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    Contains and cover methods

    CSS provides two properties to fit an image inside its container : background-size for background images and object-fit for replaced element (<img>, <video>, <canvas>, <object>...).

    contain and cover are two possible values of these properties whose effects are described here

    This JavaScript module exports two functions contain and cover.

    Given the sizes of an element and its parent:

    • contain returns the size to be applied to the element to let it fits its parent, still being fully visible and keeping its apect ratio.
    • cover returns the size to be applied to the element to let it fully fill its parent, keeping its aspect ratio and potentially overflowing vertically or horizontally.

    As a bonus, contain and cover return the x and y positions of the element to center it in its parent container.

    import { contain, cover } from "contain-cover";
    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

    Installation and usage

    This JavaScript file use ES6 Module format. You can use transpile it with TraceurJS and BabelJS. To use directly I suggest using JSPM.

    jspm install npm:contain-cover

    You can also simply install it from npm

    npm install contain-cover


    npm i contain-cover

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