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Image System Quality and Data Compression Enhancement by Excision of Isolated Single Pels and Quad Pel Groups

IP.com Disclosure Number: IPCOM000034384D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 5 page(s) / 135K

Publishing Venue

IBM

Related People

Rohe, CF: AUTHOR [+2]

Abstract

In image data systems, halftone patterns and other high amplitude noise severely impact data compression and reduce image quality. Excision of isolated (unconnected) pels and quads of pels effects significant image quality and data compression enhancement. (Image Omitted) This exposition of the present embodiment assumes that the image has been optically scanned, with each pel digitized and stored in memory. The stored image is examined and upgraded. Fig. 1 shows a single pel "X" surrounded (isolated) by white "W" pels. Fig. 2 shows a quad, or 2 by 2 group of "X" pels (which may include up to 4 black pels) isolated by the 12 "W" pels of an intact 4 by 4 perimeter. In the present embodiment all "X" pel positions meeting these criteria are converted to "W", regardless of their initial status.

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Image System Quality and Data Compression Enhancement by Excision of Isolated Single Pels and Quad Pel Groups

In image data systems, halftone patterns and other high amplitude noise severely impact data compression and reduce image quality. Excision of isolated (unconnected) pels and quads of pels effects significant image quality and data compression enhancement.

(Image Omitted)

This exposition of the present embodiment assumes that the image has been optically scanned, with each pel digitized and stored in memory. The stored image is examined and upgraded. Fig. 1 shows a single pel "X" surrounded (isolated) by white "W" pels. Fig. 2 shows a quad, or 2 by 2 group of "X" pels (which may include up to 4 black pels) isolated by the 12 "W" pels of an intact 4 by 4 perimeter. In the present embodiment all "X" pel positions meeting these criteria are converted to "W", regardless of their initial status. This effectively excises undesirable black pels by conversion to "W". Fig. 3 shows a triad of black "B" pels which, although they are completely surrounded by white "W" pels, are not excised because the 4 by 4 perimeter is broken by the "B" pel in the lower right-hand corner, which borders the inner 2 by 2 quad. This criterion improves the apparent continuity of diagonal strokes.

(Image Omitted)

Refer to Fig. 4. The stored image is scanned serially, pel by pel, left to right, one line at a time. The current pel being scanned is identified as being in the lower right-hand position, "A", of a matrix consisting of four corresponding pels of four consecutive lines, constituting a 4 by 4 "window", which is superimposed on the image and steps across and down one pel position at a time. Image pels are labeled by line and position, 5-1, 5-2, 5-3, etc., and window positions are designated by letters "A" to "P". At each position of the window the image area enclosed by the window is examined with relation to the above stated criteria. Position F is examined with relation to surrounding positions ABCEGIJK, for possible single pel excision, and simultaneously positions FGJK are examined with relation to surrounding positions ABCDEHILMNOP, for possible quad excision. It is apparent that every pel of the image appears within the window sixteen times, progressing successively from position A to position P. Fig. 5 shows the logic which examines the image pels within the window area and effects single and quad pel excision. It is seen that it consists of a series of single pel delay buffers, "T", and three first-in, first-out (FIFO) buffers. The FIFO buffers each store a full line of image data less three pels. In the aggregate these buffers constitute a pipeline push-down storage which stores, in sequenc...