+/**
+ * Bracket a given device pixel ratio to one of [1, 1.5, 2].
+ *
+ * This is useful for grabbing images on the fly with sizes based on the display
+ * density, without causing slowdown and extra thumbnail renderings on devices
+ * that are slightly different from the most common sizes.
+ *
+ * The bracketed ratios match the default 'srcset' output on MediaWiki thumbnails,
+ * so will be consistent with default renderings.
+ *
+ * @static
+ * @inheritable
+ * @return {number} Device pixel ratio
+ */
+$.bracketDevicePixelRatio = function ( baseRatio ) {
+ if ( baseRatio > 1.5 ) {
+ return 2;
+ } else if ( baseRatio > 1 ) {
+ return 1.5;
+ } else {
+ return 1;
+ }
+};
+
+/**
+ * Get reported or approximate device pixel ratio, bracketed to [1, 1.5, 2].
+ *
+ * This is useful for grabbing images on the fly with sizes based on the display
+ * density, without causing slowdown and extra thumbnail renderings on devices
+ * that are slightly different from the most common sizes.
+ *
+ * The bracketed ratios match the default 'srcset' output on MediaWiki thumbnails,
+ * so will be consistent with default renderings.
+ *
+ * - 1.0 means 1 CSS pixel is 1 hardware pixel
+ * - 1.5 means 1 CSS pixel is 1.5 hardware pixels
+ * - 2.0 means 1 CSS pixel is 2 hardware pixels
+ *
+ * @static
+ * @inheritable
+ * @return {number} Device pixel ratio
+ */
+$.bracketedDevicePixelRatio = function () {
+ return $.bracketDevicePixelRatio( $.devicePixelRatio() );
+};
+