Verfahren zur Bestimmung der Geometriedaten von Abtastvorlagen

摘要

Disclosed is a method for automatically determining the geometrical data - arrangement, measurements and relative positions - of image documents placed on the table or drum of a scanner. The scanning data related to a given document portion are used to determine and analyse the luminosity characteristics. Mainly the horizontal and vertical lines are emphasized by a digital filtering process. From the luminosity characteristics a decision is made based on a threshold value to obtain a binary picture, the contours of which are examined. The contours of the image document are determined based on the length, width and height of the areas enclosed inside the contours of the binary picture. A Hough transformation of the straight lines adapted to the contours of the image document is made to determine, based on said straight lines, the geometrical data of said document.