[OSM-dev] bad pngs from mod_tile / renderd & meta files

[Iván Sánchez Ortega]

El Sábado, 2 de Mayo de 2009, jburns escribió:
> > I see this output:
> >
> > 0000  4d 45 54 41 40 00 00 00  00 00 00 00 00 00 00 00  META at ... ........
> > 0010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ........ ........
> > sometime later in the file I see:
> > 2150  00 00 00 00 89 50 4e 47  0d 0a 1a 0a 00 00 00 0d  .....PNG ........
> >
> > which I think is the start of a PNG? Not sure. My feeling is that the
> > meta file creation is faulty somewhere. Any further clues in debugging
> > renderd?

On the contrary, the meta files seem to be right - the "META@" header, and 
later the PNG files. That's normal.

What's *not* normal is that mod_tile is serving the full meta tile instead of 
the png tiles inside the meta tile.

Also, please look that the header of the meta tile contains a pointer to the 
tiles. e.g. in this meta tile of mine:

00000000  4d 45 54 41 40 00 00 00  00 00 00 00 00 00 00 00  |META at ...........|
00000010  00 00 00 00 14 02 00 00  64 21 00 00 00 00 00 00  |........d!......|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000210  00 00 00 00 89 50 4e 47  0d 0a 1a 0a 00 00 00 0d  |.....PNG........|

"14 02" = 0x0214 is the start of a tile, and "64 21" = 0x2164 is the lenght. 
Just in case, please check that you have that right in your meta tiles 
located in /var/lib/mod_tile.

This will tell us if the problem is in renderd (faulty generation of meta 
tiles) or in mod_tile itself (faulty reading of meta tiles)


> Any idea's where to start looking in renderd.c or gen_tile.cpp? BTW, my
> platform is OpenSolaris 11.08 101b, all tools compiled using SunStudio CC.

Hhhmm. Maybe the behaviour of SSCC and GCC are different, and the python 
scripts expect the behaviour of GCC. I can't tell.


Cheers,
-- 
----------------------------------
Iván Sánchez Ortega <ivan at sanchezortega.es>

http://ivan.sanchezortega.es
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