Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1997-07-14
2001-01-30
Rogers, Scott (Department: 2724)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C382S269000, C382S271000, C382S194000
Reexamination Certificate
active
06181437
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an image processing apparatus, and in particular to an image correction processing apparatus which corrects intensities at edges of a multilevel thin line image for producing an image without jaggies at edges caused by multilevel-to-binary conversion.
DESCRIPTION OF THE BACKGROUND ART
Description of the Related Art
Generally, in image output apparatuses such as a copying machine, a facsimile and a printer, image data processing is performed for preparing output data by converting multilevel image data, which is supplied from a reading device or the like, into binary data. Various types of binary output methods have been proposed for achieving a higher image quality. However, any of them cannot perform multilevel-to-binary conversion without a problem that jaggies at edges or interruptions occur at characters or images formed of thin lines or the like, and therefore sharpness is impaired. In the prior art, a high-frequency enhancing filter such as a Laplacian filter has been used for reproducing sharp images. Also, a degree of enhancing an intensity of edge is controlled to prevent the interruptions and jaggies.
In a conventional image output device, a contrast of an edge is enhanced by enhancing the edge so as to increase the gradient of intensity change between a character and a background. However, edge enhancement by a Laplacian filter has the characteristic that an amplification rate increases with an increase in frequency of image data to be processed, so that the enhancement is strongly performed on line images and isolated points. Therefore, when a line image is read by a general image reading device using a photoelectric conversion element such as a CCD, the line image itself can be read at a high resolution owing to the edge enhancement processing. However, an isolated point and low-intensity image located near the line image are also enhanced, so that jaggies occurs at the line image when multilevel-to-binary conversion is performed. If an edge detecting level is lowered for preventing jaggies, even a weak image slant portion other than the line image is determined as an edge, resulting in increase in image noises.
FIGS. 21A and 21B
are diagrams showing distributions of an intensity of an image edge before and after edge enhancement in the prior art. The change in intensity of the edge-enhanced image, which is determined in the edge line or longitudinal direction and shown in
FIG. 21B
, is larger than that before edge-enhancement shown in FIG.
21
A. As a result, conspicuous jaggies appear at line images after the multilevel-to-binary conversion.
Further, according to a method in which intensity change is extracted by differentiation with a Laplacian filter, an interior of an image cannot be detected because a change in intensity is not present at the interior, although an edge of the image can be detected. As a result, scanning for each pixel is performed independently of surrounding pixels according to the method using the Laplacian filter, so that two-dimensional (planar) characteristics of the image cannot be acquired.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an image processing apparatus which can output a smooth contour image without jaggies independently of an intensity of an input image.
Another object of the invention is to provide an image processing apparatus which can output a contour image of a high quality.
Still another object of the invention is to provide an image processing apparatus which can produce an image without jaggies caused by multilevel-to-binary conversion.
Yet another object of the invention is to provide an image processing apparatus in which jaggies at a line image are surely prevented.
A further object of the invention is to provide an image processing apparatus which can remove isolated points.
For achieving the above objects, the invention provides an image processing apparatus including the following components. The image processing apparatus according to the invention includes: an edge determining device for determining whether a predetermined target pixel is present at an image edge or not, and an intensity converter for converting an intensity of the target pixel into a predetermined intensity based on the result of the determination.
When the target pixel is not present at the edge of the image, an edge portion of the image portion and an image interior other than the edge are detected independently of each other for converting the target pixel into a pixel of a predetermined intensity. When the edge is located at the image interior, the intensity is converted into that of the pixel of the predetermined intensity representing the image interior. Since the conversion of the intensity is performed taking surrounding pixels around each pixel into consideration, the two-dimensional characteristics of the image are acquired. Independently of the intensity of the input image, a smooth contour image without jaggies can be output.
According to another aspect, an image processing apparatus includes: an input device for inputting image data; an image data take-in device for taking in the input data in row and column directions; a counting device for counting the numbers of predetermined pixels in the taken data individually in rows and columns; a count value setting device for setting predetermined count values for the row and the column; a count value comparator for comparing the result of counting by the counting device with the set value of the count value setting device; and a converter for performing conversion of pixel data in the rows and columns based on the result of comparison by the count value comparator.
In the image processing device, the input image data is continuously taken into a scanning window in the row and column directions, and the number of the pixels having intensities in a predetermined range are counted in the row and column directions. Then, a comparison is made with a preset count value table for determining whether a predetermined target pixel is on an image edge. Conversion of the input image data is performed in accordance with the result of the comparison. Since conversion of the intensity of the input image data is performed depending on whether the target pixel is on the image edge or not, the contour image having a high quality can be output.
According to still another aspect of the invention, an image processing apparatus includes: an edge determining device for determining whether a predetermined target pixel is present on an image edge of a line image or not; and an intensity converter for converting an intensity of the target pixel into a predetermined intensity based on the result of determination.
Since the intensity for the target pixel is converted into the predetermined intensity value when it is determined that the edge of the line image contains the target pixel, the edge intensity can be uniform. As a result, it is possible to produce an image without jaggies at its edge caused by multilevel-to-binary conversion.
According to a further aspect of the invention, an image processing apparatus includes: a scanning window for inputting image data containing a target pixel in row and column directions; an image data take-in device for taking the image data into a scanning window in the row and column directions; a counting device for counting the numbers of predetermined pixels in the rows and the columns of the taken data; a line image determining device for determining, based on the result of counting, whether the pixel data in the scanning window forms a line image or not; and a converter for converting intensity data of the pixel data of the target pixel into a predetermined intensity based on the result of the determination by the line image determining device.
According to the apparatus of the above aspect, the successively received image data is taken into the scanning window in a matrix form. In the row and column directions, the number of the pixels of the prede
Minolta Co. , Ltd.
Rogers Scott
Sidley & Austin
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