want that image popup in html when user click on thumbnail.

app/helpers/application_helper.rb

@@ -1396,7 +1396,7 @@ module ApplicationHelper
 
   # Returns the javascript tags that are included in the html layout head
   def javascript_heads
-    tags = javascript_include_tag('jquery-1.8.3-ui-1.9.2-ujs-2.0.3', 'application')
+    tags = javascript_include_tag('jquery-1.8.3-ui-1.9.2-ujs-2.0.3', 'application', 'jquery.colorbox-min')
     unless User.current.pref.warn_on_leaving_unsaved == '0'
       tags << "\n".html_safe + javascript_tag("$(window).load(function(){ warnLeavingUnsaved('#{escape_javascript l(:text_warn_on_leaving_unsaved)}'); });")
     end

public/javascripts/application.js

@@ -622,3 +622,18 @@ $(document).ready(setupAjaxIndicator);
 $(document).ready(hideOnLoad);
 $(document).ready(addFormObserversForDoubleSubmit);
 
+function img_thumbnails() {
+  $('.thumbnails a').colorbox({rel:'nofollow'});
+  $('.attachments').find('a').each(function(index, element) {
+    if($(element).attr('href').indexOf('.jpg') > 0) {
+      $(element).colorbox({rel:'nofollow'});
+    }
+    if($(element).attr('href').indexOf('.png') > 0) {
+      $(element).colorbox({rel:'nofollow'});
+    }
+    if($(element).attr('href').indexOf('.gif') > 0) {
+      $(element).colorbox({rel:'nofollow'});
+    }
+  })
+}
+$(document).ready(img_thumbnails);

public/stylesheets/nyan.css

@@ -99,6 +99,76 @@ span[id^=valid_user] {
 .font_color_orange {
     color: #E8770D;
 }
+/* colorbox
+*******************************************************************************/
+/*
+    Colorbox Core Style:
+    The following CSS is consistent between example themes and should not be altered.
+*/
+#colorbox, #cboxOverlay, #cboxWrapper{position:absolute; top:0; left:0; z-index:9999; overflow:hidden;}
+#cboxWrapper {max-width:none;}
+#cboxOverlay{position:fixed; width:100%; height:100%;}
+#cboxMiddleLeft, #cboxBottomLeft{clear:left;}
+#cboxContent{position:relative;}
+#cboxLoadedContent{overflow:auto; -webkit-overflow-scrolling: touch;}
+#cboxTitle{margin:0;}
+#cboxLoadingOverlay, #cboxLoadingGraphic{position:absolute; top:0; left:0; width:100%; height:100%;}
+#cboxPrevious, #cboxNext, #cboxClose, #cboxSlideshow{cursor:pointer;}
+.cboxPhoto{float:left; margin:auto; border:0; display:block; max-width:none; -ms-interpolation-mode:bicubic;}
+.cboxIframe{width:100%; height:100%; display:block; border:0; padding:0; margin:0;}
+#colorbox, #cboxContent, #cboxLoadedContent{box-sizing:content-box; -moz-box-sizing:content-box; -webkit-box-sizing:content-box;}
+
+/* 
+    User Style:
+    Change the following styles to modify the appearance of Colorbox.  They are
+    ordered & tabbed in a way that represents the nesting of the generated HTML.
+*/
+#cboxOverlay{background:#fff;}
+#colorbox{outline:0;}
+#cboxTopLeft{width:25px; height:25px; background:url(/images/colorbox/border1.png) no-repeat 0 0;}
+#cboxTopCenter{height:25px; background:url(/images/colorbox/border1.png) repeat-x 0 -50px;}
+#cboxTopRight{width:25px; height:25px; background:url(/images/colorbox/border1.png) no-repeat -25px 0;}
+#cboxBottomLeft{width:25px; height:25px; background:url(/images/colorbox/border1.png) no-repeat 0 -25px;}
+#cboxBottomCenter{height:25px; background:url(/images/colorbox/border1.png) repeat-x 0 -75px;}
+#cboxBottomRight{width:25px; height:25px; background:url(/images/colorbox/border1.png) no-repeat -25px -25px;}
+#cboxMiddleLeft{width:25px; background:url(/images/colorbox/border2.png) repeat-y 0 0;}
+#cboxMiddleRight{width:25px; background:url(/images/colorbox/border2.png) repeat-y -25px 0;}
+#cboxContent{background:#fff; overflow:hidden;}
+.cboxIframe{background:#fff;}
+#cboxError{padding:50px; border:1px solid #ccc;}
+#cboxLoadedContent{margin-bottom:20px;}
+#cboxTitle{position:absolute; bottom:0px; left:0; text-align:center; width:100%; color:#999;}
+#cboxCurrent{position:absolute; bottom:0px; left:100px; color:#999;}
+#cboxLoadingOverlay{background:#fff url(/images/colorbox/loading.gif) no-repeat 5px 5px;}
+
+/* these elements are buttons, and may need to have additional styles reset to avoid unwanted base styles */
+#cboxPrevious, #cboxNext, #cboxSlideshow, #cboxClose {border:0; padding:0; margin:0; overflow:visible; width:auto; background:none; }
+
+/* avoid outlines on :active (mouseclick), but preserve outlines on :focus (tabbed navigating) */
+#cboxPrevious:active, #cboxNext:active, #cboxSlideshow:active, #cboxClose:active {outline:0;}
+
+#cboxSlideshow{position:absolute; bottom:0px; right:42px; color:#444;}
+#cboxPrevious{position:absolute; bottom:0px; left:0; color:#444;}
+#cboxNext{position:absolute; bottom:0px; left:63px; color:#444;}
+#cboxClose{position:absolute; bottom:0; right:0; display:block; color:#444;}
+
+/*
+  The following fixes a problem where IE7 and IE8 replace a PNG's alpha transparency with a black fill
+  when an alpha filter (opacity change) is set on the element or ancestor element.  This style is not applied to or needed in IE9.
+  See: http://jacklmoore.com/notes/ie-transparency-problems/
+*/
+.cboxIE #cboxTopLeft,
+.cboxIE #cboxTopCenter,
+.cboxIE #cboxTopRight,
+.cboxIE #cboxBottomLeft,
+.cboxIE #cboxBottomCenter,
+.cboxIE #cboxBottomRight,
+.cboxIE #cboxMiddleLeft,
+.cboxIE #cboxMiddleRight {
+    filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#00FFFFFF,endColorstr=#00FFFFFF);
+}
+
+
 
 /* 模态窗口
 *******************************************************************************/