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<!--> <!DOCTYPE> <a> <abbr> <acronym> <address> <applet> <area> <article> <aside> <audio> <b> <base> <basefont> <bdi> <bdo> <big> <blockquote> <body> <br> <button> <canvas> <caption> <center> <cite> <code> <col> <colgroup> <command> <datalist> <dd> <del> <details> <dfn> <dialog> <dir> <div> <dl> <dt> <em> <embed> <fieldset> <figcaption> <figure> <font> <footer> <form> <frame> <frameset> <head> <header> <hgroup> <h1> - <h6> <hr> <html> <i> <iframe> <img> <input> <ins> <kbd> <keygen> <label> <legend> <li> <link> <map> <mark> <menu> <meta> <meter> <nav> <noframes> <noscript> <object> <ol> <optgroup> <option> <output> <p> <param> <pre> <progress> <q> <rp> <rt> <ruby> <s> <samp> <script> <section> <select> <small> <source> <span> <strike> <strong> <style> <sub> <summary> <sup> <table> <tbody> <td> <textarea> <tfoot> <th> <thead> <time> <title> <tr> <track> <tt> <u> <ul> <var> <video> <wbr>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);
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 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 » |
HTML Canvas Reference
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