FabricJS - How to vertically center a Line object on the canvas?-JS Tutorial-php.cn

FabricJS - How to vertically center a Line object on the canvas?

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Release： 2023-09-03 15:17:02

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FabricJS – 如何将 Line 对象在画布上垂直居中？

In this tutorial, we will learn how to vertically center lines on a canvas using FabricJS. Line element is one of the basic elements provided in FabricJS. It is used to create straight lines. Since line elements are geometrically one-dimensional and contain no interiors, 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. To center the line object vertically on the canvas, we use the centerV method.

Syntax

 centerV()

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Default appearance of Line objects

Example

Let’s look at a code example without using centerV method is the appearance of our line object. In this case, the line object will not be vertically 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 has not been centered vertically 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);
   </script>
</body>
</html>

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Use centerVmethod

Example

In this example we will see how by using the centerV method we are able to place a line object exactly in the vertical center of the canvas. In this case, the object is centered 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 centerV method</h2>
   <p>
      You can see that the line object has been centered vertically 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 the centerV() method to center line object vertically
      line.centerV();
   </script>
</body>
</html>

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