We are going to use a ball for our animation studies, so let's first draw that ball onto the canvas. The following code will set us up.

The canvas rendering context provides two methods to render text:

There are a variety of demos and further explanations about canvas on these sites:

The content inside the <canvas> ... </canvas> tags can be used as a fallback for browsers which don't support canvas rendering. It's also very useful for assistive technology users (like screen readers) which can read and interpret the sub DOM in it. A good example at html5accessibility.com demonstrates how this can be done:

The ImageData object represents the underlying pixel data of an area of a canvas object. It contains the following read-only attributes:

If you would like to use the WebSocket API, it is useful if you have a server. In this article I will show you how to write one in C#. You can do it in any server-side language, but to keep things simple and more understandable, I chose Microsoft's language.

At first sight a <canvas> looks like the <img> element, with the only clear difference being that it doesn't have the src and alt attributes. Indeed, the <canvas> element has only two attributes, width and height. These are both optional and can also be set using DOM properties. When no width and height attributes are specified, the canvas will initially be 300 pixels wide and 150 pixels high. The element can be sized arbitrarily by CSS, but during rendering the image is scaled to fit its layout size: if the CSS sizing doesn't respect the ratio of the initial canvas, it will appear distorted.

Importing images into a canvas is basically a two step process:

The RTCDataChannel interface is a feature of the WebRTC API which lets you open a channel between two peers over which you may send and receive arbitrary data. The API is intentionally similar to the WebSocket API, so that the same programming model can be used for each.

This example shows you how to create a WebSocket API server using Oracle Java.

Although other server-side languages can be used to create a WebSocker server, this example uses Oracle Java to simplify the example code.