Ed,
I already thought of something like this already. However, this should
not happen. If the images are seamless (our images are seamless and do
not have any borders) in the original projection, they should also be
seamless after a reprojection. Otherwise, I would call it a bug.
I just tested an older version of Mapserver (4.6.1). That one creates
seamless results, even if the images are reprojected. Only newer
versions (tested 4.8.1) produce non-seamless images. Can someone confirm
this?
Regards,
Dirk
Ed McNierney wrote:
Dirk -
I assume your tiled source images do not overlap, and that the originals
do not have white border strips around them.
If that's the case, this may be an inevitable artifact of the
reprojection. Look at the situation along one north/south edge between
two tiles.
If you render the tiles in the source projection you'll get two adjacent
vertical lines along the edges of each file, with no gap between them.
If you reproject the tiles, then you will have two adjacent edges that
are two diagonal lines. The distance between the edges may not be 1,
and may vary by a pixel along the course of those two diagonal lines.
When that happens, the images will sometimes overlap by one pixel (you
won't notice) and will sometimes leave a one-pixel gap (which is
obvious). The obvious gaps will repeat in a regular pattern since the
phase difference between the two diagonal lines will be regular and
repeating.
- Ed
Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA 01863
[EMAIL PROTECTED]
(978) 251-4242
-----Original Message-----
From: UMN MapServer Users List [mailto:[EMAIL PROTECTED] On
Behalf Of Dirk Jesko
Sent: Tuesday, March 14, 2006 3:04 AM
To: [email protected]
Subject: [UMN_MAPSERVER-USERS] Problem with reprojected images
Hi,
I set up a WMS for aerial images. The images are projected in
Gauss-Krueger 3 and have a size of one square kilometer. The WMS also
provides other projections, e.g. Gauss-Krueger 2-5, UTM, etc. If I query
the WMS with a projection other than the original one, I get little
white lines along the edges of the tiles (see the attached image). The
image format does not matter. How do I get rid of these? I can not find
any option that might be related to this. By the way, this also happens
if the data is accessed via mapscript or as normal cgi.
Thanks for any help.
Regards,
Dirk
