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How to set the opacity of Triangle using FabricJS?
<p>In this tutorial, we are going to learn how to set the opacity of Triangle using FabricJS. Triangle is one of the various shapes provided by FabricJS. In order to create a triangle, we will have to create an instance of <em>fabric.Triangle</em> class and add it to the canvas. We can customize a triangle object by adding a fill colour to it, eliminate its borders or even make changes in its dimensions. Similarly we can also change its opacity by using the <em>opacity</em> property.</p><h2>Syntax</h2><pre class="just-code notranslate language-javascript" data-lang="javascript">new fabric.Triangle({ opacity: Number }: Object)</pre><h2>Parameters</h2><ul class="list"><li><p><strong>Options</strong><strong> (optional)</strong> − This parameter is an <em>Object</em> which provides additional customizations to our Triangle. Using this parameter colour, cursor, border width and a lot of other properties can be changed related to the object of which <em>opacity</em> is a property.</p></li></ul><h2>Options Keys</h2><ul class="list"><li><p><strong>opacity</strong><strong> </strong>− This property accepts a <strong>Number</strong> as value which allows us to control the opacity of an object. The default value of opacity property is 1.</p></li></ul><h2>Example 1</h2><p><strong>Default appearance of a Triangle object</strong></p><p>Let's see a code example to see how our Triangle object looks like with the default value of <em>opacity</em> property. We will not pass any opacity key to the class, as shown in the example below −</p><pre class="demo-code notranslate language-javascript" data-lang="javascript"><!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Default appearance of a Triangle object</h2>
<p>Notice that the triangle is fully opaque.</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiate a triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 70,
width: 90,
height: 80,
fill: "#746cc0",
stroke: "#967bb6",
strokeWidth: 5,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html></pre><h2>Example 2</h2><p><strong>Passing the <em>opacity</em> property as key</strong></p><p>In this example, we will see how assigning a value to the <em>opacity</em> property changes the opacity of the triangle object in our canvas. Here we have used 0.3 as opacity which thus makes our triangle object look translucent instead of fully opaque.</p><pre class="demo-code notranslate language-javascript" data-lang="javascript"><!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Passing the opacity property as key</h2>
<p>You can see our triangle is not fully opaque</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiate a triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 70,
width: 90,
height: 80,
fill: "#746cc0",
stroke: "#967bb6",
strokeWidth: 5,
opacity: 0.3,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html></pre>
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