// @flow
import hiDPI from './hiDPI'
/**
* The retina-image mixin is a helper to generate a retina background image and non-retina
* background image. The retina background image will output to a HiDPI media query. The mixin uses
* a _2x.png filename suffix by default.
*
* @example
* // Styles as object usage
* const styles = {
* ...retinaImage('my-img')
* }
*
* // styled-components usage
* const div = styled.div`
* ${retinaImage('my-img')}
* `
*
* // CSS as JS Output
* div {
* backgroundImage: 'url(my-img.png)',
* '@media only screen and (-webkit-min-device-pixel-ratio: 1.3),
* only screen and (min--moz-device-pixel-ratio: 1.3),
* only screen and (-o-min-device-pixel-ratio: 1.3/1),
* only screen and (min-resolution: 144dpi),
* only screen and (min-resolution: 1.5dppx)': {
* backgroundImage: 'url(my-img_2x.png)',
* }
* }
*/
function retinaImage(filename: string, backgroundSize?: string, extension?: string = 'png', retinaFilename?: string, retinaSuffix?: string = '_2x') {
if (!filename) {
throw new Error('Please supply a filename to retinaImage() as the first argument.')
}
// Replace the dot at the beginning of the passed extension if one exists
const ext = extension.replace(/^\./, '')
const rFilename = retinaFilename ? `${retinaFilename}.${ext}` : `${filename}${retinaSuffix}.${ext}`
return {
backgroundImage: `url(${filename}.${ext})`,
[hiDPI()]: {
backgroundImage: `url(${rFilename})`,
backgroundSize,
},
}
}
export default retinaImage
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