AdvanceCOMP
| Original author(s) | Andrea Mazzoleni |
|---|---|
| Initial release | May 2002 |
| Stable release | 2.1
/ February 12, 2018 |
| Repository | github |
| Engine | |
| License | GNU GPLv3 |
| Website | www |
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AdvanceCOMP is a set of cross-platform, command-line data recompression tools. The utilities allow modifying an already-compressed file, with the intent of reducing the file-size by optimizing the compressed representation. AdvanceCOMP is available under the terms of GPLv3.
AdvanceCOMP works with files using the Deflate compression algorithm, the most widely used systems. Many file formats use Deflate as part of their specification, most notably PNG, gzip and ZIP.
Other tools for reducing the size of images for use on the web are PNGOUT, pngcrush, the GIMP plugin "RIOT", and Jpegtran.[1]
Deflate encoding[edit]
Deflate specifies a stream-encoding such that any compliant decoder is able to parse any valid stream; the algorithm and program used for the compression stage are not mandated. Typically, an encoder from the zlib or gzip reference implementation is used to generate Deflate-encoded data.
For generation of compressed sections of DEFLATE data, an encoder available in the zlib/gzip reference implementation has typically been utilised. The zlib/gzip compressor offers the user a sliding scale between CPU usage and the likely amount of reduction in size achieved on a range of -0 (no compression) to -9 (maximum gzip compression).
The 7-Zip Deflate encoder, used in the AdvanceCOMP suite, effectively extends the sliding scale further. A much more detailed search of compression possibilities is performed, at the expense of significate further processor time spent searching. Effectively the 10-point scale used in gzip is extended to include extra settings above -9, the previous maximum search level. There will be no difference in decompression speed, regardless of the level of compressed size achieved or time taken to encode the data.
Included utilities[edit]
AdvanceCOMP includes four utilities:
- advpng: Optimizes PNG files by removing of ancillary chunks, concatenating all individual
IDATchunks, and re-encoding the result using the 7-Zip's Deflate method. - advmng: Optimizes MNG files. It attempts to use delta encoding, followed by re-encoding of compressed sections using 7-Zip's Deflate method.
- advdef: Optimizes Deflate steams in anything featuring a zlib stream, including PNG, MNG and GZ files.
- advzip: Optimizes the ZIP files by re-encoding their Deflate streams.
The additional searching performed during compression (and therefore additional CPU usage) can often result in an additional 5%–10% compression ratio.
See also[edit]
References[edit]
- ↑ Smith, Peter G. (2012-11-28). Optimizing Web Graphics: Image Optimization Software. Professional Website Performance: Optimizing the Front-End and Back-End. pp. 84‒85. ISBN 9781118487525 – via Google Books. Search this book on
External links[edit]
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