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AssigneeNetexpress Systems, Inc.
InventorsLawrence G. Roberts, Alex E. Henderson
Estimating the term…
A method and apparatus for selecting a reference scan line for two-dimensional image coding preferably compatible with known facsimile transmission equipment are disclosed. Selection of a reference scan line in accordance with the method and apparatus of the invention allows data compression for facsimile transmission so that the cost for use of the communication link is reduced. More than one previous scan line is considered as a candidate reference scan line. A reference scan line is selected from among a plurality of previous scan lines, for example, the immediately preceding ten scan lines. The preselected or adaptively selected scan line among the multiple prior scan lines, more particularly, the previous scan line which is most similar to the current scan line to be coded, is selected as the reference scan line. The reference scan line is then fed with the current scan line to be coded to a two-dimensional data compression coding process so as to yield optimum data compression. This reduces the amount of image data transmitted and lowers the cost of operation of the facsimile transmission apparatus. The method and apparatus are particularly effective for compressing image data representing screened pictorial images.
A method for processing image data for data compression, said image data comprising pixels and representing a two-dimensional screened image, said image data defining successive input scan lines, including a first scan line, a second scan line immediately preceding said first scan line, and a third scan line preceding said first scan line, said method comprising the steps of:
An apparatus for processing image data for data compression, said image data comprising pixels and representing a two-dimensional screened image, said image data defining successive input scan lines, including a first scan line, a second scan line immediately preceding said first scan line, and a third scan line preceding said first scan line, said apparatus comprising:
The apparatus of claim 18 wherein said comparing means further comprises:
Dependencies are inferred from the claim text.