资源说明：CHANGE LOG for Independent JPEG Group's JPEG software Version 9a 19-Jan-2014 ----------------------- Add support for wide gamut color spaces (JFIF version 2). Improve clarity and accuracy in color conversion modules. Note: Requires rebuild of test images. Extend the bit depth support to all values from 8 to 12 (BITS_IN_JSAMPLE configuration option in jmorecfg.h). jpegtran now supports N bits sample data precision with all N from 8 to 12 in a single instance. Thank to Roland Fassauer for inspiration. Try to resolve issues with new boolean type definition. Thank also to v4hn for suggestion. Enable option to use default Huffman tables for lossless compression (for hardware solution), and in this case improve lossless RGB compression with reversible color transform. Thank to Benny Alexandar for hint. Extend the entropy decoding structure, so that extraneous bytes between compressed scan data and following marker can be reported correctly. Thank to Nigel Tao for hint. Add jpegtran -wipe option and extension for -crop. Thank to Andrew Senior, David Clunie, and Josef Schmid for suggestion. Version 9 13-Jan-2013 ---------------------- Add cjpeg -rgb1 option to create an RGB JPEG file, and insert a simple reversible color transform into the processing which significantly improves the compression. The recommended command for lossless coding of RGB images is now cjpeg -rgb1 -block 1 -arithmetic. As said, this option improves the compression significantly, but the files are not compatible with JPEG decoders prior to IJG v9 due to the included color transform. The used color transform and marker signaling is compatible with other JPEG standards (e.g., JPEG-LS part 2). Remove the automatic de-ANSI-fication support (Automake 1.12). Thank also to Nitin A Kamble for suggestion. Add remark for jpeg_mem_dest() in jdatadst.c. Thank to Elie-Gregoire Khoury for the hint. Support files with invalid component identifiers (created by Adobe PDF). Thank to Robin Watts for the suggestion. Adapt full buffer case in jcmainct.c for use with scaled DCT. Thank to Sergii Biloshytskyi for the suggestion. Add type identifier for declaration of noreturn functions. Thank to Brett L. Moore for the suggestion. Correct argument type in format string, avoid compiler warnings. Thank to Vincent Torri for hint. Add missing #include directives in configuration checks, avoid configuration errors. Thank to John Spencer for the hint. Version 8d 15-Jan-2012 ----------------------- Add cjpeg -rgb option to create RGB JPEG files. Using this switch suppresses the conversion from RGB colorspace input to the default YCbCr JPEG colorspace. This feature allows true lossless JPEG coding of RGB color images. The recommended command for this purpose is currently cjpeg -rgb -block 1 -arithmetic. SmartScale capable decoder (introduced with IJG JPEG 8) required. Thank to Michael Koch for the initial suggestion. Add option to disable the region adjustment in the transupp crop code. Thank to Jeffrey Friedl for the suggestion. Thank to Richard Jones and Edd Dawson for various minor corrections. Thank to Akim Demaille for configure.ac cleanup. Version 8c 16-Jan-2011 ----------------------- Add option to compression library and cjpeg (-block N) to use different DCT block size. All N from 1 to 16 are possible. Default is 8 (baseline format). Larger values produce higher compression, smaller values produce higher quality. SmartScale capable decoder (introduced with IJG JPEG 8) required. Version 8b 16-May-2010 ----------------------- Repair problem in new memory source manager with corrupt JPEG data. Thank to Ted Campbell and Samuel Chun for the report. Repair problem in Makefile.am test target. Thank to anonymous user for the report. Support MinGW installation with automatic configure. Thank to Volker Grabsch for the suggestion. Version 8a 28-Feb-2010 ----------------------- Writing tables-only datastreams via jpeg_write_tables works again. Support 32-bit BMPs (RGB image with Alpha channel) for read in cjpeg. Thank to Brett Blackham for the suggestion. Improve accuracy in floating point IDCT calculation. Thank to Robert Hooke for the hint. Version 8 10-Jan-2010 ---------------------- jpegtran now supports the same -scale option as djpeg for "lossless" resize. An implementation of the JPEG SmartScale extension is required for this feature. A (draft) specification of the JPEG SmartScale extension is available as a contributed document at ITU and ISO. Revision 2 or later of the document is required (latest document version is Revision 3). The SmartScale extension will enable more features beside lossless resize in future implementations, as described in the document (new compression options). Add sanity check in BMP reader module to avoid cjpeg crash for empty input image (thank to Isaev Ildar of ISP RAS, Moscow, RU for reporting this error). Add data source and destination managers for read from and write to memory buffers. New API functions jpeg_mem_src and jpeg_mem_dest. Thank to Roberto Boni from Italy for the suggestion. Version 7 27-Jun-2009 ---------------------- New scaled DCTs implemented. djpeg now supports scalings N/8 with all N from 1 to 16. cjpeg now supports scalings 8/N with all N from 1 to 16. Scaled DCTs with size larger than 8 are now also used for resolving the common 2x2 chroma subsampling case without additional spatial resampling. Separate spatial resampling for those kind of files is now only necessary for N>8 scaling cases. Furthermore, separate scaled DCT functions are provided for direct resolving of the common asymmetric subsampling cases (2x1 and 1x2) without additional spatial resampling. cjpeg -quality option has been extended for support of separate quality settings for luminance and chrominance (or in general, for every provided quantization table slot). New API function jpeg_default_qtables() and q_scale_factor array in library. Added -nosmooth option to cjpeg, complementary to djpeg. New variable "do_fancy_downsampling" in library, complement to fancy upsampling. Fancy upsampling now uses direct DCT scaling with sizes larger than 8. The old method is not reversible and has been removed. Support arithmetic entropy encoding and decoding. Added files jaricom.c, jcarith.c, jdarith.c. Straighten the file structure: Removed files jidctred.c, jcphuff.c, jchuff.h, jdphuff.c, jdhuff.h. jpegtran has a new "lossless" cropping feature. Implement -perfect option in jpegtran, new API function jtransform_perfect_transform() in transupp. (DP 204_perfect.dpatch) Better error messages for jpegtran fopen failure. (DP 203_jpegtran_errmsg.dpatch) Fix byte order issue with 16bit PPM/PGM files in rdppm.c/wrppm.c: according to Netpbm, the de facto standard implementation of the PNM formats, the most significant byte is first. (DP 203_rdppm.dpatch) Add -raw option to rdjpgcom not to mangle the output. (DP 205_rdjpgcom_raw.dpatch) Make rdjpgcom locale aware. (DP 201_rdjpgcom_locale.dpatch) Add extern "C" to jpeglib.h. This avoids the need to put extern "C" { ... } around #include "jpeglib.h" in your C++ application. Defining the symbol DONT_USE_EXTERN_C in the configuration prevents this. (DP 202_jpeglib.h_c++.dpatch) Version 6b 27-Mar-1998 ----------------------- jpegtran has new features for lossless image transformations (rotation and flipping) as well as "lossless" reduction to grayscale. jpegtran now copies comments by default; it has a -copy switch to enable copying all APPn blocks as well, or to suppress comments. (Formerly it always suppressed comments and APPn blocks.) jpegtran now also preserves JFIF version and resolution information. New decompressor library feature: COM and APPn markers found in the input file can be saved in memory for later use by the application. (Before, you had to code this up yourself with a custom marker processor.) There is an unused field "void * client_data" now in compress and decompress parameter structs; this may be useful in some applications. JFIF version number information is now saved by the decoder and accepted by the encoder. jpegtran uses this to copy the source file's version number, to ensure "jpegtran -copy all" won't create bogus files that contain JFXX extensions but claim to be version 1.01. Applications that generate their own JFXX extension markers also (finally) have a supported way to cause the encoder to emit JFIF version number 1.02. djpeg's trace mode reports JFIF 1.02 thumbnail images as such, rather than as unknown APP0 markers. In -verbose mode, djpeg and rdjpgcom will try to print the contents of APP12 markers as text. Some digital cameras store useful text information in APP12 markers. Handling of truncated data streams is more robust: blocks beyond the one in which the error occurs will be output as uniform gray, or left unchanged if decoding a progressive JPEG. The appearance no longer depends on the Huffman tables being used. Huffman tables are checked for validity much more carefully than before. To avoid the Unisys LZW patent, djpeg's GIF output capability has been changed to produce "uncompressed GIFs", and cjpeg's GIF input capability has been removed altogether. We're not happy about it either, but there seems to be no good alternative. The configure script now supports building libjpeg as a shared library on many flavors of Unix (all the ones that GNU libtool knows how to build shared libraries for). Use "./configure --enable-shared" to try this out. New jconfig file and makefiles for Microsoft Visual C++ and Developer Studio. Also, a jconfig file and a build script for Metrowerks CodeWarrior on Apple Macintosh. makefile.dj has been updated for DJGPP v2, and there are miscellaneous other minor improvements in the makefiles. jmemmac.c now knows how to create temporary files following Mac System 7 conventions. djpeg's -map switch is now able to read raw-format PPM files reliably. cjpeg -progressive -restart no longer generates any unnecessary DRI markers. Multiple calls to jpeg_simple_progression for a single JPEG object no longer leak memory. Version 6a 7-Feb-96 -------------------- Library initialization sequence modified to detect version mismatches and struct field packing mismatches between library and calling application. This change requires applications to be recompiled, but does not require any application source code change. All routine declarations changed to the style "GLOBAL(type) name ...", that is, GLOBAL, LOCAL, METHODDEF, EXTERN are now macros taking the routine's return type as an argument. This makes it possible to add Microsoft-style linkage keywords to all the routines by changing just these macros. Note that any application code that was using these macros will have to be changed. DCT coefficient quantization tables are now stored in normal array order rather than zigzag order. Application code that calls jpeg_add_quant_table, or otherwise manipulates quantization tables directly, will need to be changed. If you need to make such code work with either older or newer versions of the library, a test like "#if JPEG_LIB_VERSION >= 61" is recommended. djpeg's trace capability now dumps DQT tables in natural order, not zigzag order. This allows the trace output to be made into a "-qtables" file more easily. New system-dependent memory manager module for use on Apple Macintosh. Fix bug in cjpeg's -smooth option: last one or two scanlines would be duplicates of the prior line unless the image height mod 16 was 1 or 2. Repair minor problems in VMS, BCC, MC6 makefiles. New configure script based on latest GNU Autoconf. Correct the list of include files needed by MetroWerks C for ccommand(). Numerous small documentation updates. Version 6 2-Aug-95 ------------------- Progressive JPEG support: library can read and write full progressive JPEG files. A "buffered image" mode supports incremental decoding for on-the-fly display of progressive images. Simply recompiling an existing IJG-v5-based decoder with v6 should allow it to read progressive files, though of course without any special progressive display. New "jpegtran" application performs lossless transcoding between different JPEG formats; primarily, it can be used to convert baseline to progressive JPEG and vice versa. In support of jpegtran, the library now allows lossless reading and writing of JPEG files as DCT coefficient arrays. This ability may be of use in other applications. Notes for programmers: * We changed jpeg_start_decompress() to be able to suspend; this makes all decoding modes available to suspending-input applications. However, existing applications that use suspending input will need to be changed to check the return value from jpeg_start_decompress(). You don't need to do anything if you don't use a suspending data source. * We changed the interface to the virtual array routines: access_virt_array routines now take a count of the number of rows to access this time. The last parameter to request_virt_array routines is now interpreted as the maximum number of rows that may be accessed at once, but not necessarily the height of every access. Version 5b 15-Mar-95 --------------------- Correct bugs with grayscale images having v_samp_factor > 1. jpeg_write_raw_data() now supports output suspension. Correct bugs in "configure" script for case of compiling in a directory other than the one containing the source files. Repair bug in jquant1.c: sometimes didn't use as many colors as it could. Borland C makefile and jconfig file work under either MS-DOS or OS/2. Miscellaneous improvements to documentation. Version 5a 7-Dec-94 -------------------- Changed color conversion roundoff behavior so that grayscale values are represented exactly. (This causes test image files to change.) Make ordered dither use 16x16 instead of 4x4 pattern for a small quality improvement. New configure script based on latest GNU Autoconf. Fix configure script to handle CFLAGS correctly. Rename *.auto files to *.cfg, so that configure script still works if file names have been truncated for DOS. Fix bug in rdbmp.c: didn't allow for extra data between header and image. Modify rdppm.c/wrppm.c to handle 2-byte raw PPM/PGM formats for 12-bit data. Fix several bugs in rdrle.c. NEED_SHORT_EXTERNAL_NAMES option was broken. Revise jerror.h/jerror.c for more flexibility in message table. Repair oversight in jmemname.c NO_MKTEMP case: file could be there but unreadable. 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 considerably! 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.

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