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