正则: <(\s*)(?i:img)(\s)*(((?!<).(\n)*)*)((>)|(/>)|(</(\s*)(?i:img)>))
示例
String str = "<a href=\"http://finance.qq.com/a/20161110/033628.htm\" target=\"_blank\" class=\"pic\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/772348163_150120/0\" alt=\"财政部设立个人所得税处 税改将加快进度\"></a><div class=\"info\">\n" + "<h3><a href=\"http://finance.qq.com/a/20161110/033628.htm\" target=\"_blank\">财政部设立个人所得税处 税改将加快进度</a></h3>\n" + "<p>2016-11-10 17:01:01</p>\n" + "<p class=\"txt\">财联社10日讯，财政部近日调整了部分处室机构设置，单独设立个人所得税处。这或许意味着个税改革将加快进度。个人所得税原由税政司所得税处负责管理，此次调整中，原所得税处被拆分为企业所得税处和个人所得税处两个处。更多精彩内容欢迎搜索关注微信公众号：腾讯财经（financeapp）。</p>\n" + "</div>\n" + "</li>\n" + "<li class=\"clearfix\">\n" + "<a href=\"http://news.qq.com/a/20161110/037497.htm\" target=\"_blank\" class=\"pic\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/773289166_150120/0\" alt=\"“农妇太原派出所死亡案”一审宣判 值班主办警察获刑5年\"></a><div class=\"info\">\n" + "<h3><a href=\"http://news.qq.com/a/20161110/037497.htm\" target=\"_blank\">“农妇太原派出所死亡案”一审宣判 值班主办警察获刑5年</a></h3>\n" + "<p>2016-11-10 18:40:58</p>\n" + "<p class=\"txt\">“农妇太原派出所死亡案”一审宣判 值班主办警察获刑5年</p>\n" + "</div>\n" + "</li>\n" + "<li class=\"clearfix noPic\"><div class=\"info\">\n" + "<h3><a href=\"http://news.qq.com/a/20161110/032227.htm\" target=\"_blank\">不明飞行器部件坠落缅甸山区，带有中文</a></h3>\n" + "<div class=\"picMode\">\n" + "<a href=\"http://news.qq.com/a/20161110/032227.htm\" class=\"picI\" target=\"_blank\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/772248566_200160/0\"></a><a href=\"http://news.qq.com/a/20161110/032227.htm\" class=\"picI\" target=\"_blank\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/772248567_200160/0\"></a><a href=\"http://news.qq.com/a/20161110/032227.htm\" class=\"picI\" target=\"_blank\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/772248568_200160/0\"></a>\n" + "</div>\n" + "<p>2016-11-10 16:22:59</p>\n" + "</div></li>\n" + "<li class=\"clearfix noPic\"><div class=\"info\">\n" + "<h3><a href=\"http://news.qq.com/a/20161110/038603.htm\" target=\"_blank\">奇葩违建占通道 居民走“狗洞”回家</a></h3>\n" + "<div class=\"picMode\">\n" + "<a href=\"http://news.qq.com/a/20161110/038603.htm\" class=\"picI\" target=\"_blank\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/773387406_200160/0\"></a><a href=\"http://news.qq.com/a/20161110/038603.htm\" class=\"picI\" target=\"_blank\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/773387407_200160/0\"></a><a href=\"http://news.qq.com/a/20161110/038603.htm\" class=\"picI\" target=\"_blank\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/773387408_200160/0\"></a>\n" + "</div>\n" + "<p>2016-11-10 19:44:34</p>\n" + "</div></li>\n" + "<li class=\"clearfix\">\n" + "<a href=\"http://news.qq.com/a/20161110/000832.htm\" target=\"_blank\" class=\"pic\"><img src=\"http://inews.gtimg.com/newsapp_ls/0/771270525_150120/0\" alt=\"河北救援6岁坠井男童超100小时 亲戚称井底没见到孩子踪影\"></a><div class=\"info\">\n" + "<h3><a href=\"http://news.qq.com/a/20161110/000832.htm\" target=\"_blank\">河北救援6岁坠井男童超100小时 亲戚称井底没见到孩子踪影</a></h3>";
String s = str.replaceAll("<(\\s*)(?i:img)(\\s)*(((?!<).(\\n)*)*)((>)|(/>)|(</(\\s*)(?i:img)>))", "<!--IMAGE#0-->");
