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How to add animation in Line using FabricJS?
In this tutorial, we are going to learn how to add animation in Line using FabricJS. A Line element is one of the basic elements provided in FabricJS. It is used for creating straight lines. Because line elements are geometrically one-dimensional and do not contain an interior, 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. In order to animate a line instance we use the animate method.
Syntax
animate(property: String | Object, value: Number | Object)
Parameters
property ? This property accepts a String or Object value which determines which properties we want to animate.
value ? This property accepts a Number or Object value which determines the values to animate properties.
Default appearance of the Line object
Let's see a code example to see how our line object looks when the animate method is not used. In this case, no animation is displayed.
<!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 has no animation</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>
Using the animate method
In this example, we will see how by using the animate method we can easily create our own animation. The first argument is the property we want to animate. Here, for example, we have used the angle and left property as an argument in order to change its angle and position. This property also allows us to use relative values just as we have specified the value as +=100 and 90 which makes the line move and change angle 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>Using the animate method </h2>
<p>You can see the animation now</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,
});
// Using the animate method
line.animate("left", "+=100", {
onChange: canvas.renderAll.bind(canvas),
});
line.animate("angle", "90", {
onChange: canvas.renderAll.bind(canvas),
});
// Add it to the canvas
canvas.add(line);
</script>
</body>
</html>
Key Points
The
animate()method requires two parameters: the property to animate and the target value.Use relative values like
"+=100"to animate from the current position.The
onChangecallback withcanvas.renderAll.bind(canvas)ensures the canvas updates during animation.Multiple animations can be chained by calling
animate()multiple times on the same object.
Conclusion
The FabricJS animate method provides a simple way to add smooth animations to Line objects. By specifying properties like position and rotation, you can create dynamic visual effects that enhance user interaction.
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