1TurboJPEG Java Wrapper 2====================== 3 4The TurboJPEG shared library can optionally be built with a Java Native 5Interface wrapper, which allows the library to be loaded and used directly from 6Java applications. The Java front end for this is defined in several classes 7located under org/libjpegturbo/turbojpeg. The source code for these Java 8classes is licensed under a BSD-style license, so the files can be incorporated 9directly into both open source and proprietary projects without restriction. A 10Java archive (JAR) file containing these classes is also shipped with the 11"official" distribution packages of libjpeg-turbo. 12 13TJExample.java, which should also be located in the same directory as this 14README file, demonstrates how to use the TurboJPEG Java API to compress and 15decompress JPEG images in memory. 16 17 18Performance Pitfalls 19-------------------- 20 21The TurboJPEG Java API defines several convenience methods that can allocate 22image buffers or instantiate classes to hold the result of compress, 23decompress, or transform operations. However, if you use these methods, then 24be mindful of the amount of new data you are creating on the heap. It may be 25necessary to manually invoke the garbage collector to prevent heap exhaustion 26or to prevent performance degradation. Background garbage collection can kill 27performance, particularly in a multi-threaded environment (Java pauses all 28threads when the GC runs.) 29 30The TurboJPEG Java API always gives you the option of pre-allocating your own 31source and destination buffers, which allows you to re-use those buffers for 32compressing/decompressing multiple images. If the image sequence you are 33compressing or decompressing consists of images of the same size, then 34pre-allocating the buffers is recommended. 35 36 37Installation Directory 38---------------------- 39 40The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library 41(libturbojpeg.so, libturbojpeg.jnilib, or turbojpeg.dll) in the system library 42paths or in any paths specified in LD_LIBRARY_PATH (Un*x), DYLD_LIBRARY_PATH 43(Mac), or PATH (Windows.) Failing this, on Un*x and Mac systems, the wrapper 44will look for the JNI library under the library directory configured when 45libjpeg-turbo was built. If that library directory is 46/opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and 47vice versa. 48 49If you installed the JNI library into another directory, then you will need 50to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or 51manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory 52containing the JNI library. 53