FabricJS – How to center a Line object horizontally and vertically on a canvas?

In this tutorial, we are going to learn how to center a Line object horizontally and vertically on canvas using FabricJS. A Line element is one of the basic elements provided in FabricJS. It is used for creating straight lines. Because line elements are geometrically one-dimensional and do not contain an interior, they are never filled. We can create a line object by creating an instance of fabric.Line, specifying the x and y coordinates of the line and adding it to the canvas. In order to center the line object horizontally and vertically on the canvas we use the center method.

Syntax

center()

Default appearance of the Line object

Example

Let’s see a code example to see how our line object looks when the center method is not used. In this case, the line object will not be centered on the canvas.


<!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 the Line object</h2>
   <p>You can see that the line object is not centered</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 Line object
      var line = new fabric.Line([200, 100, 100, 40], {
         stroke: "blue",
         strokeWidth: 20,
      });
      
      // Add it to the canvas
      canvas.add(line);
   </script>
</body>
</html>

Using the center method

Example

In this example, we will see how by using the center method, we are able to place the line object exactly at the center of the canvas. In this case, the object is centered horizontally and vertically.


<!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>Using the center method</h2>
   <p>You can see that the line object has been centered on the canvas</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 Line object
      var line = new fabric.Line([200, 100, 100, 40], {
         stroke: "blue",
         strokeWidth: 20,
      });
      
      // Add it to the canvas
      canvas.add(line);
      
      // Using center() to center the line object on the canvas
      line.center();
   </script>
</body>
</html>