Importance

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Abstract

Foreground information is separated from background information on a document where the foreground information is superimposed in an additive or subtractive manner on the background information. The document is divided into a plurality of segments and a frequency distribution of extreme values of the signal intensity in each of the segments is determined. The frequency distribution so determined exhibits one main mode (background mode) which essentially contains the background information. If an adequate foreground/background separation cannot be achieved with the first two steps, the determination of a frequency distribution of signal intensities of the whole document is effected in a third step and a sharper separation effected by a fourth step in which a joint evaluation of the two frequency distributions is determined. To determine a threshold value of a signal intensity for the background information in the document, this threshold value is derived in a fifth step, either from the flank of the background mode towards the foreground information or from one of the flanks of a further main mode opposite the background mode, preferably by a linear approximation of a point on one of the flanks of the two main modes.

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First Claim