A brief guide to the basic features of HTML Canvas

In this article, we are going to show you how to use the <canvas> element as outlined in Skilled.co's Canvas cheat sheet. You will have a basic understanding of how to write script using this element by the end of this article.

Keep in mind that the skills outlined in this brief tutorial are only the barest skills needed to use the <canvas> element. Even so, they are among the most critical skills and commands that you will need throughout your entire experience with Canvas. Learning the basics will provide the designer with a solid foundation from which to build more extensive skills with Canvas as time goes on. So, we will now begin with our example <canvas> element and start down the rabbit hole.

As an example, we'll draw a box. This box will be surround by a line of red, a border. We'll make the box yellow. Inside the box, we'll write the word "hello" and colour the word red. This exercise will utilize all the basic commands a designer would need to sufficiently use Canvas. When working with Canvas, there will always be two parts of a code: One is the <canvas> element command, and the other is the actual JavaScript.

The Canvas element part is structured:

<canvas> ... </canvas>

Inside this command, you will include identification:

<canvas> canvas id="Example" ... </canvas>

Be sure to surround the element identification with quotes. Then, you will need to include height and width parameters after the identification. The final product should look like this:

<canvas> canvas id="Example" width=150 height=60> </canvas>

If your browser is out of date, you will be prompted with a "fallback" message that tells you to update your browser first.

For the JavaScript script segment, we will place it directly beneath the <canvas> element command for tutorials sake, but it is usually moved into a separate JavaScript ( .js ) file. In this example, we'll place the script in a <script> ... </script> tag.

This part of the script is broken up into three steps for three separate commands:

First, we need to load the HTML <canvas> tag. We called it "Canvas" and accomplished the loading process in our example by saving it within a variable:

[var canvas = document.getElementById('ExampleCanvas')]

The image does not directly generate in the HTMLCanvasElement. It generates in its context, which is an internal CanvasRenderingContext2D object. We saved the object in another variable and named it:

[var context = canvas.getContext('2d').]

We are ready to draw and create! This is easily accomplished by modifying properties like color by calling methods:

context.fillStyle = 'red';

The above method will make the object red.

context.fillRect (0,0,150,60);

The above method will generate [.fillRect (0,0,150,60);]

context.fillStyle = 'yellow';

The above method will make the object yellow.

context.fillRect (5,5,140,50);

The above method will create [context.fillRect (5,5,140,50)]

context.fillStyle = 'red';

The above method will return the object back to red.

context.font = '40pt Arial';

The above method will specify the font.

context.fillText ('Hello',10,50);

The above method will write the text, "Hello."

The picture is generated in the context and describes all of its needs for execution. This is the bulk of using the <canvas> element. These basic steps should give you a basic understanding and a solid foundation to work from while using Canvas to create interesting designs.

Happy coding!

Editor’s note: There are several other commands that you can experiment with in the cheat sheet, which you can find here.

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13 Apr 2017, 3:02 p.m.