如何使用FabricJS禁用矩形的居中缩放？

WBOY 转载: 2023-08-24 20:53:07 759浏览

在本教程中，我们将学习如何使用FabricJS禁用矩形的居中缩放。矩形是FabricJS提供的各种形状之一。为了创建一个矩形，我们需要创建一个fabric.Rect类的实例，并将其添加到画布上。当通过控制器进行缩放时，将centeredScaling属性赋值为true，使用中心作为对象的变换起点。

语法

new fabric.Rect({ centeredScaling: Boolean }: Object)

Parameters

Options (optional) − This parameter is an Object which provides additional customizations to our rectangle. Using this parameter, properties such as colour, cursor, stroke width and a lot of other properties can be changed related to the object of which centeredScaling is a property.

Options Keys

centeredScaling − This property accepts a Boolean value. When this property is true, the object uses the center as its origin of transformation.

Example 1

Passing centeredScaling as key and assigning a “true” value to it

Let’s see a code example to see how a rectangle object behaves when centeredScaling property is enabled. When we scale the object up the origin of transformation is the center of the rectangle.

<!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>Passing centeredScaling as key and assigning a "true" value to it</h2>
   <p>Try scaling the rectangle to see that centered scaling has been enabled</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 rectangle object
      var rect = new fabric.Rect({
         left: 125,
         top: 90,
         width: 170,
         height: 70,
         fill: "#cf1020",
         borderColor: "black",
         borderScaleFactor: 3,
         centeredScaling: true,
      });

      // Add it to the canvas
      canvas.add(rect);
   </script>
</body>
</html>

示例2

禁用centeredScaling属性

我们可以通过将其赋值为False来禁用centeredScaling属性。这将不再使用矩形的中心作为变换的中心。下面是一个代码示例来演示这一点 -

<!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>Disabling the centeredScaling property</h2>
   <p>Try scaling the rectangle to see that centered scaling has been disabled</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 rectangle object
      var rect = new fabric.Rect({
         left: 125,
         top: 90,
         width: 170,
         height: 70,
         fill: "#cf1020",
         borderColor: "black",
         borderScaleFactor: 3,
         centeredScaling: false,
      });

      // Add it to the canvas
      canvas.add(rect);
   </script>
</body>
</html>

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