setting an image as xy background on a 3-D plot

[Francesco Potortì]

Since I got no answers to my previous question, I'll try with a new one.

I have a background image on which I need to plot 3-D data.  Using the
approach that I have sketched below, I obtain partially satisfying
results, so I am thinking about something different.

It would be perfect if I managed to make a stem3 plot (a sort of 3D
plot) while using a background image for the xy plane.  Any ideas on how
to do that, if ever possible?

-- 
Francesco Potortì (ricercatore)        Voice:  +39.050.621.3058
ISTI - Area della ricerca CNR          Mobile: +39.348.8283.107
via G. Moruzzi 1, I-56124 Pisa         Skype:  wnlabisti
(entrance 20, 1st floor, room C71)     Web:    http://fly.isti.cnr.it

------- Start of forwarded message -------
Date: 28 Apr 2016 18:37:00 +0200
From: "Francesco Potortì" <address@hidden>
To: Octave users list <address@hidden>
Subject: superimposing a heatmap on an image
Organization: CNR-ISTI, via Moruzzi 1, I-56124 Pisa, +39-0503153058

I know how to plot over an image: I can superimpose lines and graphical
objects on a background.

This time I need to superimpose a heatmap (for example one obtained with
imagesc from a data matrix) transparently over a background image.

After some tricks, I managed to obtain what I want:  I did it
by taking the background image, then taking my data matrix, converting
it to RGB using a colormap and merging it with the background image.

But I obtain an image, not the same thing as imagesc does.  The axes are
not what I want, and I can not plot over it using the right coordinates.

Is there a way to call imagesc on the background image, hold on, then
imagesc again?

- -- 
Francesco Potortì (ricercatore)        Voice:  +39.050.621.3058
ISTI - Area della ricerca CNR          Mobile: +39.348.8283.107
via G. Moruzzi 1, I-56124 Pisa         Skype:  wnlabisti
(entrance 20, 1st floor, room C71)     Web:    http://fly.isti.cnr.it
------- End of forwarded message -------