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JPEG Developers Package 02/18/2014 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This package contains source code for special JPEG decompression and recompression routines, which may help developers as a framework in building their own JPEG recompression applications or as a base for other JPEG related projects. These routines were designed from scratch and are also used in packJPG now. Instructions on how to begin your own JPEG recompression algorithm (for anyone interested) are included in the source code. BSD License ~~~~~~~~~~~ All programs in this package are free software. Except for lpaqJPEGtest, which uses code by Matt Mahoney and is released under the terms of the GPL, you may use any binaries and software included in this package under the terms of the BSD. Read more about the terms of the BSD here: http://www.linfo.org/bsdlicense.html. Included Programs ~~~~~~~~~~~~~~~~~ A short explanations for each of the included programs is given in the following paragraphs. For more detailed information please refer to the programs integrated help function or the source code. In any program you can view the integrated help by just running it from the command line without any parameters. uncmpJPG v2.4a ~~~~~~~~~~~~~~ uncmpJPG is the name of the special core JPEG codec used in packJPG. Compared to other JPEG codecs the main difference is that this codec performs decompression and recompression without introducing any further loss - a JPEG file that goes in it is bytewise identical to the JPEG file that goes out. As such, this codec is well suited to be used in lossless JPEG recompression projects. There are some rare cases in which a JPEG file can't be processed losslessly. In these cases uncmpJPG will display a error message. uncmpJPG accepts JPEG and UJG (Uncompressed JpeG) files as input - JPEG are converted to UJG and vice versa. An UJG file consists of all information needed to losslessly reconstruct the original JPEG file. Contained are JFIF file header, decompressed DCT coefficients and, if needed, some special file reconstruction information. lpaqJPGtest v2.4 alpha 1 ~~~~~~~~~~~~~~~~~~~~~~~~ lpaqJPEGtest is a sample JPEG recompression application build on top of uncmpJPG using a slightly modified version of Matt Mahoney's and Alexander Ratushnyak's lpaq1v2 for compression and decompression. It's here as an example on how to modify uncmpJPG to do recompression to a JPEG file. Other than uncmpJPG or packJPG, lpaqJPGtest currently only accepts one file per run. Please note: lpaqJPGtest is in alpha stage and by no means intended to be used to archive your images. I've tested it without any problems, but still, it might crash and/or compress files to a state where they can't be decompressed. There are better, faster, more reliable, and more comfortable alternatives around (why not use packJPG?). tranDCT v0.9b ~~~~~~~~~~~~~ tranDCT is a tool for examining dependencies between DCT coefficients in an image. It should be useful not only for JPEG but basically for all DCT transformation based 2D compression schemes. tranDCT accepts input files of type PGM (Portable GrayMap), DCT (DCT coefficients with header), and TDS (TranDct Script) and writes PGM, DCT, RWC (RaW Coefficients), or CSV (Comma Separated Values) as output. By default it converts PGM to DCT and vice versa. Be warned though, as this is not fully lossless due to roundoff errors in the IDCT/FDCT. Transformed DCT coeffients from a PGM file can be visualized in various formats. Please refer to the integrated help or to the included sample files for more information. If a TDS file and one or more PGM files are given as input, the output is an Excel/OpenOffice.Org compatible CSV file containing coefficient data for analysis. For the structure of a TDS file please refer to the included sample TDS file. jpeginfo v1.0b ~~~~~~~~~~~~~~ jpeginfo processes one or more JPEG files and writes a single Excel/OpenOffice compatible CSV (Comma Separated Values) called "JPEGinfo.csv". The resulting table contains, for each image, basic and advanced information such as estimated quality of the image, type of color subsampling or JPEG coding mode. makepgm v2.0a ~~~~~~~~~~~~~ makepgm converts a given (binary) file to a PGM image, viewable in most common graphic viewing programs. It is especially useful for visualization of f.e. uncmpJPGs output. Various options for setting the width/height of the resulting image and format of the input data are included. By default, makepgm uses a heuristic matching algorithm to find the width/height that matches best with the given input data. hcheck v2.0 ~~~~~~~~~~~ hcheck estimates the 0th to 4th order entropy of any given input file. Entropy is a measure for the theoretically possible compression on a given stream of data, for more info please refer to http://en.wikipedia.org/wiki/Entropy_(information_theory). hcheck displays all relevant information on screen, but it it can also write a Excel/OpenOffice.Org compatible CSV file. extrjpg v0.1 ~~~~~~~~~~~~ extrjpg scans one or more input files for embedded JPEG files and extracts all found images to the disk. Such embedded images are very often, for example, contained in PDF files. Please note that extrJPG is still in an early stage and might, in some rare cases, dump non-JPEG files as well. Large file support (LFS) for files larger than 4GB is disabled by default but can be enabled by defining "LFS" in the source code. modjpg v0.9 ~~~~~~~~~~~ modJPG works in a similar way to JPEGinfo in that it can process a number of JPEG files and output some basic and advanced information to a CSV file called ‘JPEGinfo.csv’. Additionally there is some functionality to modify existing JPEG files without introducing unnecessary loss. Modification functionality in modJPG includes the following: o Discard meta information o Discard garbage data o Strip restart markers o Requantize all coefficients with a factor of your choice o Modify quantization tables modJPG was coded from existing packJPG code on request by Prof. Dr. Seelmann of HTW Aalen University. You may freely use it and the included source code under the terms of the BSD. Acknowledgements ~~~~~~~~~~~~~~~~ Prof. Dr. Gerhard Seelmann from Hochschule Aalen supported my research in JPEG compression with his extensive knowledge in the field of data compression. Without his advice, this package would not be possible. lpaqJPGtest contains slightly modified arithmetic compression routines originally written by Matt Mahoney and further improved by Alexander Ratushnyak known as "LPAQ1 ver 2". LPAQ1 belongs to the excellent series of PAQ archivers by Matt Mahoney and others. Its unaltered source code and corresponding windows executables can be found here: http://www.cs.fit.edu/~mmahoney/compression/. Contact ~~~~~~~ The official developer blog for packJPG: http://packjpg.encode.ru/ For questions and bug reports: packjpg (at) matthiasstirner.com ____________________________________________________ JPEG Developers Package by Matthias Stirner, 01/2016