Browse Prior Art Database

Method of Maintaining a Lower Bound on Compression Ratio

IP.com Disclosure Number: IPCOM000050274D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Franklin, RE: AUTHOR

Abstract

In printing digitized facsimile images, it is usually necessary to store data for one entire page before printing. Because of the large volume of data in a facsimile image, it is necessary to compress the data. The program routine described herein guarantees that the cumulative compression ratio for the page will not go below a desired limit. In other words, the data will compress to a level such that storage is available for the image. This is accomplished by scanning the image for blocks of uniform gray levels and thereafter converting that block into a gray level pattern code. This code is transmitted so that the receiver in the facsimile system stores only the code and not a large number of bits for uniform gray level.

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Method of Maintaining a Lower Bound on Compression Ratio

In printing digitized facsimile images, it is usually necessary to store data for one entire page before printing. Because of the large volume of data in a facsimile image, it is necessary to compress the data. The program routine described herein guarantees that the cumulative compression ratio for the page will not go below a desired limit. In other words, the data will compress to a level such that storage is available for the image. This is accomplished by scanning the image for blocks of uniform gray levels and thereafter converting that block into a gray level pattern code. This code is transmitted so that the receiver in the facsimile system stores only the code and not a large number of bits for uniform gray level. As the routine may degrade the image somewhat, it is only invoked in the event that the cumulative compression ratio for the page is going lower than an acceptable bound.

A flow diagram for the programming routine is shown above. Initially, at decision block 10 the system checks whether the cumulative compression ratio is below the desired limit. If it is not, normal compression continues and the routine continually checks the ratio. If the ratio is below the desired limit, then decision block 12 checks whether a segementation algorithm has yielded a "blob" free area of 24 x 24 picture elements (pels). Blobs are defined as significantly large black or white features within the 24 x 24 pel...