CHANGE LOG for Independent JPEG Group's JPEG software+
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+
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Version 6b  27-Mar-1998+
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-----------------------+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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Huffman tables are checked for validity much more carefully than before.+
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+
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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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+
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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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+
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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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+
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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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+
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djpeg's -map switch is now able to read raw-format PPM files reliably.+
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+
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cjpeg -progressive -restart no longer generates any unnecessary DRI markers.+
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+
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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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+
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+
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Version 6a  7-Feb-96+
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--------------------+
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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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+
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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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+
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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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+
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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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+
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New system-dependent memory manager module for use on Apple Macintosh.+
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+
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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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+
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Repair minor problems in VMS, BCC, MC6 makefiles.+
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+
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New configure script based on latest GNU Autoconf.+
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+
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Correct the list of include files needed by MetroWerks C for ccommand().+
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+
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Numerous small documentation updates.+
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+
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+
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Version 6  2-Aug-95+
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-------------------+
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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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+
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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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+
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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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+
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+
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Version 5b  15-Mar-95+
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---------------------+
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+
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Correct bugs with grayscale images having v_samp_factor > 1.+
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+
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jpeg_write_raw_data() now supports output suspension.+
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+
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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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+
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Repair bug in jquant1.c: sometimes didn't use as many colors as it could.+
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+
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Borland C makefile and jconfig file work under either MS-DOS or OS/2.+
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+
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Miscellaneous improvements to documentation.+
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+
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+
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Version 5a  7-Dec-94+
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--------------------+
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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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+
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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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+
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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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+
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Fix bug in rdbmp.c: didn't allow for extra data between header and image.+
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+
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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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+
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Fix several bugs in rdrle.c.+
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+
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NEED_SHORT_EXTERNAL_NAMES option was broken.+
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+
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Revise jerror.h/jerror.c for more flexibility in message table.+
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+
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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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+
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Version 5  24-Sep-94+
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--------------------+
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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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+
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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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+
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+
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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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