[Tilesathome] t at h server next generation

[spaetz]

On Fri, Jul 04, 2008 at 03:15:48PM -0500, Ian Dees wrote:
> On Fri, Jul 4, 2008 at 3:24 AM, spaetz <osm at sspaeth.de> wrote:
> 
> > On Thu, Jul 03, 2008 at 02:49:24PM -0500, Ian Dees wrote:
> > > What are the tilesGen.pl modifications? I've been working on a similar
> > > thing, but for Google AppEngine (also in Python).
> >
> > Ahh. as I do it in django, we seem to be basically doing the same thing
> > :-). oops.. Join forces?
> 
> 
> Sounds good to me. One limitation with AppEngine is that you can't zip/unzip
> tilesets, so the client needs to be modified more extensively to upload
> individual tiles or the whole tilestrips. I like your implementation better
> so far :)

Thanks. Doesn' AppEngine contain the standard python libraries? In any case, my implementation can deal with any archive that can be uncompressed. In the long term it woulg be great if the client could upload tileset files directly, but I took a more evolutionary approach. Uploading z12 tilesets seams to work flawlessly now. Of course I have no idea yet how the tile serving from a tileset file scales yet. tests will be needed.

Tileset file description
========================
I have a converter that converts the single tiles into tileset files. Tileset files contain.

0: a tileset file version(currently 1), so I can modify the file format at a later point
2: user id of user who uploaded the thing
4: offset of tile 1 (z0x0y0)
8: offeset of tile 2  (z1x0y0)
12 offset of file 3 (z1x1y0)
...
5468:offset after tile 1365(points to end of file)
5472:data png1
...

offset is either a pointer to the file position where the png data is, or it can also be a blankness value:
0=unknown
1=land
2=sea
3=transparent (not implemented yet)

There are no recursive blankness lookups, all blank tiles in a tilesetfile will have the blankness set. I plan to maintain a database of completely blank tilesets, to save the 6kb files in the pacific ocean etc, but that's not implemented yet.

spaetz

P.S. I will try to put all this in the wiki soon