diff --git a/app/controllers/attachments_controller.rb b/app/controllers/attachments_controller.rb
index edae9b0cc..74a11a1c7 100644
--- a/app/controllers/attachments_controller.rb
+++ b/app/controllers/attachments_controller.rb
@@ -61,7 +61,7 @@ class AttachmentsController < ApplicationController
   end
 
   def thumbnail
-    if @attachment.thumbnailable? && Setting.thumbnails_enabled? && thumbnail = @attachment.thumbnail
+    if @attachment.thumbnailable? && thumbnail = @attachment.thumbnail(:size => params[:size])
       if stale?(:etag => thumbnail)
         send_file thumbnail,
           :filename => filename_for_content_disposition(@attachment.filename),
diff --git a/app/models/attachment.rb b/app/models/attachment.rb
index 9aeee07d0..a1c232d16 100644
--- a/app/models/attachment.rb
+++ b/app/models/attachment.rb
@@ -171,9 +171,17 @@ class Attachment < ActiveRecord::Base
 
   # Returns the full path the attachment thumbnail, or nil
   # if the thumbnail cannot be generated.
-  def thumbnail
+  def thumbnail(options={})
     if thumbnailable? && readable?
-      size = Setting.thumbnails_size.to_i
+      size = options[:size].to_i
+      if size > 0
+        # Limit the number of thumbnails per image
+        size = (size / 50) * 50
+        # Maximum thumbnail size
+        size = 800 if size > 800
+      else
+        size = Setting.thumbnails_size.to_i
+      end
       size = 100 unless size > 0
       target = File.join(self.class.thumbnails_storage_path, "#{id}_#{digest}_#{size}.thumb")
 
diff --git a/config/routes.rb b/config/routes.rb
index 87e656475..d904c9b9e 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -264,7 +264,7 @@ RedmineApp::Application.routes.draw do
   match 'attachments/:id/:filename', :controller => 'attachments', :action => 'show', :id => /\d+/, :filename => /.*/, :via => :get
   match 'attachments/download/:id/:filename', :controller => 'attachments', :action => 'download', :id => /\d+/, :filename => /.*/, :via => :get
   match 'attachments/download/:id', :controller => 'attachments', :action => 'download', :id => /\d+/, :via => :get
-  match 'attachments/thumbnail/:id', :controller => 'attachments', :action => 'thumbnail', :id => /\d+/, :via => :get
+  match 'attachments/thumbnail/:id(/:size)', :controller => 'attachments', :action => 'thumbnail', :id => /\d+/, :via => :get, :size => /\d+/
   resources :attachments, :only => [:show, :destroy]
 
   resources :groups do
diff --git a/lib/redmine/wiki_formatting/macros.rb b/lib/redmine/wiki_formatting/macros.rb
index cd1d83596..81e5999f8 100644
--- a/lib/redmine/wiki_formatting/macros.rb
+++ b/lib/redmine/wiki_formatting/macros.rb
@@ -116,6 +116,24 @@ module Redmine
         @included_wiki_pages.pop
         out
       end
+
+      desc "Displays a clickable thumbnail of an attached image. Examples:\n\n<pre>{{thumbnail(image.png)}}\n{{thumbnail(image.png, size=300, title=Thumbnail)}}</pre>"
+      macro :thumbnail do |obj, args|
+        args, options = extract_macro_options(args, :size, :title)
+        filename = args.first
+        raise 'Filename required' unless filename.present?
+        size = options[:size]
+        raise 'Invalid size parameter' unless size.nil? || size.match(/^\d+$/)
+        size = size.to_i
+        size = nil unless size > 0
+        if obj && obj.respond_to?(:attachments) && attachment = Attachment.latest_attach(obj.attachments, filename)
+          title = options[:title] || attachment.title
+          img = image_tag(url_for(:controller => 'attachments', :action => 'thumbnail', :id => attachment, :size => size), :alt => attachment.filename)
+          link_to(img, url_for(:controller => 'attachments', :action => 'show', :id => attachment), :class => 'thumbnail', :title => title)
+        else
+          raise "Attachment #{filename} not found"
+        end
+      end
     end
   end
 end
diff --git a/test/functional/attachments_controller_test.rb b/test/functional/attachments_controller_test.rb
index 949ed3979..11c3faa95 100644
--- a/test/functional/attachments_controller_test.rb
+++ b/test/functional/attachments_controller_test.rb
@@ -262,43 +262,44 @@ class AttachmentsControllerTest < ActionController::TestCase
     def test_thumbnail
       Attachment.clear_thumbnails
       @request.session[:user_id] = 2
-      with_settings :thumbnails_enabled => '1' do
-        get :thumbnail, :id => 16
-        assert_response :success
-        assert_equal 'image/png', response.content_type
-      end
+
+      get :thumbnail, :id => 16
+      assert_response :success
+      assert_equal 'image/png', response.content_type
+    end
+
+    def test_thumbnail_should_not_exceed_maximum_size
+      Redmine::Thumbnail.expects(:generate).with {|source, target, size| size == 800}
+
+      @request.session[:user_id] = 2
+      get :thumbnail, :id => 16, :size => 2000
+    end
+
+    def test_thumbnail_should_round_size
+      Redmine::Thumbnail.expects(:generate).with {|source, target, size| size == 250}
+
+      @request.session[:user_id] = 2
+      get :thumbnail, :id => 16, :size => 260
     end
 
     def test_thumbnail_should_return_404_for_non_image_attachment
       @request.session[:user_id] = 2
-      with_settings :thumbnails_enabled => '1' do
-        get :thumbnail, :id => 15
-        assert_response 404
-      end
-    end
 
-    def test_thumbnail_should_return_404_if_thumbnails_not_enabled
-      @request.session[:user_id] = 2
-      with_settings :thumbnails_enabled => '0' do
-        get :thumbnail, :id => 16
-        assert_response 404
-      end
+      get :thumbnail, :id => 15
+      assert_response 404
     end
 
     def test_thumbnail_should_return_404_if_thumbnail_generation_failed
       Attachment.any_instance.stubs(:thumbnail).returns(nil)
       @request.session[:user_id] = 2
-      with_settings :thumbnails_enabled => '1' do
-        get :thumbnail, :id => 16
-        assert_response 404
-      end
+
+      get :thumbnail, :id => 16
+      assert_response 404
     end
 
     def test_thumbnail_should_be_denied_without_permission
-      with_settings :thumbnails_enabled => '1' do
-        get :thumbnail, :id => 16
-        assert_redirected_to '/login?back_url=http%3A%2F%2Ftest.host%2Fattachments%2Fthumbnail%2F16'
-      end
+      get :thumbnail, :id => 16
+      assert_redirected_to '/login?back_url=http%3A%2F%2Ftest.host%2Fattachments%2Fthumbnail%2F16'
     end
   else
     puts '(ImageMagick convert not available)'
diff --git a/test/integration/routing/attachments_test.rb b/test/integration/routing/attachments_test.rb
index ba4bb2c36..fc54dea41 100644
--- a/test/integration/routing/attachments_test.rb
+++ b/test/integration/routing/attachments_test.rb
@@ -49,6 +49,10 @@ class RoutingAttachmentsTest < ActionController::IntegrationTest
            { :method => 'get', :path => "/attachments/thumbnail/1" },
            { :controller => 'attachments', :action => 'thumbnail', :id => '1' }
          )
+    assert_routing(
+           { :method => 'get', :path => "/attachments/thumbnail/1/200" },
+           { :controller => 'attachments', :action => 'thumbnail', :id => '1', :size => '200' }
+         )
     assert_routing(
            { :method => 'delete', :path => "/attachments/1" },
            { :controller => 'attachments', :action => 'destroy', :id => '1' }
diff --git a/test/unit/lib/redmine/wiki_formatting/macros_test.rb b/test/unit/lib/redmine/wiki_formatting/macros_test.rb
index abc880068..4bea9a57d 100644
--- a/test/unit/lib/redmine/wiki_formatting/macros_test.rb
+++ b/test/unit/lib/redmine/wiki_formatting/macros_test.rb
@@ -119,4 +119,24 @@ class Redmine::WikiFormatting::MacrosTest < ActionView::TestCase
   def test_macro_child_pages_without_wiki_page_should_fail
     assert_match /can be called from wiki pages only/, textilizable("{{child_pages}}")
   end
+
+  def test_macro_thumbnail
+    assert_equal '<p><a href="/attachments/17" class="thumbnail" title="testfile.PNG"><img alt="testfile.PNG" src="/attachments/thumbnail/17" /></a></p>',
+      textilizable("{{thumbnail(testfile.png)}}", :object => Issue.find(14))
+  end
+
+  def test_macro_thumbnail_with_size
+    assert_equal '<p><a href="/attachments/17" class="thumbnail" title="testfile.PNG"><img alt="testfile.PNG" src="/attachments/thumbnail/17/200" /></a></p>',
+      textilizable("{{thumbnail(testfile.png, size=200)}}", :object => Issue.find(14))
+  end
+
+  def test_macro_thumbnail_with_title
+    assert_equal '<p><a href="/attachments/17" class="thumbnail" title="Cool image"><img alt="testfile.PNG" src="/attachments/thumbnail/17" /></a></p>',
+      textilizable("{{thumbnail(testfile.png, title=Cool image)}}", :object => Issue.find(14))
+  end
+
+  def test_macro_thumbnail_with_invalid_filename_should_fail
+    assert_include 'test.png not found',
+      textilizable("{{thumbnail(test.png)}}", :object => Issue.find(14))
+  end
 end