Cannot execute imread

[Yoshiyuki Watanabe]

I tried to install octave for aim of image processing, but
I couldn't execute imread function.

The result is like this.

octave:2> imread('20071004_3.jpg')
error: `imread' undefined near line 2 column 1
octave:2>

I don't knot what to do to solve this problem.
My platform is mac osx Leopard.
I want any information to availave such functions
for image processing.

Thank you.