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How to create a canvas with Polyline using FabricJS?
We can create a Polyline object by creating an instance of fabric.Polyline. A polyline object can be characterised by 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 like angle, opacity etc.
Syntax
new fabric.Polyline(points: Array, options: Object)
Parameters
points ? This parameter accepts an Array which denotes the array of points that make up the polyline object.
options (optional) ? This parameter is an Object which provides additional customizations to our object. Using this parameter origin, stroke width and a lot of other properties can be changed related to the Polyline object.
Example 1: Creating an instance of fabric.Polyline() and adding it to our canvas
Let's see a code example of how we can add a polyline object to our canvas. The only required parameter is the points Array whereas the second argument is the optional options 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>Creating an instance of fabric.Polyline() and adding it to our canvas</h2>
<p>You can see that the polyline object has been added</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiating a points array
var points = [
{ x: 30, y: 50 },
{ x: 0, y: 0 },
{ x: 60, y: 0 },
];
// Initiating a polyline object
var polyline = new fabric.Polyline(points, {
left: 100,
top: 40,
fill: "white",
strokeWidth: 4,
stroke: "green",
});
// Adding it to the canvas
canvas.add(polyline);
</script>
</body>
</html>
Example 2: Manipulating the Polyline object by using the set method
In this example, we have assigned the properties to the Polyline object by using the set method which is a setter for values. Any property related to stroke, strokeWidth, angle, scaling, rotation, etc., can be mutated by using this method.
<!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>Manipulating the Polyline object by using the set method</h2>
<p>You can see the Polyline object in canvas now with set values</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiating a points array
var points = [
{ x: 30, y: 50 },
{ x: 0, y: 0 },
{ x: 60, y: 0 },
];
// Initiating a polyline object
var polyline = new fabric.Polyline(points);
// Set the properties
polyline.set("stroke", "blue");
polyline.set("strokeWidth", 5);
polyline.set("top", 50);
polyline.set("left", 100);
polyline.set("scaleX", 2);
polyline.set("scaleY", 2);
// Adding it to the canvas
canvas.add(polyline);
</script>
</body>
</html>
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