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FabricJS – How to scale an Image object to a given height?
In this tutorial, we are going to learn how to scale an Image object to a given height using FabricJS. We can create an Image object by creating an instance of fabric.Image. Since it is one of the basic elements of FabricJS, we can also easily customize it by applying properties like angle, opacity etc. In order to scale an Image object to a given height, we use the scaleToHeight method.
Syntax
scaleToHeight(value: Number, absolute: Boolean): fabric.Object
Parameters
value ? This parameter accepts a Number which determines the new height value of our Image object.
absolute ? This parameter accepts a Boolean value which determines whether the viewport is to be ignored or not.
Default appearance of the Image object
Let's see a code example to see how our image object looks when the scaleToHeight method is not used. In this case, our image object will not be scaled in horizontal or vertical directions.
<!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 Image object</h2>
<p>
You can see that the object has not been scaled in horizontal or vertical direction
</p>
<canvas id="canvas"></canvas>
<img src="https://www.tutorialspoint.com/images/logo.png" id="img1" style="display: none" />
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiating the image element
var imageElement = document.getElementById("img1");
// Initiate an Image object
var image = new fabric.Image(imageElement, {
top: 50,
left: 110,
});
// Add it to the canvas
canvas.add(image);
</script>
</body>
</html>
Using scaleToHeight method with a custom value
In this example, we will see how assigning a value to the scaleToHeight method scales our image object to a given height. Since we have passed the value as 100, that will be the new height of our image object.
<!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 scaleToHeight method with a custom value</h2>
<p>You can see that the new height of our image object is 100</p>
<canvas id="canvas"></canvas>
<img src="https://www.tutorialspoint.com/images/logo.png" id="img1" style="display: none" />
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiating the image element
var imageElement = document.getElementById("img1");
// Initiate an Image object
var image = new fabric.Image(imageElement, {
top: 50,
left: 110,
});
// Using scaleToHeight method
image.scaleToHeight(100, false);
// Add it to the canvas
canvas.add(image);
</script>
</body>
</html>
Understanding the absolute parameter
The absolute parameter determines how the scaling calculation is performed. When set to false, the scaling is relative to the current transformation. When set to true, it scales to the absolute height regardless of current transformations.
Conclusion
The scaleToHeight method in FabricJS provides an easy way to resize image objects to a specific height while maintaining aspect ratio. Use the absolute parameter to control whether viewport transformations are considered during scaling.
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