MapGuide Enterprise Wishes

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*Andy Morsell
Message 1 of 1 (154 Views)

Color Image Transparency

154 Views, 0 Replies
04-14-2006 08:46 PM

I know I've been harping on Autodesk for literally
years about this, but it has not been fixed and therefore the problem
continues and I won't shut up about it.  I have run into this problem
developing MapGuide apps for multiple clients and others have reported similar
issues, so it's not an isolated wish. 

 

The fact that the existing MapGuide 6.5 and
below does not support transparency for non-bitonal images has been a major
problem for several of my clients.  The problem that arises is that tiled
imagery is often obtained from a source in one coordinate system and then is
transformed to the desired map coordinate system.  This results in black
"wedges" along all of the edges of the resultant orthogonal image. 
MapGuide 6.5 does not allow you to specify a null color value (to non-bitonal
images) so when image tiles are viewed together, the sliver from one image
blocks part of another image.  To get around this, the clients have had to
spend a large amount of time, resources and money (for special image software)
pre-processing the imagery.  We end up having to mosaic all of the
projected images into one gigantic image and then tile them back out into
orthogonal pieces and then build the MapGuide raster image catalog. 
This is the kind of processing that you kick off and let the server run all
night and day before it's done.

 

One example is a client that obtained
satellite images from a State DNR.  The images were in a UTM coordinate
system and their MapGuide maps in State Plane.  So, the images had to be
transformed.  We used Blue Marble Geographic Transformer since it will
transform a 1 GB image in under 5 minutes - it's amazing.  This is where it
should stop - we should be able to create a raster image catalog from these
images and specify that color 0,0,0 is null and should be treated as transparent
but MapGuide doesn't support that.  Instead, we have to use the above
described methods to get around this problem.  This customer had to
purchase another $5,000 worth of high-end imaging softare, PCI Geomatica in this
case (Raster Design is woefully underpowered for this kind of thing) and
thye spent at least another $5,000 in labor to process and manage the
data.  Some might think that I should be happy that they had to
pay us to do this work, but I see it as a design flaw and would like to
see the problem fixed.

 

 If MapGuide ever supports raster
re-projection on the fly, this will also be an issue.

 

Attached is a screenshot from MapGuide 6.5
that illustrates this problem.  Each of the image tiles has been
transformed resulting in the null data areas either as solid white or solid
black.  If these areas were transparent, you would either see valid image
data from an adjoining tile or underlying MaGuide layer information.  This
example is from a different client than the one I described above and they opted
to leave it the way it is because they did not have the budget to mosaic and
tile.  Instead, they turn on and off individual images if they need to see
the data underneath of an adjoining one. 


Thanks for considering
this.



--
Andy Morsell, P.E.
Spatial
Integrators, Inc.

href="http://www.SpatialGIS.com">http://www.SpatialGIS.com

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