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Hash : 51d021bf
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Date : 2024-06-24T12:17:22
TurboJPEG: Fix 12-bit-per-sample arith-coded compr (Regression introduced by 7bb958b732e6b4f261595e2d1527d46964fe3aed) Because of 7bb958b732e6b4f261595e2d1527d46964fe3aed, the TurboJPEG compression and encoding functions no longer transfer the value of TJPARAM_OPTIMIZE into cinfo->data_precision unless the data precision is 8. The intent of that was to prevent using_std_huff_tables() from being called more than once when reusing the same compressor object to generate multiple 12-bit-per-sample JPEG images. However, because cinfo->optimize_coding is always set to TRUE by jpeg_set_defaults() if the data precision is 12, calling applications that use 12-bit data precision had to unset cinfo->optimize_coding if they set cinfo->arith_code after calling jpeg_set_defaults(). Because of 7bb958b732e6b4f261595e2d1527d46964fe3aed, the TurboJPEG API stopped doing that except with 8-bit data precision. Thus, attempting to generate a 12-bit-per-sample arithmetic-coded lossy JPEG image using the TurboJPEG API failed with "Requested features are incompatible." Since the compressor will always fail if cinfo->arith_code and cinfo->optimize_coding are both set, and since cinfo->optimize_coding has no relevance for arithmetic coding, the most robust and user-proof solution is for jinit_c_master_control() to set cinfo->optimize_coding to FALSE if cinfo->arith_code is TRUE. This commit also: - modifies TJBench so that it no longer reports that it is using optimized baseline entropy coding in modes where that setting is irrelevant, - amends the cjpeg documentation to clarify that -optimize is implied when specifying -progressive or '-precision 12' without -arithmetic, and - prevents jpeg_set_defaults() from uselessly checking the value of cinfo->arith_code immediately after it has been set to FALSE.
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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.