[udig-devel] GeoTiff Zoom -- A slick feature is marred by a glitch

["Gary Lucas" <gwlucas@xxxxxxxxxxxxx>]

I've observed a glitch in the zoom function when working with
GeoTiffs that marrs what would otherwise be a pretty
slick implementation in uDig 1.1.RC6a   

I was given a somewhat large (25 Meg) Tiff image
with a high level of detail and asked to plot it.
Because the size of the image was so much larger than the
screen, it was initially shown at much less than its full
resolution.  Intending to observe a finer level of detail,
I pressed the magnifying glass icon a few times in rapid 
succession to zoom in.  As I did, uDig
immediately responded with a "zoomed" image by blooming
the pixels.  When I stopped clicking, there was a pause and
then the correctly rendered image (with a higher resolution)
popped in.

I say that this WOULD have been a very slick implementation
(and an idea I intend to copy for my own applications in the future)
had it not been for a glitch.  For whatever 
reason, while rendering the zoomed image, the map view
was blanked out and filled with white. Since this process
took a few seconds, it was rather distracting. But, worse, it
spoiled what would have been a very nice effect.

Anyway I do admire what the uDig developers were able to
accomplish, and I hope that you can correct this glitch in
some future release because it would really make for a nice 
feature.


-----

On a related note, I must add that I'm not really sure that the
image I have is a proper GeoTiff...  I think it might actually be
a ESRI World format (related to the GeoTools WorldImageReader class).
While that might have some bearing on the problem, the real issue
here is that it is often very difficult to figure out what
is going on with uDig.  For example, when I first tried to load the tiff
it just wouldn't show up. I imported it into the Catalog, tried to add
it to a new map, and got an empty view for my troubles.  I tried it a 
couple more times and finally, for reasons that escape me, it showed up.
It's worked everytime since.  I'm a bit worried about that because I have
no idea why it works now or what I will do if it ever stops working.

What I see missing in uDig in general is a set of clear signals to the
user as to what is going on and how to proceed with performing 
basic tasks. For example, when data doesn't plot, it would be nice
to know why not. Because the application is so new, I'm sure that this
is not entire unexpected. Still I think that the user's experience
of flow of operations through the session is something that could
stand more attention.  

Also, I still can't combine the Tiff image with any geo-referenced
data from other sources. As I said, I suspect that my subject data is
not a proper GeoTiff (there is a .tfw file that came with it). I'll figure
it out eventually...  But what's lacking here are some diagnostics that
would help the user. Ideally, when I hit across a "gumption trap" of
this sort, I'd like to have some way of obtaining details on the
data to see what's gone wrong. Perhaps something so simply as a 
"properties" menu to tell me what kind of data I'm looking at.
Maybe you, the uDig developers, have ways of knowing why something
doesn't plot, but at least this particular user does not.
The information in the Operations/Layer Summary and 
Operations/Resource Summary may be a start in the right direction
but I'm not sure what the information currently presented really
tells me.


Finally I want to say that I truly hope that uDig will become
a very successful application. And I think that there is a danger
that this lack of communicativeness on the part of the application
is going to hamper its effectiveness every bit as much as any
perceived lack of features.  So I hope readers of this note
will take my remarks in the proper light

Gary





---
Gary W. Lucas, Senior Software Engineer
Sonalysts, Inc
215 Parkway North
Waterford, CT 06320
(860) 326-3682