FabricJS – Implementing object duplication programmatically on a Polygon?

We can create a Polygon object by creating an instance of fabric.Polygon. A polygon object can be characterized by any closed shape consisting of a set of connected straight-line segments. Since it is one of the basic elements of FabricJS, we can also easily customize it by applying properties like angle, opacity etc. In order to implement object duplication programmatically we need to implement duplicate control using the clone method

Syntax

clone( callback: Object, propertiesToInclude: Array)

Parameters

  • Callback (optional) βˆ’ This parameter is a callback function which is invoked with a clone.

  • propertiesToInclude (optional) βˆ’ This parameter includes any additional properties that we want to be included in the clone canvas instance. This must be in the form of an Array.

Example 1: Implementing Object Duplication Programmatically on Polygon

Let’s see a code example to understand how we can attain object duplication on a Polygon. Firstly, we have initiated a polygon object and its respective points array and add it to clipboard. We have also one button which when clicked fires the duplicate() function. duplicate() will get the object from clipboard and will clone the copied object with a offset and add it to the canvas using canvas.add.

<!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>Implementing object duplication programmatically on Polygon</h2>
   <p>
      You can click on Duplicate button to see object duplication in action
   </p>
   <button onclick="duplicate()" style="padding: 3px">Duplicate</button>
   <canvas id="canvas"></canvas>
   <script>
      
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas");
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
      
      // Initiating duplicate() function which pastes
      
      // the object to canvas, adds offset and
      
      // makes the object active
      function duplicate() {
         _clipboard.clone(function (clonedObj) {
            canvas.discardActiveObject();
            clonedObj.set({
               left: clonedObj.left + 10,
               top: clonedObj.top + 10,
               evented: true,
            });
            canvas.add(clonedObj);
            _clipboard.top += 10;
            _clipboard.left += 10;
            canvas.setActiveObject(clonedObj);
            canvas.requestRenderAll();
         });
      }
      
      // Initiating a points array
      var points = [
         { x: 30, y: 50 },
         { x: 70, y: 50 },
         { x: 0, y: 0 },
         { x: 70, y: 0 },
      ];
      
      // Initiating a polygon object
      var polygon = new fabric.Polygon(points, {
         left: 100,
         top: 40,
         fill: "#1e90ff",
         strokeWidth: 4,
         stroke: "green",
         scaleX: 2,
         scaleY: 2,
      });
      
      // Clone the object to clipboard
      polygon.clone(function (cloned) {
         _clipboard = cloned;
      });
      
      // Adding it to the canvas
      canvas.add(polygon);
   </script>
</body>
</html>

Example 2: Implementing Object Duplication Programmatically on Circle

Let’s see a code example to see how we can implement object duplication programmatically using FabricJS on a circle. In this case, we have initiated a circle instead of a polygon object and followed the same procedure. Therefore, the duplicate of the circle will be created. 

<!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>Implementing object duplication programmatically on Circle</h2>
   <p>
      You can click on Duplicate button to see object duplication in action
   </p>
   <button onclick="duplicate()" style="padding: 3px">Duplicate</button>
   <canvas id="canvas"></canvas>
   <script>
      
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas");
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
      
      // Initiating duplicate() function which pastes
      // the object to canvas, adds offset and
      // makes the object active
      function duplicate() {
         _clipboard.clone(function (clonedObj) {
            canvas.discardActiveObject();
            clonedObj.set({
               left: clonedObj.left + 10,
               top: clonedObj.top + 10,
               evented: true,
            });
            canvas.add(clonedObj);
            _clipboard.top += 10;
            _clipboard.left += 10;
            canvas.setActiveObject(clonedObj);
            canvas.requestRenderAll();
         });
      }
      
      // Initiating a circle object
      var circle = new fabric.Circle({
         left: 100,
         top: 40, 
         fill: "#1e90ff",
         radius: 40,
         strokeWidth: 4,
         stroke: "green",
         scaleX: 2,
         scaleY: 2,
      });
      
      // Clone the object to clipboard
      circle.clone(function (cloned) {
         _clipboard = cloned;
      });
      
      // Adding it to the canvas
      canvas.add(circle);
   </script>
</body>
</html>

Conclusion

In this tutorial, we used two simple examples to demonstrate how you can implement object duplication programmatically using FabricJS.

Updated on: 02-Jan-2023

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