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CHANGE LOG for Independent JPEG Group's JPEG software
Version 5 24-Sep-94
Version 5 represents a nearly complete redesign and rewrite of the IJG
software. Major user-visible changes include:
* Automatic configuration simplifies installation for most Unix systems.
* A range of speed vs. image quality tradeoffs are supported.
This includes resizing of an image during decompression: scaling down
by a factor of 1/2, 1/4, or 1/8 is handled very efficiently.
* New programs rdjpgcom and wrjpgcom allow insertion and extraction
of text comments in a JPEG file.
The application programmer's interface to the library has changed completely.
Notable improvements include:
* We have eliminated the use of callback routines for handling the
uncompressed image data. The application now sees the library as a
set of routines that it calls to read or write image data on a
scanline-by-scanline basis.
* The application image data is represented in a conventional interleaved-
pixel format, rather than as a separate array for each color channel.
This can save a copying step in many programs.
* The handling of compressed data has been cleaned up: the application can
supply routines to source or sink the compressed data. It is possible to
suspend processing on source/sink buffer overrun, although this is not
supported in all operating modes.
* All static state has been eliminated from the library, so that multiple
instances of compression or decompression can be active concurrently.
* JPEG abbreviated datastream formats are supported, ie, quantization and
Huffman tables can be stored separately from the image data.
* And not only that, but the documentation of the library has improved
The last widely used release before the version 5 rewrite was version 4A of
18-Feb-93. Change logs before that point have been discarded, since they
are not of much interest after the rewrite.