HTML5 Canvas

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

What is Canvas?

The HTML5 canvas element uses JavaScript to draw graphics on a web page.

A canvas is a rectangular area, and you control every pixel of it.

The canvas element has several methods for drawing paths, boxes, circles, characters, and adding images.

Add a canvas element to the HTML5 page.

Specify the id, width, and height of the element:

The canvas element has no drawing abilities of its own. All drawing must be done inside a JavaScript:

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JavaScript uses the id to find the canvas element:

var c=document.getElementById("myCanvas");

Then, create a context object:

var cxt=c.getContext("2d");

The getContext("2d") object is a built-in HTML5 object, with many methods to draw paths, boxes, circles, characters, images and more.

The next two lines draws a red rectangle:

cxt.fillStyle="#FF0000";
cxt.fillRect(0,0,150,75);

The fillStyle method makes it red, and the fillRect method specifies the shape, position, and size.

The fillRect method above had the parameters (0,0,150,75).

This means: Draw a 150x75 rectangle on the canvas, starting at the top left corner (0,0).

The canvas' X and Y coordinates are used to position drawings on the canvas.

Mouse over the rectangle below to see the coordinates:

Below are more examples of drawing on the canvas element:

Draw a line by specifying where to start, and where to stop:

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Draw a circle by specifying the size, color, and position:

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Draw a gradient background with the colors you specify:

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Put an image on the canvas:

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