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4349 | Serge | 1 | README for libpng version 1.6.5 - September 14, 2013 (shared library 16.0) |
2 | See the note about version numbers near the top of png.h |
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3 | |||
4 | See INSTALL for instructions on how to install libpng. |
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5 | |||
6 | Libpng comes in several distribution formats. Get libpng-*.tar.gz or |
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7 | libpng-*.tar.xz or if you want UNIX-style line endings in the text files, |
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8 | or lpng*.7z or lpng*.zip if you want DOS-style line endings. |
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9 | |||
10 | Version 0.89 was the first official release of libpng. Don't let the |
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11 | fact that it's the first release fool you. The libpng library has been in |
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12 | extensive use and testing since mid-1995. By late 1997 it had |
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13 | finally gotten to the stage where there hadn't been significant |
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14 | changes to the API in some time, and people have a bad feeling about |
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15 | libraries with versions < 1.0. Version 1.0.0 was released in |
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16 | March 1998. |
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17 | |||
18 | **** |
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19 | Note that some of the changes to the png_info structure render this |
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20 | version of the library binary incompatible with libpng-0.89 or |
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21 | earlier versions if you are using a shared library. The type of the |
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22 | "filler" parameter for png_set_filler() has changed from png_byte to |
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23 | png_uint_32, which will affect shared-library applications that use |
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24 | this function. |
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25 | |||
26 | To avoid problems with changes to the internals of png_info_struct, |
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27 | new APIs have been made available in 0.95 to avoid direct application |
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28 | access to info_ptr. These functions are the png_set_ |
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29 | png_get_ |
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30 | accessing/storing the info_struct data, rather than manipulating it |
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31 | directly, to avoid such problems in the future. |
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32 | |||
33 | It is important to note that the APIs do not make current programs |
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34 | that access the info struct directly incompatible with the new |
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35 | library. However, it is strongly suggested that new programs use |
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36 | the new APIs (as shown in example.c and pngtest.c), and older programs |
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37 | be converted to the new format, to facilitate upgrades in the future. |
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38 | **** |
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39 | |||
40 | Additions since 0.90 include the ability to compile libpng as a |
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41 | Windows DLL, and new APIs for accessing data in the info struct. |
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42 | Experimental functions include the ability to set weighting and cost |
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43 | factors for row filter selection, direct reads of integers from buffers |
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44 | on big-endian processors that support misaligned data access, faster |
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45 | methods of doing alpha composition, and more accurate 16->8 bit color |
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46 | conversion. |
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47 | |||
48 | The additions since 0.89 include the ability to read from a PNG stream |
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49 | which has had some (or all) of the signature bytes read by the calling |
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50 | application. This also allows the reading of embedded PNG streams that |
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51 | do not have the PNG file signature. As well, it is now possible to set |
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52 | the library action on the detection of chunk CRC errors. It is possible |
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53 | to set different actions based on whether the CRC error occurred in a |
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54 | critical or an ancillary chunk. |
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55 | |||
56 | The changes made to the library, and bugs fixed are based on discussions |
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57 | on the PNG-implement mailing list and not on material submitted |
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58 | privately to Guy, Andreas, or Glenn. They will forward any good |
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59 | suggestions to the list. |
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60 | |||
61 | For a detailed description on using libpng, read libpng-manual.txt. For |
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62 | examples of libpng in a program, see example.c and pngtest.c. For usage |
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63 | information and restrictions (what little they are) on libpng, see |
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64 | png.h. For a description on using zlib (the compression library used by |
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65 | libpng) and zlib's restrictions, see zlib.h |
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66 | |||
67 | I have included a general makefile, as well as several machine and |
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68 | compiler specific ones, but you may have to modify one for your own needs. |
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69 | |||
70 | You should use zlib 1.0.4 or later to run this, but it MAY work with |
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71 | versions as old as zlib 0.95. Even so, there are bugs in older zlib |
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72 | versions which can cause the output of invalid compression streams for |
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73 | some images. You will definitely need zlib 1.0.4 or later if you are |
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74 | taking advantage of the MS-DOS "far" structure allocation for the small |
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75 | and medium memory models. You should also note that zlib is a |
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76 | compression library that is useful for more things than just PNG files. |
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77 | You can use zlib as a drop-in replacement for fread() and fwrite() if |
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78 | you are so inclined. |
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79 | |||
80 | zlib should be available at the same place that libpng is, or at zlib.net. |
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81 | |||
82 | You may also want a copy of the PNG specification. It is available |
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83 | as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find |
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84 | these at http://www.libpng.org/pub/png/documents/ |
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85 | |||
86 | This code is currently being archived at libpng.sf.net in the |
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87 | [DOWNLOAD] area, and at ftp://ftp.simplesystems.org. If you can't find it |
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88 | in any of those places, e-mail me, and I'll help you find it. |
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89 | |||
90 | If you have any code changes, requests, problems, etc., please e-mail |
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91 | them to me. Also, I'd appreciate any make files or project files, |
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92 | and any modifications you needed to make to get libpng to compile, |
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93 | along with a #define variable to tell what compiler/system you are on. |
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94 | If you needed to add transformations to libpng, or wish libpng would |
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95 | provide the image in a different way, drop me a note (and code, if |
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96 | possible), so I can consider supporting the transformation. |
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97 | Finally, if you get any warning messages when compiling libpng |
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98 | (note: not zlib), and they are easy to fix, I'd appreciate the |
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99 | fix. Please mention "libpng" somewhere in the subject line. Thanks. |
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100 | |||
101 | This release was created and will be supported by myself (of course |
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102 | based in a large way on Guy's and Andreas' earlier work), and the PNG |
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103 | development group. |
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104 | |||
105 | Send comments/corrections/commendations to png-mng-implement at |
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106 | lists.sourceforge.net (subscription required; visit |
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107 | https://lists.sourceforge.net/lists/listinfo/png-mng-implement |
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108 | to subscribe) or to glennrp at users.sourceforge.net |
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109 | |||
110 | You can't reach Guy, the original libpng author, at the addresses |
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111 | given in previous versions of this document. He and Andreas will |
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112 | read mail addressed to the png-implement list, however. |
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113 | |||
114 | Please do not send general questions about PNG. Send them to |
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115 | png-mng-misc at lists.sf.net (subscription required; visit |
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116 | https://lists.sourceforge.net/lists/listinfo/png-mng-misc to |
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117 | subscribe). If you have a question about something |
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118 | in the PNG specification that is related to using libpng, send it |
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119 | to me. Send me any questions that start with "I was using libpng, |
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120 | and ...". If in doubt, send questions to me. I'll bounce them |
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121 | to others, if necessary. |
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122 | |||
123 | Please do not send suggestions on how to change PNG. We have |
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124 | been discussing PNG for eighteen years now, and it is official and |
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125 | finished. If you have suggestions for libpng, however, I'll |
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126 | gladly listen. Even if your suggestion is not used immediately, |
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127 | it may be used later. |
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128 | |||
129 | Files in this distribution: |
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130 | |||
131 | ANNOUNCE => Announcement of this version, with recent changes |
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132 | CHANGES => Description of changes between libpng versions |
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133 | KNOWNBUG => List of known bugs and deficiencies |
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134 | LICENSE => License to use and redistribute libpng |
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135 | README => This file |
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136 | TODO => Things not implemented in the current library |
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137 | Y2KINFO => Statement of Y2K compliance |
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138 | example.c => Example code for using libpng functions |
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139 | libpng.3 => manual page for libpng (includes libpng-manual.txt) |
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140 | libpng-manual.txt => Description of libpng and its functions |
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141 | libpngpf.3 => manual page for libpng's private functions |
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142 | png.5 => manual page for the PNG format |
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143 | png.c => Basic interface functions common to library |
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144 | png.h => Library function and interface declarations (public) |
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145 | pngpriv.h => Library function and interface declarations (private) |
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146 | pngconf.h => System specific library configuration (public) |
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147 | pngstruct.h => png_struct declaration (private) |
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148 | pnginfo.h => png_info struct declaration (private) |
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149 | pngdebug.h => debugging macros (private) |
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150 | pngerror.c => Error/warning message I/O functions |
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151 | pngget.c => Functions for retrieving info from struct |
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152 | pngmem.c => Memory handling functions |
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153 | pngbar.png => PNG logo, 88x31 |
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154 | pngnow.png => PNG logo, 98x31 |
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155 | pngpread.c => Progressive reading functions |
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156 | pngread.c => Read data/helper high-level functions |
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157 | pngrio.c => Lowest-level data read I/O functions |
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158 | pngrtran.c => Read data transformation functions |
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159 | pngrutil.c => Read data utility functions |
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160 | pngset.c => Functions for storing data into the info_struct |
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161 | pngtest.c => Library test program |
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162 | pngtest.png => Library test sample image |
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163 | pngtrans.c => Common data transformation functions |
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164 | pngwio.c => Lowest-level write I/O functions |
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165 | pngwrite.c => High-level write functions |
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166 | pngwtran.c => Write data transformations |
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167 | pngwutil.c => Write utility functions |
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168 | arm => Contains optimized code for the ARM platform |
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169 | contrib => Contributions |
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170 | examples => Example programs |
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171 | gregbook => source code for PNG reading and writing, from |
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172 | Greg Roelofs' "PNG: The Definitive Guide", |
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173 | O'Reilly, 1999 |
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174 | libtests => Test programs |
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175 | pngminim => Minimal decoder, encoder, and progressive decoder |
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176 | programs demonstrating use of pngusr.dfa |
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177 | pngminus => Simple pnm2png and png2pnm programs |
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178 | pngsuite => Test images |
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179 | tools => Various tools |
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180 | visupng => Contains a MSVC workspace for VisualPng |
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181 | projects => Contains project files and workspaces for |
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182 | building a DLL |
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183 | owatcom => Contains a WATCOM project for building libpng |
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184 | visualc71 => Contains a Microsoft Visual C++ (MSVC) |
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185 | workspace for building libpng and zlib |
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186 | vstudio => Contains a Microsoft Visual C++ (MSVC) |
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187 | workspace for building libpng and zlib |
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188 | scripts => Directory containing scripts for building libpng: |
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189 | (see scripts/README.txt for the list of scripts) |
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190 | |||
191 | Good luck, and happy coding. |
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192 | |||
193 | -Glenn Randers-Pehrson (current maintainer, since 1998) |
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194 | Internet: glennrp at users.sourceforge.net |
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195 | |||
196 | -Andreas Eric Dilger (former maintainer, 1996-1997) |
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197 | Internet: adilger at enel.ucalgary.ca |
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198 | Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ |
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199 | |||
200 | -Guy Eric Schalnat (original author and former maintainer, 1995-1996) |
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201 | (formerly of Group 42, Inc) |
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202 | Internet: gschal at infinet.com> |