Improve view of google icon

app/views/hooks/_view_account_login_bottom.html.erb

@@ -3,7 +3,7 @@
 <% if Setting.plugin_redmine_omniauth_google[:oauth_authentification] %>
   <%= link_to oauth_google_path do %>
     <%= button_tag class: 'button-login' do %>
-      <%= image_tag('/plugin_assets/redmine_omniauth_google/images/google_login_icon.jpg', class: 'button-login-icon', alt: l(:login_via_google)) %>
+      <%= image_tag('/plugin_assets/redmine_omniauth_google/images/google_login_icon.png', class: 'button-login-icon', alt: l(:login_via_google)) %>
       <%= content_tag :div, l(:login_via_google), class: 'button-login-text' %>
     <% end %>
   <% end %>

assets/stylesheets/buttons.css

@@ -12,7 +12,8 @@
 
 .button-login-icon {
   float: left;
-  height: 25px;
+  height: 18px;
+  padding: 1px 0px 0px 4px;
 }
 
 .button-login-text {