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How to set the width of the selection area border on the canvas using FabricJS?

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2023-09-03 14:53:111455browse

如何使用 FabricJS 设置画布上选择区域边框的宽度？

In this article, we will learn how to set the width of the selection area border on the canvas using FabricJS. The selection area represents the area selected with the mouse, and all objects under this area will be selected. FabricJS allows us to adjust the width of the selection area border using the selectionLineWidth property.

Syntax

new fabric.Canvas(element: HTMLElement|String, { selectionLineWidth: Number }: Object)

Parameters

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

  • Options (optional) - This parameter is an object that provides additional customization of our canvas. Using this parameter, you can change many properties related to the canvas, such as color, cursor, and border width, among which selectionLineWidth is one property. It accepts a number that determines the width of the line used in the selection border. The default value is 1.

Example 1

Pass selectionLineWidth key to class

Let's look at a code example to understand how to use FabricJS settings The width of the selection area border in the canvas. The SelectionLineWidth parameter accepts a number as a value. The larger the number we set, the wider the border of the canvas area will be. 

<!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>Setting the width of the selection area border in canvas using FabricJs</h2>
   <p>Select an area around the object to see the width of the selection area border.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionLineWidth: 23,
      });
      // Creating an instance of the fabric.Rect class
      var rect = new fabric.Rect({
         left: 170,
         top: 90,
         width: 60,
         height: 80,
         fill: "#006400",
         angle: 90,
      });
      // Adding it to the canvas
      canvas.add(rect);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>

Example 2

Using selectionLineWidth with selectionColor and selectionBorderColor

We can combine the selectionLineWidth parameter with other parameters Using properties such as selectionColor and selectionBorderColor, they allow us to set the color of a selection and adjust the border color of that selection respectively. Let’s see what the code looks like: 

<!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>Setting the width of selection area border in canvas using Fabric</h2>
   <p>Select an area around the object to see the selection color and selection border color.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionLineWidth: 3,
         selectionColor: "rgba(42,82,190,0.3)",
         selectionBorderColor: "black",
      });
      // Creating an instance of the fabric.Rect class
      var rect = new fabric.Rect({
         left: 170,
         top: 90,
         width: 60,
         height: 80,
         fill: "#006400",
         angle: 90,
      });
      // Adding it to the canvas
      canvas.add(rect);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>

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