[R-SIG-Mac] newbie - jpeg and libpng not seen by R

[Simone Gabbriellini]

Dear list,
I followed all the step to install jpeg and libpng I found on http:// 
www.economia.unimi.it/R/
Everything went ok during installation process, no warnings no errors
but still capabilities() says:

jpeg        png        tcltk        X11        http/ftp         
sockets        libxml        fifo
FALSE    FALSE  TRUE   TRUE     TRUE         TRUE           
TRUE        TRUE
cledit        IEEE754    iconv
TRUE       TRUE         TRUE

How can I tell R those libraries are in the system?

Should I write a Rprofile file by myself?

thank you,
simone