Moritz Barsnick (2018-12-10): > That was my interpretation. It's a density, if units != 0, otherwise > the aspect ratio. (Would a density not correspond to the SAR? I.e. not > make sense with square pixels?)
I did not follow the beginning of the discussion, but just in case it can help and was not obvious in the first place: Having a density makes sense even for square pixels to carry the information of the physical size of the image. It makes sense if the original has a well-defined physical size, like a scanned document. Also, the density can give the aspect ratio, but there is a catch: if the density is 20 px/mm horizontally and 10 px/mm vertically, that means pixels are (1/20)×(1/10) mm², hence their aspect ratio is 10/20 = 1/2, not 20/10 = 2/1. Regards, -- Nicolas George
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