|Extension TIFF Tag Indexed|
TIFF Tag Reference
TIFF Tag Indexed
Aims to broaden the support for indexed images to include support for any color space.
Indexed images are images where the pixels do not represent color values, but rather an index (usually 8-bit) into a separate color table, the ColorMap.
ColorMap is required for an Indexed image.
The specification supplement defines these values:
0 = not indexed
The specification supplement not being very clear, presumably it means that palette images can be coded either:
- With PhotometricInterpretation = PaletteColor. A ColorMap must be included, and the ColorMap values are RGB.
If the Indexed field is included, it must equal 0, but it is probably best to not include it in this case.
In both cases, SamplesPerPixel must be 1.
This explaines the specification supplement warning not to use both the Indexed flag and PhotometricInterpretation = PaletteColor for the same image.