brandonb927 · December 1, 2019 15:38 · joshuabaker · Aug 6, 2014 · brandonb927 · Oct 4, 2014
diff --git a/image-2x.less b/image-2x.less
 /**
 * I converted the SCSS mixin to LESS for the awesome coders like myself in response to a blog post on 37Signals - http://37signals.com/svn/posts/3271-easy-retina-ready-images-using-scss
 * 
 * Update: 2014-08-04 - Updated a long-standing bug where retina images were shown no matter what in the first background-image property.
 *                    - Updated retina media query to be more reliable ()
 * Update: 2013-11-13 - Picked up another technique thanks to reading this post from Tyler Tate, auto-fill in the second filename for the retina image, http://tylertate.com/blog/2013/06/11/retina-images-using-media-queries-and-LESS-CSS.html
 * Update: 2013-04-16 - Have recently found a few use cases when using a retina pattern from Subtle Patterns on the <body>, this has come in handy
 * Update: 2013-04-05 - Some research in the Wordpress Core(http://core.trac.wordpress.org/ticket/22238#comment:5) was pointed out that some tests may be redundant (Thanks @kbav) so I've cleaned these up
 * Update: 2012-12-29 - Updated AGAIN to add MS IE10 declaration and fix wonky 'min--moz-' declaration which Mozilla engineers are aware of
 * Update: 2012-11-21 - Updated again based on information from an article I found, added dppx and changed opera ratio to target more devices (http://www.uifuel.com/hd-retina-display-media-queries/)
 * Update: 2012-11-17 - Updated based on Wordpress Core to target even more devices! Thanks @Wordpress <3 (http://core.trac.wordpress.org/changeset/22629)
 */

 .image-2x(@image, @width, @height, @repeat: no-repeat) {
  @filename  : ~`/(.*)\.(jpg|jpeg|png|gif)/.exec(@{image})[1]`;
  @extension : ~`/(.*)\.(jpg|jpeg|png|gif)/.exec(@{image})[2]`;
  background-image: ~`"url(@{filename}.@{extension})"`;
  background-repeat: @repeat;
  
  @media
    only screen and (-webkit-min-device-pixel-ratio: 2),
    only screen and (   min--moz-device-pixel-ratio: 2),
    only screen and (     -o-min-device-pixel-ratio: 2/1),
    only screen and (        min-device-pixel-ratio: 2),
    only screen and (                min-resolution: 192dpi),
    only screen and (                min-resolution: 2dppx) {
      /* on retina, use image that's scaled by 2 */
      background-image: ~`"url(@{filename}@2x.@{extension})"`;
      background-size: @width @height;
  }
 }

 /**
 * The filename convention for the retina-sized image is [email protected], 
 * but of course you can change this in the mixin when you use it
 */

 .image-logo {
  width: 100px;
  height: 50px;
  .image-2x('image.png', 100px, 50px);
 }

 .reapeating-background-image {
  background-color: #444;
  .image-2x('image.png', 200px, 200px, repeat);
 }
	/**
	* I converted the SCSS mixin to LESS for the awesome coders like myself in response to a blog post on 37Signals - http://37signals.com/svn/posts/3271-easy-retina-ready-images-using-scss
	*
	* Update: 2014-08-04 - Updated a long-standing bug where retina images were shown no matter what in the first background-image property.
	* - Updated retina media query to be more reliable ()
	* Update: 2013-11-13 - Picked up another technique thanks to reading this post from Tyler Tate, auto-fill in the second filename for the retina image, http://tylertate.com/blog/2013/06/11/retina-images-using-media-queries-and-LESS-CSS.html
	* Update: 2013-04-16 - Have recently found a few use cases when using a retina pattern from Subtle Patterns on the <body>, this has come in handy
	* Update: 2013-04-05 - Some research in the Wordpress Core(http://core.trac.wordpress.org/ticket/22238#comment:5) was pointed out that some tests may be redundant (Thanks @kbav) so I've cleaned these up
	* Update: 2012-12-29 - Updated AGAIN to add MS IE10 declaration and fix wonky 'min--moz-' declaration which Mozilla engineers are aware of
	* Update: 2012-11-21 - Updated again based on information from an article I found, added dppx and changed opera ratio to target more devices (http://www.uifuel.com/hd-retina-display-media-queries/)
	* Update: 2012-11-17 - Updated based on Wordpress Core to target even more devices! Thanks @Wordpress <3 (http://core.trac.wordpress.org/changeset/22629)
	*/

	.image-2x(@image, @width, @height, @repeat: no-repeat) {
	@filename : ~`/(.*)\.(jpg\|jpeg\|png\|gif)/.exec(@{image})[1]`;
	@extension : ~`/(.*)\.(jpg\|jpeg\|png\|gif)/.exec(@{image})[2]`;
	background-image: ~`"url(@{filename}.@{extension})"`;
	background-repeat: @repeat;

	@media
	only screen and (-webkit-min-device-pixel-ratio: 2),
	only screen and ( min--moz-device-pixel-ratio: 2),
	only screen and ( -o-min-device-pixel-ratio: 2/1),
	only screen and ( min-device-pixel-ratio: 2),
	only screen and ( min-resolution: 192dpi),
	only screen and ( min-resolution: 2dppx) {
	/* on retina, use image that's scaled by 2 */
	background-image: ~`"url(@{filename}@2x.@{extension})"`;
	background-size: @width @height;
	}
	}

	/**
	* The filename convention for the retina-sized image is [email protected],
	* but of course you can change this in the mixin when you use it
	*/

	.image-logo {
	width: 100px;
	height: 50px;
	.image-2x('image.png', 100px, 50px);
	}

	.reapeating-background-image {
	background-color: #444;
	.image-2x('image.png', 200px, 200px, repeat);
	}