Add instructions to generate title graphic.

* README: Add recreation instructions.

README

@@ -56,3 +56,28 @@ License
 
   This project is released under the GPL version 3.0 or later (see the
   file `COPYING').
+
+
+Title graphic of my bachelor thesis
+===================================
+
+  To recreate the title graphic of my bachelor thesis, run
+  ,----
+  | gp -q <<EOF | sed -E 's/\[|,|\]//g' >coeffs.txt
+  | S = [ 6,  2,  2,  2,  2,  0;\\
+  |       2,  6,  4,  4, -2,  2;\\
+  |       2,  4,  6,  4, -2,  2;\\
+  |       2,  4,  4,  6,  0,  2;\\
+  |       2, -2, -2,  0,  6,  2;\\
+  |       0,  2,  2,  2,  2,  6];
+  | 
+  | [mf, F, v] = mffromqf(S);
+  | 
+  | print(mfcoefs(F, 1500));
+  | EOF
+  | 
+  | polyplot -p120 -R4000 coeffs.txt # ~35 min with 8 threads (a bit overkill)
+  | 
+  | # replace transparency with grey background
+  | convert out.png -background "rgb(181,181,181)" -alpha remove -alpha off out_w_background.png
+  `----