TIFF Tag MaskedAreas
|Code||50830 (hex 0xC68E)|
|Type||SHORT or LONG|
|Count||4 * number of rectangles|
Used in Raw IFD of DNG files.
This tag contains a list of non-overlapping rectangle coordinates of fully masked pixels, which can be optionally used by DNG readers to measure the black encoding level.
The order of each rectangle's coordinates is: top, left, bottom, right.
If the raw image data has already had its black encoding level subtracted, then this tag should not be used, since the masked pixels are no longer useful.
Note that DNG writers are still required to include estimate and store the black encoding level using the black level DNG tags. Support for the MaskedAreas tag is not required of DNG readers.