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EP0206401A1
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Method of enlarging/reducing 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
Abstract
Abstract 1. A method of enlarging/reducing a dithered image obtained from a rastered gray level image by means of a dither matrix, consisting of the following steps: a) reconstruction of the gray level image from the dithered image, b) enlargement/reduction of the gray level image resulting from step a), and c) dithering the enlarged/reduced gray level image resulting from step b) by means of a dither matrix. This method is easily carried out and avoids Moire distortion without increasing the signal/noise ratio.
Inventors
- 👤 Martinus Johannes Maria Waaijer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 10:28
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/387; H04N1/393; H04N1/3935; H04N1/40; H04N1/40075
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
66 words
A method of enlarging/reducing a dithered image obtained from a rastered gray level image by means of a dither matrix, characterised by the following steps: a) reconstruction of the gray level image from the dithered image, b) enlargement/reduction of the gray level image resulting from step a), and c) dithering the enlarged/reduced gray level ' image resulting from step b) by means of a dither matrix.
Claim 2
Independent Claim
66 words
A method of enlarging/reducing a dithered image obtained from a rastered gray level image by means of a dither matrix, characterised by the following steps: a) reconstruction of the gray level image from the dithered image, b) enlargement/reduction of the gray level image resulting from step a), and c) dithering the enlarged/reduced gray level ' image resulting from step b) by means of a dither matrix.
Claim 3
Dependent Claim
119 words
A method according to claim 1, characterised in that in step a) the gray level for each picture element in a dithered image is determined by counting the number of pixels having the value 1 in a closed area around the picture element under consideration, said area 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 corresponding to full black.
Claim 4
Dependent Claim
29 words
A method according to claim 1 or 2, characterised in that a bi-linear interpolation known per se is used in step b) for enlargement/reduction of the gray level image.
Claim 5
Dependent Claim
100 words
A method according to claim 1 or 2, characterised in that for the purpose of performing step b), 1) the reconstructed gray level image is divided into a number of equal sub-images in accordance with a specific raster, 2) each sub-image is allocated an image point of the enlarged/reduced image in a manner in which the mutual ordering of the image points corresponds to the matual ordering of the sub-images, 3) the average gray level within each sub-image is determined, and 4) the determined average gray level of each sub-image is allocated to the image point corresponding to this sub-image.
References Cited (Backward Citations)
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