Basic structure of Bio-Rad LUT files
------------------------------------

Bio-Rad LUT files specify a color Look Up Table for a Bio-Rad
PIC file.  The LUT maps the grayscale values of a raw dataset
to Red, Green and Blue values.  LUT files are simple ASCII
text files with 2 numbers per line separated by a comma.
There can be as many as 256*3 = 768 lines in the file, where
the first 256 lines are dedicated for mapping a red component
to each of the possible 256 (i.e. 0-255; 8-bit) intensities 
in a PIC file; the next 256 map the green component; and the
final 256 map the blue component -- i.e. each intensity can
be assigned its own R, G and B values. The simplest LUT file
is a minimum of 6 lines.  For example:

----TOP OF FILE----
0,0
255,255
0,0
255,0
0,0
255,0
----END OF FILE----

This LUT file maps only the red channel to the default
grayscale values (i.e. intensity 0 [default black] gets
R=0,G=0,B=0 [still black] and intensity 255 [default white]
gets R=255, G=0, B=0 [now full red]).  The intensities
between 0-255 get a linear ramping of black to full
intensity red.

The above, broken down into components for the purpose of
explanation:

---------------
0,0       }  "red" section; 0 [default black] = black;
255,255   }   255 [default white] = full intensity red
---------------
0,0       }  "green" section
255,0     }  intensities 0-255 have no green component
---------------
0,0       }  "blue" section
255,0     }   intensities 0-255 have no blue component
---------------

The important thing to remember is that for each "section":
R, G and B, the first line of the section must be "0,x" and
the last section must be "255,x", such that all 256 entries
are specified.  The "x" can be any number between 0-255 which
specifies the intensity of the R, G or B component.  Mapping
of colours between intensity ranges is linear, so an entry
for each and every intensity is not mandatory (but is
possible!)

One final example:

----TOP OF FILE----
0,0
128,255
210,0
255,0
0,0
255,0
0,0
210,0
255,255
----END OF FILE----

This specifies that intensities 0-128 will contain a black to
full red ramp; intensities 128-210 will contain a full red to
black (i.e. reverse) ramp; intensities 210-255 will contain a
black to full blue ramp.  Note that no green component is
specified for the entire intensity range (0-255) and that
there is no overlap between red and blue ramps.

LUT files can be created using a simple text editor, and
should be saved with the extension "LUT" (e.g. "cell.lut").
These can then be loaded into a program such as Confocal
Assistant.

Hopefully these examples will provide enough information to
get you started.  This info is not copied from a Bio-Rad
manual, but rather was made up entirely by me, so it may not
be 100% accurate, but it does appear to work!

Regards,

--Lance.
