How to add stroke to a Circle using FabricJS?



In this tutorial, we are going to learn how to add stroke to a Circle using FabricJS. Circle is one of the various shapes provided by FabricJS. In order to create a circle, we will create an instance of fabric.Circle class and add it to the canvas. Our circle object can be customized in various ways like changing its dimensions, adding a background color or by changing the colour of the line drawn around the object. We can do this by using the stroke property.

Syntax

new fabric.Circle({ stroke : String }: Object)

Parameters

  • options (optional) − This parameter is an Object which provides additional customizations to our circle. Using this parameter, properties such as colour, cursor, stroke width and a lot of other properties can be changed related to the object of which stroke is a property.

Options Keys

  • stroke − This property accepts a String and determines the colour of that object's border.

Example 1

Passing stroke as key with a hexadecimal value

Let's see an example to understand how our circle object appears when the stroke property is used. A hexadecimal colour code starts with a "#" followed by a six-digit number representing a colour. In this case, we have used "#ff4500" which is an orange-red colour.

<!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>Adding stroke to a circle using FabricJS</h2>
      <p>Notice the orange-red outline around the circle. It appears as we have applied the    <b>stroke</b> property and assigned it a hexadecimal color code. </p>
      <canvas id="canvas"></canvas>

      <script>
         // Initiate a canvas instance
         var canvas = new fabric.Canvas("canvas");
         var circle = new fabric.Circle({
            left: 50,
            top: 90,
            radius: 50,
            fill: "#4169e1",
            stroke: "#ff4500",
            strokeWidth: 5
         });
         canvas.add(circle);
         canvas.setWidth(document.body.scrollWidth);
         canvas.setHeight(250);
      </script>
   </body>
</html>

Example 2

Passing an 'rgba' value to the stroke property

In this example we will see how to assign an rgba value to the stroke property. We can use an RGBA value, instead of a hexadecimal colour code, which stands for: red, blue, green and alpha. The alpha parameter specifies the opacity of a colour. In this example, we have used the rgba value (255,69,0,0.5) which is an orange-red color with 0.5 opacity.

<!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>Adding stroke to a circle using FabricJS</h2>
      <p>Notice the outline around the circle. Here we have applied the <b>stroke</b> property and assigned it an 'rgba' value. </p>
      <canvas id="canvas"></canvas>

      <script>
         // Initiate a canvas instance
         var canvas = new fabric.Canvas("canvas");
         var circle = new fabric.Circle({
            left: 50,
            top: 90,
            radius: 50,
            fill: "#4169e1",
            stroke: "rgba(255,69,0,0.5)",
            strokeWidth: 5
         });
         canvas.add(circle);
         canvas.setWidth(document.body.scrollWidth);
         canvas.setHeight(250);
      </script>
   </body>
</html>

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