Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1987-12-21
1989-08-15
Shepperd, John W.
Facsimile and static presentation processing
Facsimile
Recording apparatus
358 13, 358135, H04N 7137, H04N 1104
Patent
active
048580260
ABSTRACT:
Pixel information representing an image for display is coded using data compression. The data compression consists in obtaining the pixel information as a first matrix of high resolution pixel values, subtracting from this first matrix a second matrix composed of lower resolution pixel values, produced by low pass filtering the first matrix, to produce a third matrix of difference values, sub-sampling the second matrix to produce a fourth matrix of less density lower resolution pixel values and coding the third and fourth matrices. Complementary decoding consists in restituting the second matrix by interpolation filtering the decoded fourth matrix, and combining the restituted second matrix with the decoded third matrix. Loss of accuracy in the decoding method is reduced by coding and then decoding the fourth matrix during the coding method before it is interpolated to full pixel density to form the restituted second matrix which is subtracted from the first matrix to produce the third matrix of difference values. In this way, any sub-sampling and interpolation errors in the restituted fourth matrix occur in both the coding method and the decoding method and therefore cancel out.
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Briody Thomas A.
Haken Jack E.
Shepperd John W.
Slobod Jack D.
U.S. Philips Corporation
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