function image do't work!

[小笨童]

dear all:

I'm a new comer of octave. Here is my computer spec:

PowerPC G4 1.33MHz 1G RAM

OSX 10.4.11

I use octave 3.0.0 with gnuplot 4.0 & aquaterm1.0.1

My problem is, when I try to use imshow() or image, the output figure is whole blank, exepct the grid line..

here is an example:

img=zeros([20 20]);

[sizeY sizeX]=size(img);

offset=2;

img((sizeY/2-offset):(sizeY/2+1+offset), (sizeX/2-offset):(sizeX/2+1+offset))=1;

figure; imshow(img, [min(min(img)) max(max(img))]);

Does anyone have the same problem ?

Please give me some advices, thanks a lot!