How to add dashes to the border of a selection area on a canvas using FabricJS?

FabricJSJavascriptHTML5 Canvas

In this article, we are going to learn how to add dashes to the border of a selection area on a canvas using FabricJS. We can achieve this by using the selectionDashArray property. It allows us to make the border of a selection area dashed.

Syntax

new fabric.Canvas(element: HTMLElement|String, { selectionDashArray: Array }: Object)

Parameters

  • element − This parameter is the <canvas> element itself which can be derived using document.getElementById() or the id of the <canvas> element itself. The FabricJS canvas will be initialized on this element.

  • options (optional) − This parameter is an Object which provides additional customizations to our canvas. Using this parameter color, cursor, border width and a lot of other properties can be changed related to the canvas, of which selectionDashArray is a property. It accepts an array which determines the dash pattern that we want.

Example 1

Passing the selectionDashArray as key to the class

selectionDashArray allows us to make the border of a selection area dashed. The way to define a dash pattern is by specifying the length of dashes in an array. In the example below we have taken a [7,6] array. This means, there would be a 7px long line followed by a 6px gap and so on.

<!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 dashes to the border of a selection area on a canvas</h2>
   <p>Select an area around the object. The border of the selection area would have dashed lines.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionDashArray: [7, 6],
         selectionBorderColor: "red"
      });
      // Creating an instance of the fabric.Rect class
      var circle = new fabric.Circle({
         left: 200,
         top: 100,
         radius: 40,
         fill: "blue",
      });
      // Adding it to the canvas
      canvas.add(circle);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>

Example 2

Using selectionDashArray in combination with selectionLineWidth and selectionBorderColor

The selectionDashArray property can be used in a number of ways. One way is to use it in combination with selectionLineWidth and selectionBorderColor which specify the width of the border of a selection and the color of the border of the selection, respectively.

<!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 dashes to the border of a selection area on a canvas</h2>
   <p>Select an area around the object and observe the outline of the selection area. </p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionDashArray: [13, 16],
         selectionLineWidth: 5,
         selectionBorderColor: "green",
      });
      // Creating an instance of the fabric.Rect class
      var circle = new fabric.Circle({
         left: 200,
         top: 100,
         radius: 40,
         fill: "blue",
      });
      // Adding it to the canvas
      canvas.add(circle);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>
raja
Updated on 19-May-2022 13:40:08

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