A document processing system including a digital image capture system, character recognition circuitry, document encoding systems, endorsers, audit trail printers and an in-line microfilm record system enable documents to be read, endorsed, encoded, digitally imaged, filmed and sorted in a single continuous pass through the document processor by way of a modular transport system. The encoding of the continuously moving documents is accomplished by a plurality of fixed dies, electronically controlled hammers, and an ink bearing ribbon interposed between the documents and the fixed dies. the ribbon being momentarily transported at the same velocity as the documents. Scanning and digitizing of the documents is effected by continuously transporting the documents across the focal plane of a stationary scanner where the documents are repetitively scanned in a single axis, two scanners being employed to permit scanning and digitization of both sides of a particular document in a single pass through the transport mechanism. Circuitry is included in the scanner which permits the presence or absence of a document to be detected and allows dynamic adjustment of threshold levels. thereby accomodating documents which utilize shaded backgrounds. The system includes apparatus for visually displaying an image which corresponds to a plurality of stored digital values, the apparatus including an image memory and circuitry enabling the display to be partitioned into discrete portions of variable sizes, each portion of which may be utilized either to display a selected portion of the image within the image memory or to display a plurality of alphanumeric characters. Additionally, circuitry is provided which allows image rotation, mirror imaging and discrete video attribute selection within each portion of the display. Video data compression apparatus and method are employed for use in minimizing the amount of data necessary to store and recall a black and white video image. An image initially obtained by vertically scanning a selected document is represented by a series of consecutive vertical scans identifying particular sections or cells of the image as black or white. A plurality of consecutive scans are then temporarily stored and analyzed horizontally. analysis circuitry being utilized to identify certain consecutive biack or white sections of the image, repetitions of previous sections of the image or repetitions of certain selectable patterns within the image. The coded output of the analysis circuitry is then stored and utilized to reconstruct the image.