Not the same font in gnuplot when using command line or gnuplot commands

1
votes

I have a file containing some commands :

    $ cat components.plg
    set terminal png
    set output output
    set font "Helvetica,10"
    unset xtics
    unset ytics
    unset border
    plot "reportGraph_0" with lines title "Component 0", "reportGraph_1" with lines title "Component 1", "aoi.txt" with lines title "Area of interest"
    $

I won't display the contents of reportGraph_# here, but anything with 2 points in them is valid.

I then launch gnuplot with this file as parameter, and I get a warning about Arial (I'm not entirely sure why).

    $ gnuplot -e "output='footprint.png' " components.plg 
    Could not find/open font when opening font "arial", using internal non-scalable font
    $

However, the result image has its text in non-Helvetica (but more in something like Monospace sans).

Here are the two images (first the output of the command line, second the output of the same sequence of commands launched in a gnuplot shell, and exporting the result image). There is one difference, I didn't use the first two commands (set terminal png and set output output) in gnuplot - I merely "exported" the image as png. image from shell command line image from gnuplot commands

The question is : why don't I have the same font in these two images? I would like to have Helvetica (or Lucida Grande, but not a monospace font).

2
linuxshellfontsgnuplot

2 Answers

1
votes

Gnuplot has a large variety of terminals. When you launch an interactive gnuplot session and plot you probably use the wxt or qt terminal. By exporting the image from the plot window you save the image as theyes were created by those terminals.

Now, with set terminal png you use a different and quite old terminal, with different capabilities, especially regarding font rendering.

If you want to save your image directly as png, use the pngcairoterminal, which produces higher quality images (the result should be equivalent to that of the exported image from wxt).

The pngcairo, or the pdfcairo terminals should also handle your fonts properly.

1
votes

The png terminal is older than pngcairo, but it can still use a specified font. You can just specify a path to a .ttf or .pfa font file:

set terminal png font "/path/to/your/Helvetica.pfa"

or a comma-separated pair of the font file path and point size:

set terminal png font '/usr/share/fonts/liberation/LiberationSans-Regular.ttf,9'

gnuplot uses libgd so if you set the environment variable GDFONTPATH to the directory containing your .ttf or .pfa font files, you can specify just the font name instead of the full path:

set terminal png font 'LiberationSans-Regular'

Documentation for setting fonts with different terminals is available within gnuplot under help fonts gd, help fonts cairo, and help fonts postscript.