The three values of Palette Color Lookup Table Descriptor (0028,1101-1103) describe the format
of the Lookup Table Data in the corresponding Data Element (0028,1201-1203) or (0028,1221-
1223).
The first value is the number of entries in the lookup table. When the number of table entries is
equal to 216 then this value shall be 0.
The second value is the first stored pixel value mapped. This pixel value is mapped to the first
entry in the Lookup Table Data. All image pixel values less than the first value mapped are also
mapped to the first entry in the Lookup Table Data. An image pixel value one greater than the
first value mapped is mapped to the second entry in the Lookup Table Data. Subsequent image
pixel values are mapped to the subsequent entries in the Lookup Table Data up to an image pixel
value equal to number of entries + first value mapped – 1, which is mapped to the last entry in the
Lookup Table Data. Image pixel values greater than or equal to number of entries + first value
mapped are also mapped to the last entry in the Lookup Table Data.
The third value specifies the number of bits for each entry in the Lookup Table Data. It shall take
the value of 8 or 16. The LUT Data shall be stored in a format equivalent to 8 or 16 bits allocated
where the high bit is equal to bits allocated-1.
When the Palette Color Lookup Table Descriptor (0028,1101-1103) are used as part of the
Palette Color Lookup Table Module or the Supplemental Palette Color Lookup Table Module, the
third value shall be equal to 16.
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发表于 2003-3-28 15:16:04