intrinsic-scale

Replicate background-size: cover/contain for canvas/CSS/Node/… on any type of media.

Given a original height and width, and a desired height and width, get the width, height, and scale that the original object should have to fit the desired object.

Many libraries that take care of replicating background-size/object-fit’s cover/contain have this functionality embedded. You can use this function anywhere, from the browser to calculate sizing on a canvas, to node when doing some image file resizing.

This module doesn't concern itself with getting the sizes or applying the values. You provide numbers, you get numbers.

Install

npm install --save intrinsic-scale

import {cover, contain} from 'intrinsic-scale';

Usage

/*
Given an 50px 50px element in a 100px 200px parent
To be contains in its parent it must be of size 100px 100px
and be positioned at 0px 50px to be centered.
*/
let { width, height, x, y } = contain(100, 200, 50, 50);
console.log(width, height, x, y);
//100 100 0 50
 
 
/*
Given an 50px 50px element in a 100px 200px parent
To be covered in its parent it must be of size 200px 200px
and be positioned at -50px 0px to be centered.
*/
let { width, height, x, y } = cover(100, 200, 50, 50);
console.log(width, height, x, y);
//200 200 -50 0

Dependencies

No dependencies. It works in the browser and in node.

Used on

• https://fregante.github.io/art-cropper/ — Crops images making them fill a pre-set area.
• https://away.gorving.com/ — The video always covers the header

License

Forked and extended from https://github.com/sroucheray/contain-cover

MIT © Federico Brigante