Contents
HTML canvas Tutorial: Main Tips
- The
<canvas>element provides a fixed-size drawing space, allowing developers to create HTML graphics. However, graphic creation with the<canvas>is usually done by using JavaScript. - The created canvas has a default size of 300px x 150px.
- This HTML
<canvas>tutorial lists the possibilities of using this element: combining multiple photos, drawing graphs, generating animations.
Use and Purpose of canvas
This HTML <canvas> tutorial explains that <canvas> HTML defines an area of the webpage that becomes a space for rendering HTML graphics. Alternative HTML graphics element is <svg>.
Remember: it is necessary to use the closing </canvas> tag.
In the example below, we set the drawing space:
<canvas id="canvas01" width="400" height="300" style="border: 1px solid #eee;"></canvas>
Note: it is possible to manipulate the size of <canvas> by using HTML height and width attributes. They are the attributes this element accepts.
<canvas> in HTML allows developers to create rectangles. Different shapes have to be generated by adding together one or multiple paths. This HTML <canvas> tutorial explains how to draw rectangles with three functions:
fillRect(x, y, width, height)- creates a filled rectangle.strokeRect(x, y, width, height)- creates a rectangular outline.clearRect(x, y, width, height)- makes the rectangular transparent.
All three functions accept the same parameters. x and y indicate the position on the canvas of the top-left corner of the rectangle.
In this HTML <canvas> example, we create a filled rectangle:
<script>
function draw() {
var canvas = document.getElementById('canvas');
if (canvas.getContext) {
var ctx = canvas.getContext('2d');
ctx.fillRect(30, 30, 100, 100);
}
}
</script>The following HTML <canvas> example shows how to create a rectangular outline:
<script>
function draw() {
var canvas = document.getElementById('canvas');
if (canvas.getContext) {
var ctx = canvas.getContext('2d');
ctx.fillRect(30, 30, 100, 100);
ctx.clearRect(45, 45, 60, 60);
ctx.strokeRect(50, 50, 50, 50);
}
}
</script>Attributes for canvas
width
The width attribute sets width in pixels for a canvas element. Default is 300 pixels.
<canvas id="canvas02" width="400" style="border: 1px solid #eee;"></canvas>
height
The height sets height in pixels for a canvas element. Default is 150 pixels.
<canvas id="canvas03" height="300" style="border: 1px solid #eee;"></canvas>