functions in color.i - b

             brighten, factor  
          or brighten  
 
     brighten the current palette by the specified FACTOR.  
     The FACTOR is the slope of the transfer function for the color value  
     (see to_hsv for a description of the hsv color system); a value of  
     1.0 always remains 1.0, but values near 0.0 change by FACTOR.  
     FACTOR= 1.0 is a no-op.  The default factor is 4.0.  
interpreted function, defined at i/color.i   line 38