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

jburns jzburns at gmail.com
Sat May 2 11:39:00 BST 2009


> Are you trying to use the .meta file as a png or the file returned via
the URL? 

through the browser, not direct (ie meta file) access. The first request
times out as per renderd readme, and the second produces the 0.png download
in my browser, which then seems to be malformed.

running this command:
$ ./convert_meta -u
Converting tiles in layer Default

I get the error message:

Meta file /var/lib/mod_tile/Default/0/0/0/0/0/0.meta too small to contain

so my feeling is that the meta file production is breaking somewhere, and
hence the png's are not being produced correctly either. 

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.

I appreciate all your help.


Jon Burgess-2 wrote:
> On Fri, 2009-05-01 at 10:59 -0700, jburns wrote:
>> Hi,
>> I am having a problem in that the pngs being generated and returned by my
>> apache & renderd & mapnik process are not "proper" pngs in that they are
>> rejected by various file viewers as being malformed.
>> I have compiled, built and run renderd against the latest mapnik svn. I
>> have
>> configured apache and renderd  gets invoked correctly to generate the
>> meta
>> files. Typical renderd output is:
>> from the request:
>> I see the renderd output:
>> Render fd(6) xml(Default), z(1), x(0), y(0)
>> META TILE 1 0-1 0-1
>> DONE TILE Default 1 0-1 0-1
>> Produced .meta: /var/lib/mod_tile/Default/1/0/0/0/0/0.meta
>> Furthermore, my postgres is being queried properly. Running
>> generate_image.py (ie, testing mapnik / osm.xml) works and produces
>> beautiful pngs.
>> Any ideas or tips where to start debugging this one?
> Are you trying to use the .meta file as a png or the file returned via
> the URL? 
> The .meta file is an archive of 64 individual tile pngs you will need to
> unpack them using the "convert_meta" utility if you want to access them
> directly. This utility needed a minor update to add support for the
> multiple layers which I just added to SVN so do an update before you try
> to use it.
> $ ./convert_meta -u
> Converting tiles in layer Default
> Produced tile: /var/lib/mod_tile/Default/5/0/0/0/0/128.png
> Produced tile: /var/lib/mod_tile/Default/5/0/0/0/0/129.png
> Produced tile: /var/lib/mod_tile/Default/5/0/0/0/0/130.png
> Produced tile: /var/lib/mod_tile/Default/5/0/0/0/0/131.png
> Produced tile: /var/lib/mod_tile/Default/5/0/0/0/0/132.png
> Produced tile: /var/lib/mod_tile/Default/5/0/0/0/0/133.png
> ...
> These png files should be valid:
> $ file /var/lib/mod_tile/Default/5/0/0/0/0/131.png
> /var/lib/mod_tile/Default/5/0/0/0/0/131.png: PNG image, 256 x 256, 8-bit
> colormap, non-interlaced
> $ file /var/lib/mod_tile/Default/14/0/17/245/184/119.png
> /var/lib/mod_tile/Default/14/0/17/245/184/119.png: PNG image, 256 x 256,
> 1-bit colormap, non-interlaced
> 	Jon
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