EP0024902A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Apparatus and method for converting one-bit image data into gray scale image data
Assignee: Xerox Corp
•
Filing: 1980-08-22
•
Granted: —
•
Expires: 2000-08-22
Abstract
Abstract A method and apparatus for rescreening a halftone image to produce an edge-enhanced halftone copy from a halftone original. The halftone original is scanned by a raster input scanner and the resultant analog voltage thresholded to produce a one bit per pixel bit stream. A six bit per pixel gray scale output is produced therefrom by adding an integrated value and an edge ehancement value for each input pixel received. The integrated value is calculated by summing the number of one bits in the seven by nine bit section surrounding each pixel. The edge enhancement value is calculated by determining the difference between the number of one bits in the right and left halves, and upper and lower halves, of the six by seven bit section surrounding each pixel. A set of equations is used to process these differences to produce an edge enhancement value which is added to the integrated value. From this six bit per pixel gray scale output the six bit output can be preserved, or a halftone copy can be produced by any well-known process. A simple and inexpensive circuit to perform the above functions at high data rates is also disclosed.
Inventors
- 👤 Henry H Liao
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 09:16
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/409; H04N1/4092; G; G06; G06T; G06T5/00; G06T5/90; G06T5/92; H04N1/40075
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
109 words
Apparatus for converting one bit per pixel input image data into multiple bit per pixel gray scale output image data, characterised by: an integrator (20) for summing the number of input bits of one state in an area surrounding and including the instant input bit, an edge extractor (21) for determining an edge correction value by calculating the rate at which the input image bits in the said area are changing in color in orthogonal directions, and an adder (22) for adding the sum produced by said integrator (20) and the value produced by said edge extractor (21) to produce multiple bit per pixel gray scale output image data.
Claim 2
Dependent Claim
109 words
Apparatus for converting one bit per pixel input image data into multiple bit per pixel gray scale output image data, characterised by: an integrator (20) for summing the number of input bits of one state in an area surrounding and including the instant input bit, an edge extractor (21) for determining an edge correction value by calculating the rate at which the input image bits in the said area are changing in color in orthogonal directions, and an adder (22) for adding the sum produced by said integrator (20) and the value produced by said edge extractor (21) to produce multiple bit per pixel gray scale output image data.
Claim 3
Dependent Claim
160 words
The apparatus of claim 1, characterised in that said edge extractor (21) comprises: a first circuit (25) for determining the difference between the number of input bits of one state in columns (and rows) 2, 3 and 4 of a matrix into which the said area is subdivided, and the number of bits of the same state in columns (and rows) 5, 6 and 7, of rows (columns) 1 through 7, a second circuit (25) for determining the difference between the number of input bits of one state in columns (and rows) 1,2 and 3 and the number of bits of the same state in columns (and rows) 4, 5 and 6, of rows (and columns) 1 through 7, where the instant input bit is defined as the center bit of a matrix of columns 0 through 8 and rows 1 through 7 of input bits, and a third circuit (33) for computing an edge correction value from said differences.
Claim 4
Dependent Claim
33 words
The apparatus of claim 2 characterised in that said integrator (20) sums the number of input bits of one state in a seven row by nine column matrix surrounding the instant input pixel.
Claim 5
Dependent Claim
55 words
The apparatus of claim 2 or 3, characterised in that said third circuit (33) also determines the four possible root mean square values of a column difference and a row difference, and determines which of said root mean square values is to be added to or subtracted from the sum produced by said integrator (20).
Claim 6
Independent Claim
172 words
The method of converting one bit per pixel input image data into multiple bit per pixel gray scale output image data, where the instant input bit is defined as the center bit of a matrix of columns 0 through 8 and rows 1 through 7 of input bits, characterised by the steps of: summing the bits of one state in said matrix; determining the difference in the number of bits in columns 2, 3 and 4, and in 5, 6 and 7, and also the difference between columns 1, 2 and 3, and 4, 5 and 6, in rows 1 through 7; determining the difference in the number of bits in rows 2, 3, 4 and 5, 6, 7, and also the difference between rows 1, 2, 3, and 4, 5, 6, in columns 1 through 7; determining the four possible root mean square values of a row difference and a column difference, and adding or subtracting one of said root mean square values to said sum of bits of one state.
Claim 7
Independent Claim
172 words
The method of converting one bit per pixel input image data into multiple bit per pixel gray scale output image data, where the instant input bit is defined as the center bit of a matrix of columns 0 through 8 and rows 1 through 7 of input bits, characterised by the steps of: summing the bits of one state in said matrix; determining the difference in the number of bits in columns 2, 3 and 4, and in 5, 6 and 7, and also the difference between columns 1, 2 and 3, and 4, 5 and 6, in rows 1 through 7; determining the difference in the number of bits in rows 2, 3, 4 and 5, 6, 7, and also the difference between rows 1, 2, 3, and 4, 5, 6, in columns 1 through 7; determining the four possible root mean square values of a row difference and a column difference, and adding or subtracting one of said root mean square values to said sum of bits of one state.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.