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EP0207548A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Method of reconstructing a gray level image from a dithered image

Assignee: Canon Production Printing Netherlands BV
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Filing: 1986-06-11
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Granted: —
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Expires: 2006-06-11
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Abstract

Abstract A method of calculating the gray scale value for each pixel (3) of a dithered image by counting the number of black pixels within an integration area (1). The integration area (1) is a closed area containing the same number of pixels as the number of different threshold values in the dither matrix that was used to obtain the dithered image. The percentage of black pixels within the integration area (1) gives the gray scale value (3'), which is assigned to the pixel (3) in or near the centre of the integration area (1). The gray scale value (4') of the next pixel (4) is calculated from the number of black pixels within an integration area (2) that is moved one pixel position.

Inventors

  • 👤 Martinus Johannes Maria Waaijer

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-09 22:17
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/40075

Claims Analysis

Total Claims: 5
Claim 1
Independent Claim 138 words
A method of reconstructing a gray level image from a dithered image, the dithered image being obtained from the original analog image by dithering with a dither matrix, characterised in that the gray level for each picture element is determined by counting the number of pixels having the value 1 in a closed area (1) around the picture element under consideration (3), said area (1) containing a number of pixels equal to the number of different thresholds in the dither matrix and each pixel being obtained by dithering with a dif­ferent threshold, and equating the sum of said number of pixels having the value of 1 with the gray level, a sum equal to 0 corresponding to full white and a sum equal to the number of picture elements in the said area (1) corresponding to full black.
Claim 2
Independent Claim 138 words
A method of reconstructing a gray level image from a dithered image, the dithered image being obtained from the original analog image by dithering with a dither matrix, characterised in that the gray level for each picture element is determined by counting the number of pixels having the value 1 in a closed area (1) around the picture element under consideration (3), said area (1) containing a number of pixels equal to the number of different thresholds in the dither matrix and each pixel being obtained by dithering with a dif­ferent threshold, and equating the sum of said number of pixels having the value of 1 with the gray level, a sum equal to 0 corresponding to full white and a sum equal to the number of picture elements in the said area (1) corresponding to full black.
Claim 3
Dependent Claim 34 words
A method according to claim 1, characterised in that the area (1) is selected so that the picture element under consideration (3) is situated at least approximately in the middle of the area (1).
Claim 4
Dependent Claim 42 words
A method according to claim 1 or 2, characterised in that if a dither matrix is used in which all the thresholds occur once, the area (1) is selected to be identical to the dither matrix in respect of size and shape.
Claim 5
Dependent Claim 68 words
A method according to claim 1 or 2, characterised in that if a dither matrix is used in which each of the thresholds occurs several times, a sub-matrix of adjoining thresholds is defined in such a manner that each of the possible thresholds occurs once in the sub­matrix and in that the area is (1) selected to be identical to the submatrix in respect of size and shape.

References Cited (Backward Citations)

US3524020A Cited
EP0024902A2 Cited
EP0065281A2 Cited

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