Jody (and others):
I work with Ajay, and here is the (potentially) offensive code snippet:
GridCoverage2D gc = curConfig.getGc();
Envelope bbox = request.getBBox();
double[] initSrcPoint = {bbox.getMinX(), bbox.getMaxY(),
bbox.getMaxX(), bbox.getMinY()};
// Assume UTM now
// pack an empty array
double[] finalPoint = {0, 0, 0, 0};
GridGeometry gg = gc.getGridGeometry();
MathTransform initialTransform = gg.getGridToCRS();
//GridCoverageRenderer gcr = new
GridCoverageRenderer(gg, null);
try {
MathTransform inverseTransform =
initialTransform.inverse();
inverseTransform.transform(initSrcPoint, 0,
finalPoint, 0, 2);
} catch (TransformException e) {
getLogger().error("Unable to perform math transform
on [" + geoTiffPath + "] Reason [" + e + "]");
}
Rectangle desiredSegment = new Rectangle();
desiredSegment.x = (int) finalPoint[0];
desiredSegment.y = (int) finalPoint[1];
// Determine width and height based on nw corner - se
corner
// absolute pixel differences
desiredSegment.width = (int) Math.abs(finalPoint[0] -
finalPoint[2]);
desiredSegment.height = (int) Math.abs(finalPoint[1] -
finalPoint[3]);
PlanarImage planarImage = (PlanarImage)
gc.getRenderedImage();
BufferedImage sourceImage;
try {
Rectangle2D rect = new
Rectangle2D.Double(finalPoint[0],finalPoint[1],desiredSegment.width,desi
redSegment.height);
sourceImage =
planarImage.getAsBufferedImage(rect.getBounds(), null);
} catch (IllegalArgumentException iae) {
// most likely requested image dimensions are not
contained
// in the image file
getLogger().debug("Requested image dimension [" +
desiredSegment.toString() + "] not found in planar image.",
iae);
return unshiftedImage;
}
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Jody Garnett
Sent: Friday, July 18, 2008 6:29 PM
To: AJ R
Cc: [email protected]
Subject: Re: [Geotools-gt2-users] Issue regarding alignment of geotiff
and postgis layer
AJ R wrote:
> Now coming to the issue we are facing. When the layers are rendered on
> the map due to some weird inexplicable reason the 'ez' layer and
> 'mapBackGround' layer do not seem to be aligning properly. There is a
> slight difference in the rendering of the two layers. In addition as
> we move from top left hand side of the screen to the bottom right
> hand, the deviation increases. At higher zoom levels, the layers line
> up almost exactly but not perfectly.
Interesting.
> Has any one ever faced a similar situation.
I got a report of a similar problem (feature data and a MRSID file not
lining up) three weeks ago - until I am able to reproduce the problem I
was not going to annoy anyone.
> If yes could you take a guess at where in the whole (PostGRes - WMS
> server - GeoTiff renderer - PostGIS renderer - Mapbuilder/OpenLayer)
> hierarchy could the problem lie?
I suspect the raster resample code code - but that is only because it is
how the problem was first reported to me.
When we do a "resample" we actually take the inverse of the transform
used by the feature data...
DATA WORLD SCREEN
Geometry -transform-> Geometry -transform-> Shape
Image <-transform-> GridCoverage <-transform- pixel
The Data to World MathTransform is based on the referencing moodule, and
usually the EPSG database; you are using epsg-hsql or something?
epsg-wkt may not be quite as accurate.
So the kind of error you are talking about could be due to
MathTransform.inverse() not being quiet as accurate as the origional. To
test try setting up a MathTransform in each direction and see how close
the transformation is in one of the areas you are having problem.
The World to Screen is usually an AffineTransform and is going to be of
similar accuracy in both direction.
> Also could you let me know if there is a more effective way to render
> geotiff files as compared to the general mechanism i suggested in the
> Rendering section above
You are using the resample operation right?
> In case the above information is not helpful I would be glad to
> provide more information. I would appreciate any help with this issue.
We should report the bug; and if your data is not private some screen
snaps showing the problem would be helpful.
All the best,
Jody
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