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

[Roger André]

Hi Dane,

Thanks very much for the testing.  Sounds like maybe there is a problem
then.

So far, the only workaround that I have found which seems to work well is
one that is somewhat akin to fixing the missing scanlines in Landsat data.
I create a very low resolution version of the data and serve it underneath
the high-res layer.  It fills in the missing row of pixels without being
noticeable, and looks pretty good.  Not sure if it will work with all data
sets though, and it's at best a bandaid fix.
--


On Mon, Oct 27, 2008 at 4:58 PM, Dane Springmeyer <blake at hailmail.net>wrote:

> 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
>> --
>>
>> _______________________________________________
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>> FWTools at lists.maptools.org
>> http://lists.maptools.org/mailman/listinfo/fwtools
>> http://fwtools.maptools.org/
>>
>>
>>
> <bug.map>
>
>
>
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