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Re: image.m and gnuplot 4

From: Fredrik Lingvall
Subject: Re: image.m and gnuplot 4
Date: Wed, 09 Mar 2005 10:14:25 +0100
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

John W. Eaton wrote:

On  8-Mar-2005, Fredrik Lingvall <address@hidden> wrote:

| I've have adapted image.m to use the pm3d map mode
| available in gnuplot 4. Now it should be possible to
| do for example:
| | image(x,y,A); | | and get axis tics given by x and y. | | The script tests if gnuplot 4 (or 3.8) is installed and if not
| it should fall back to the old methods (using xv or ImageMagick).

If gnuplot is used for plotting, it might be nice to use it for
displaying images as well.  The problem I see is that to do that, you
have to change a lot of gnuplot settings.  Will any of those changes
affect subsequent plots?  To avoid problems, I suppose we could have
Octave keep track of all plot related settings and then use reset
followed by setting the plot state prior to each plot.  But then any
gset commands issued by a user would be wiped out by a new plot
command.  I don't see a clean fix for this problem.
Is that a problem only for 2D plots (images)?  From what I can see
mesh.m (3D) also changes some gnuplot settings which could interfere
with prior gset commands. Moreover, plot (1D) sets:

gset nologscale
gset nopolar

To view images with gnuplot I used (+ the gset:s that is used in mesh.m):

gset pm3d map;
gset pm3d corners2color c1;
gset size ratio -1;
gset cbrange [0:64];

IMHO the advantage with using gnuplot for viewing images is
greater than the disadvantage of wiping out prior gset commands
since it enables high quality postscript output with titles, axis lables,
axis scales etc.

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