Drawable

A way to make styling canvas elements like text and images nicer. This lib uses node-canvas, please see instructions on how to get this working on your computer.

Why

The idea is to create a somewhat familiar way to style a canvas element to leverage the ability to turn the canvas drawing into an image. Images are more sharable and if done correctly more printable as well :D. This lib leverages node-canvas to be able to do this server side currently, but its goal is to eventually be universal for client and server technologies. That way you could render some awesome interactive charts and then potentially render them also into something like a Github README. Not quite there yet tho.

Be careful

This is currently in some flux, and currently only works on a node server.

Installation

npm i drawable --save

Usage

Drawable is really just a canvas that is meant to use some CSS like syntax to be able to add text and images to a canvas.

Creating a drawable

import Drawable from 'drawable'
 
const drawable = new Drawable({ width: 200, height: 200, backgroundColor: 'white' });

There are a few styles that are passed here: width, height, and backgroundColor. This does exactly what you would think it would do. It makes a canvas with the width of 200px height of 200px and the backgroundColor of white. If you have used canvas before you would notice that backgroundColor is not a thing. All this is really doing is creating a rectangle that fills the background of the canvas with a fill of the color passed. By default this is transparent.

Styles for constructor

Styles key	description	default
width	The width of the canvas	0
height	The height of the canvas	0
backgroundColor	The background color of the canvas	transparent

Adding in some text

const text = Drawable.text('Here is some text', {
  fontSize: 12,
  top: 20,
  left: 20,
  right: 20,
  textAlign: 'center'
});
 
// append text to drawable instance
drawable.append(text);

This is where the magic of drawable starts to shine. With drawable text we automatically will wrap text based on the size of the canvas and the values passed in for the right and left options. Then we calculate the alignment of the text using textAlign option.

Styles for text

Styles key	Description	Default
top	The top alignment of the text container	0
left	The left alignment of the text container	0
right	The right alignment of the text container	0
color	The color of the text	#222
textAlign	Can be: 'center', 'left', or 'right'	left
lineHeight	The line height of the text	0
fontSize	The size of the text in pixels	0
fontFamily	The font used in the canvas	sans-serif

Adding in a image

const image = Drawable.image('./path/to/image.jpg', {
  top: 20,
  left: 20,
});
 
// append text to drawable instance
drawable.append(image);

Images are pretty basic, you give the image a left and top coordinate and it should render. If you are trying to emulate something like a background image you could also use the objectFit style which should allow you to cover or contain the image in the canvas.

Styles for image

Styles key	Description	Default
top	The top alignment of the image	0
left	The left alignment of the image	0
width	The width of the image	images.width
height	The height of the image	images.height
objectFit	object-fit css current values supported are "cover" and "contain"	none

Note: when using object fit it will override the left, top, width, and height values.

TODO

• make api work on both client and server
• solidify output methods toBuffer and toDataURI
• make a public way to expose canvas element ( for appending to DOM )
• make a few adapters to work with react and ember