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Flagged Run Length Coded Data Format

IP.com Disclosure Number: IPCOM000079199D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Min, PJ: AUTHOR [+2]

Abstract

The traditional format for digitally scanned data is one which maps some gray level or black-white status to each spot of the scanned image. A typical representation for this type of data format is illustrated in Fig. 1. Each spot is assigned a 0 or 1 value depending on whether the spot is white or black, respectively. The amount of storage required to store a facsimile image in this format is a function of the size of the original image, and the scan resolution, and is generally quite large. However, this storage requirement can be reduced by storing the image data in "flagged run-length coded format".

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Flagged Run Length Coded Data Format

The traditional format for digitally scanned data is one which maps some gray level or black-white status to each spot of the scanned image. A typical representation for this type of data format is illustrated in Fig. 1. Each spot is assigned a 0 or 1 value depending on whether the spot is white or black, respectively. The amount of storage required to store a facsimile image in this format is a function of the size of the original image, and the scan resolution, and is generally quite large. However, this storage requirement can be reduced by storing the image data in "flagged run-length coded format".

To store image data in run-length coded form only the transition points from black to white, or white to black are recorded. All of the points lying between transition points can be assumed to be black or white, depending on what state the image is in between successive transitions. An equivalent run-length coded format for SCAN LINES 1 and 2 is illustrated in Fig. 2.

In addition to storing transition points, a flag can be stored with each transition to indicate whether the transition is from black to white or vice-versa. In Fig. 3, a "1" flag indicates a transition to black, while a "2" flag indicates a transition to white. These flags are utilized during image processing to specify data status (processed, or unprocessed), and data type (line data, character data, etc.). In Fig. 4, "1, 2" flags indicate that a run is still unp...