Canvas globalAlpha Property
Example
Draw a red rectangle. Set transparency (globalAlpha) to 0.5. Then draw a blue and a green rectangle:
JavaScript:
const canvas = document.getElementById("myCanvas");
const ctx = canvas.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 »
Description
The globalAlpha
property sets or returns the transparency value of the context.
The globalAlpha
property value must be a number between 0.0 (Fully transparent)
and 1.0 (Default. No transparancy).
Syntax
context.globalAlpha = number |
Property Values
Value | Description | Play it |
---|---|---|
number | The transparency 0.0 = full transparancy 1.0 = no transparancy |
Play it » |
Browser Support
The <canvas>
element is an HTML5 standard (2014).
globalAplha
is supported in all modern browsers:
Chrome | Edge | Firefox | Safari | Opera | IE |
Yes | Yes | Yes | Yes | Yes | 9-11 |
❮ Canvas Reference