How to set the angle of rotation of a Triangle using FabricJS?



<p>In this tutorial, we are going to set the angle of rotation of a 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.</p><p>The <em>angle</em> property in FabricJS defines the angle of 2D rotation of an object. We also have the centeredRotation property that allows us to use the center point of a triangle as the origin of transformation.</p><h2>Syntax</h2><pre class="just-code notranslate language-javascript" data-lang="javascript">new fabric.Triangle({ angle: Number, centeredRotation: Boolean }: 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, properties such as colour, cursor, stroke width, and a lot of other properties can be changed related to the triangle of which <em>angle</em> and <em>centeredRotation</em> are properties.</p></li></ul><h2>Options Keys</h2><ul class="list"><li><p><strong>angle</strong> − This property accepts a <strong>Number</strong> which specifies the angle of rotation of a triangle in degrees.</p></li><li><p><strong>centeredRotation</strong> − This property accepts a <strong>Boolean</strong> value which determines whether the center of the triangle is the origin of transformation or not.</p></li></ul><h2>Example 1</h2><p><strong>Passing angle as key with a custom value and disabling the centered rotation for the Triangle</strong></p><p>Let's see a code example to set the angle of rotation of a Triangle in FabricJS. A negative angle specifies counter-clockwise direction whereas a positive angle specifies a clockwise direction. Since we have assigned <em>centeredRotation</em> a false value, the triangle will rotate while using its corner point as the center of rotation.</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 angle as key with a custom value and disabling the centered rotation for the Triangle</h2>    <p>Rotate the triangle to see that centered rotation has been disabled.</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: 60,          width: 100,          height: 70,          fill: "#deb887",          centeredRotation: false,          angle: 15,       });       // Add it to the canvas       canvas.add(triangle);    </script> </body> </html></pre><h2>Example 2</h2><p><strong>Enabling centered rotation for the triangle</strong></p><p>As we can see from this example, by setting the <em>centeredRotation</em> property as true, our triangle now uses its center as the center of rotation. Prior to version 1.3.4, <em>centeredScaling</em> and <em>centeredRotation</em> were enclosed within one single property called centerTransform.</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>Enabling centered rotation for the triangle</h2>    <p>Rotate the triangle to see that centered rotation has been enabled</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: 60,          width: 100,          height: 70,          fill: "#deb887",          centeredRotation: true,          angle: 15,       });       // Add it to the canvas       canvas.add(triangle);    </script> </body> </html></pre>

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