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