1 | /*--------------------------------------------------------------------------- |
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2 | |
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3 | rpng2 - progressive-model PNG display program readpng2.c |
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4 | |
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5 | --------------------------------------------------------------------------- |
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6 | |
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7 | Copyright (c) 1998-2007 Greg Roelofs. All rights reserved. |
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8 | |
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9 | This software is provided "as is," without warranty of any kind, |
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10 | express or implied. In no event shall the author or contributors |
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11 | be held liable for any damages arising in any way from the use of |
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12 | this software. |
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13 | |
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14 | The contents of this file are DUAL-LICENSED. You may modify and/or |
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15 | redistribute this software according to the terms of one of the |
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16 | following two licenses (at your option): |
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17 | |
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18 | |
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19 | LICENSE 1 ("BSD-like with advertising clause"): |
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20 | |
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21 | Permission is granted to anyone to use this software for any purpose, |
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22 | including commercial applications, and to alter it and redistribute |
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23 | it freely, subject to the following restrictions: |
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24 | |
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25 | 1. Redistributions of source code must retain the above copyright |
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26 | notice, disclaimer, and this list of conditions. |
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27 | 2. Redistributions in binary form must reproduce the above copyright |
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28 | notice, disclaimer, and this list of conditions in the documenta- |
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29 | tion and/or other materials provided with the distribution. |
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30 | 3. All advertising materials mentioning features or use of this |
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31 | software must display the following acknowledgment: |
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32 | |
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33 | This product includes software developed by Greg Roelofs |
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34 | and contributors for the book, "PNG: The Definitive Guide," |
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35 | published by O'Reilly and Associates. |
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36 | |
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37 | |
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38 | LICENSE 2 (GNU GPL v2 or later): |
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39 | |
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40 | This program is free software; you can redistribute it and/or modify |
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41 | it under the terms of the GNU General Public License as published by |
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42 | the Free Software Foundation; either version 2 of the License, or |
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43 | (at your option) any later version. |
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44 | |
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45 | This program is distributed in the hope that it will be useful, |
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46 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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47 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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48 | GNU General Public License for more details. |
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49 | |
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50 | You should have received a copy of the GNU General Public License |
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51 | along with this program; if not, write to the Free Software Foundation, |
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52 | Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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53 | |
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54 | ---------------------------------------------------------------------------*/ |
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55 | |
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56 | |
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57 | #include <stdlib.h> /* for exit() prototype */ |
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58 | #include <setjmp.h> |
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59 | |
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60 | #include <zlib.h> |
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61 | #include "png.h" /* libpng header from the local directory */ |
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62 | #include "readpng2.h" /* typedefs, common macros, public prototypes */ |
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63 | |
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64 | |
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65 | /* local prototypes */ |
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66 | |
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67 | static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr); |
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68 | static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row, |
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69 | png_uint_32 row_num, int pass); |
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70 | static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr); |
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71 | static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg); |
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72 | |
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73 | |
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74 | |
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75 | |
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76 | void readpng2_version_info(void) |
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77 | { |
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78 | fprintf(stderr, " Compiled with libpng %s; using libpng %s\n", |
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79 | PNG_LIBPNG_VER_STRING, png_libpng_ver); |
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80 | |
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81 | fprintf(stderr, " and with zlib %s; using zlib %s.\n", |
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82 | ZLIB_VERSION, zlib_version); |
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83 | } |
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84 | |
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85 | |
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86 | |
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87 | |
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88 | int readpng2_check_sig(uch *sig, int num) |
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89 | { |
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90 | return !png_sig_cmp(sig, 0, num); |
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91 | } |
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92 | |
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93 | |
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94 | |
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95 | |
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96 | /* returns 0 for success, 2 for libpng problem, 4 for out of memory */ |
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97 | |
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98 | int readpng2_init(mainprog_info *mainprog_ptr) |
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99 | { |
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100 | png_structp png_ptr; /* note: temporary variables! */ |
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101 | png_infop info_ptr; |
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102 | |
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103 | |
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104 | /* could also replace libpng warning-handler (final NULL), but no need: */ |
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105 | |
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106 | png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr, |
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107 | readpng2_error_handler, NULL); |
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108 | if (!png_ptr) |
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109 | return 4; /* out of memory */ |
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110 | |
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111 | info_ptr = png_create_info_struct(png_ptr); |
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112 | if (!info_ptr) { |
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113 | png_destroy_read_struct(&png_ptr, NULL, NULL); |
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114 | return 4; /* out of memory */ |
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115 | } |
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116 | |
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117 | |
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118 | /* we could create a second info struct here (end_info), but it's only |
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119 | * useful if we want to keep pre- and post-IDAT chunk info separated |
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120 | * (mainly for PNG-aware image editors and converters) */ |
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121 | |
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122 | |
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123 | /* setjmp() must be called in every function that calls a PNG-reading |
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124 | * libpng function, unless an alternate error handler was installed-- |
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125 | * but compatible error handlers must either use longjmp() themselves |
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126 | * (as in this program) or exit immediately, so here we are: */ |
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127 | |
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128 | if (setjmp(mainprog_ptr->jmpbuf)) { |
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129 | png_destroy_read_struct(&png_ptr, &info_ptr, NULL); |
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130 | return 2; |
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131 | } |
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132 | |
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133 | |
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134 | #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED |
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135 | /* prepare the reader to ignore all recognized chunks whose data won't be |
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136 | * used, i.e., all chunks recognized by libpng except for IHDR, PLTE, IDAT, |
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137 | * IEND, tRNS, bKGD, gAMA, and sRGB (small performance improvement) */ |
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138 | { |
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139 | /* These byte strings were copied from png.h. If a future libpng |
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140 | * version recognizes more chunks, add them to this list. If a |
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141 | * future version of readpng2.c recognizes more chunks, delete them |
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142 | * from this list. */ |
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143 | static /* const */ png_byte chunks_to_ignore[] = { |
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144 | 99, 72, 82, 77, '\0', /* cHRM */ |
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145 | 104, 73, 83, 84, '\0', /* hIST */ |
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146 | 105, 67, 67, 80, '\0', /* iCCP */ |
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147 | 105, 84, 88, 116, '\0', /* iTXt */ |
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148 | 111, 70, 70, 115, '\0', /* oFFs */ |
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149 | 112, 67, 65, 76, '\0', /* pCAL */ |
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150 | 112, 72, 89, 115, '\0', /* pHYs */ |
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151 | 115, 66, 73, 84, '\0', /* sBIT */ |
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152 | 115, 67, 65, 76, '\0', /* sCAL */ |
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153 | 115, 80, 76, 84, '\0', /* sPLT */ |
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154 | 115, 84, 69, 82, '\0', /* sTER */ |
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155 | 116, 69, 88, 116, '\0', /* tEXt */ |
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156 | 116, 73, 77, 69, '\0', /* tIME */ |
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157 | 122, 84, 88, 116, '\0' /* zTXt */ |
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158 | }; |
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159 | |
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160 | png_set_keep_unknown_chunks(png_ptr, 1 /* PNG_HANDLE_CHUNK_NEVER */, |
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161 | chunks_to_ignore, sizeof(chunks_to_ignore)/5); |
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162 | } |
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163 | #endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */ |
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164 | |
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165 | |
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166 | /* instead of doing png_init_io() here, now we set up our callback |
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167 | * functions for progressive decoding */ |
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168 | |
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169 | png_set_progressive_read_fn(png_ptr, mainprog_ptr, |
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170 | readpng2_info_callback, readpng2_row_callback, readpng2_end_callback); |
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171 | |
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172 | |
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173 | /* make sure we save our pointers for use in readpng2_decode_data() */ |
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174 | |
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175 | mainprog_ptr->png_ptr = png_ptr; |
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176 | mainprog_ptr->info_ptr = info_ptr; |
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177 | |
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178 | |
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179 | /* and that's all there is to initialization */ |
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180 | |
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181 | return 0; |
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182 | } |
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183 | |
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184 | |
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185 | |
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186 | |
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187 | /* returns 0 for success, 2 for libpng (longjmp) problem */ |
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188 | |
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189 | int readpng2_decode_data(mainprog_info *mainprog_ptr, uch *rawbuf, ulg length) |
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190 | { |
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191 | png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr; |
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192 | png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr; |
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193 | |
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194 | |
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195 | /* setjmp() must be called in every function that calls a PNG-reading |
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196 | * libpng function */ |
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197 | |
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198 | if (setjmp(mainprog_ptr->jmpbuf)) { |
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199 | png_destroy_read_struct(&png_ptr, &info_ptr, NULL); |
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200 | mainprog_ptr->png_ptr = NULL; |
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201 | mainprog_ptr->info_ptr = NULL; |
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202 | return 2; |
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203 | } |
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204 | |
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205 | |
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206 | /* hand off the next chunk of input data to libpng for decoding */ |
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207 | |
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208 | png_process_data(png_ptr, info_ptr, rawbuf, length); |
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209 | |
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210 | return 0; |
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211 | } |
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212 | |
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213 | |
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214 | |
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215 | |
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216 | static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr) |
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217 | { |
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218 | mainprog_info *mainprog_ptr; |
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219 | int color_type, bit_depth; |
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220 | png_uint_32 width, height; |
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221 | #ifdef PNG_FLOATING_POINT_SUPPORTED |
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222 | double gamma; |
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223 | #else |
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224 | png_fixed_point gamma; |
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225 | #endif |
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226 | |
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227 | |
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228 | /* setjmp() doesn't make sense here, because we'd either have to exit(), |
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229 | * longjmp() ourselves, or return control to libpng, which doesn't want |
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230 | * to see us again. By not doing anything here, libpng will instead jump |
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231 | * to readpng2_decode_data(), which can return an error value to the main |
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232 | * program. */ |
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233 | |
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234 | |
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235 | /* retrieve the pointer to our special-purpose struct, using the png_ptr |
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236 | * that libpng passed back to us (i.e., not a global this time--there's |
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237 | * no real difference for a single image, but for a multithreaded browser |
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238 | * decoding several PNG images at the same time, one needs to avoid mixing |
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239 | * up different images' structs) */ |
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240 | |
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241 | mainprog_ptr = png_get_progressive_ptr(png_ptr); |
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242 | |
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243 | if (mainprog_ptr == NULL) { /* we be hosed */ |
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244 | fprintf(stderr, |
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245 | "readpng2 error: main struct not recoverable in info_callback.\n"); |
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246 | fflush(stderr); |
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247 | return; |
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248 | /* |
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249 | * Alternatively, we could call our error-handler just like libpng |
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250 | * does, which would effectively terminate the program. Since this |
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251 | * can only happen if png_ptr gets redirected somewhere odd or the |
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252 | * main PNG struct gets wiped, we're probably toast anyway. (If |
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253 | * png_ptr itself is NULL, we would not have been called.) |
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254 | */ |
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255 | } |
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256 | |
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257 | |
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258 | /* this is just like in the non-progressive case */ |
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259 | |
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260 | png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, |
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261 | NULL, NULL, NULL); |
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262 | mainprog_ptr->width = (ulg)width; |
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263 | mainprog_ptr->height = (ulg)height; |
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264 | |
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265 | |
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266 | /* since we know we've read all of the PNG file's "header" (i.e., up |
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267 | * to IDAT), we can check for a background color here */ |
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268 | |
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269 | if (mainprog_ptr->need_bgcolor && |
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270 | png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD)) |
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271 | { |
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272 | png_color_16p pBackground; |
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273 | |
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274 | /* it is not obvious from the libpng documentation, but this function |
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275 | * takes a pointer to a pointer, and it always returns valid red, |
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276 | * green and blue values, regardless of color_type: */ |
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277 | png_get_bKGD(png_ptr, info_ptr, &pBackground); |
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278 | |
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279 | /* however, it always returns the raw bKGD data, regardless of any |
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280 | * bit-depth transformations, so check depth and adjust if necessary */ |
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281 | if (bit_depth == 16) { |
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282 | mainprog_ptr->bg_red = pBackground->red >> 8; |
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283 | mainprog_ptr->bg_green = pBackground->green >> 8; |
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284 | mainprog_ptr->bg_blue = pBackground->blue >> 8; |
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285 | } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) { |
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286 | if (bit_depth == 1) |
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287 | mainprog_ptr->bg_red = mainprog_ptr->bg_green = |
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288 | mainprog_ptr->bg_blue = pBackground->gray? 255 : 0; |
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289 | else if (bit_depth == 2) |
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290 | mainprog_ptr->bg_red = mainprog_ptr->bg_green = |
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291 | mainprog_ptr->bg_blue = (255/3) * pBackground->gray; |
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292 | else /* bit_depth == 4 */ |
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293 | mainprog_ptr->bg_red = mainprog_ptr->bg_green = |
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294 | mainprog_ptr->bg_blue = (255/15) * pBackground->gray; |
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295 | } else { |
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296 | mainprog_ptr->bg_red = (uch)pBackground->red; |
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297 | mainprog_ptr->bg_green = (uch)pBackground->green; |
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298 | mainprog_ptr->bg_blue = (uch)pBackground->blue; |
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299 | } |
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300 | } |
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301 | |
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302 | |
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303 | /* as before, let libpng expand palette images to RGB, low-bit-depth |
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304 | * grayscale images to 8 bits, transparency chunks to full alpha channel; |
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305 | * strip 16-bit-per-sample images to 8 bits per sample; and convert |
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306 | * grayscale to RGB[A] */ |
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307 | |
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308 | if (color_type == PNG_COLOR_TYPE_PALETTE) |
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309 | png_set_expand(png_ptr); |
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310 | if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) |
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311 | png_set_expand(png_ptr); |
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312 | if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) |
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313 | png_set_expand(png_ptr); |
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314 | #ifdef PNG_READ_16_TO_8_SUPPORTED |
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315 | if (bit_depth == 16) |
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316 | # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED |
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317 | png_set_scale_16(png_ptr); |
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318 | # else |
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319 | png_set_strip_16(png_ptr); |
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320 | # endif |
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321 | #endif |
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322 | if (color_type == PNG_COLOR_TYPE_GRAY || |
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323 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA) |
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324 | png_set_gray_to_rgb(png_ptr); |
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325 | |
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326 | |
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327 | /* Unlike the basic viewer, which was designed to operate on local files, |
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328 | * this program is intended to simulate a web browser--even though we |
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329 | * actually read from a local file, too. But because we are pretending |
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330 | * that most of the images originate on the Internet, we follow the recom- |
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331 | * mendation of the sRGB proposal and treat unlabelled images (no gAMA |
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332 | * chunk) as existing in the sRGB color space. That is, we assume that |
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333 | * such images have a file gamma of 0.45455, which corresponds to a PC-like |
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334 | * display system. This change in assumptions will have no effect on a |
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335 | * PC-like system, but on a Mac, SGI, NeXT or other system with a non- |
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336 | * identity lookup table, it will darken unlabelled images, which effec- |
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337 | * tively favors images from PC-like systems over those originating on |
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338 | * the local platform. Note that mainprog_ptr->display_exponent is the |
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339 | * "gamma" value for the entire display system, i.e., the product of |
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340 | * LUT_exponent and CRT_exponent. */ |
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341 | |
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342 | #ifdef PNG_FLOATING_POINT_SUPPORTED |
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343 | if (png_get_gAMA(png_ptr, info_ptr, &gamma)) |
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344 | png_set_gamma(png_ptr, mainprog_ptr->display_exponent, gamma); |
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345 | else |
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346 | png_set_gamma(png_ptr, mainprog_ptr->display_exponent, 0.45455); |
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347 | #else |
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348 | if (png_get_gAMA_fixed(png_ptr, info_ptr, &gamma)) |
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349 | png_set_gamma_fixed(png_ptr, |
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350 | (png_fixed_point)(100000*mainprog_ptr->display_exponent+.5), gamma); |
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351 | else |
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352 | png_set_gamma_fixed(png_ptr, |
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353 | (png_fixed_point)(100000*mainprog_ptr->display_exponent+.5), 45455); |
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354 | #endif |
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355 | |
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356 | /* we'll let libpng expand interlaced images, too */ |
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357 | |
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358 | mainprog_ptr->passes = png_set_interlace_handling(png_ptr); |
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359 | |
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360 | |
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361 | /* all transformations have been registered; now update info_ptr data and |
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362 | * then get rowbytes and channels */ |
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363 | |
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364 | png_read_update_info(png_ptr, info_ptr); |
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365 | |
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366 | mainprog_ptr->rowbytes = (int)png_get_rowbytes(png_ptr, info_ptr); |
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367 | mainprog_ptr->channels = png_get_channels(png_ptr, info_ptr); |
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368 | |
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369 | |
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370 | /* Call the main program to allocate memory for the image buffer and |
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371 | * initialize windows and whatnot. (The old-style function-pointer |
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372 | * invocation is used for compatibility with a few supposedly ANSI |
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373 | * compilers that nevertheless barf on "fn_ptr()"-style syntax.) */ |
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374 | |
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375 | (*mainprog_ptr->mainprog_init)(); |
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376 | |
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377 | |
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378 | /* and that takes care of initialization */ |
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379 | |
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380 | return; |
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381 | } |
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382 | |
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383 | |
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384 | |
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385 | |
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386 | |
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387 | static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row, |
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388 | png_uint_32 row_num, int pass) |
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389 | { |
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390 | mainprog_info *mainprog_ptr; |
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391 | |
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392 | |
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393 | /* first check whether the row differs from the previous pass; if not, |
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394 | * nothing to combine or display */ |
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395 | |
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396 | if (!new_row) |
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397 | return; |
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398 | |
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399 | |
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400 | /* retrieve the pointer to our special-purpose struct so we can access |
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401 | * the old rows and image-display callback function */ |
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402 | |
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403 | mainprog_ptr = png_get_progressive_ptr(png_ptr); |
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404 | |
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405 | |
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406 | /* save the pass number for optional use by the front end */ |
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407 | |
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408 | mainprog_ptr->pass = pass; |
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409 | |
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410 | |
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411 | /* have libpng either combine the new row data with the existing row data |
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412 | * from previous passes (if interlaced) or else just copy the new row |
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413 | * into the main program's image buffer */ |
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414 | |
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415 | png_progressive_combine_row(png_ptr, mainprog_ptr->row_pointers[row_num], |
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416 | new_row); |
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417 | |
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418 | |
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419 | /* finally, call the display routine in the main program with the number |
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420 | * of the row we just updated */ |
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421 | |
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422 | (*mainprog_ptr->mainprog_display_row)(row_num); |
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423 | |
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424 | |
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425 | /* and we're ready for more */ |
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426 | |
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427 | return; |
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428 | } |
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429 | |
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430 | |
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431 | |
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432 | |
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433 | |
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434 | static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr) |
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435 | { |
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436 | mainprog_info *mainprog_ptr; |
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437 | |
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438 | |
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439 | /* retrieve the pointer to our special-purpose struct */ |
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440 | |
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441 | mainprog_ptr = png_get_progressive_ptr(png_ptr); |
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442 | |
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443 | |
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444 | /* let the main program know that it should flush any buffered image |
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445 | * data to the display now and set a "done" flag or whatever, but note |
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446 | * that it SHOULD NOT DESTROY THE PNG STRUCTS YET--in other words, do |
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447 | * NOT call readpng2_cleanup() either here or in the finish_display() |
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448 | * routine; wait until control returns to the main program via |
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449 | * readpng2_decode_data() */ |
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450 | |
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451 | (*mainprog_ptr->mainprog_finish_display)(); |
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452 | |
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453 | |
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454 | /* all done */ |
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455 | |
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456 | return; |
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457 | } |
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458 | |
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459 | |
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460 | |
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461 | |
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462 | |
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463 | void readpng2_cleanup(mainprog_info *mainprog_ptr) |
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464 | { |
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465 | png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr; |
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466 | png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr; |
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467 | |
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468 | if (png_ptr && info_ptr) |
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469 | png_destroy_read_struct(&png_ptr, &info_ptr, NULL); |
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470 | |
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471 | mainprog_ptr->png_ptr = NULL; |
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472 | mainprog_ptr->info_ptr = NULL; |
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473 | } |
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474 | |
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475 | |
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476 | |
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477 | |
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478 | |
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479 | static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg) |
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480 | { |
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481 | mainprog_info *mainprog_ptr; |
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482 | |
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483 | /* This function, aside from the extra step of retrieving the "error |
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484 | * pointer" (below) and the fact that it exists within the application |
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485 | * rather than within libpng, is essentially identical to libpng's |
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486 | * default error handler. The second point is critical: since both |
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487 | * setjmp() and longjmp() are called from the same code, they are |
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488 | * guaranteed to have compatible notions of how big a jmp_buf is, |
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489 | * regardless of whether _BSD_SOURCE or anything else has (or has not) |
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490 | * been defined. */ |
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491 | |
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492 | fprintf(stderr, "readpng2 libpng error: %s\n", msg); |
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493 | fflush(stderr); |
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494 | |
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495 | mainprog_ptr = png_get_error_ptr(png_ptr); |
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496 | if (mainprog_ptr == NULL) { /* we are completely hosed now */ |
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497 | fprintf(stderr, |
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498 | "readpng2 severe error: jmpbuf not recoverable; terminating.\n"); |
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499 | fflush(stderr); |
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500 | exit(99); |
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501 | } |
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502 | |
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503 | /* Now we have our data structure we can use the information in it |
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504 | * to return control to our own higher level code (all the points |
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505 | * where 'setjmp' is called in this file.) This will work with other |
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506 | * error handling mechanisms as well - libpng always calls png_error |
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507 | * when it can proceed no further, thus, so long as the error handler |
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508 | * is intercepted, application code can do its own error recovery. |
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509 | */ |
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510 | longjmp(mainprog_ptr->jmpbuf, 1); |
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511 | } |
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