Southern Illinois University

Mcgraw-hill School Education Holdings LLC

Lalit Gupta

Randal B Fry

Raghuveer Kanneganti

Ahmed Freidoon Fadhil

A method, system, and algorithm detects graphite responses in optical mark recognition documents using inexpensive visible-light scanners. The invention is invariant to the numerous background colors and artwork in typical optical mark recognition documents. A superposition of a graphite response image and a background image is modeled. The background image in turn is modeled as a superposition of screening, artwork, lines, and machine text components. A sequence of image processing operations and a pattern recognition algorithm is used to isolate the graphite response image from a test document by systematically removing the components of the background image. The image processing operations consist of grayscale and color segmentation and the application of the Hough transform. Components that are not removed by image processing operations are identified by calculating their texture features, and removed using a multivariate Gaussian classifier.

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Carbondale, IL, United States of America

Lalit Gupta