fb6f5e8b01
IIRC, this was only necessary with the version of Java 1.5 that shipped
with OS X 10.4 "Tiger". Apple's implementation of Java 6 ("Java for
OS X Systems") supported both .jnilib and .dylib extensions for JNI
libraries, but Oracle's implementation of Java has only ever supported
the .dylib extension.
53 lines
2.5 KiB
Plaintext
53 lines
2.5 KiB
Plaintext
TurboJPEG Java Wrapper
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======================
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The TurboJPEG shared library can optionally be built with a Java Native
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Interface wrapper, which allows the library to be loaded and used directly from
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Java applications. The Java front end for this is defined in several classes
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located under org/libjpegturbo/turbojpeg. The source code for these Java
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classes is licensed under a BSD-style license, so the files can be incorporated
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directly into both open source and proprietary projects without restriction. A
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Java archive (JAR) file containing these classes is also shipped with the
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"official" distribution packages of libjpeg-turbo.
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TJExample.java, which should also be located in the same directory as this
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README file, demonstrates how to use the TurboJPEG Java API to compress and
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decompress JPEG images in memory.
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Performance Pitfalls
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--------------------
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The TurboJPEG Java API defines several convenience methods that can allocate
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image buffers or instantiate classes to hold the result of compress,
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decompress, or transform operations. However, if you use these methods, then
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be mindful of the amount of new data you are creating on the heap. It may be
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necessary to manually invoke the garbage collector to prevent heap exhaustion
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or to prevent performance degradation. Background garbage collection can kill
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performance, particularly in a multi-threaded environment (Java pauses all
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threads when the GC runs.)
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The TurboJPEG Java API always gives you the option of pre-allocating your own
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source and destination buffers, which allows you to re-use those buffers for
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compressing/decompressing multiple images. If the image sequence you are
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compressing or decompressing consists of images of the same size, then
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pre-allocating the buffers is recommended.
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Installation Directory
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----------------------
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The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library
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(libturbojpeg.so, libturbojpeg.dylib, or turbojpeg.dll) in the system library
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paths or in any paths specified in LD_LIBRARY_PATH (Un*x), DYLD_LIBRARY_PATH
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(Mac), or PATH (Windows.) Failing this, on Un*x and Mac systems, the wrapper
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will look for the JNI library under the library directory configured when
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libjpeg-turbo was built. If that library directory is
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/opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and
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vice versa.
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If you installed the JNI library into another directory, then you will need
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to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or
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manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory
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containing the JNI library.
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