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113 lines
4.6 KiB
Plaintext
113 lines
4.6 KiB
Plaintext
CHANGE LOG for Independent JPEG Group's JPEG software
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Version 6 2-Aug-95
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-------------------
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Progressive JPEG support: library can read and write full progressive JPEG
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files. A "buffered image" mode supports incremental decoding for on-the-fly
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display of progressive images. Simply recompiling an existing IJG-v5-based
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decoder with v6 should allow it to read progressive files, though of course
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without any special progressive display.
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New "jpegtran" application performs lossless transcoding between different
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JPEG formats; primarily, it can be used to convert baseline to progressive
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JPEG and vice versa. In support of jpegtran, the library now allows lossless
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reading and writing of JPEG files as DCT coefficient arrays. This ability
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may be of use in other applications.
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Notes for programmers:
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* We changed jpeg_start_decompress() to be able to suspend; this makes all
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decoding modes available to suspending-input applications. However,
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existing applications that use suspending input will need to be changed
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to check the return value from jpeg_start_decompress(). You don't need to
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do anything if you don't use a suspending data source.
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* We changed the interface to the virtual array routines: access_virt_array
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routines now take a count of the number of rows to access this time. The
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last parameter to request_virt_array routines is now interpreted as the
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maximum number of rows that may be accessed at once, but not necessarily
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the height of every access.
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Version 5b 15-Mar-95
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---------------------
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Correct bugs with grayscale images having v_samp_factor > 1.
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jpeg_write_raw_data() now supports output suspension.
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Correct bugs in "configure" script for case of compiling in
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a directory other than the one containing the source files.
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Repair bug in jquant1.c: sometimes didn't use as many colors as it could.
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Borland C makefile and jconfig file work under either MS-DOS or OS/2.
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Miscellaneous improvements to documentation.
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Version 5a 7-Dec-94
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--------------------
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Changed color conversion roundoff behavior so that grayscale values are
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represented exactly. (This causes test image files to change.)
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Make ordered dither use 16x16 instead of 4x4 pattern for a small quality
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improvement.
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New configure script based on latest GNU Autoconf.
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Fix configure script to handle CFLAGS correctly.
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Rename *.auto files to *.cfg, so that configure script still works if
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file names have been truncated for DOS.
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Fix bug in rdbmp.c: didn't allow for extra data between header and image.
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Modify rdppm.c/wrppm.c to handle 2-byte raw PPM/PGM formats for 12-bit data.
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Fix several bugs in rdrle.c.
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NEED_SHORT_EXTERNAL_NAMES option was broken.
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Revise jerror.h/jerror.c for more flexibility in message table.
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Repair oversight in jmemname.c NO_MKTEMP case: file could be there
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but unreadable.
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Version 5 24-Sep-94
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--------------------
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Version 5 represents a nearly complete redesign and rewrite of the IJG
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software. Major user-visible changes include:
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* Automatic configuration simplifies installation for most Unix systems.
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* A range of speed vs. image quality tradeoffs are supported.
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This includes resizing of an image during decompression: scaling down
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by a factor of 1/2, 1/4, or 1/8 is handled very efficiently.
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* New programs rdjpgcom and wrjpgcom allow insertion and extraction
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of text comments in a JPEG file.
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The application programmer's interface to the library has changed completely.
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Notable improvements include:
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* We have eliminated the use of callback routines for handling the
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uncompressed image data. The application now sees the library as a
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set of routines that it calls to read or write image data on a
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scanline-by-scanline basis.
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* The application image data is represented in a conventional interleaved-
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pixel format, rather than as a separate array for each color channel.
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This can save a copying step in many programs.
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* The handling of compressed data has been cleaned up: the application can
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supply routines to source or sink the compressed data. It is possible to
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suspend processing on source/sink buffer overrun, although this is not
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supported in all operating modes.
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* All static state has been eliminated from the library, so that multiple
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instances of compression or decompression can be active concurrently.
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* JPEG abbreviated datastream formats are supported, ie, quantization and
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Huffman tables can be stored separately from the image data.
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* And not only that, but the documentation of the library has improved
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considerably!
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The last widely used release before the version 5 rewrite was version 4A of
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18-Feb-93. Change logs before that point have been discarded, since they
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are not of much interest after the rewrite.
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