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Browse Prior Art Database

Fast Gray Level Display of Binary Images

IP.com Disclosure Number: IPCOM000100398D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Chevion, D: AUTHOR [+3]

Abstract

The handling of paper documents is still a daily routine in today's office. When these documents are scanned into a computer system, a relatively high resolution must be used in order to maintain their legibility, hence large storage space is needed. For example, an A4 size page (11 by 8.5 inch, 297 by 210 mm), scanned at 240 pels/inch (where a pel is either a black or white dot), requires about 2600 by 2000 pixels (picture elements).

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

Fast Gray Level Display of Binary Images

       The handling of paper documents is still a daily routine
in today's office.  When these documents are scanned into a computer
system, a relatively high resolution must be used in order to
maintain their legibility, hence large storage space is needed.  For
example, an A4 size page (11 by 8.5 inch, 297 by 210 mm), scanned at
240 pels/inch (where a pel is either a black or white dot), requires
about 2600 by 2000 pixels (picture elements).

      Unfortunately, current state of the art displays are incapable
of accommodating such high resolution images. Indeed, typical high
quality displays have only about half the desired resolution, i.e.,
only 1000 by 1000 pixels can be displayed, corresponding to only
about a quarter of a single A-4 page. While it is possible to shift
from one part of the page to another by the means of scrolling, this
is inconvenient for the user. Frequently, it is desirable to view the
entire page at the same time.

      The approach to be described takes avail of the fact that some
modern displays are capable of displaying a number of shades of gray.
 This feature can be utilized to compensate for the reduced
resolution.
 The proposed approach comprises the following four stages:
1.   Subsampling:  This stage is, in fact, a conventional subsampling
operation where the entire image is subsampled by a factor of 2, both
in the X and Y directions. 1
2.   Preliminary display:  The subsampled file is then written into
the bit-plane which corresponds to the most-significant bit.  As a
result, an immediate (albeit low quality) image display is achieved.
3.   Shifted subsampling:  Here, subsampling similar to stage 1 is
performed but with the sampling grid shifted one pixel down a...