A Java program has been made to generate the figures. Click here to download this program (version 1.2). When you have problems running it, then upgrade to the latest Java JRE (at least version 1.5).
Alternatively you can also run an applet in your browser. Click here to start the applet.
Furthermore, I made a screensaver generating the figures ( requiring at least version 1.5 of the Java JRE). Click here for the windows installer of the screensaver. (Note that sometimes the screen remains black, probably due to a bug in the Java saverbeans package ;)
Menu items  
File  
Save SVG

Save the figure in SVG format. 
Save image

Save the figure in PNG format or in JPEG format, depending on the filename's extension. 
Exit

Stop the program. 
Help  
Show

Show or hide the numerator and denominator at the bottom left corner. 
About

Display the program's version. 
Widgets  
Numerator  
First

Initial value of numerator. 
Delta

Increment
of numerator. Looping
only happens for positive values. Negative values are not allowed. 
Last

Upperbound of numerator. 
Current

Current value of numerator. 
Denominator  
First

Initial value of denominator. 
Delta

Increment of denominator Looping only happens for positive values. Negative values are not allowed. 
Last

Upperbound of denominator. 
Current

Current value of denominator. 
Start  Generate figures according the Numerator and Denominator. In fact a double loop is executed: the Denominator values in the innerloop, and the Numerator in the outerloop. 
Stop  Stop generating figures (also after Random). 
Pause  Pause generating figures. You can change now attributes, or regenerate previous figures. 
Continue  Continue generating figures. 
Previous  Generate the previous figure (in Pause state). 
Next  Generate the next figure (in Pause state), optionally after clicking the Previous button. 
Random  Generate random figures. You can now also Pause generating to regenerate previous figures. 
Redraw  Redraw the current figure, useful after changing attributes 
Mode  Generate a figure at once (Draw) or slowly (Animate). 
Type  Allow Odd values, or Even values, or Both types of values for the Numerator. Useful for random figures. 
Diameter  Diameter (in pixels) of drawn lines. 
Speed  In case of mode Animate, the number of rendered linepieces are approximately 1000 for speed value 60, and 200 for value 300. 
Background  The background color of the figure's panel, either Black or White. 
Foreground  The foreground color of the figure, either Black or White or all Rainbow's colors. 
Shape  The shape of the figure between 3 and 8, or a random value between these bounds. 