Media Cybernetics CUT File Format

The Media Cybernetics CUT file format is a device-independent image storage
file format. It is used by most Media Cybernetics applications products to allow
transmission of image data between different types of hardware environments.
HALO does not directly implement this format, but it is implemented through
HALO calls.

CUT files feature run-length encoded image compression, normalized (one
pixel per byte) pixel representation, and allow any rectangular region of image
data to be stored.

File Organization

A CUT fiie begins with a header in the following form:

Bytes     Name    Description

1-2      width    Width of image in pixels
3-4      height   Height of image in lines
5-6      0        Not used

All 16 bit quantities are stored in INTEL (LSB,MSB) format.

After the header, a CUT file contains records. There is one record for each line
of image data. The record has the following form:

Bytes     Name     Description

1-2       length  Length of line record in bytes
3-...     data    One line of image data stored
                  in run-length encoded form

The run-length encoding scheme used in CUT files (like that in GWRlTE files)
compresses redundant data out of lines of image data. This is done by identifying
when there is a run of pixels in a line of the same color index. When this occurs,
the number of matching pixels is recorded in the file rather than the actual
pixels. Run-length encoding is implemented in two parts: a compression flag
byte followed by one or more image data bytes. Compression flag bytes are as
follows:

Flag (in binary)Meaning
1 nnn nnnn      Indicates that there is one data byte to follow
                that is to be duplicated nnn nnnn (127 maximum)
                times.


0 nnn nnnn      Indicates that there are nnn nnnn bytes of image
                data to follow (127 bytes maximum) and that
                there are no duplications.

n 000 0000      End of line field. Indicates the end of a line
                record. The value of n may be either zero or one.
                Note that the end of line field is required and
                that it is reflected in the length of line record
                field mentioned above.

To read a CUT file, the following steps should be taken:

1. Open the CUT file.

2. Read the header, including the width and height of the CUT.

3. For line = 1 to height

          Read integer count.
          Read count bytes into arrayl.
          Uncompress data from arrayl into array2.
          Unnormalize data from array2 into array3.

4. Close the file.


-- 
Roger Fujii - Media Cybernetics        Phone: (301)495-3305 x259
Internet: rmf%media@uunet.uu.net        UUCP: {uunet,hqda-ai}!media!rmf