HTML 5 <canvas> Tag

<!DOCTYPE html>
<html>
<head>
<script type="application/x-javascript">
function displayCanvas()
	{
      var canvas = document.getElementById("myCanvas");
      if (canvas.getContext) {
        var ctx = canvas.getContext("2d");

        ctx.fillStyle = "rgb(200,0,0)";
        ctx.fillRect (0, 0, 150, 75);

        ctx.fillStyle = "rgba(0, 0, 200, 0.5)";
        ctx.fillRect (40, 30, 125, 75);

        ctx.fillStyle = "rgb(0,0,150)";
        ctx.strokeRect (20, 20, 50, 100); 
      }
    }
</script>
</head>
<body onload="displayCanvas();">
<canvas id="myCanvas" width="300" height="200">Your browser does not support the canvas tag. At the time of writing, Firefox, Opera, and Chrome support this tag.</p> 
<p>Here's an <a href="/pix/html_5/tags/html_canvas_tag.gif">image of what it's supposed to look like</a>.</canvas>
</body>
</html>

The HTML <canvas> tag is used for creating graphics on the fly. It can be used for rendering graphs, game graphics, or other visual images.

To draw on the canvas, the <canvas> tag is used in conjunction with the getContext(contextId) method.

Any content between the <canvas></canvas> tags is "fallback content"- meaning, it will be displayed only if the canvas cannot be displayed.

The <canvas> tag was introduced in HTML 5.

Attributes

HTML tags can contain one or more attributes. Attributes are added to a tag to provide the browser with more information about how the tag should appear or behave. Attributes consist of a name and a value separated by an equals (=) sign, with the value surrounded by double quotes. Here's an example, style="color:black;".

There are 3 kinds of attributes that you can add to your HTML tags: Element-specific, global, and event handler content attributes.

The attributes that you can add to this tag are listed below.

Element-Specific Attributes

The following table shows the attributes that are specific to this tag/element.

Attribute	Description
width	Specifies the canvas width in pixels. The default value is 300. Possible values: [Non-negative integer] (for example, 300)
height	Specifies the canvas height in pixels. The default value is 150. Possible values: [Non-negative integer] (for example, 150)

Attribute

Description

width

Specifies the canvas width in pixels. The default value is 300.

Possible values:

[Non-negative integer] (for example, 300)

height

Specifies the canvas height in pixels. The default value is 150.

Possible values:

[Non-negative integer] (for example, 150)

Global Attributes

The following attributes are standard across all HTML 5 tags.

accesskey
class
contenteditable
contextmenu
dir
draggable
dropzone
hidden
id
itemid
itemprop
itemref
itemscope
itemtype
lang
spellcheck
style
tabindex
title
translate

For a full explanation of these attributes, see HTML 5 global attributes.

Event Handler Content Attributes

Event handler content attributes enable you to invoke a script from within your HTML. The script is invoked when a certain "event" occurs. Each event handler content attribute deals with a different event.

Here are the standard HTML 5 event handler content attributes.

onabort
oncancel
onblur
oncanplay
oncanplaythrough
onchange
onclick
oncontextmenu
ondblclick
ondrag
ondragend
ondragenter
ondragexit
ondragleave
ondragover
ondragstart
ondrop
ondurationchange
onemptied
onended
onerror
onfocus
onformchange
onforminput
oninput
oninvalid
onkeydown
onkeypress
onkeyup
onload
onloadeddata
onloadedmetadata
onloadstart
onmousedown
onmousemove
onmouseout
onmouseover
onmouseup
onmousewheel
onpause
onplay
onplaying
onprogress
onratechange
onreadystatechange
onscroll
onseeked
onseeking
onselect
onshow
onstalled
onsubmit
onsuspend
ontimeupdate
onvolumechange
onwaiting

For a full explanation of these attributes, see HTML 5 event handler content attributes.