negative size shape is allowed

[mdsumner]

I noticed that values of shape can be negative, this doesn't seem desirable, it has the effect of flipping the transform as expected.

from odc.geo.geobox import GeoBox
ex = [-120, -100, 35, 55]

g = GeoBox.from_bbox([140, -43, 160, -23],
   "EPSG:4326", 
   shape = [-1, 1])
g
#GeoBox((-1, 1), Affine(20.0, 0.0, 140.0,
#       0.0, 20.0, -60.0), CRS('EPSG:4326'))

I only noticed because I wanted to do the GDAL thing of setting one of the dimensions to zero, whereby you only need to use the shape of one side and it helpfully calculates the other from the aspect ratio of the extent. This is nice because it gives a very short heuristic for "about this detailed" that matches how images work, rather than having to specify a specific resolution or do gymnastics to work out the ratio.

So, maybe negative shape should be disallowed, and if it's of interest I could PR the shape = [0, n] or shape = [n, 0].

Thanks!

[Kirill888]

Thanks Michael, we should probably raise ValueError on such inputs, PR is welcome. 0 should be allowed though, I would not clip to 0 however, raise an error when negative dimensions are requested, or whatever numpy.zeros would do in such case , which is ValueError: negative dimensions are not allowed.

[mdsumner]

sorry, is that typo about allowing 0?

I can't tell if you mean

• allow 0 (for infinitely thin or infinitely short y- x- intervals), you wouldn't want a 0,0 geobox I'm assuming
• disallow 0
• allow 0 for one of rows/columns, which expands to a normal non-zero based on the non-zero value (for auto-aspect aware dimension-ing so the user doesn't have to do gymnastics to determine the right complementary value)

or something else I'm not understanding (?)

[Kirill888]

0 is ok, less than 0 is not

[mdsumner]

I was just getting into this ... thanks! haha