http://www.libpng.org/pub/png/libpng.html
http://libpng.sourceforge.net/
http://japan.cnet.com/news/sec/story/0,2000050480,20070284,00.htm
http://slashdot.jp/article.pl?sid=04/08/06/028205&topic=36&mode=nested
http://wai-emu-web.hp.infoseek.co.jp/iflibpng.shtml