Index: includes/Linker.php
===================================================================
--- includes/Linker.php	(revision 16089)
+++ includes/Linker.php	(working copy)
@@ -455,7 +455,7 @@
 	}
 
 	/** @todo document */
-	function makeImageLinkObj( $nt, $label, $alt, $align = '', $width = false, $height = false, $framed = false,
+	function makeImageLinkObj( $nt, $label, $alt, $align = '', $width = false, $height = false, $unit="px", $framed = false,
 	  $thumb = false, $manual_thumb = '', $page = null )
 	{
 		global $wgContLang, $wgUser, $wgThumbLimits, $wgGenerateThumbnailOnParse;
@@ -473,7 +473,7 @@
 		$url   = $img->getViewURL();
 		$error = $prefix = $postfix = '';
 
-		wfDebug( "makeImageLinkObj: '$width'x'$height', \"$label\"\n" );
+		wfDebug( "makeImageLinkObj: '$width'x'$height$unit', \"$label\"\n" );
 
 		if ( 'center' == $align )
 		{
@@ -517,24 +517,38 @@
 			if ( $height == false )
 				$height = -1;
 			if ( $manual_thumb == '') {
-				$thumb = $img->getThumbnail( $width, $height, $wgGenerateThumbnailOnParse );
-				if ( $thumb ) {
-					// In most cases, $width = $thumb->width or $height = $thumb->height.
-					// If not, we're scaling the image larger than it can be scaled,
-					// so we send to the browser a smaller thumbnail, and let the client do the scaling.
+				if( $unit == "px" ) {
+					$thumb = $img->getThumbnail( $width, $height, $wgGenerateThumbnailOnParse );
+					if ( $thumb ) {
+						// In most cases, $width = $thumb->width or $height = $thumb->height.
+						// If not, we're scaling the image larger than it can be scaled,
+						// so we send to the browser a smaller thumbnail, and let the client do the scaling.
 
-					if ($height != -1 && $width > $thumb->width * $height / $thumb->height) {
-						// $height is the limiting factor, not $width
-						// set $width to the largest it can be, such that the resulting
-						// scaled height is at most $height
-						$width = floor($thumb->width * $height / $thumb->height);
+						if ($height != -1 && $width > $thumb->width * $height / $thumb->height) {
+							// $height is the limiting factor, not $width
+							// set $width to the largest it can be, such that the resulting
+							// scaled height is at most $height
+							$width = floor($thumb->width * $height / $thumb->height);
+						}
+						$height = round($thumb->height * $width / $thumb->width);
+
+						wfDebug( "makeImageLinkObj: client-size set to '$width x $height'\n" );
+						$url = $thumb->getUrl();
+					} else {
+						$error = htmlspecialchars( $img->getLastError() );
 					}
-					$height = round($thumb->height * $width / $thumb->width);
-
-					wfDebug( "makeImageLinkObj: client-size set to '$width x $height'\n" );
-					$url = $thumb->getUrl();
-				} else {
-					$error = htmlspecialchars( $img->getLastError() );
+				} elseif( $unit == "ex" || $unit == "em" ) {
+					if( $height == -1 ) {
+						$height = ($img->height/$img->width)*$width;
+					} else {
+						if( ($width/$img->width) < ($height/$img->height) ) {
+							$height = ($img->height/$img->width)*$width;
+						} else {
+							$width = ($img->width/$img->height)*$height;
+						}
+					}
+					$width = round($width,3);
+					$height = round($height,3);
 				}
 			}
 		} else {
@@ -542,6 +556,7 @@
 			$height = $img->height;
 		}
 
+
 		wfDebug( "makeImageLinkObj2: '$width'x'$height'\n" );
 		$u = $nt->escapeLocalURL();
 		if ( $error ) {
@@ -551,11 +566,11 @@
 			//$s .= "<br />{$alt}<br />{$url}<br />\n";
 		} else {
 			$s = '<a href="'.$u.'" class="image" title="'.$alt.'">' .
-				 '<img src="'.$url.'" alt="'.$alt.'" ' .
+				 '<img src="'.$url.'" alt="'.$alt.'" style="' .
 				 ( $width
-				 	? ( 'width="'.$width.'" height="'.$height.'" ' )
+				 	? ( 'width:'.$width.$unit.'; height:'.$height.$unit.'; ' )
 				 	: '' ) .
-				 'longdesc="'.$u.'" /></a>';
+				 '" longdesc="'.$u.'" /></a>';
 		}
 		if ( '' != $align ) {
 			$s = "<div class=\"float{$align}\"><span>{$s}</span></div>";
Index: includes/Parser.php
===================================================================
--- includes/Parser.php	(revision 16089)
+++ includes/Parser.php	(working copy)
@@ -4105,7 +4105,7 @@
 	 * Parse image options text and use it to make an image
 	 */
 	function makeImage( &$nt, $options ) {
-		global $wgUseImageResize;
+		global $wgUseImageResize, $wgAllowEmExImageSizes;
 
 		$align = '';
 
@@ -4126,13 +4126,15 @@
 		$mwLeft   =& MagicWord::get( 'img_left' );
 		$mwRight  =& MagicWord::get( 'img_right' );
 		$mwNone   =& MagicWord::get( 'img_none' );
-		$mwWidth  =& MagicWord::get( 'img_width' );
+		$mwPxWidth  =& MagicWord::get( 'img_width_px' );
+		$mwEmWidth  =& MagicWord::get( 'img_width_em' );
+		$mwExWidth  =& MagicWord::get( 'img_width_ex' );
 		$mwCenter =& MagicWord::get( 'img_center' );
 		$mwFramed =& MagicWord::get( 'img_framed' );
 		$caption = '';
 
 		$width = $height = $framed = $thumb = false;
-		$manual_thumb = '' ;
+		$manual_thumb = $unit = '' ;
 
 		foreach( $part as $key => $val ) {
 			if ( $wgUseImageResize && ! is_null( $mwThumb->matchVariableStartToEnd($val) ) ) {
@@ -4153,8 +4155,8 @@
 			} elseif ( ! is_null( $mwNone->matchVariableStartToEnd($val) ) ) {
 				# remember to set an alignment, don't render immediately
 				$align = 'none';
-			} elseif ( $wgUseImageResize && ! is_null( $match = $mwWidth->matchVariableStartToEnd($val) ) ) {
-				wfDebug( "img_width match: $match\n" );
+			} elseif ( $wgUseImageResize && ! is_null( $match = $mwPxWidth->matchVariableStartToEnd($val) ) ) {
+				wfDebug( "img_width_px match: $match\n" );
 				# $match is the image width in pixels
 				if ( preg_match( '/^([0-9]*)x([0-9]*)$/', $match, $m ) ) {
 					$width = intval( $m[1] );
@@ -4162,6 +4164,27 @@
 				} else {
 					$width = intval($match);
 				}
+				$unit = 'px';
+			} elseif ( $wgAllowEmExImageSizes && ! is_null( $match = $mwEmWidth->matchVariableStartToEnd($val) ) ) {
+				wfDebug( "img_width_em match: $match\n" );
+				# $match is the image width in em units
+				if ( preg_match( '/^([0-9]*)x([0-9]*)$/', $match, $m ) ) {
+					$width = intval( $m[1] );
+					$height = intval( $m[2] );
+				} else {
+					$width = intval($match);
+				}
+				$unit = 'em';
+			} elseif ( $wgAllowEmExImageSizes && ! is_null( $match = $mwExWidth->matchVariableStartToEnd($val) ) ) {
+				wfDebug( "img_width_ex match: $match\n" );
+				# $match is the image width in pixels
+				if ( preg_match( '/^([0-9]*)x([0-9]*)$/', $match, $m ) ) {
+					$width = intval( $m[1] );
+					$height = intval( $m[2] );
+				} else {
+					$width = intval($match);
+				}
+				$unit = 'ex';
 			} elseif ( ! is_null( $mwFramed->matchVariableStartToEnd($val) ) ) {
 				$framed=true;
 			} else {
@@ -4179,7 +4202,7 @@
 
 		# Linker does the rest
 		$sk =& $this->mOptions->getSkin();
-		return $sk->makeImageLinkObj( $nt, $caption, $alt, $align, $width, $height, $framed, $thumb, $manual_thumb );
+		return $sk->makeImageLinkObj( $nt, $caption, $alt, $align, $width, $height, $unit, $framed, $thumb, $manual_thumb );
 	}
 
 	/**
Index: languages/MessagesEn.php
===================================================================
--- languages/MessagesEn.php	(revision 16089)
+++ languages/MessagesEn.php	(working copy)
@@ -240,7 +240,9 @@
 	'img_right'              => array( 1,    'right'                  ),
 	'img_left'               => array( 1,    'left'                   ),
 	'img_none'               => array( 1,    'none'                   ),
-	'img_width'              => array( 1,    '$1px'                   ),
+	'img_width_px'              => array( 1,    '$1px'                   ),
+	'img_width_em'              => array( 1,    '$1em'                   ),
+	'img_width_ex'	              => array( 1,    '$1ex'                   ),
 	'img_center'             => array( 1,    'center', 'centre'       ),
 	'img_framed'             => array( 1,    'framed', 'enframed', 'frame' ),
 	'int'                    => array( 0,    'INT:'                   ),