Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1997-09-10
2001-05-15
Boudreau, Leo (Department: 2621)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
Reexamination Certificate
active
06233366
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image processing method and apparatus and to a zoom processing method used when bi-level image data is zoomed and output to a recording device having a high pixel density, particularly a zoom processing method used when bi-level image data, which includes a pseudo-halftone image employed in a facsimile machine or electronic file, is subjected to a resolution conversion and then output to a recording device.
Many methods such as the SPC method, 9 segmentation method and projection method have been studied and announced as methods of zooming bi-level images. First, the SPC method performs zooming by simply duplicating or subsampling pixels or lines. Since this method has a simple hardware configuration, it is employed in comparatively inexpensive facsimile machines. The projection method is accompanied by arithmetic processing, unlike the SPC method, and involves projecting a zoomed image on an original image and calculating the density value of zoomed image data from the density of the original image and the percentage of the area which the original image occupies in a zoomed pixel subdivision. This method provides comparatively good results with regard to a bi-level image such as a character or line drawing.
A disadvantage of these methods is that a pseudo-halftone image obtained by error diffusion method or the like develops a moiré pattern and undergoes a conspicuous deterioration in image quality.
FIG. 12
illustrates the result of enlarging image data, which consists of eight pixels in the main-scan direction and eight pixels in the sub-scan direction, by a factor of {fraction (5/4)} by the SPC method. As shown in
FIG. 12
, the fourth and eighth rows in the sub-scan direction are duplicated by processing and so are the fourth and eighth columns in the main-scan direction. The SPC method is such that regardless of the fact that the ratio of black to white pixels in the original image is 1:1, the ratio of black to white pixels in the image data produced by processing is 46:54, meaning that the density of the original image has not been preserved. It will be understood that the expression of halftones is poor.
A combination of the projection method and error diffusion method and a combination of a binary-multivalue conversion by filtering and error diffusion method have been proposed as methods of obtaining comparatively good results when applied to pseudo-halftone images. With these techniques, however, considerable hardware resources such as multipliers and line buffers, the latter of which are for error diffusion method, are required. This results in a more costly apparatus.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is provide an image processing method and apparatus through which the zooming of a bi-level image inclusive of a pseudo-halftone image binarized by error diffusion method or the like is realized by a hardware arrangement, such as for logical operation, simpler than that of the prior art, and wherein it is possible to obtain a density-preserving, excellent zoomed image, which is devoid of the moire seen with the SPC method or 9 segmentation method, even with regard to a pseudo-halftone image.
According to the present invention, the foregoing object is attained by providing an image processing apparatus for subjecting bi-level image data to zoom processing, comprising converting means for converting a processed block of the bi-level image data to a block having a size conforming to magnification of the zoom processing, and deciding means for deciding, based upon a pixel pattern of the bi-level image data, output values within the processed block converted by the converting means; the deciding means deciding the output values in such a manner that pixel density of the bi-level image data is preserved within the converted processed block.
According to the present invention, the foregoing object is attained by providing an image processing method for subjecting bi-level image data to zoom processing, comprising the steps of converting a processed block of the bi-level image data to a block having a size conforming to magnification of the zoom processing, and deciding, based upon a pixel pattern of the bi-level image data, output values within the converted processed block; the deciding step deciding the output values in such a manner that pixel density of the bi-level image data is preserved within the converted processed block.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
REFERENCES:
patent: 4717964 (1988-01-01), Abe et al.
patent: 4903142 (1990-02-01), Hasebe et al.
patent: 5259042 (1993-11-01), Matsuki et al.
patent: 5293254 (1994-03-01), Eschbach
patent: 5359423 (1994-10-01), Loce
patent: 5448654 (1995-09-01), Katayama et al.
patent: 5638188 (1997-06-01), Moro et al.
patent: 5644366 (1997-07-01), Ushida et al.
patent: 5832141 (1998-11-01), Ishida et al.
patent: 5832184 (1998-11-01), Konno et al
Boudreau Leo
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Patel Kanji
LandOfFree
Image processing method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image processing method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image processing method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2474245