# rect-cover

> Computes a transform between two rectangles the same way as background-size cover

Latest version **1.0.0** (published 2018-03-17) · MIT license · 0 weekly downloads

## Install

```sh
npm install rect-cover
pnpm add rect-cover
yarn add rect-cover
bun add rect-cover
```

## Health

**Score 20/100 (F)** — status: abandoned.

Positive: esm support; no vulnerabilities.

Warnings: low downloads; no types.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.0.0 |
| Published | 2018-03-17 |
| First published | 2018-03-16 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | ESM + CommonJS |
| Node | >=6 |
| Dependencies | 0 |
| Unpacked size | 125.9 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 1 |
| Author | Travis Fischer |
| Maintainers | fisch0920 |
| Keywords | rect, cover, background-size |

## Links

- npm: https://www.npmjs.com/package/rect-cover
- Repository: https://github.com/transitive-bullshit/rect-cover
- npm.io page: https://npm.io/package/rect-cover

## Recent versions

- 1.0.0 (latest) — 2018-03-17
- 0.1.0 — 2018-03-16

## README

# rect-cover ([demo](https://transitive-bullshit.github.io/rect-cover/))

> Computes a transform between two rectangles the same way as `background-size: cover`.

[![NPM](https://img.shields.io/npm/v/rect-cover.svg)](https://www.npmjs.com/package/rect-cover) [![Build Status](https://travis-ci.org/transitive-bullshit/rect-cover.svg?branch=master)](https://travis-ci.org/transitive-bullshit/rect-cover) [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com)

## Intro

Simulating `background-size: cover` is very useful for canvas animations, drawing sprites in games, and rendering videos. This module is used as part of our video rendering pipeline at [Automagical](https://automagical.ai/).

## Install

```bash
npm install --save rect-cover
```

## Usage

Check out the [demo](https://transitive-bullshit.github.io/rect-cover/) to understand what this module does.

```js
const rectCover = require('rect-cover')

const {
  scale,
  translate
} = rectCover({ width: 500, height: 500 }, { width: 1280, height: 720 })

// CSS transforms apply the rightmost operation first.
// Note that this assumes a transform-origin of `top left`.
const transform = `translate(${translate.x}px, ${translate.y}px) scale(${scale})`
```

## API

### rectCover(viewport, image)

Returns a 2D affine transform defined by `{ scale: Number, translate: { x: Number, y: Number } }` such that the given `image` will fully cover the `viewport` while maintaining its original aspect ratio.

Note that you'll want to apply the `scale` transform first followed by the `translate`.

#### viewport

Type: `{ width: Number, height: Number }`

The viewport you want to draw the image into.

#### image

Type: `{ width: Number, height: Number }`

The dimensions of the image to be drawn.

## Related

- [rect-contain](https://github.com/transitive-bullshit/rect-contain)
- [rect-crop](https://github.com/gre/rect-crop) if you need to mimic rect-cover with a `zoom` ratio and `center` point (eg, for [kenburns effects](https://github.com/gre/kenburns))
- [css background-size](https://developer.mozilla.org/en-US/docs/Web/CSS/background-size)

## License

MIT © [Travis Fischer](https://github.com/transitive-bullshit)

---
_Source: https://npm.io/package/rect-cover · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._