( Please ensure installation of OpenCL prior to running these programs )
This code was developed to demonstrate successful leveraging of OpenCL within
ImageJ using JOCL both locally and remotely (as a binary web service).
The folder structure of the source consists of the following folders:
src - Java and OpenCL source files (extension .cl)
sourcedata - PSF and 3D data used as a small sample data set for the FHT3D
Example.
lib - Libraries needed for classes using JOCL, ImageJ, and Hessian 4.0.7
native - Contains the dynamic libraries needed for runtime execution of
OpenCL code on various operating systems
Background
----------
To use OpenCL from Java in ImageJ we leverage JOCL. JOCL uses JNI to make calls
into the OpenCL API. The OpenCL code you write can also leverage JOCL to
accelerate execution of ImageJ plugins from Java. Since each OS has different
native JOCL native libraries, the runtime environment must be configured such
that the Java code can load the needed native libraries. For these samples,
three native libraries are needed: gluegen-rt, jocl, and
JOCL-'platform'-'arch'. If you look in the lib folder, you will find
-natives-xyz.jar files containing the respective libraries. Simply unzip each
of the three jar files and copy the dynamic files into the parent directory if
they are not already present. Then ensure that the platform specific jar (E.g.
JOCL-0.1.4-beta) is exported during the project build.
Notice the files fht.cl and sobel.cl in the source (src) directory. The Java
code in provided in the examples compile these two files for execution on the
OpenCL enabled device that is programmatically chosen at runtime. It is runtime
compilation of OpenCL that allows execution on any potential OpenCL enabled
device.
Start exploring the examples by viewing the developer comments in the file
SobelFilterExample.java. Notice the Main() method calls run() which use an
awt.Image type as an input parameter. Modify and run the Main() method as a
Java application with the VM Arguments -Xmx1024m.
Without modification, SobelFilterExample.java loads an image from a web server,
process it locally using OpenCL, and displays the results. There is nothing
novel about this example. It simply allows runtime testing of several system
configuration steps to ensure working configuration of JOCL and OpenCL native
libraries. Modify this example to suite your needs, but please ensure proper
JOCL and OpenCL configuration before proceeding.
Working within ImageJ: If developing an ImageJ plugin using OpenCL realize that
programatic control is passed to your plugin inside the PlugIn (or
PluginFilter) run() method. An example of this can be found in
src.demos.OpenCL_SobelFilter.java. For this plugin to run within ImageJ, the
JOCL jars and native libraries respective to the target platform will need to
be available by the ImageJ classloader. The supporting JOCL native libraries
can be copied into the plugin directory within ImageJ to allow plugin
implementations using OpenCL from Java to reference the installed native
libraries provided by the OpenCL installation.
Now that you have demonstrated use of OpenCL from Java and within ImageJ, you
may wish to see an a compute intensive example demonstrating modification of an
existing Java implementation that delegates a portion of its implementation to
OpenCL. Take a look at the developer comments in the
FHT3D_3D_Deconvolution.java example to see what steps are used for brokering of
data between Java and OpenCL between steps within an algorithm's
implementation.
Finally, the need may arise where the GPU compute capabilities you wish to
leverage are not on the same computer that ImageJ is running on. The
FHTEJBService and Iterative_Deconvolve_3D_WS classes demonstrate how to
remotely serve up the functionality leveraging standard, open source J2EE
technologies.