# US 4,393,452 A · Method of reproducing a picture having improved resolution

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- Number: US 4,393,452 A
- Document ID: US4393452A
- Status: Granted
- Kind: A
- Application number: 06/155,179
- Filed: 1980-06-02
- Granted: 1983-07-12
- Earliest claimed: 1979-06-02
- Assignees: Ricoh Company, Ltd.
- Inventors: Keiji Sekigawa
- Web page: https://patentgrep.com/patent/US4393452A

## CPC

- H04N 1/40075: {Descreening, i.e. converting a halftone signal into a corresponding continuous-tone signal; Rescreening, i.e. combined descreening and halftoning}
- G06T 3/40: Scaling of whole images or parts thereof, e.g. expanding or contracting
- H04N 1/4051: {producing a dispersed dots halftone pattern, the dots having substantially the same size (different sizes H04N1/4057)}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

In a picture processing method, the density data of picture elements in a particular picture element region in a 4.times.4 arrangement which is provided by decomposing an original picture into a number of picture elements are subjected to n-base quantization to provide density levels thereof, and the particular picture element region is divided into an aimed picture element region consisting of four picture elements in the central part of the particular picture element region and a surrounding region consisting of twelve picture elements surrounding the aimed picture element region. The aimed picture element region is converted into a minute picture element region in 3.times.3 arrangement consisting of nine minute picture elements. The estimation density levels of these minute picture elements are calculated according to particular equations by using the density levels of the picture elements in the particular picture element region, and are compared with the threshold levels in a predetermined threshold pattern provided for the minute picture element region, to determine whether the level of each minute picture element is "black" or "white".

## Claims

### Claim 1

A method of reproducing a picture including half-tones through estimation with binary outputs, wherein said picture is divided into a predetermined number of picture elements defining a matrix and each picture element within said matrix is assigned a density level, comprising the steps of:
subdividing said matrix of picture elemtns into plural 2.times.2 sub-matrices;
converting each 2.times.2 sub-matrix into a higher resolution 3.times.3 sub-matrix of picture elements, comprising,
calculating density levels for each of said picture elements in said 3.times.3 sub-matrix according to predetermined equations including weight factors for each of the density levels of said picture elements in the 2.times.2 sub-matrix and those of the picture elements surrounding said 2.times.2 sub-matrix;
comparing the calculated density levels with respective predetermined threshold levels, thereby to determine an output level of each picture element of each of said 3.times.3 sub-matrices is black or white in dependence on whether or not the calculated density levels exceed the predetermined threshold levels, and
reproducing said picture based on the respective output levels of each of said picture elements of each of said 3.times.3 matrices determined in said comparing step; in which said predetermined equations are
q.sub.1 =a.sub.1 .multidot.Q.sub.1 +a.sub.2 .multidot.Q.sub.2 +a.sub.2 .multidot.Q.sub.5 +a.sub.3 .multidot.Q.sub.6
q.sub.2 =a.sub.6 .multidot.Q.sub.2 +a.sub.6 .multidot.Q.sub.3 +a.sub.4 .multidot.Q.sub.6 +a.sub.4 .multidot.Q.sub.7
q.sub.3 =a.sub.2 .multidot.Q.sub.3 +a.sub.1 .multidot.Q.sub.4 +a.sub.3 .multidot.Q.sub.7 +a.sub.2 .multidot.Q.sub.8
q.sub.4 =a.sub.6 .multidot.Q.sub.5 +a.sub.4 .multidot.Q.sub.6 +a.sub.6 .multidot.Q.sub.9 +a.sub.4 .multidot.Q.sub.10
q.sub.5 =a.sub.5 .multidot.Q.sub.6 +a.sub.5 .multidot.Q.sub.7 +a.sub.5 .multidot.Q.sub.10 +a.sub.5 .multidot.Q.sub.11
q.sub.6 =a.sub.4 .multidot.Q.sub.7 +a.sub.6 .multidot.Q.sub.8 +a.sub.4 .multidot.Q.sub.11 +a.sub.6 .multidot.Q.sub.12
q.sub.7 =a.sub.2 .multidot.Q.sub.9 +a.sub.3 .multidot.Q.sub.10 +a.sub.1 .multidot.Q.sub.13 +a.sub.2 .multidot.Q.sub.14
q.sub.8 =a.sub.4 .multidot.Q.sub.10 +a.sub.4 .multidot.Q.sub.11 +a.sub.6 .multidot.Q.sub.14 +a.sub.6 .multidot.Q.sub.15
q.sub.9 =a.sub.3 .multidot.Q.sub.11 +a.sub.2 .multidot.Q.sub.12 +a.sub.2 .multidot.Q.sub.15 +a.sub.1 .multidot.Q.sub.16
where q.sub.1 through q.sub.9 are the calculated density levels of said picture elements of said 3.times.3 matrix, Q.sub.1 through Q.sub.16 are the density levels of said picture elements in said 2.times.2 sub-matrix and of said picture elements surrounding said 2.times.2 sub-matrix and are expressed in multi-base quantization, and a.sub.1 through a.sub.6 are the weight factors for said minute picture elements, with a.sub.1 +2a.sub.2 +a.sub.3 =1, 2a.sub.6 +2a.sub.4 =1 and 4a.sub.5 =1.