How to set the opacity of Textbox using FabricJS?

In this tutorial, we are going to learn how to set the opacity of Textbox using FabricJS. Textbox is one of the various shapes provided by FabricJS. In order to create a textbox, we will have to create an instance of fabric.Textbox class and add it to the canvas. We can customize a textbox object by adding a fill colour to it, eliminate its borders or even make changes in its dimensions. Similarly, we can also change its opacity by using the opacity property.

Syntax

new fabric.Textbox(text: String, { opacity: Number }: Object)

Parameters

text − This parameter accepts a String which is the text string that we want to display inside our textbox.
options (optional) − This parameter is an Object which provides additional customizations to our textbox. Using this parameter, properties such as colour, cursor, border width and a lot of other properties can be changed related to the object of which opacity is a property.

Options Keys

opacity − This property accepts a Number that allows us to control the opacity of an object. Default value of opacity property is 1.

Example 1

Default appearance of a textbox object

Let’s see a code example to see how our textbox object looks like with the default value of opacity property. In this example, we will not pass any opacity key to the class, as given below −


<!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 a textbox object</h2>
	<p>You can see our textbox is fully opaque</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 textbox object
		var textbox = new fabric.Textbox("Positive thoughts lead to positive results.", {
			left: 110,
			top: 45,
			fill: "orange",
			stroke: "green",
			width: 400,
			backgroundColor: "#f3e5ab",
		});
		
		// Add it to the canvas
		canvas.add(textbox);
	</script>
</body>
</html>

Example 2

Passing the opacity property as key

In this example, we will see how assigning a value to the opacity property changes the opacity of the textbox object in our canvas. Here we have used 0.3 as opacity which thus makes our textbox object look translucent instead of fully opaque.


<!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 the opacity property as key</h2>
	<p>You can see our textbox is not fully opaque</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 textbox object
		var textbox = new fabric.Textbox("Positive thoughts lead to positive results.", {
			left: 110,
			top: 45,
			fill: "orange",
			stroke: "green",
			width: 400,
			backgroundColor: "#f3e5ab",
			opacity: 0.3,
		});
		
		// Add it to the canvas
		canvas.add(textbox);
	</script>
</body>
</html>