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HTML canvas globalAlpha Property

Canvas Object Reference Canvas Object

Example

First, draw a red rectangle, then set transparency (globalAlpha) to 0.5, and then draw a blue and a green rectangle:

YourbrowserdoesnotsupporttheHTML5canvastag.

JavaScript:

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.fillStyle="red";
ctx.fillRect(20,20,75,50);
// Turn transparency on
ctx.globalAlpha=0.2;
ctx.fillStyle="blue";
ctx.fillRect(50,50,75,50);
ctx.fillStyle="green";
ctx.fillRect(80,80,75,50);

Try it yourself »

Browser Support

Internet Explorer Firefox Opera Google Chrome Safari

Internet Explorer 9, Firefox, Opera, Chrome, and Safari support the globalAlpha property.

Note: Internet Explorer 8 and earlier versions, do not support the <canvas> element.


Definition and Usage

The globalAlpha property sets or returns the current alpha or transparency value of the drawing.

The globalAlpha property value must be a number between 0.0 (fully transparent) and 1.0 (no transparancy).

Default value: 1.0
JavaScript syntax: context.globalAlpha=number;

Property Values

Value Description Play it
number The transparency value. Must be a number between 0.0 (fully transparent) and 1.0 (no transparancy) Play it »


Canvas Object Reference Canvas Object

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