218 lines
9.1 KiB
Plaintext
Executable File
218 lines
9.1 KiB
Plaintext
Executable File
CHANGE LOG for Independent JPEG Group's JPEG software
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Version 6b 27-Mar-1998
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-----------------------
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jpegtran has new features for lossless image transformations (rotation
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and flipping) as well as "lossless" reduction to grayscale.
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jpegtran now copies comments by default; it has a -copy switch to enable
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copying all APPn blocks as well, or to suppress comments. (Formerly it
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always suppressed comments and APPn blocks.) jpegtran now also preserves
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JFIF version and resolution information.
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New decompressor library feature: COM and APPn markers found in the input
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file can be saved in memory for later use by the application. (Before,
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you had to code this up yourself with a custom marker processor.)
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There is an unused field "void * client_data" now in compress and decompress
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parameter structs; this may be useful in some applications.
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JFIF version number information is now saved by the decoder and accepted by
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the encoder. jpegtran uses this to copy the source file's version number,
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to ensure "jpegtran -copy all" won't create bogus files that contain JFXX
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extensions but claim to be version 1.01. Applications that generate their
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own JFXX extension markers also (finally) have a supported way to cause the
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encoder to emit JFIF version number 1.02.
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djpeg's trace mode reports JFIF 1.02 thumbnail images as such, rather
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than as unknown APP0 markers.
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In -verbose mode, djpeg and rdjpgcom will try to print the contents of
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APP12 markers as text. Some digital cameras store useful text information
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in APP12 markers.
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Handling of truncated data streams is more robust: blocks beyond the one in
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which the error occurs will be output as uniform gray, or left unchanged
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if decoding a progressive JPEG. The appearance no longer depends on the
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Huffman tables being used.
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Huffman tables are checked for validity much more carefully than before.
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To avoid the Unisys LZW patent, djpeg's GIF output capability has been
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changed to produce "uncompressed GIFs", and cjpeg's GIF input capability
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has been removed altogether. We're not happy about it either, but there
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seems to be no good alternative.
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The configure script now supports building libjpeg as a shared library
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on many flavors of Unix (all the ones that GNU libtool knows how to
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build shared libraries for). Use "./configure --enable-shared" to
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try this out.
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New jconfig file and makefiles for Microsoft Visual C++ and Developer Studio.
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Also, a jconfig file and a build script for Metrowerks CodeWarrior
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on Apple Macintosh. makefile.dj has been updated for DJGPP v2, and there
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are miscellaneous other minor improvements in the makefiles.
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jmemmac.c now knows how to create temporary files following Mac System 7
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conventions.
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djpeg's -map switch is now able to read raw-format PPM files reliably.
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cjpeg -progressive -restart no longer generates any unnecessary DRI markers.
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Multiple calls to jpeg_simple_progression for a single JPEG object
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no longer leak memory.
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Version 6a 7-Feb-96
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--------------------
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Library initialization sequence modified to detect version mismatches
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and struct field packing mismatches between library and calling application.
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This change requires applications to be recompiled, but does not require
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any application source code change.
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All routine declarations changed to the style "GLOBAL(type) name ...",
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that is, GLOBAL, LOCAL, METHODDEF, EXTERN are now macros taking the
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routine's return type as an argument. This makes it possible to add
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Microsoft-style linkage keywords to all the routines by changing just
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these macros. Note that any application code that was using these macros
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will have to be changed.
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DCT coefficient quantization tables are now stored in normal array order
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rather than zigzag order. Application code that calls jpeg_add_quant_table,
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or otherwise manipulates quantization tables directly, will need to be
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changed. If you need to make such code work with either older or newer
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versions of the library, a test like "#if JPEG_LIB_VERSION >= 61" is
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recommended.
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djpeg's trace capability now dumps DQT tables in natural order, not zigzag
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order. This allows the trace output to be made into a "-qtables" file
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more easily.
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New system-dependent memory manager module for use on Apple Macintosh.
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Fix bug in cjpeg's -smooth option: last one or two scanlines would be
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duplicates of the prior line unless the image height mod 16 was 1 or 2.
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Repair minor problems in VMS, BCC, MC6 makefiles.
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New configure script based on latest GNU Autoconf.
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Correct the list of include files needed by MetroWerks C for ccommand().
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Numerous small documentation updates.
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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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