);
    context.fillStyle = 'red';
    context.fill();

    // Draw the blue circle
    context.beginPath();
    context.arc(130,60,50,0, 2 * Math.PI * 2, false);
    context.fillStyle = 'blue';
    context.fill();
</script>

SVG

<svg  width="200" height="120" version="1.1">
    
    <!-- The red rectangle -->
    <rect x="10" y="10" width="50" height="50" fill="red"></rect>
    
    <-- The blue circle -->
    <circle cx="130" cy="60" r="50" fill="blue"></circle>
</svg>

The output of the SVG example is more or less the same as the canvas version but the difference comes in how the two are created. As you can see the SVG code required is far smaller even in this small example.

About HTML5 charts

What makes the canvas and SVG tags good for producing charts is the ability to interact seamlessly with both the user and the rest of the page. The charts that RGraph produces are all made from JavaScript so output from other JavaScript code can be used with ease.

Modern browsers that support HTML5 also support canvas and SVG, including Internet Explorer 9 and upwards (with version 9 you may need to use the HTML5 doctype, but not from version 10).

About canvas text

The canvas tag, despite being very versatile, does not render text very well. As far as the quality is concerned it gets worse at higher zoom levels. It's also not "real" text - so you can't select it or copy it to your clipboard and paste it elsewhere.

So for this reason RGraph has an accessible text option. What this does is wrap the canvas in a div tag and use a combination of relative and absolute positioning to position <span> tags over the canvas that contain the relevant text. Its not perfect for every situation and there's a list (that's not comprehensive) of caveats on that page.

It does make text look much better though, and as less is being rendered on to the canvas it can make a noticable improvement in performance - particularly in canvas based effects and animations.

Contributions

Thanks go to:

 

Contact information and support

If you have a support question you can send me a message using the form on this page.

Connect with RGraph on Facebook RGraph on Facebook
You can connect with RGraph on Facebook by going to the RGraph Facebook profile .


Connect with RGraph on RGraph on Twitter
You can connect with RGraph on Twitter by going to the RGraph Twitter profile. Posts on Twitter sometimes point to larger articles on (for example) the Facebook page or the RGraph blog.