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IMPORTANT: Tested only with zlib ver. 1.13, libpng ver. 1.05, jpeg ver. 6b
===============================================================================

1) You need libpng, zlib and jpeg sources (available, e.g., from
   ftp.uu.net/graphics/[png,jpeg].

2) Their sources must be unpacked in sub-directories of this dir.
   zlib and libpng sources must be in  sub-dirs named 'zlib' and
   'libpng' (these fixed names are required by libpng documentation).
   Example:
   > unzip -d zlib zlib113.zip
   > tar xzvf libpng-1.05.tar.gz
   > mv libpng-1.05 libpng
   > tar xzvf jpegsrc.vb6.tar.gz
   If jpeg version is different from 6b, edit 'Makefile' and change 
   the definition of JPEGDIR.

3) Then,
   > make
   should build  Rbitmap.dll and install it in the R_HOME/bin.