Plotting spectrograms

Hi,

I use gnuplot to plot some spectrograms over audio data. So far I have 
been using pm3d, but since it's a 3D plot I get a lot of extra space 
around the plot (for rotating the 3D plot), which I have not been able 
to remove.

Instead I've looked at the image plotting style. It fills the entire 
canvas and thus solves the space issue. But when I compare a pm3d-plot 
with an image-plot of the same data, the image plot looks a lot more 
pixelated. Is the pm3d style doing some kind of interpolation to smooth 
the plot?

Furthermore the tic marks on the X- and Y-axis disappear when I use the 
image style. I cannot get them back by setting xtics and ytics.

I would like to either have the space removed from the pm3d plot or have 
the tic marks on the image plot. Any ideas?

I'm using gnuplot version 4.2.2

Regards,
Morten