METHOD AND DEVICE FOR PROCESSING COLOUR INFORMATION OF A PATTERN HAVING CLUTTERED AND USEFUL INFORMATION CHARACTERS

摘要

In a method for processing of color information of a document provided with noise characters and usable characters, a digital image of the document is generated comprised of image points. At least one image region of a first type is selected corresponding to a region of the document that contains noise characters but no usable characters. A brightness value range based on brightness value ranges of image points of the first type is established. For saturation values of image points of the first type whose brightness values lie in the established brightness value range, a frequency with which these saturation values occur in the image region of the first type is determined. Based on these saturation values whose determined frequency exceeds a predetermined value, a saturation value range containing these saturation values is established. For color tone values of image points of the first type whose brightness values lie in the established brightness value range, a frequency with which these color tone values occur in the image region of the first type is determined. Based on color tone values whose determined frequency exceeds a predetermined value, a color tone value range containing these color tone values is established. Colors of those image points whose brightness values lie in the established brightness value range, whose saturation values lie in the established saturation value range, and whose color tone values lie in the established color tone value range are associated with a first color class of colors corresponding to the noise characters. Colors of image points of the first type that are not associated with the first color class are associated with a second color class of colors corresponding to a character-less document. At least one image region of a second type is selected known to correspond to a region that contains neither noise nor usable characters. Colors of image points of the second type whose brightness values lie in the established brightness value range, whose saturation values lie in the established saturation value range, and whose color tone values lie in the established color tone value range are excluded from the first color class and are associated with the second color class.