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e1929140 RR |
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. |