Image analysis – Image enhancement or restoration – Image filter
Reexamination Certificate
1997-12-01
2001-08-21
Rogers, Scott (Department: 2624)
Image analysis
Image enhancement or restoration
Image filter
C382S264000, C382S275000, C382S218000
Reexamination Certificate
active
06278804
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image processing apparatus having a functional feature of smoothing the profile of an image. It also relates to an image processing method and to an image-forming apparatus realized by using such a method.
An image processing apparatus, which may be a copying machine, optically reads the original image and forms an electrostatic latent copy image of the original on a photosensitive dram, which operates as image carrier. Then, the electrostatic latent image is visualized by means of a developer and transferred onto a sheet of paper.
A smoothing technique is typically used for processing images in a copying machine. With this technique, the image is divided into a predetermined number of pixel blocks, which are sequentially sampled to produce a pixel matrix. The produced pixel matrix then provides sampled image data. Each of the sampled image data is then compared with a set of reference image data, which are also referred to template image data and contained in a look-up table that is stored in advance in the copying machine. If the sampled image data finds a matching reference data, data for black or white pixels are appropriately added to the profile of the black image that is represented by the sampled image data and expressed by the corresponding coordinate values in order to produce a smoothed profile that is free from jags.
FIG. 21
of the accompanying drawing illustrates the effect of a smoothing technique. Known smoothing methods include the one disclosed in Japanese Patent Application TOKKAI No. 7-57102.
While a smoothing technique may suitably be used on characters, it is not adapted to photographic images showing delicate tonal gradations because intermediate gradations are adversely affected by the smoothing effect to damage the quality of the copied image.
In order to cope with this problem, copying machines are currently adapted to discriminate character regions and photograph regions of images so that the photograph regions may be exempted from smoothing.
When an image is binarized by means of a pseudo-gradation technique such as error propagation, a very small island-like region comprising a set of black pixels and contained in a photograph region can often be mistaken for that of a character region.
Then, the photograph region is automatically subjected to a smoothing process to consequently damage the quality of the photograph.
More specifically, with error propagation, an intermediary gradation is expressed by the average of the gradations of a plurality of pixels (referred to as areal gradation). When a photograph region that has been processed by error propagation is smoothed, the gradation expressed by the average of the gradations of a plurality of pixels can be differentiated, if slightly, from the real gradation of the region to consequently damage the quality of the photograph. Such differentiation can result in a noise pattern of black spots appearing in intermediately gradated areas of an image as schematically illustrated in
FIG. 22
of the accompanying drawings. As schematically illustrated in
FIG. 23
, such a black spot of a noise pattern is given rise to when one or more than one new pixels are added to a (photograph) region that is to be expressed by a predetermined number (four in
FIG. 23
) of pixels.
BRIEF SUMMARY OF THE INVENTION
In view of the above identified circumstances, it is therefore an object of the present invention to provide an image processing apparatus or an image-forming apparatus that reliably prevents any unnecessary smoothing operation from being conducted on the photograph region(s), if any, of the image being processed and hence any undesired degradation in the quality of the image from taking place.
Another object of the present invention is to provide an image processing method that reliably prevents any unnecessary smoothing operation from being conducted on the photograph region(s), if any, of the image being processed and hence any undesired degradation in the quality of the image from taking place.
In order to achieve the above objects, according to the invention, there is provided an image processing apparatus comprising means for smoothing the profile of an image constituted by image data, means for discriminating one or more than one specific regions, if any, each containing a set of pixels fewer than a predetermined number in the image on the basis of the number and the correlations of the profile spots of the image constituting the profile and means for determining whether a smoothing operation is to be performed by using the smoothing means in accordance with the outcome of the discriminating operation of the discriminating means.
Each of the specific regions containing a set of pixels fewer than a predetermined number is processed as a region within a picture image and no smoothing operation is conducted on it.
Preferably, an image processing apparatus according to the invention further comprises matrix forming means for forming a pixel matrix by sequentially sampling input image data and providing the image data of the pixel matrix as sampled image data and detecting means for detecting the profile of the black image component or each of the black component images, if any, from the sampled image data provided by the matrix forming means. The discriminating means includes means for discriminating one or more than one island-like regions (the specific region or regions), if any, having a surface area smaller than a predetermined value in the sampled image data when the number of profile spots of the black image component or each of the black image components detected by the detecting means is smaller than a predetermined value. The determining means includes image data switching means for selecting either the image data processed by the smoothing means or the sampled image data of the matrix forming means and producing the selected data as output.
Preferably, an image processing apparatus according to the invention further comprises image region determining means for determining the sampled image data provided by the matrix forming means are for a character region or a photographic region, wherein the data switching means selects the image processed by the smoothing means when the discriminating means does not discriminate any island-like region and the image region determining means determines that the sampled image data are for a character region and otherwise selects the sampled image data provided by the matrix forming means. With the above arrangement, no smoothing operation is conducted on a region determined to be a character region by the image region determining means if it is discriminated as an island-like region by the discriminating means.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 5005139 (1991-04-01), Tung
patent: 5014124 (1991-05-01), Fujisawa
patent: 5535013 (1996-07-01), Murata
patent: 5689582 (1997-11-01), Murakami
patent: 487 026 (1992-05-01), None
patent: 554 985 (1993-08-01), None
patent: 618 717 (1994-10-01), None
patent: 663 758 (1995-07-01), None
patent: 672 999 A1 (1995-09-01), None
patent: 7-57102 (1995-03-01), None
Foley & Lardner
Kabushiki Kaisha Toshiba
Rogers Scott
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