ever so slightly update the white paper

-adrian

docs/white-paper/gimp-white-paper.tex

@@ -199,10 +199,26 @@ modify a subset of the channels.
 
 \subsection{Brushes}
 
+All brushes in gimp are implemented as greyscale bitmap masks. They
+are 8-bit greyscale and provide 256 levels of grey. 
+
+The format for the Brush file is the .gbr format (Gimp brush). Gimp
+includes a file plugin to load and save this format, so brushes can be
+created and edited using GIMP itself. 
+
+These brushes can be used by any of the paint tools (paintbrush,
+airbrush, clone, etc). 
+
+Brushes are completely customizable and are not limited to simple 
+pre-made shapes. Any greyscale image can conceivibly used as a brush.
+
 \section{Selections}
 
 \section{Tools}
 
+\section{xcf format}
+
+
 \subsection{Gradient tool}
 
 The gradient tool lets the user easily create color gradients.  It
@@ -270,7 +286,24 @@ The \gimp\ core consists of 215\footnote{In version 0.99.16.  This
 number tends to go up with time.} procedures which operate on images
 in a great variety of ways.
 
+The procedures register themselves in the Procedural Database (or
+PDB). All plugins have access to all the procedures in the PDB, and
+most of the scripting extentions provide full access to the PDB. The
+PDB is basically an API for programming high level internal \gimp\
+functions and procedures. 
+
+
+
+
+
+
+ 
+
 \FIXME{General overview}
 
 
 \end{document}
+
+
+
+