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Hash : e69dd40c
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Date : 2024-01-23T13:26:41
Reorganize source to make things easier to find - Move all libjpeg documentation, except for README.ijg, into the doc/ subdirectory. - Move the TurboJPEG C API documentation from doc/html/ into doc/turbojpeg/. - Move all C source code and headers into a src/ subdirectory. - Move turbojpeg-jni.c into the java/ subdirectory. Referring to #226, there is no ideal solution to this problem. A semantically ideal solution would have involved placing all source code, including the SIMD and Java source code, under src/ (or perhaps placing C library source code under lib/ and C test program source code under test/), all header files under include/, and all documentation under doc/. However: - To me it makes more sense to have separate top-level directories for each language, since the SIMD extensions and the Java API are technically optional features. src/ now contains only the code that is relevant to the core C API libraries and associated programs. - I didn't want to bury the java/ and simd/ directories or add a level of depth to them, since both directories already contain source code that is 3-4 levels deep. - I would prefer not to separate the header files from the C source code, because: 1. It would be disruptive. libjpeg and libjpeg-turbo have historically placed C source code and headers in the same directory, and people who are familiar with both projects (self included) are used to looking for the headers in the same directory as the C source code. 2. In terms of how the headers are used internally in libjpeg-turbo, the distinction between public and private headers is a bit fuzzy. - It didn't make sense to separate the test source code from the library source code, since there is not a clear distinction in some cases. (For instance, the IJG image I/O functions are used by cjpeg and djpeg as well as by the TurboJPEG API.) This solution is minimally disruptive, since it keeps all C source code and headers together and keeps java/ and simd/ as top-level directories. It is a bit awkward, because java/ and simd/ technically contain source code, even though they are not under src/. However, other solutions would have been more awkward for different reasons. Closes #226
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README
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TurboJPEG Java Wrapper ====================== The TurboJPEG shared library can optionally be built with a Java Native Interface wrapper, which allows the library to be loaded and used directly from Java applications. The Java front end for this is defined in several classes located under org/libjpegturbo/turbojpeg. The source code for these Java classes is licensed under a BSD-style license, so the files can be incorporated directly into both open source and proprietary projects without restriction. A Java archive (JAR) file containing these classes is also shipped with the "official" distribution packages of libjpeg-turbo. TJExample.java, which should also be located in the same directory as this README file, demonstrates how to use the TurboJPEG Java API to compress and decompress JPEG images in memory. Performance Pitfalls -------------------- The TurboJPEG Java API defines several convenience methods that can allocate image buffers or instantiate classes to hold the result of compress, decompress, or transform operations. However, if you use these methods, then be mindful of the amount of new data you are creating on the heap. It may be necessary to manually invoke the garbage collector to prevent heap exhaustion or to prevent performance degradation. Background garbage collection can kill performance, particularly in a multi-threaded environment (Java pauses all threads when the GC runs.) The TurboJPEG Java API always gives you the option of pre-allocating your own source and destination buffers, which allows you to re-use those buffers for compressing/decompressing multiple images. If the image sequence you are compressing or decompressing consists of images of the same size, then pre-allocating the buffers is recommended. Installation Directory ---------------------- The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library (libturbojpeg.so, libturbojpeg.dylib, or turbojpeg.dll) in the system library paths or in any paths specified in LD_LIBRARY_PATH (Un*x), DYLD_LIBRARY_PATH (Mac), or PATH (Windows.) Failing this, on Un*x and Mac systems, the wrapper will look for the JNI library under the library directory configured when libjpeg-turbo was built. If that library directory is /opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and vice versa. If you installed the JNI library into another directory, then you will need to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory containing the JNI library.