Sometimes, it is necessary to create the RT version of an image that will be used from a template or from a stylesheet. However, symmetric images can be automatically generated avoiding the necessity to create a mirrored version of an image and furthermore avoiding maintenance cost.
The web resource filter uses the same naming pattern as the skin service. When an image ends with the -rt suffix, the portal will attempt to locate the original image and create a mirror of it.
For instance: requesting the image /GateInResources/skin/DefaultSkin/webui/component/UITabSystem/UITabs/background/NormalTabStyle-rt.gif returns a mirror of the image /GateInResources/skin/DefaultSkin/webui/component/UITabSystem/UITabs/background/NormalTabStyle.gif.
It is important to consider whether the image to be mirrored is symmetrical as this will impact its final appearance.
Here is an example combining stylesheet and images:
line-height: 24px;
background: url('background/NavigationTab.gif') no-repeat right top; /* orientation=lt */
background: url('background/NavigationTab-rt.gif') no-repeat left top; /* orientation=rt */
padding-right: 2px; /* orientation=lt */
padding-left: 2px; /* orientation=rt */