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Hash : ed79114a
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Date : 2024-06-18T13:06:30
TJBench: Test end-to-end grayscale comp./decomp. Because the TurboJPEG API originated in VirtualGL and TurboVNC as a means of compressing from/decompressing to extended RGB framebuffers, its earliest incarnations did not handle grayscale packed-pixel images. Thus, TJBench has always converted the input image (even if it is grayscale) to an extended RGB source buffer prior to compression, and it has always decompressed JPEG images (even if they are grayscale) into an extended RGB destination buffer. That allows TJBench to benchmark the RGB-to-grayscale and grayscale-to-RGB color conversion paths used by VirtualGL and TurboVNC when grayscale subsampling (AKA the grayscale JPEG colorspace) is selected. However, more recent versions of the TurboJPEG API handle grayscale packed-pixel images, so it is beneficial to allow TJBench to benchmark the end-to-end grayscale compression and decompression paths. This commit accomplishes that by adding a new command-line option (-gray) that causes TJBench to use a grayscale source buffer (which only works if the input image is PGM or grayscale BMP), to decompress JPEG images (even if they are full-color) into a grayscale destination buffer, and to save output images in PGM or grayscale BMP format.
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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.