configure: error: libpng.(a|so) not found.

["SMJ" <simon@xxxxxxxxx>]

Hi, installing php 5 on a x64 system with gd support but the ./configure 
fails with configure: error: libpng.(a|so) not found.

I have installed libpng-devel and libjpeg-devel in addition to the other 
required dependencies but configure still fails with this error, i've tried:

../configure --enable-libxml --with-mysql --with-gd --with-zlib

and

../configure --enable-libxml --with-mysql --with-gd --with-zlib  --with-jpeg-dir=/usr/lib64/

distro CENTO 4.4 x64

[root@db1 php-5.2.1]# locate libpng.so
/usr/lib/libpng.so.3.1.2.7
/usr/lib/libpng.so.3
/usr/lib64/libpng.so
/usr/lib64/libpng.so.2.1.0.16
/usr/lib64/libpng.so.3.1.2.7
/usr/lib64/libpng.so.3
/usr/lib64/libpng.so.2

anyone know how to fix this?

thanks!

SMJ