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ADAPTIVE GRAY SCALE MAPPING TO REMOVE REGISTRATION NOISE IN DIFFERENCE PICTURES

IP.com Disclosure Number: IPCOM000128467D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Sep-16

Publishing Venue

Software Patent Institute

Related People

Delp, Edward J.: AUTHOR [+4]

Abstract

Difference pictures are used in various image processing applications such as change detection, radar imaging, remote sensing, and biomedical image analysis. The difference picture, or difference image, is found by subtracting one image from another. One practical problem with difference pictures is that, if the images are not in perfect spatial registration before subtraction, the difference picture will contain artifacts caused by incomplete cancellation of the unchanged background objects. These artifacts (registration noise) show up as extraneous light and dark regions on either side of the background objects. Usually, this noise is ignored, or is reduced by either smoothing (blurring), or thresholding the difference image. This paper describes a new method to reduce registration noise using adaptive gray scale mapping. This simple digital filter reduces registration noise as well as, or better than, previous methods, without degrading the real difference image.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

ADAPTIVE GRAY SCALE MAPPING TO REMOVE REGISTRATION NOISE IN DIFFERENCE PICTURES

Edward J. Delp and Thomas F. Knoll

CRL-TR-5-84

THE UNIVERSITY OF MICHIGAN COMPUTING RESEARCH LABORATORY1

JANUARY 1984

Room 1079, East Engineering Building
Ann Arbor, Michigan 48109
USA
Tel: (313) 763 Adaptive Gray Scale Mapping to Remove Registration Noise in Difference Pictures
Edward J. Delp and Thomas F. Knoll
Computer, Information, and Control Engineering and
Department of Electrical and Computer Engineering University of Michigan
Ann Arbor, Michigan

Abstract

Difference pictures are used in various image processing applications such as change detection, radar imaging, remote sensing, and biomedical image analysis. The difference picture, or difference image, is found by subtracting one image from another. One practical problem with difference pictures is that, if the images are not in perfect spatial registration before subtraction, the difference picture will contain artifacts caused by incomplete cancellation of the unchanged background objects. These artifacts (registration noise) show up as extraneous light and dark regions on either side of the background objects. Usually, this noise is ignored, or is reduced by either smoothing (blurring), or thresholding the difference image. This paper describes a new method to reduce registration noise using adaptive gray scale mapping. This simple digital filter reduces registration noise as well as, or better than, previous methods, without degrading the real difference image.

1. Introduction

The difference picture can be simply thought of as an image that indicates change between two images. The difference picture is found by spatially aligning the two images as well as possible and, pixel by pixel, subtracting one image from the other. To avoid having to process negative gray level values, the difference picture gray levels are often offset so that zero (no difference) is represented as middle gray. We shall assume in this paper that there is no appreciable illumination difference between the two images, so that the difference picture can be used as a

1 This research was partially sponsored by the Biomedical Research Council and the Office of the Vice-President for Research, University of Michigan. Any opinions, findings, and conclusions or recommendations, expressed in this publication are those of the authors, and do not necessarily reflect the views of the funding agency.

University of Michigan Computing Research Laboratory Page 1 Jan 01, 1984

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ADAPTIVE GRAY SCALE MAPPING TO REMOVE REGISTRATION NOISE IN DIFFERENCE PICTURES

measure of what is actually different between the two scenes. In many applications one would have to adjust for illumination effects before the difference picture could be found.

Difference pictures have been used to detect changes in aerial photographs, 2 radar images, 3 Landsat images, 4 and xrays of bo...