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| 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. |
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