Get the vertical data layout associated with an image format, expressed as a coordinate system parity sign.


The format name; one of SUPPORTED_FORMATS

Either +1 or -1, depending on the format’s preferred parity. FITS has +1 and
everything else has -1 (for now).


See Image.get_parity_sign() for a discussion of general parity concepts. While parity should be associated with coordinate systems, rather than image file formats, there is a connection in the vertical data layout that different file formats are assumed to use. In particular, WWT assumes that most image file formats use a “top-down” data layout: if the data buffer is a 2D array expressed in standard C/Python conventions, the zeroth row (data[0,:]) is located at the top of the image. FITS formats, on the other hand, are assumed to be bottoms-up: the zeroth row is at the bottom. While proper WCS coordinates can convey either parity in a FITS file, WWT’s renderer assumes bottoms-up.