README

		     THE UTAH RASTER TOOLKIT LIBRARY
                      Version 3.1c - Dec 5, 2012

The utahrle library from the Utah Raster Toolkit is a collection of C routines
for dealing with raster images commonly encountered in computer graphics.  It
provides the following major functions:

  * A device and system independent image format for storing images and
    information about them.  Called the RLE format, it uses run length encoding
    to reduce storage space for most images.

  * A library of C routines for reading, writing and manipulating images stored
    in the RLE format.


The Format:

  The device independent RLE file has two parts, the header, which stores
  information about the image (size, position, channel information,
  color maps, comments, etc), and the actual image data in a run length
  encoded format.  The RLE format often requires about a third of the
  available space for most "image synthesis" style images.  If the image
  does not compress well, the RLE format stores it as straight pixel data
  with little extra overhead.  The format was first developed around
  1983 at the University of Utah.

The Library:

  C routines are provided for setting up and reading the image header,
  and for reading and writing the image a scanline at a time.  Images can
  be read or written using two different methods.  Using the "row" method,
  the library performs the RLE encoding and decoding.  With the "raw" method,
  scanlines are constructed directly with RLE opcodes.  Additional routines
  are available for generating dither matrices (e.g., for display programs
  running on devices with less than 24 bits of color).

NOTES ABOUT THIS COPY:

  The programs included with the original URT distributions have been removed -
  we include only the C library.