Simone,
So I have various maps in geotiff format. Usually the coordinate system used in
the maps I use is the old Finnish Uniform coordinate system (EPSG:2393). These
maps are available for whole Finland, but they come in tiles. The size of the
tile depends, of course, on the scale of the map. The address map used in the
example has a tile size of roughly 10 km x 10 km and pixel size of 10000 x
10000. In order to have a map for certain area it's necessary to combine
several tiles.
Now my data itself can be in almost every coordinate system: ETRS89, WGS84, old
Finnish systems etc. I store and plot the data separately. I only use GeoTools
to do various transformations, and mainly to plot the background map in the
coordinate system of the actual data. I plot the background map into
BufferImages of size 400 x 400 px in separate thread to speed up panning and
zooming the map -- kind of a Google maps like effect.
So the whole procedure is as follows:
// First a map context in constructed
crs = CRS.decode("EPSG:2392"); // Coordinate system depends on the actual data
mapContext = new DefaultMapContext(crs);
mapContext.setTitle("Background maps");
// Then user can add various background maps to the context
// via UI. Background map can be a shape file or geotiff or
// what ever GeoTools supports
AbstractGridFormat format = GridFormatFinder.findFormat(file);
AbstractGridCoverage2DReader reader = format.getReader(file, hints);
[...]
mapContext.addLayer(reader, style);
[...]
// Different map tile
mapContext.addLayer(reader, style);
[...]
// Different map tile
mapContext.addLayer(reader, style);
// Now there are, for example, three GeoTiffs covering a certain area
// Then the actual plotting of the background map in separate thread
// The corners of the tile to be plotted (in CRS of the data)
double x1, y1, x2, y2;
BufferedImage image = [...]
Graphics2D g = image.createGraphics();
StreamingRenderer renderer = new StreamingRenderer();
renderer.setContext(mapContext);
renderer.paint(g, new Rectangle(0, 0,
image.getWidth(),
image.getHeight()),
new ReferencedEnvelope(y1, y2, x1, x2,
mapContext.getCoordinateReferenceSystem()));
// Notify the UI that a new image is available
[...]
Then I just plot all the images side by side in the UI view and plot my data
model on top of it. I am not sure if this is the bast way to do it, but this
works perfectly with shape files and also with geotiffs that happen to be in
the same coordinate reference system as my data. The only problem so far is
that the method produces borders when it is necessary to do transformations for
the geotiffs.
Thank you very much for any hints!
Markus
________________________________
From: [email protected] [mailto:[email protected]] On Behalf Of Simone
Giannecchini
Sent: Thursday, October 07, 2010 2:44 AM
To: Sunela Markus
Cc: [email protected]
Subject: Re: [Geotools-gt2-users] How to change border color used when
transforming geotiff?
Dear Markus,
we have added the aforementioned parameter lately therefore it is not well
documented yet (daniele can you please provide some info?).
Aside, I think that your problem requires a different solution since if you
reproject the single images separately you will still get a bad result even if
you manage to
tweak the bkg color. What you need is to mosaic the images in their original
CRS and then reproject the entire thing afterwards. This way you would not get
this annoying effect at the edges.
In order to be more specific I would need a bit more info about what you are
doing.
Regards,
Simone.
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On Wed, Oct 6, 2010 at 1:55 PM, Sunela Markus
<[email protected]<mailto:[email protected]>> wrote:
Hello,
In my project I need to render a map that consists of several GeoTiff-files,
which are in EPSG:2393, in EPSG:2392. While GeoTools makes the transformation
fine, but it leaves black or brown (value 0.0) borders around the geotiffs when
rendering. The transformation involves rotating the geotiffs. Because of this,
the single geotiffs have very large and visible seams instead of forming a nice
and continuous map.
This is illustrated in the attached picture with two different geotiffs
(different maps altogether) used as a background. I render the map context with
different geotiffs added as layers in pieces of 400x400 px which are stored in
a cache.
Is there a way to change how the borders are handled? Preferrably the renderer
should draw only the existing data or draw the borders with full transparency.
I noticed that there is Resample.BACKGROUND_VALUES hint in
org.geotools.coverage.processing.operation. Is it the right thing to use and
how can I pass it to the rendering pipeline?
Thank you very much,
Markus
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