友善最小系统 安装运行Qt4.7程序问题

1.安装友善最小系统
2.把编译后的qt4.7.tgz解压到/opt目录下
3.编辑好/bin/setqt4env环境变量文件
4.复制HelloQt4到/bin
5.
[root@FriendlyARM /bin]# chmod +x HelloQt4
[root@FriendlyARM /bin]# . setqt4env                                                                              
[root@FriendlyARM /bin]# HelloQt4 -qws  

./HelloQt4: error while loading shared libraries: libpng14.so.14: cannot open shared object file: No such file or directory

出现上面错误，是怎么回事？