Abstract: A method for compression and decompression of dithered images is disclosed. Logical units (tiles) of the binary representation are classified into equivalence classes which are then compressed. Each equivalence class represents tiles having similar gray levels (i.e. the same number of black pixels), but which may have different sequences of black and white pixels. Each equivalence class has associated with it a predefined set of rendering exemplars. Each of the exemplars has a similar gray level. Upon decompression, each instance of an equivalence class takes on the value of one of the rendering exemplars which is selected pseudo-randomly.

Abstract: The present invention includes a housing for providing space to hold elements of the scanning system, a document holder is used for holding a document, which can be separated from the scanning system. Further, the document holder consists of a first cover and a second cover. One end of the first cover is connected to one end of the second cover via a pair of pins. The document holder can be pivotally opened for feeding the document into the document holder. A plate having an opening is connected to the housing. The opening is used to provide a path for feeding the document holder into the scanning system. An image capture device is set in the scanning system for capturing the image of the document. A pair of tracks respectively are attached on the inner side walls of the housing for holding the document holder. Document holder rejecting means is utilized for rejecting the document holder.

Abstract: An apparatus and concomitant method for decomposing an image stream into units of local contrast. A temporal contrast transform (pyramid), comprises a spatial filter, a cascade of lowpass temporal filters and a plurality of subtractors and dividers. The spatial filter is followed by a cascade of lowpass temporal filters, producing a set of temporally lowpass, spatially low pass images. Adjacent filter outputs are then subtracted, producing a set of temporally bandpass (Laplacian) images. Finally, each Laplacian image is divided by a lower level temporal lowpass image, to produce a set of temporally bandpass contrast images.