[mapserver-users] Re: [FWTools] Can someone help test a potential bug for me?

[Dane Springmeyer]

Roger,

Yes, I can replicate the 'edge' effect you describe in Mapnik as well,  
by either viewing a TileCache Mapnik layer in OL or specifically  
requesting of mapnik (using nik2img) the BBOX that tilecache requests.

The lines (actually missing pixel rows it seems) appear on the bottom  
edge of tile where the raster data is unrendered but not where vector  
data is effectively rendered.

These two bbox's trigger a one-pixel red line(where the raster file is  
not rendered) at the bottom of the image:

1) -20037508.34,10018754.17,-10018754.17,20037508.34
2) -20037508.34,0.0,0.0,20037508.34

...when requested as 256x256 tiles, while requesting a 255,256 tile  
will clip off the missing pixel row.


Sample image attached (not the upper red band is truly lacking data  
while the single pixel row on the bottom is the un-rendered data)

Dane



On Oct 27, 2008, at 11:58 AM, Roger André wrote:

> Hi Dane,
>
> A sample image will be too large to upload - it's just under 300 MB,  
> but I've attached a mapfile.  I can send a .tfw for anyone who isn't  
> able to add georeferencing to the image after they have created it.
>
> I would be interested in knowing from you whether a WMS request of  
> the same nature, but made to Mapnik, will yield the same results.   
> And I have already posted the same question to the GeoServer list as  
> well.
>
> Thanks,
>
> Roger
> --
>
> On Mon, Oct 27, 2008 at 10:54 AM, Dane Springmeyer  
> <blake at hailmail.net> wrote:
> Roger,
>
> Uploading a test case with a sample image and sample mapfile  
> prepackaged would be really useful to speed testing and keep  
> consistent.
>
> Dane
>
>
>
> On Oct 27, 2008, at 9:40 AM, Roger André wrote:
>
>> Hi,
>>
>> I'd like to ask for some help from a couple people running  
>> MapServer.  I would like to know if others are able to replicate  
>> some strange behavior I have noticed lately, and what versions of  
>> MapServer they are using.  Below are the steps needed, they don't  
>> take very long.
>>
>> Step 1.  Create a large rectangular image of Size 14400 x 7200.
>>
>> Step 2.  Assign georeferencing to the image:
>> gdal_translate -a_ullr -180 90 180 -90 -a_srs "EPSG:4326"  
>> big_black.tif wgs84_big_black.tif
>>
>> Step 3. Load this image into a MapServer layer and set a  
>> contrasting IMAGECOLOR in the mapfile (red works well).
>>
>> Step 4. Make sure you have a spherical mercator projection defined  
>> in your epsg file.
>> <900913> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0  
>> +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs <>
>>
>> Step 5. Make a WMS request for a tile that replicates one that  
>> TileCache makes:
>> http://localhost/cgi-bin/mapserv?map=/var/www/mapfiles/test/test.map
>> &layers=imagery
>> &srs=EPSG%3A900913
>> &version=1.1.1
>> &bbox=-20037508.34%2C-
>> 20037508.34%2C-10018754.1704%2C-10018754.1704
>> &service=WMS
>> &width=256
>> &styles=
>> &format=image%2Fpng
>> &request=GetMap
>> &height=256
>>
>> Step 6. Look at your resulting tile. Is it full of data from top to  
>> bottom, or is there a band of IMAGECOLOR at the bottom?
>>
>> Step 7.  Let me know your results.
>>
>> Thanks very much!
>>
>> Roger
>> --
>>
>> _______________________________________________
>> FWTools mailing list
>> FWTools at lists.maptools.org
>> http://lists.maptools.org/mailman/listinfo/fwtools
>> http://fwtools.maptools.org/
>
>
> <bug.map>

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