Method for compressing scanned, colored and gray-scaled documents

摘要

Scanned, colored and gray-scale documents are compressed. The digital image of the scanned document is divided into three image planes. These image planes are a foreground image, a background image and a binary mask image. The mask image describes which areas of the document belong to the foreground and which to the background. Components of the foreground are text and graphic elements. The color and intensity of these foreground areas is described by the foreground image. The background areas include the text background as well as the pictures contained in the document. The color or brightness information of the background as well as the images contained in the document are contained in the background image. Each of the three images is coded separately with a suitable image coding method. For the decoding, the document is assembled once again from the foreground and background images. In this connection, the binary mask image describes the areas in which the reconstructed document is to be generated from the foreground image or from the background image.