Browse Prior Art Database

High Speed Scaling Method for Double Byte Character Support on Fax

IP.com Disclosure Number: IPCOM000111119D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 100K

Publishing Venue

IBM

Related People

Daley, DJ: AUTHOR [+3]

Abstract

A high-speed fax image scaling algorithm using runend compression is disclosed. This algorithm provides fast scaling of fax images while preserving black pel information.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

High Speed Scaling Method for Double Byte Character Support on Fax

      A high-speed fax image scaling algorithm using runend
compression is disclosed.  This algorithm provides fast scaling of
fax images while preserving black pel information.

      This is a fast algorithm for scaling fax images while
preserving black pels.  Black pel information tends to be the most
important image information in typical fax applications.  This
invention was especially useful in DBCS (Double Byte Character
Support) fax applications where the DBCS characters' readability is
dictated primarily by the black pels.

      The "or" scaling algorithm utilizes runend compression pairs
which are produced as an intermediary step to the final compressed G3
fax standard.  The algorithm is called every nth line to "or" scan
lines together for the vertical scale.  For horizontal scaling,
runend pairs are modified to delete every nth pel using the following
rules:

o   A.  If the nth pel to be removed is in a run which is more than 1
    pel wide, simply shorten the run by 1.

o   B.  If the nth pel to be removed is a single pel wide run, and is
    found next to a multiple pel run, the pel will be removed from
    the adjacent run to preserve the single pel information.

o   C.  If the nth pel to be removed is between two single pel runs,
    the black information will be preserved and the white pel will be
    removed.

      This algorithm tends to preserve all vertical information of
the image and preserves horizontal black information.  The good
performance is achieved due to the fact that the image is represented
in a more efficient manner (i.e., runends) thus saving loading and
examining each pel of information, and that this representation is an
intermediate step to producing the G3 compressed image.

      The horizontal scaling technique can be more clearly understood
by considering the following representation of the image data:

      line X's pels
 --------------------------------------------------------------------
  BBBWwBBBWwWWBBbBBBBwBWWBbWWBWbWBWWwW....
 --------------------------------------------------------------------
 A          A          A         B          A           C           A

      The  ideal  pels  to delete for an 80% scale are shown in lower
case letters and the above scale rules that apply are indicated below
each lowercase letter.
The runend integer pairs of above scan data are represented as:

1,3 6,8 13,19 21,21 24,25 28,28 30,30 32,32 ...

      Using the above described algorithm and rules,  the  result  of
the 80% scale algorithm is as follows:

SCALED line X's pels
 --------------------------------------------------------------------
 |B|B|B|W|B|B|B|W|W|W|B|B|B|B|B|W|B|W|W|B|W|W|B|W|B|B|W|W|W|W|
 --------------------------------------------------------------------

     ...