HTML canvas globalAlpha Property
Example
First, draw a red rectangle, then set transparency (globalAlpha) to 0.5, and then draw a blue and a green rectangle:
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
The numbers in the table specify the first browser version that fully supports the property.
| Property | |||||
|---|---|---|---|---|---|
| globalAlpha | 4.0 | 9.0 | 3.6 | 4.0 | 10.1 |
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
