Newsletters - MATLAB Digest

Exporting Figures for Publication: Part 2

The article "Exporting Figures for Publication" in the June, 2000 MATLAB digest introduced the MATLAB function exportfig.m as a tool to help produce publication-quality output of figures and plots. The main goal of the function is to make it easier to control the size, the font sizes, the line widths and the color of the output. This article describes some of the features in a new version of exportfig.m and introduces three new functions previewfig.m, applytofig.m and restorefig.m to complement the functionality of exportfig.m. Download these files individually by clicking on the provided links and place the downloaded files on your MATLAB path.

The roles of these four functions are summarized in the table:

`exportfig.m`	export the figure to a file
`previewfig.m`	preview the figure
`applytofig.m`	apply the export options directly to the figur
`restorefig.m`	restore the figure to the original state

There are many new features in the exportfig.m family, but this article will focus on these four features:

Tight bounding box
Color-to-style mapping
Preferences
Separate text and bitmap output

Each of these features will be explained and illustrated with the plot created by executing the following MATLAB code: x=0:.1:20;

y1=sin(x); y2=cos(x); plot(x,y1,x,y2); legend('sin','cos'); axis([0 20 -2 2]); grid on; title('Plot of sin and cos'); xlabel('x');

Now resize the plot until it is a few inches in height and looks roughly like the illustration below:

Click on image to see enlarged view

Notice how the title and x-label are cut off. One of the new features of the exportfig family is the "tight bounding box" option, which resizes the figure so that all the plots and labels fit perfectly inside the figure without any extra space around the edges, and without clipping any text objects. The command:

exportfig(gcf,'test.eps','bounds','tight');

will export the figure with a tight bounding box to the file 'test.eps'. To create a preview of the figure as it would export with a tight bounding box type

previewfig(gcf,'bounds','tight');

The preview will appear in a separate figure window which you should close after viewing. The preview should look like this:

Click on image to see enlarged view

To change the figure to have a tight bounding box type

oldstate = applytofig(gcf,'bounds','tight');

and to restore the figure to its original state type

restorefig(gcf,oldstate);

The value returned by applytofig is a structure storing the figure's state as it existed before calling applytofig. If you make several changes to a figure using applytofig make sure you don't overwrite the original state structure, since the call to restorefig only restores the figure to the supplied state. Another new feature in exportfig.m is the ability to map line colors to line styles, which is very useful when exporting a color plot to a black-and-white format. The command:

exportfig(gcf,'test.eps','linestylemap','bw');

will export the current figure with all colored lines mapped to the four line styles using the default mapping. You can customize the algorithm used to perform the mapping by supplying the name of a function to evaluate. For example, the command:

exportfig(gcf,'test.eps','linestylemap','mylinemap');

would execute the user function mylinemap instead of applying the default function. For our example figure the output of the command:

previewfig(gcf,'bounds','tight','linestylemap','bw');

would look like:

Click on image to see enlarged view

Since it's tedious to have to type out all the options to exportfig every time, the new function allows you to collect those options into a structure and pass only the structure, or to set the options to be the default options. For example, type

opts = struct('bounds','tight','linestylemap','bw');

to create a structure with the field names 'bounds' and 'linestylemap' having the values 'tight' and 'bw', respectively. You can now type

previewfig(gcf, opts); instead of previewfig(gcf,'bounds','tight','linestylemap','bw');

Also, if you type in R12

setpref('exportfig','defaults',opts);

then opts will be used as the default options for all of the exportfig functions and so you can simply type

previewfig(gcf);

The options specified in setpref are stored in your preferences file and will be automatically used in future MATLAB sessions.

The final new feature of exportfig is the ability to export bitmap images to one file and vector-format text to another file. In our example of plotting sin and cosine this feature is not needed since the entire plot can be rendered in a vector format. But some plots, like those involving transparency, can only be rendered in a bitmap format, and so the text would become pixelized and hard to read. The command:

exportfig(gcf,'test.eps','separatetext',1);

will create two files: test.eps and test_t.eps. The first file contains exactly what exportfig would normally produce except that all the text has been hidden. The second file contains only the text. You must overlay the two pictures in the destination document to obtain the true image. For example, to overlay two EPS files test.eps and test_t.eps that are 3 inches high you could use the TeX commands

\includegraphics{test.eps} \vskip -3in \includegraphics{test_t.eps}

Using this technique the text is drawn at the printer's resolution and so it produces much higher quality images than could be produced using bitmaps alone.

These are only the most important new features of exportfig family. For more details about the capabilities of exportfig.m, type

help exportfig to read the function's documentation.