# Fixing PostScript Lines3

Posted by Jiro Doke,

Jiro's pick this week is fix_lines by Oliver Woodford.

Have you ever generated PostScript files (such as EPS files) from your MATLAB graphs? I had to do that numerous times when I was in grad school and creating graphics for my publications. You can do extensive customization of your plot using basic plotting commands or handle graphics. I also wrote a guest blog post, "Making Pretty Graphs", on Loren's Blog.

Oliver's fix_lines comes into play at the final step. Let's say that we have the following graph. A lot of journal publications only accept black and white graphics. In that case, we have to make use of different line styles and thicknesses, instead of color.

x = 0:0.01:10;
y1 = sin(x);
y2 = cos(x);
y3 = sin(0.7*x) + 0.5*cos(1.3*x);
y4 = 1.5*sin(0.5*x) + 0.8*cos(0.9*x);
h = plot(x, y1, 'k-', x, y2, 'k:', x, y3, 'k-.', x, y4, 'k--');
set(h, 'LineWidth', 1.5);
legend('Data 1', 'Data 2', 'Data 3', 'Data 4', 'Location', 'Best');

We can create an EPS file.

print -deps2 -r600 fig1.eps

As we can seen below (left), the dotted and dash-dot lines need a little bit of tweaking. One way is to edit the EPS file using an external software. Or, you can use fix_lines.

fix_lines('fig1.eps', 'fig1_fixed.eps');

Notice that the lines look better after it's been "fixed" (right).

I love this because it allows me to do everything in MATLAB, from analysis to the final graph. Oliver's code is very well commented, so it's easy to follow what he's doing. Let us know what you think here.

Get the MATLAB code

Published with MATLAB® 7.9

Oliver Woodford replied on : 1 of 3

Thanks, Jiro.

It’s worth mentioning that the problem of line dashes becoming relatively shorter as line thickness increases (i.e. the problem which fix_lines solves) affects bitmap outputs as well. To avoid this you can export to eps, use fix_lines, then rasterize the resulting eps using ghostscript. If you want to avoid doing the last step outside MATLAB then one option is to use export_fig (also on the FEX) with the ‘-painters’ option, which will conveniently do all three steps for you.

Oliver

jiro replied on : 2 of 3

Thanks, Oliver. I did notice your “export_fig” submission, which looks very nice. I may try to do a sequel pick on it sometime.

Jody Klymak replied on : 3 of 3

Hi Jiro,

What I still don’t understand is why Matlab does not allow this to happen directly, on the screen.

In Matplotlib, the python Matlab knockoff, dashed lines look right. Line thickness from 0.5, 0.75, 1, 1.25 all look different, not just in the printed output, but in the screen rendering as well. Don’t most modern graphics backends support anti-aliasing, and isn’t the slight computational overhead irrelevant compared to modern computers and graphics chips? I’ve just about decided to switch from Matlab because this is an ongoing problem for the last 15 years – it seems no one with any say cares about making publication-quality figures w/o jumping through hoops.

Jody

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