A.73.4.2 Pixel Padding, Real World Value Mapping and Palette Color LUT

A.73.4.2 Pixel Padding, Real World Value Mapping and Palette Color LUT (Current)
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When a Corneal Topography Map is superimposed on the corresponding source image, the background color of the map that is specified by the Pixel Padding Value (0028,0120) Attribute may be rendered "transparently" so that parts of the underlying source image become visible (see Section B.5.1.17 “Corneal Topography Map Storage SOP Class” in PS3.4). To support this rendering, no mapping shall be defined in the Real World Value Mapping Sequence (0040,9096) for the value of the Pixel Padding Value (0028,0120) Attribute. The Pixel Padding Range Limit (0028,0121) Attribute shall not be used for this IOD.

Note

In order to facilitate the rendering and to preserve backward compatibility with existing implementations, it is suggested that a value of 0 for the Pixel Padding Value (0028,0120) Attribute be used, and to explicitly define this background color in the Palette Color Lookup Table as black (i.e. the corresponding entry in Red, Green and Blue Palette Color Lookup Table Data (0028,1201-1203) is set to 0).
There is no reason to specify a range of Pixel Padding Values, since the Corneal Topography Map is the result of a calculation and the background color can, therefore, be specified as a distinct value.