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-------------------- J P R O J . 4 --------------------
This is the first release of a JNI wrap of the main proj4 functions.
PLEASE read the following information.
For more information on the JPROJ4 maintenance please contact me through the
web page at:
http://www.hydrologis.com
---------------------------------------------------
Compilation:
-------------
With the right flag during configuration time (see ./configure --help), the
native part of the jproj lib is compiled inside the main proj library and the
java part is automatically built into the jproj.jar library.
The java part on it's own part is compiled by running ant inside the "jniwrap" folder.
This will compile the classes and archive them in a jar library.
This applies to Linux, Macos and Windows (and virtually to every system
supporting java).
Requirements:
-------------
Beyond the ones already put by proj, you need:
- j2sdk, the java standard development kit
- ant, to run the build
- doxygen for the documentation generation
Documentation:
--------------
The documentation is held inside the code and can be retrieved by running
doxygen inside the folder jniwrap. This will create the html format
documentation inside of jniwrap/docs
License:
--------
GPL
Authors:
--------
Andrea Antonello (andrea.antonello@hydrologis.com)
Usage & a fast example:
-----------------------
The jproj.jar is all is needed to implement proj support in java applications.
The whole job is done by the proj4, so there are just a couple of functions that
be used.
The best way is to see everything through an example.
In the following example we read projection informations and data from a file
and then transform the data and query the information.
________________________________________________________________________________
First step:
create a text file, let's say test.txt, with the following in it:
srcProj: +proj=latlong +datum=WGS84
destProj: +init=epsg:32632
rows: 1
46 11 194.0
This contains info about a source and destination projection, the number of data
triplets and then the data (in this case just one point)
________________________________________________________________________________
Step two:
create a test code. Simply copy the following into a file called Main.java. The
code is commented to see what we are doing:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedHashMap;
import org.proj4.Proj4;
import org.proj4.ProjectionData;
public class Main
{
public static void main(String[] args) throws IOException
{
// print out the usage if no argument was given
if (args.length < 1)
{
System.out.println();
System.out.println("Usage: Proj datafile");
System.out.println();
System.exit(0);
}
// now the input file is going to be read
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(new File(args[0]))));
LinkedHashMap mapHeader = new LinkedHashMap();
// read the header
String line = null;
for (int i = 0; i < 3; i++)
{
if ((line = br.readLine()) != null)
{
String[] header = line.split(":", 2);
if (header.length <= 2)
{
mapHeader.put(header[0].trim(), header[1].trim());
}
else
{
System.out.println("Wrong file format");
System.exit(0);
}
}
}
// with what you see above, the header was read
// now I can define the number of rows of data triplets
int rows = new Integer((String) mapHeader.get("rows")).intValue();
double[][] testCoord = new double[rows][2];
double[] testValues = new double[rows];
System.out.println("Source coordinates and values:");
// start reading the data
for (int i = 0; i < rows; i++)
{
if ((line = br.readLine()) != null)
{
String[] values = line.split(" +");
if (values.length == 3)
{
testCoord[i][0] = new Double(values[0].trim()).doubleValue();
testCoord[i][1] = new Double(values[1].trim()).doubleValue();
testValues[i] = new Double(values[2].trim()).doubleValue();
System.out.println("x = " + testCoord[i][0] + " y = "
+ testCoord[i][1] + " z = " + testValues[i]);
}
else
{
System.out.println("Wrong file format or empty line found");
}
}
}
// create the dataset
// this is necessary to be able to transform
ProjectionData dataTP = new ProjectionData(testCoord, testValues);
// here we go with the instantiation of the proj4 object
Proj4 testProjection = new Proj4((String) mapHeader.get("srcProj"),
(String) mapHeader.get("destProj"));
// the instantiation of the proj4 object instantiated also the projection
// objects for source and destination projection
// therefore we can already print the projection infos:
testProjection.printSrcProjInfo();
testProjection.printDestProjInfo();
// and transform, passing as parameter the created dataset:
testProjection.transform(dataTP, 1, 1);
// if we need the parameters as Hashmap for a later use:
LinkedHashMap testMap = testProjection.getSrcProjInfo();
// and let us print them to screen to see them
System.out.println();
System.out.println("Proj as a Hashmap");
System.out.println("******************************************************");
System.out.println(testMap.toString());
}
}
________________________________________________________________________________
Step three
compile the Main code:
we assume that proj was compiled with the right flag to support jproj.
Therefore we have a library called jproj.jar.
Thus we compile the Main.java with the command:
javac -classpath <path to the jar library>/jproj.jar Main.java
and execute the created test case with:
java -cp .:<path to the jar library>/jproj.jar -Djava.library.path=<path to the libproj, if needed> Main test.txt
That's it, enjoy!
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