Browse Prior Art Database

Adaptive Control For Gray Scale Image Processing

IP.com Disclosure Number: IPCOM000123849D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Hillery, J: AUTHOR [+3]

Abstract

A two step video processing system is disclosed that conditions the intensity level of each pixel in a digitized image. This is achieved by adjusting the gray scale video value for each pixel to optimize image quality.

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This is the abbreviated version, containing approximately 81% of the total text.

Adaptive Control For Gray Scale Image Processing

   A two step video processing system is disclosed that
conditions the intensity level of each pixel in a digitized image.
This is achieved by adjusting the gray scale video value for each
pixel to optimize image quality.

   Scanners are calibrated to provide a fixed dynamic video
range such that the expected levels of white and black fall into a
predetermined digitized video range.  Once calibrated, the settings
are used for all subsequent document scanned images.  For documents
that span a smaller subset of the video range,  the resulting gray
scale image is perceived to have poor quality (the images are
generally darker).

   Disclosed is a method that allows the scanner to adapt to
the characteristics of each document (light to dark range) so that
the image quality of the resulting image can be improved.

   The solution consists of two steps.

   In the first step, the image is compensated for all
illumination, imaging and electronic irregularities via calibration.
A histogram of the compensated image is generated (may be based on
sparse sampling of the image bitmap).  This gives a measure of video
range and image darkness.  The values are then mapped to a video gain
factor,  and the gain factor is digitized to one of several values.

   In the second step, the video data is passed through a
capped gain process to enhance its gray range.  The gain value is
selected during the first step.

   The capped gai...