1 CHANGE LOG for Independent JPEG Group's JPEG software 2 3 4 Version 6b 27-Mar-1998 5 ----------------------- 6 7 jpegtran has new features for lossless image transformations (rotation 8 and flipping) as well as "lossless" reduction to grayscale. 9 10 jpegtran now copies comments by default; it has a -copy switch to enable 11 copying all APPn blocks as well, or to suppress comments. (Formerly it 12 always suppressed comments and APPn blocks.) jpegtran now also preserves 13 JFIF version and resolution information. 14 15 New decompressor library feature: COM and APPn markers found in the input 16 file can be saved in memory for later use by the application. (Before, 17 you had to code this up yourself with a custom marker processor.) 18 19 There is an unused field "void * client_data" now in compress and decompress 20 parameter structs; this may be useful in some applications. 21 22 JFIF version number information is now saved by the decoder and accepted by 23 the encoder. jpegtran uses this to copy the source file's version number, 24 to ensure "jpegtran -copy all" won't create bogus files that contain JFXX 25 extensions but claim to be version 1.01. Applications that generate their 26 own JFXX extension markers also (finally) have a supported way to cause the 27 encoder to emit JFIF version number 1.02. 28 29 djpeg's trace mode reports JFIF 1.02 thumbnail images as such, rather 30 than as unknown APP0 markers. 31 32 In -verbose mode, djpeg and rdjpgcom will try to print the contents of 33 APP12 markers as text. Some digital cameras store useful text information 34 in APP12 markers. 35 36 Handling of truncated data streams is more robust: blocks beyond the one in 37 which the error occurs will be output as uniform gray, or left unchanged 38 if decoding a progressive JPEG. The appearance no longer depends on the 39 Huffman tables being used. 40 41 Huffman tables are checked for validity much more carefully than before. 42 43 To avoid the Unisys LZW patent, djpeg's GIF output capability has been 44 changed to produce "uncompressed GIFs", and cjpeg's GIF input capability 45 has been removed altogether. We're not happy about it either, but there 46 seems to be no good alternative. 47 48 The configure script now supports building libjpeg as a shared library 49 on many flavors of Unix (all the ones that GNU libtool knows how to 50 build shared libraries for). Use "./configure --enable-shared" to 51 try this out. 52 53 New jconfig file and makefiles for Microsoft Visual C++ and Developer Studio. 54 Also, a jconfig file and a build script for Metrowerks CodeWarrior 55 on Apple Macintosh. makefile.dj has been updated for DJGPP v2, and there 56 are miscellaneous other minor improvements in the makefiles. 57 58 jmemmac.c now knows how to create temporary files following Mac System 7 59 conventions. 60 61 djpeg's -map switch is now able to read raw-format PPM files reliably. 62 63 cjpeg -progressive -restart no longer generates any unnecessary DRI markers. 64 65 Multiple calls to jpeg_simple_progression for a single JPEG object 66 no longer leak memory. 67 68 69 Version 6a 7-Feb-96 70 -------------------- 71 72 Library initialization sequence modified to detect version mismatches 73 and struct field packing mismatches between library and calling application. 74 This change requires applications to be recompiled, but does not require 75 any application source code change. 76 77 All routine declarations changed to the style "GLOBAL(type) name ...", 78 that is, GLOBAL, LOCAL, METHODDEF, EXTERN are now macros taking the 79 routine's return type as an argument. This makes it possible to add 80 Microsoft-style linkage keywords to all the routines by changing just 81 these macros. Note that any application code that was using these macros 82 will have to be changed. 83 84 DCT coefficient quantization tables are now stored in normal array order 85 rather than zigzag order. Application code that calls jpeg_add_quant_table, 86 or otherwise manipulates quantization tables directly, will need to be 87 changed. If you need to make such code work with either older or newer 88 versions of the library, a test like "#if JPEG_LIB_VERSION >= 61" is 89 recommended. 90 91 djpeg's trace capability now dumps DQT tables in natural order, not zigzag 92 order. This allows the trace output to be made into a "-qtables" file 93 more easily. 94 95 New system-dependent memory manager module for use on Apple Macintosh. 96 97 Fix bug in cjpeg's -smooth option: last one or two scanlines would be 98 duplicates of the prior line unless the image height mod 16 was 1 or 2. 99 100 Repair minor problems in VMS, BCC, MC6 makefiles. 101 102 New configure script based on latest GNU Autoconf. 103 104 Correct the list of include files needed by MetroWerks C for ccommand(). 105 106 Numerous small documentation updates. 107 108 109 Version 6 2-Aug-95 110 ------------------- 111 112 Progressive JPEG support: library can read and write full progressive JPEG 113 files. A "buffered image" mode supports incremental decoding for on-the-fly 114 display of progressive images. Simply recompiling an existing IJG-v5-based 115 decoder with v6 should allow it to read progressive files, though of course 116 without any special progressive display. 117 118 New "jpegtran" application performs lossless transcoding between different 119 JPEG formats; primarily, it can be used to convert baseline to progressive 120 JPEG and vice versa. In support of jpegtran, the library now allows lossless 121 reading and writing of JPEG files as DCT coefficient arrays. This ability 122 may be of use in other applications. 123 124 Notes for programmers: 125 * We changed jpeg_start_decompress() to be able to suspend; this makes all 126 decoding modes available to suspending-input applications. However, 127 existing applications that use suspending input will need to be changed 128 to check the return value from jpeg_start_decompress(). You don't need to 129 do anything if you don't use a suspending data source. 130 * We changed the interface to the virtual array routines: access_virt_array 131 routines now take a count of the number of rows to access this time. The 132 last parameter to request_virt_array routines is now interpreted as the 133 maximum number of rows that may be accessed at once, but not necessarily 134 the height of every access. 135 136 137 Version 5b 15-Mar-95 138 --------------------- 139 140 Correct bugs with grayscale images having v_samp_factor > 1. 141 142 jpeg_write_raw_data() now supports output suspension. 143 144 Correct bugs in "configure" script for case of compiling in 145 a directory other than the one containing the source files. 146 147 Repair bug in jquant1.c: sometimes didn't use as many colors as it could. 148 149 Borland C makefile and jconfig file work under either MS-DOS or OS/2. 150 151 Miscellaneous improvements to documentation. 152 153 154 Version 5a 7-Dec-94 155 -------------------- 156 157 Changed color conversion roundoff behavior so that grayscale values are 158 represented exactly. (This causes test image files to change.) 159 160 Make ordered dither use 16x16 instead of 4x4 pattern for a small quality 161 improvement. 162 163 New configure script based on latest GNU Autoconf. 164 Fix configure script to handle CFLAGS correctly. 165 Rename *.auto files to *.cfg, so that configure script still works if 166 file names have been truncated for DOS. 167 168 Fix bug in rdbmp.c: didn't allow for extra data between header and image. 169 170 Modify rdppm.c/wrppm.c to handle 2-byte raw PPM/PGM formats for 12-bit data. 171 172 Fix several bugs in rdrle.c. 173 174 NEED_SHORT_EXTERNAL_NAMES option was broken. 175 176 Revise jerror.h/jerror.c for more flexibility in message table. 177 178 Repair oversight in jmemname.c NO_MKTEMP case: file could be there 179 but unreadable. 180 181 182 Version 5 24-Sep-94 183 -------------------- 184 185 Version 5 represents a nearly complete redesign and rewrite of the IJG 186 software. Major user-visible changes include: 187 * Automatic configuration simplifies installation for most Unix systems. 188 * A range of speed vs. image quality tradeoffs are supported. 189 This includes resizing of an image during decompression: scaling down 190 by a factor of 1/2, 1/4, or 1/8 is handled very efficiently. 191 * New programs rdjpgcom and wrjpgcom allow insertion and extraction 192 of text comments in a JPEG file. 193 194 The application programmer's interface to the library has changed completely. 195 Notable improvements include: 196 * We have eliminated the use of callback routines for handling the 197 uncompressed image data. The application now sees the library as a 198 set of routines that it calls to read or write image data on a 199 scanline-by-scanline basis. 200 * The application image data is represented in a conventional interleaved- 201 pixel format, rather than as a separate array for each color channel. 202 This can save a copying step in many programs. 203 * The handling of compressed data has been cleaned up: the application can 204 supply routines to source or sink the compressed data. It is possible to 205 suspend processing on source/sink buffer overrun, although this is not 206 supported in all operating modes. 207 * All static state has been eliminated from the library, so that multiple 208 instances of compression or decompression can be active concurrently. 209 * JPEG abbreviated datastream formats are supported, ie, quantization and 210 Huffman tables can be stored separately from the image data. 211 * And not only that, but the documentation of the library has improved 212 considerably! 213 214 215 The last widely used release before the version 5 rewrite was version 4A of 216 18-Feb-93. Change logs before that point have been discarded, since they 217 are not of much interest after the rewrite. 218
