canvas-elements

Canvas Elements

Canvas Elements is a library of commonly used components for HTML5 canvas made easy to use with JavaScript and Node.js. It wraps the structure and the styling of elements into one which makes it easy to create new elements on the canvas.

Installation

Using NPM

To use Canvas Elements in Node.js, install the npm package by using the command below.

npm install canvas-elements

Using CDN

The project also includes a minified CDN file in the build/cdn directory of the project.

https://unpkg.com/canvas-elements/build/cdn/canvas-elements.min.js

Using the library

Using Node

var CanvasElements = require('canvas-elements');
// All elements are in CanvasElements object. Example: CanvasElements.Circle, CanvasElements.Text

// Using ES6 import, specifically choose elements that you need
import { Circle, Text } from 'canvas-elements';

Note: If you are using ES6 import, ignore CanvasElements object in the following documentation.

Using CDN

CDN exposes a CanvasElements object to the window which contains the constructors of all the elements.

var circle = new CanvasElements.Circle({
   // options
});

Example usage

This example program creates a circle with blue rounded rectangle which has 'Hello Canvas' text at the center.
Check it on JSFiddle

var canvas = document.getElementsByTagName('canvas')[0]; // Get the canvas element reference
var ctx = canvas.getContext('2d'); // Get context of the canvas

// Create a circle
var circle = new CanvasElements.Circle({
  x: 80,
  y: 80,
  r: 60,
  background: 'white',
  borderWidth: 4,
  borderColor: '#000',
  ctx: ctx
});

// Creates a blue rounded rectangle 
var text = new CanvasElements.Rect({
  x: 25,
  y: 63,
  r: 20,
  w: 110,
  h: 30,
  background: '#03a9f4',
  ctx: ctx
})

// Create 'Hello Canvas' text
var text = new CanvasElements.Text({
  x: 80,
  y: 80,
  background: '#ffffff',
  text: 'Hello Canvas',
  size: 16,
  align: 'center',
  baseline: 'middle',
  weight: '600',
  ctx: ctx
});

Options Reference

All the elements constructors take options object which allows you to configure the structure and style of the element.

Common options

These options are common between all the elements included in the library.

Option	Type	Description
x	number (required)	X coordinate of the element in canvas
y	number (required)	Y coordinate of the element in canvas
ctx	CanvasRenderingContext2D (required)	Context of the canvas to which the element must be drawn
background	string (optional)	Fill color. Eg. #6ddad0, rgba(20, 30, 40, 0.5)
borderWidth	number (optional)	Thickness of the border
borderColor	string (optional)	Color of the border
rotation	number (optional)	Rotation of the element in radians. Center is geometric center for shapes and starting coordinates for Text element

Circle

Some exclusive options for Circle element.

Option	Type	Description
r	number (required)	Radius of the circle

Rect (Rectangle)

Some exclusive options for Rect element to create rectangles.

Option	Type	Description
w	number (required)	Width of the rectangle
h	number (required)	Height of the rectangle
r	number (optional)	Roundness of every corner. Same as border-radius CSS property

Ellipse

Some exclusive options for Ellipse element.

Option	Type	Description
radiusX	number (required)	Horizontal radius of the ellipse
radiusY	number (required)	Vertical radius of the ellipse

Line

Some exclusive options for Line element.

Option	Type	Description
x2	number (optional)	Ending x coordinate of the line
y2	number (optional)	Ending y coordinate of the line
r	number (optional)	Distance from (x, y) for Polar system
angle	number (optional)	Angle from the horizontal axis in radians (Clockwise is positive) for Polar system
lineCap	string (optional)	Style for the ends of the line. Takes values square (default), round, butt

Text

Some exclusive options for Text element to render text.

Option	Type	Description
text	string (required)	Text to be shown
size	number (required)	Font size
font	string (optional)	Font family
align	string (optional)	Horizontal text alignment
baseline	string (optional)	Vertical text alignment
weight	string (optional)	Text weight

Contributing

To contribute to the development of this project, you must first fork this project into your own account. Make sure you have a recent version of Node.js installed. Then follow the given commands

git clone https://github.com/your-username/canvas-elements
cd canvas-elements
npm install

The source code is located in the src folder. Once the project is built or bundled, build directory would be created which contains the code for distribution.

To run the development server

Playground is included in the project in playground directory. This is used to test features of Canvas Elements during development. Do not commit changes in playground.

npm run dev

This will start a live development server on port 3030.

To build the project

npm run build

To bundle and minify source

npm run bundle

Bundled CDN file would be located in build/cdn directory.

License

This project is under MIT License