[Tilesathome] Empty land tiles

[spaetz]

While purging the blank tile database, I searched for small png files and found tons like this one:
http://tah.dev.openstreetmap.org/Tiles/tile/7/71/63.png
which is a real uploaded png file as can be seen from the info:
http://tah.dev.openstreetmap.org/Tiles/info.php?x=71&y=63&z=7&layer=tile

But it's simply empty land which should never have been uploaded. It was uploaded on 2007-06-02, so it's rather recent as well. Question:
 1) Does the t at h client make sure that we really don't upload empty land or sea tiles? I know it checks for black tiles already. Should it for blue/land tiles as well?

2) How can I best identify and delete those tiles? This one is 164 bytes large. Is that the smallest size for a 1-color png? should searching for those be sufficient? Or do I need some Image::gd tricks to make sure they have the correct color?

I am currently counting the number of 164 byte tiles files, but that can take some days :-).
What strategy would you recommend for getting rid of these?

spaetz
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