[mapguide-internals] tile edge effects using gdal provider in tiledmode

Tom Fukushima tom.fukushima at autodesk.com
Tue Feb 20 12:21:56 EST 2007

Hi Paul,

This is a problem with the tiling code when it creates a tile with a
raster (using the Autodesk raster provider or the GDAL provider).  I
debugged into this a while back and it looks like either: 1) the
extracted image (from the source feature source) used to create the tile
is sometimes offset incorrectly (like you say, this is a rounding error)
and/or 2) the image is not being stretched to fill the whole area of the
tile (GDRenderer.cpp line 553, has comment //TODO: do we need +1?). 

I tried #2 but the lines still came up a bit faded.  Someone with more
time is going to have to look into this.


-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org
[mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Paul
Spencer (External)
Sent: Tuesday, February 20, 2007 9:11 AM
To: MapGuide Internals Mail List
Subject: [mapguide-internals] tile edge effects using gdal provider in

I've got a client using the GDAL provider to render an ECW file.   
He's set up the map/viewer to use tiles rather than straight map draws
and he is getting some edge effects (white lines in this case) in his
tiles.  I've attached a small screengrab of part of the problem.

Any ideas?  Could this be a problem with the provider or is it more
likely a problem elsewhere?  Note that the edge effects do not appear on
every tile, nor on every edge of every tile, so perhaps it is a rounding
issue in tile generation somewhere?  Or in the provider?

|Paul Spencer                          pspencer at dmsolutions.ca    |
|Chief Technology Officer                                         |
|DM Solutions Group Inc                http://www.dmsolutions.ca/ |

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