- Trending Categories
Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to make a star with Polygon class using FabricJS?
We can create a Polygon object by creating an instance of fabric.Polygon. A polygon object can be characterized by 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 like angle, opacity etc.
Syntax
new fabric.Polygon( points: Array, options: Object )
Parameters
points − This parameter accepts an Array which denotes the array of points that make up the polygon 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 Polygon object.
Example 1: Default Appearance of Polygon Object
Let’s see a code example of how we can draw any general polygon object. We need to specify an array of points where each point is an object with "x" and "y". Specifying the array of points is crucial without which our polygon object would not be rendered onto the canvas.
<!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 polygon object</h2>
<p>You can see that a polygon object has been added to the canvas</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: "black",
stroke: "blue",
strokeWidth: 2,
}
);
// Adding it to the canvas
canvas.add(polygon);
</script>
</body>
</html>
Example 2: Drawing a Star using Polygon
Let’s see a code example to understand how we can draw a star using Polygon. A star or pentagram consists of 10 isosceles triangles. The length of the unequal sides in these isosceles triangles bear a golden ratio of 1.618. We can select the coordinates in such a way that the shape forms a star 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>Drawing a Star using Polygon</h2>
<p>You can see that a star object has been added to the canvas</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: 349.9, y: 75, },
{ x: 379, y: 160.9,},
{ x: 469, y: 160.9,},
{ x: 397, y: 214.9,},
{ x: 423, y: 300.9,},
{ x: 350, y: 249.9,},
{ x: 276.9, y: 301,},
{ x: 303, y: 215,},
{ x: 231, y: 161,},
{ x: 321, y: 161,},
];
// Initiating a polygon object
var polygon = new fabric.Polygon(points, {
left: 100,
top: 10,
fill: "#D81B60",
strokeWidth: 4,
stroke: "green",
cornerColor: "blue",
});
// Adding it to the canvas
canvas.add(polygon);
</script>
</body>
</html>
Conclusion
In this tutorial, we used two simple examples to demonstrate how you can make a star symbol with Polygon using FabricJS.
314 Views
