Home > Article > Web Front-end > How to make a polygon object react to zoom events using FabricJS?

How to make a polygon object react to zoom events using FabricJS?

WBOYforward: 2023-08-29 11:57:06889browse

如何使用 FabricJS 使多边形对象对缩放事件做出反应？

We can create a Polygon object by creating an instance of fabric.Polygon. A polygon object can be characterized as any closed shape consisting of a set of connected straight line segments. Since it is one of the basic elements of FabricJS, we can also easily customize it by applying properties such as angle, opacity, etc. We use the scaling event to demonstrate how polygonal objects react to scaling.

grammar

polygon.on(“scaling”, callbackFunction);

Example 1: Show how an object responds to zoom events

Let's look at a code example to see how a polygon object reacts when the Scale event occurs. We can scale the object by dragging any corner control. Here, when the object is scaled, the scale event will be triggered continuously.

<!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>Displaying how the object reacts to the scaling event</h2>
   <p>
      You can scale the polygon object and open the console from dev tools to see the logged output
   </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 polygon instance
      var polygon = new fabric.Polygon(
         [
            { x: 0, y: 0 },
            { x: 0, y: 50 },
            { x: 50, y: 50 },
            { x: 50, y: 0 },
         ],
         {
            left: 100,
            top: 30,
            fill: "red",
            stroke: "blue",
            strokeWidth: 3,
            objectCaching: false,
         }
      );
      
      // Adding it to the canvas
      canvas.add(polygon);
      
      // Using the scaling event
      polygon.on("scaling", () => {
         canvas.renderAll();
         console.log("The object is being scaled");
      });
   </script>
</body>
</html>

Example 2: Changing stroke color when zooming

Let's look at a code example to see how to change the stroke color when a zoom event occurs. We use the set method to set the polygon's stroke color to "orange". So when we scale the object, its stroke color will change to orange.

<!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>Changing the stroke colour when scaling happens</h2>
   <p>
      You can see that the stroke colour changes when the polygon is scaled
   </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 polygon instance
      var polygon = new fabric.Polygon(
         [
            { x: 500, y: 20 },
            { x: 550, y: 60 },
            { x: 550, y: 200 },
            { x: 350, y: 200 },
            { x: 350, y: 60 },
            { x: 500, y: 20 },
         ],
         {
            fill: "red",
            stroke: "blue",
            strokeWidth: 5,
            objectCaching: false,
            top: 50,
            left: 30,
            scaleX: 0.5,
            scaleY: 0.5
         }
      );

      // Adding it to the canvas
      canvas.add(polygon);

      // Using the scaling event
      polygon.on("scaling", () => {
         polygon.set("stroke", "orange")
         canvas.renderAll();
      });
   </script>
</body>
</html>

in conclusion

In this tutorial, we use two simple examples to demonstrate how to make a polygon object react to zoom events using FabricJS.

The above is the detailed content of How to make a polygon object react to zoom events using FabricJS?. For more information, please follow other related articles on the PHP Chinese website!

Statement：

This article is reproduced at:tutorialspoint.com. If there is any infringement, please contact admin@php.cn delete

Previous article：Getting Started with Paper.js: Creating Animated ImagesNext article：Getting Started with Paper.js: Creating Animated Images

See more

How to make a polygon object react to zoom events using FabricJS?

grammar

Example 1: Show how an object responds to zoom events

Example 2: Changing stroke color when zooming

in conclusion

Related articles