A problem with fonts and/or printing PNG files?

[John W. Eaton]

On 28-Feb-2008, Petr Mikulik wrote:

| >    I'm having a problem when I try to print a plot in PNG format.  Here's
| >    a simple script that reproduces the problem on my machine:
| > 
| >      x = 1:10 ;
| >      plot (x);
| >      title ('My plot');
| >      print myplot.png -dpng
| > 
| >    When I type the print command, I get this error message:
| > 
| >      gdImageStringFT: Could not find/open font while printing string My plot
| > with font Helvetica
| > 
| >    It only seems to happen when I try to print PNG.  JPG, GIF and SVG
| >    formats all print fine.
| 
| It seems to me that all, including the postscript output, are wrong.
| See the postscript code generated by
| 	print myplot.eps -deps
| According to
| 	drawnow("postscript","/dev/null",false,"debugeps.gp")
| Octave sends to gnuplot
| 	set title "My plot" font "helvetica,10";
| which is wrong, because the postscript font name is "Helvetica", no 
| "helvetica". This needs a bug fix in Octave.

This is fixed now.

| In the case of
| 	print myplot.png -dpng
| the gd+freetype library used by gnuplot cannot find file "helvetica.ttf" and 
| thus producing the error message. I don't see any such file on my Linux box. 
| I think that another font, e.g. arial (arial.ttf exists) should be used 
| instead.

On my system (Debian testing, up to date) I also see the error if I
use gnuplot directly and ask for Arial:

  gnuplot> plot sin(x)                           
  gnuplot> set title "foobar" font "Arial,10"    
  gnuplot> set term png                      
  Terminal type set to 'png'
  Options are 'nocrop medium '
  gnuplot> set output "foo.png"              
  gnuplot> replot
  gdImageStringFT: Could not find/open font while printing string foobar with font Arial

so what package do I need to get Arial?

I'd consider switching the default to Arial.  Matlab specifies that
the default font is Helvetica, so a change would break any code that
expects that.  OTOH, this probably doesn't affect much real code, so
it would probably be OK.

| Output to GIF or JPG does not work either. It seems to me that gnuplot's 
| "set term gif|jpeg" is not used as 
| 	print('myplot.jpg', '-djpg', '-S800,600')
| 	print('myplot.gif', '-dgif', '-S800,600')
| does not work. I propose Octave uses gnuplot for this output, not a 
| conversion via postscript.

I'd consider a patch.

Thanks,

jwe