scaleDownThumbnail.js
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scaleDownThumbnail.js
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	/**
	* Popups thumbnails are requested from the server at a size
	* relative to the screen DPI. Since we're not making that
	* server request, instead using predefined models, we have to
	* scale the thumbnail dimensions down manually for low-dpi displays.
	*
	* We're only scaling images down and not up since the correct
	* behaviour for popup is to not display an image if it's too small.
	* An image that's too big wouldn't be requested in the first place.
	*
	* It's best to define hi-dpi images in the models, unless the purpose
	* is to display the thumbnail on a low-dpi display and not a hi-dpi one.
	*/

	import { default as CONSTANTS } from '../../src/constants';


	/**
	* Scaled down thumbnails for low-dpi displays.
	* @param {Object} thumbnail - PagePreviewModel.thumbnail property
	* @return {Object} PagePreviewModel.thumbnail property
	*/
	export default function scaleDownThumbnail( thumbnail ) {
	const
	x = thumbnail.width,
	y = thumbnail.height,
	ratio = Math.min(CONSTANTS.THUMBNAIL_SIZE / x, CONSTANTS.THUMBNAIL_SIZE / y),
	thumbSrc = thumbnail.source,
	maxPxSize = CONSTANTS.THUMBNAIL_SIZE + 'px',
	scaledSrc = thumbSrc.replace( /\d*.px/, maxPxSize );

	return Object.assign({}, thumbnail, {
	source: scaledSrc,
	width: x * ratio,
	height: y * ratio,
	});
	}