Enhance NPM | npm.io

Enhance

A flexible node.js module for serving high-res images to high pixel density devices.

Installation

Add enhance to your package.json file and run npm install.

Alternatively, you can run npm install enhance --save.

If you're using Hem, make sure to add it to your slug.json file as a dependency.

Usage

Require Enhance in your app, optionally passing in initialization options, and typically set to a global variable. In CoffeeScript, it would look something like:

Enhance = require('enhance')(options)

You can also use the browserified version by including build/enhance.js in your app and passing in your options to the Enhance object on the window.

Enhance(options).render('image.png')

`render`

Given no configuration options, Enhance falls back to Apple's convention of suffixing image file names with @2x before the extension if a Retina or other high DPI display is detected.

For example, consider calling the main function render on a Retina device:

Enhance.render('image.png')
# => "image@2x.png"

If the device does not have a high DPI, the call to render will simply return the file name unaltered (unless initialization options have been passed).

`isHiDPI`

You can use the available method isHiDPI to check if a device is one of high DPI. The default device pixel ratio is 1.3, but isHiDPI takes an optional ratio parameter to use as a threshold.

`isMobileDevice`

To detect whether a user is on a mobile device, you can call isMobileDevice, which uses max-width media queries as a test.

By default, tablets are not considered mobile devices. However, you can consider them by enabling the tabletAsMobile option when initializing Enhance:

Additionally, you can override the width breakpoints for both mobile and tablet devices, see configuration. The default breakpoints are:

phoneBreakpoint:  480
tabletBreakpoint: 1024

Configuration

Enhance accepts initial configuration options to provide flexibility if your app doesn't follow Apple's Retina naming convention.

host

Prepends the given host value to file names passed to the call to render.

Default: null

Enhance = require('enhance')(host: 'http://www.example.com')
Enhance.render('image.png')
# => "http://www.example.com/image@2x.png" (high DPI)

suffix

The string to prepend before the file name extension.

Default: "@2x"

Enhance = require('enhance')(suffix: '_2x')
Enhance.render('image.png')
# => "image_2x.png" (high DPI)

render

Custom callback function to use in place of the default render method. Passes in a helper object that makes available the following:

isHiDPI
_ - lodash function with additional extensions:
- joinURIComponents - Joins any number of URI string component arguments while preserving double slashes (i.e. the case of http://)
src - String argument of render
Any and all other parameters passed upon initialization or the call to render

options =
  host: 'http://example.com/transform'
  suffix: '_2x'
  render: (helpers) ->
    if helpers.isHiDPI()
      path = "#{encodeURIComponent(helpers.src)}/resize/#{helpers.width*2}x#{helpers.height*2}#"
    else
      path = "#{encodeURIComponent(helpers.src)}/resize/#{helpers.width}x#{helpers.height}#"
    helpers._.joinURIComponents(helpers.host, path)

Enhance = require('enhance')(options)

Enhance.render('image.png', width: 50, height: 100)