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blank tiles

I'd opt for a tinyint or boolean or whatever denoting whether the tile is blank or not. In an ideal world, the system generating the tile can know exactly that it is blank, and pass an appropriate message to the server, which updates the database accordingly (and puts a symlink in the file system where the tile would be expected). For the time being, we would simply have the import script set blank=true if the size of the file is less than a defined treshold, or, if one wanted to be more precise, whenever the size is below a certain treshold, decompress the image and look a the contents to decide whether it is empty or not. The details of this mechanism can be worked out at any time in the future, but I think that a positive statement "this tile is blank" is much better than a vague "this tile has 939 bytes". --Frederik Ramm 22:40, 27 February 2007 (UTC)