How to set the minimum allowed scale value of an Ellipse using FabricJS?

In this tutorial, we are going to learn how to set the minimum allowed scale of Ellipse using FabricJS. Ellipse is one of the various shapes provided by FabricJS. In order to create an ellipse, we will create an instance of fabric.Ellipse class and add it to the canvas. We can customize an ellipse object by adding a fill color to it, eliminate its borders or even make changes in its dimensions. Similarly, we can also set its minimum allowed scale by using the minScaleLimit property.

Syntax

new fabric.Ellipse({ minScaleLimit : Number }: Object)

Parameters

options (optional) − This parameter is an Object which provides additional customizations to our ellipse. Using this parameter color, cursor, border width and a lot of other properties can be changed related to the object of which minScaleLimit is a property.

Options Keys

minScaleLimit − This property accepts a Number as a value that allows us to control the minimum allowed scale of an ellipse.

Example 1

Default appearance of the ellipse object

Let's take an example to see how our ellipse object looks like when the minScaleLimit property is not used. In this case, we will be able to freely scale our object since there is no minimum limit set.

<!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>How to set the minimum allowed scale value of Ellipse using FabricJS?</h2>
      <p>Here you can select the object and scale it up freely to any extent, as we have not used the <b>minScaleLimit</b> property. </p>
      <canvas id="canvas"></canvas>

      <script>
         // Initiate a canvas instance
         var canvas = new fabric.Canvas("canvas");

         // Initiate an ellipse instance
         var ellipse = new fabric.Ellipse({
            left: 115,
            top: 50,
            rx: 80,
            ry: 50,
            fill: "#ff1493",
         });

         // Adding it to the canvas
         canvas.add(ellipse);
         canvas.setWidth(document.body.scrollWidth);
         canvas.setHeight(250);
      </script>
   </body>
</html>

Example 2

Passing the minScaleLimit property as key with a custom value

In this example, we will see how assigning a value to the minScaleLimit property changes the minimum allowed scale value of the ellipse object in our canvas. Here we have used 0.8 as the value which means we will not be able to scale down our object lesser than a horizontal radius of 64px and a vertical radius of 40px which is calculated by radius * limit (0.8 * 80 = 64px, 0.8 * 50 = 40px).

<!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>How to set the minimum allowed scale value of Ellipse using FabricJS?</h2>
      <p>Select the object and try to scale it down. Here we have set the <b>minScaleLimit</b> to 0.8 beyond which the ellipse cannot be reduced further in size. </p>
      <canvas id="canvas"></canvas>

      <script>
         // Initiate a canvas instance
         var canvas = new fabric.Canvas("canvas");

         // Initiate an ellipse instance
         var ellipse = new fabric.Ellipse({
            left: 115,
            top: 50,
            rx: 80,
            ry: 50,
            fill: "#ff1493",
            minScaleLimit: 0.8,
         });

         // Adding it to the canvas
         canvas.add(ellipse);
         canvas.setWidth(document.body.scrollWidth);
         canvas.setHeight(250);
      </script>
   </body>
</html>