Patent ID: 6731800
Filing Date: 2004-05-04
Classification: H04N

Abstract:
A method for compressing scanned, colored and/or gray-scale documents, the digital image of the scanned document being divided into three image planes, a foreground image, a background image and a binary mask image, a locally variable threshold value image being produced from the original document and a bitonal quantized image being produced with the original image by quantizing (binarizing), whereinthe quantizing is carried out by means of a defined, reduced original image, a text detection (segmentation) from the quantized image and the original image takes place, which divides the document into foreground and background regions, certain regions, particularly text and graphic elements, are assigned to the foreground image and the text background and images are assigned to the background image, the result of the segmenting is stored in a binary mask image, which is equal in size to the original image, the foreground image, produced from the original image and the mask image with a resolution, which is reduced relative to the original image, describes the color of the foreground regions, the reduced foreground image is produced in that the thinned binary mask image as well as the original image are divided into blocks and the average values of the thinned foreground regions of these blocks are entered in the reduced foreground image and expanded and, subsequently, the regions of the foreground image, which have not yet been determined, are filed in by averaging over the determined regional a constant gray value being included as an additional portion in the averaging, the background image, produced from the original image and the mask image, is produced with a lesser resolution than that of the original image and subsequently the binary mask image, the foreground image and the background image are coded with a known image coder.