Browse Prior Art Database

Image Data Compression Method

IP.com Disclosure Number: IPCOM000043612D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Asano, H: AUTHOR [+2]

Abstract

The present method enhances a compression ratio of image data by converting all black pels (picture elements) in an edge region to white pels. This conversion is done prior to a conventional compression process, such as the Modified READ. Referring to the figure, a scanner (not shown) usually produces a shadow region 10 containing a number of black pels at the periphery of a scanned image data 12. This is due to the fact that a gap is created within the scanner when a paper document is fed through a paper feed path. The gap produces a shadow at the edge portion of the document. The scanner recognizes the shadow as a black image and generates black pel signals, e.g., binary ones.

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Image Data Compression Method

The present method enhances a compression ratio of image data by converting all black pels (picture elements) in an edge region to white pels. This conversion is done prior to a conventional compression process, such as the Modified READ. Referring to the figure, a scanner (not shown) usually produces a shadow region 10 containing a number of black pels at the periphery of a scanned image data 12. This is due to the fact that a gap is created within the scanner when a paper document is fed through a paper feed path. The gap produces a shadow at the edge portion of the document. The scanner recognizes the shadow as a black image and generates black pel signals, e.g., binary ones. If the image data 12 containing the shadow region 10 is compressed, the compression ratio would be significantly reduced, as compared with an image data containing no shadow region. Furthermore, a printer (not shown) generally ignores the shadow region 10 because the effective print width of the printer is narrower than the width of the image data 12, e.g., 1728 bits. In this method, the shadow region 10 is entirely converted to a white image region 14 by forcing white pels therein. This can be accomplished in various ways. For example, an image buffer (not shown) is initially reset to all 0's corresponding to pure white. When the image data 12 is to be stored in the buffer, only pels in an internal region 16 are actually stored in corresponding locations. Su...