-
Show log
Commit
-
Hash : df9dbff8
Author :
Date : 2023-11-11T12:25:03
TurboJPEG: New param to limit virt array mem usage This corresponds to max_memory_to_use in the jpeg_memory_mgr struct in the libjpeg API, except that the TurboJPEG parameter is specified in megabytes. Because this is 2023 and computers with less than 1 MB of memory are not a thing (at least not within the scope of libjpeg-turbo support), it isn't useful to allow a limit less than 1 MB to be specified. Furthermore, because TurboJPEG parameters are signed integers, if we allowed the memory limit to be specified in bytes, then it would be impossible to specify a limit larger than 2 GB on 64-bit machines. Because max_memory_to_use is a long signed integer, effectively we can specify a limit of up to 2 petabytes on 64-bit machines if the TurboJPEG parameter is specified in megabytes. (2 PB should be enough for anybody, right?) This commit also bumps the TurboJPEG API version to 3.0.1. Since the TurboJPEG API version no longer tracks the libjpeg-turbo version, it makes sense to increment the API revision number when adding constants, to increment the minor version number when adding functions, and to increment the major version number for a complete overhaul. This commit also removes the vestigial TJ_NUMPARAM macro, which was never defined because it proved unnecessary. Partially implements #735
-
README
-
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.