HTMLCanvas Graphics
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.
What is HTML Canvas?
The HTML<canvas> element is used to draw graphics, on the fly, via JavaScript.
The<canvas> element is only a container for graphics. You must use JavaScript to actually draw the graphics.
Canvas has several methods for drawing paths, boxes, circles, text, and adding images.
Canvas is supported by all major browsers.
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:
Note: Always specify anid attribute (to be referred to in a script), and awidth andheight attribute to define the size of the canvas. To add a border, use thestyle attribute.
Here is an example of a basic, empty canvas:
Add a JavaScript
After creating the rectangular canvas area, you must add a JavaScript to do the drawing.
Here are some examples:
Draw a Line
Example
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.moveTo(0, 0);
ctx.lineTo(200, 100);
ctx.stroke();
</script>
Draw a Circle
Example
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(95, 50, 40, 0, 2 * Math.PI);
ctx.stroke();
</script>
Draw a Text
Example
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.fillText("Hello World", 10, 50);
</script>
Stroke Text
Example
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.strokeText("Hello World", 10, 50);
</script>
Draw Linear Gradient
Example
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);
</script>
Draw Circular Gradient
Example
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);
</script>
Draw Image
Example
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = document.getElementById("scream");
ctx.drawImage(img, 10, 10);
</script>
HTML Canvas Tutorial
To learn more about<canvas>, please read ourHTML Canvas Tutorial.
