HTML5 Canvas

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The HTML <canvas> element is used to draw graphics on a web page.

The graphic to the left is created with <canvas>. It shows four elements: a red rectangle, a gradient rectangle, a multicolor rectangle, and a multicolor text.

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What is HTML Canvas?

The HTML <canvas> element is used to draw graphics, on the fly, via scripting (usually JavaScript).

The <canvas> element is only a container for graphics. You must use a script to actually draw the graphics.

Canvas has several methods for drawing paths, boxes, circles, text, and adding images.

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Browser Support

The numbers in the table specify the first browser version that fully supports the <canvas> element.

Element
<canvas>	4.0	9.0	2.0	3.1	9.0

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Canvas Examples

A canvas is a rectangular area on an HTML page. By default, a canvas has no border and no content.

The markup looks like this:

<canvas id="myCanvas" width="200" height="100"></canvas>

Note: Always specify an id attribute (to be referred to in a script), and a width and height attribute to define the size of the canvas.

To add a border, use the style attribute:

Basic Canvas Example

<canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;"> </canvas>

Drawing with JavaScript

var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d");
ctx.fillStyle = "#FF0000";
ctx.fillRect(0,0,150,75);

Draw a Line

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.moveTo(0,0);
ctx.lineTo(200,100);
ctx.stroke();

Draw a Circle

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(95,50,40,0,2*Math.PI);
ctx.stroke();

Draw a Text

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.fillText("Hello World",10,50);

Stroke Text

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.strokeText("Hello World",10,50);

Draw Linear Gradient

var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d");
// Create gradient var grd = ctx.createLinearGradient(0,0,200,0);
grd.addColorStop(0,"red");
grd.addColorStop(1,"white");
// Fill with gradient ctx.fillStyle = grd;
ctx.fillRect(10,10,150,80);

Draw Circular Gradient

var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d");
// Create gradient var grd = ctx.createRadialGradient(75,50,5,90,60,100);
grd.addColorStop(0,"red");
grd.addColorStop(1,"white");
// Fill with gradient ctx.fillStyle = grd;
ctx.fillRect(10,10,150,80);

Draw Image

var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d"); var img = document.getElementById("scream");
ctx.drawImage(img,10,10);