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########################################################################
##
## Copyright (C) 2007-2025 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
function interpimages (d, nm, typ)
if (strcmp (typ, "txt"))
image_as_txt (d, nm);
return;
endif
set_graphics_toolkit ();
set_print_size ();
hide_output ();
outfile = fullfile (d, [nm "." typ]);
if (strcmp (typ, "png"))
set (groot, "defaulttextfontname", "*");
endif
if (strcmp (typ, "eps"))
d_typ = "-depsc2";
else
d_typ = ["-d", typ];
endif
if (strcmp (nm, "interpft"))
t = 0 : 0.3 : pi; dt = t(2)-t(1);
n = length (t); k = 100;
ti = t(1) + [0 : k-1]*dt*n/k;
y = sin (4*t + 0.3) .* cos (3*t - 0.1);
yp = sin (4*ti + 0.3) .* cos (3*ti - 0.1);
plot (ti, yp, "g", ti, interp1 (t, y, ti, "spline"), "b", ...
ti, interpft (y, k), "c", t, y, "r+");
legend ("sin(4t+0.3)cos(3t-0.1)", "spline", "interpft", "data");
print (outfile, d_typ);
elseif (strcmp (nm, "interpn"))
x = y = z = -1:1;
f = @(x,y,z) x.^2 - y - z.^2;
[xx, yy, zz] = meshgrid (x, y, z);
v = f (xx,yy,zz);
xi = yi = zi = -1:0.1:1;
[xxi, yyi, zzi] = ndgrid (xi, yi, zi);
vi = interpn (x, y, z, v, xxi, yyi, zzi, "spline");
mesh (zi, yi, squeeze (vi(1,:,:)));
print (outfile, d_typ);
elseif (strcmp (nm, "interpderiv1"))
t = -2:2;
dt = 1;
ti =-2:0.025:2;
dti = 0.025;
y = sign (t);
ys = interp1 (t,y,ti,"spline");
yp = interp1 (t,y,ti,"pchip");
plot (ti, ys,"r-", ti, yp,"g-");
legend ("spline","pchip", "location", "southeast");
print (outfile, d_typ);
elseif (strcmp (nm, "interpderiv2"))
t = -2:2;
dt = 1;
ti =-2:0.025:2;
dti = 0.025;
y = sign (t);
ddys = diff (diff (interp1 (t,y,ti,"spline"))./dti)./dti;
ddyp = diff (diff (interp1 (t,y,ti,"pchip"))./dti)./dti;
plot (ti(2:end-1),ddys,"r*", ti(2:end-1),ddyp,"g+");
legend ("spline", "pchip");
print (outfile, d_typ);
endif
hide_output ();
endfunction
## This function no longer sets the graphics toolkit; That is now done
## automatically by C++ code which will ordinarily choose 'qt', but might
## choose gnuplot on older systems. Only a complete lack of plotting is a
## problem.
function set_graphics_toolkit ()
if (isempty (available_graphics_toolkits ()))
error ("no graphics toolkit available for plotting");
elseif (strcmp ("qt", graphics_toolkit ()))
## Use qt with QOffscreenSurface for plot
elseif (! strcmp ("gnuplot", graphics_toolkit ()))
if (! any (strcmp ("gnuplot", available_graphics_toolkits ())))
error ("no graphics toolkit available for offscreen plotting");
else
graphics_toolkit ("gnuplot");
endif
endif
endfunction
function set_print_size ()
image_size = [5.0, 3.5]; # in inches, 16:9 format
border = 0; # For postscript use 50/72
set (groot, "defaultfigurepapertype", "<custom>");
set (groot, "defaultfigurepaperorientation", "landscape");
set (groot, "defaultfigurepapersize", image_size + 2*border);
set (groot, "defaultfigurepaperposition", [border, border, image_size]);
## FIXME: Required until listener for legend exists (bug #39697)
set (groot, "defaultfigureposition", [ 72*[border, border, image_size] ]);
endfunction
## Use this function before plotting commands and after every call to print
## since print() resets output to stdout (unfortunately, gnuplot can't pop
## output as it can the terminal type).
function hide_output ()
hf = figure (1, "visible", "off");
endfunction
## generate something for the texinfo @image command to process
function image_as_txt (d, nm)
fid = fopen (fullfile (d, [nm ".txt"]), "wt");
fputs (fid, "\n");
fputs (fid, "+---------------------------------+\n");
fputs (fid, "| Image unavailable in text mode. |\n");
fputs (fid, "+---------------------------------+\n");
fclose (fid);
endfunction
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