[OSM-dev] NOT-saving empty Mapnik tiles

Igor Podolskiy igor.podolskiy at vwi-stuttgart.de
Fri Aug 12 19:02:27 BST 2011


Hi Markus,

sorry, I misread your first mail, it's not a PIL.Image but a 
mapnik.Image - it doesn't have all those fancy methods of a PIL Image. I 
don't know how to convert from mapnik to PIL now, either :( My fault.

But I just had another idea.

If your current method works for you and it's just about reducing disk 
IO, you just could use StringIO [1] or the like and save the PNG image 
to a buffer first, then check its length and conditionally save it to disk:

import StringIO
buf = StringIO.StringIO()
# ... render the image somehow here ...
im.save(buf, 'png256')
if buf.len > 116:
    f = open(tile_name, 'wb')
    f.write(buf.getvalue())
    f.close()
buf.close()

Bye
Igor

[1] http://docs.python.org/library/stringio.html



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