Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-05-28
2002-05-21
Wallerson, Mark (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S448000, C382S199000, C382S266000
Reexamination Certificate
active
06392759
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an edge-enhancement processing apparatus and method for performing edge enhancement processing based on multi-level image data representing an image with pixels in dot matrix, and a medium containing an edge-enhancement processing program.
2. Description of the Prior Art
Conventionally, image-processing software programs for performing edge enhancement processing to enhance edge portions on image data representing a photograph or the like are known. These programs read image data into a computer, convert the image data at different edge enhancement levels by trial and error. An operator checks the converted result on a display screen by visual observation, thus adjusting it to have appropriately enhanced edge portions.
Japanese Patent Application Laid-Open No. 6-68252 discloses obtaining high frequency components in edge areas of an image by using a high-frequency band filter, judging the sharpness of the image based on the mean value of the high frequency components and controlling an edge enhancement parameter.
In the former case, since the converted result must be checked by the operator's visual observation, an appropriate enhancing level cannot be automatically set.
In the latter case, since the high frequency components are obtained by using the high-frequency band filter, the processing is complicated.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an edge-enhancement processing apparatus and method capable of judging the sharpness of an image with simpler method and automatically performing optimum edge enhancement processing.
The edge-enhancement processing apparatus provided by the present invention is an edge-enhancement processing apparatus comprising: image-data obtaining unit which obtains multi-level image data representing an image with pixels in dot matrix; summation processing unit which calculates a change level of each pixel based on differences of luminance or substitute values for luminance between the pixel and peripheral pixels, as a vector value, and sums up vector values of pixels having large vector values; edge-enhancement element determination unit which determines an edge enhancement element while judging a sharpness level of the image based on the result of summation; and edge-enhancement unit which performs edge enhancement processing on respective edge pixels based on the determined edge enhancement element.
In the present invention having the above construction, when the image-data obtaining unit obtains multi-level image data representing an image with pixels in dot matrix, the summation processing unit calculates a change level of each pixel based on differences of luminance or substitute values for luminance between the pixel and peripheral pixels, as a vector value, and sums up vector values of pixels having large vector values. On the other hand, the edge-enhancement element determination unit determines an edge enhancement element while judging the sharpness level of the image based on the result of summation. The edge enhancement unit performs edge enhancement processing on respective edge pixels based on the determined edge enhancement element.
That is, upon calculating the sharpness level of the image from change levels of respective pixels on the premise that the enhancement level is not necessarily greatly raised if the image is sharp, the change level of each pixel is calculated based on the differences of luminance or substitute values for luminance between the pixel and peripheral pixels, as a vector value. The image change levels are obtained in pixel units on the premise that the image data is composed of pixels in dot matrix.
On the other hand, assuming that an object to be image-sensed is called a subject and the area other than the subject is called a background, the operator considers edge enhancement processing only based on the sharpness level of the subject and takes little account of the background. In this case, the subject is usually sharper than the background. Accordingly, when the sharpness level of the image is judged based on the result of summation with respect to pixels having large change level, the judgment is made on the same condition as that for judgment with respect to the subject.
According to the present invention, as a vector value is calculated based on the differences of luminance or substitue values for luminance between each pixel and peripheral pixels, to determine the edge enhancement element, an edge-enhancement processing apparatus which automatically performs edge enhancement processing can be provided with a simple construction.
As described above, when calculating the sharpness level of the image from change levels of respective pixels, the calculation of a vector value based on the differences of luminance or substitute values for luminance between each pixel and peripheral pixels are not necessarily realized by a hardware apparatus, but may be realized as a method for the apparatus. Accordingly, the present invention provides an edge-enhancement processing method for performing edge enhancement processing on multi-level image data representing an image with pixels in dot matrix, comprising: a step of calculating a change level of each pixel based on differences of luminance or substitute values for luminance between the pixel and peripheral pixels, as a vector value, and summing up vector values of pixels having large vector values; a step of determining an edge enhancement element while a judging sharpness level of the image based on the result of summation, while; and a step of performing edge enhancement processing on respective edge pixels based on the determined edge enhancement element.
That is, the edge enhancement processing is effective not only when embodied with a hardware apparatus but when embodied as a method for the apparatus.
The summation processing unit calculates a change level of each pixel based on differences of luminance or substitute values for luminance between the pixel and peripheral pixels, as a vector value. If the image data has pixel data in dot matrix arranged in vertical and lateral directions, there are eight adjacent pixels around a pixel of interest. However, in evaluation, comparison may not be necessarily made with all these adjacent pixels.
Accordingly, another object of the present invention is to provide an example of the summation processing unit. To attain the object, in the edge-enhancement processing apparatus provided by the present invention, when the summation processing unit calculates a change level of each pixel based on differences of luminance or substitute values for luminance between the pixel and peripheral pixels, as a vector value, employs the differences of luminance or substitute values for luminance among a plurality of pixels which are not arrayed in a linear direction.
According to the present invention having the above construction, as the vector is generated based on the differences of luminance or substitute values for luminance among a plurality of pixels which are not arrayed in a linear direction, the number of pixels taken into consideration upon vector generation is the half of that in the previous construction. That is, in case of pixels adjacent to each other, the vector elements arrayed in a linear direction interact with each other, therefore, evaluation on these pixels may be omitted without significant influence.
In this manner, according to the present invention, the vectors can be obtained in pixel units with small amount of calculation processing.
Further, as the summation processing unit to sum up the change levels of the pixels to judge the sharpness level of the image, various types of processing units may be employed.
Further, another object of the present invention is to provide an example of the summation processing unit.
In the edge-enhancement processing apparatus provided by the present invention, said summation processing unit performs the summation such that as the vect
Kuwata Naoki
Nakami Yoshihiro
Seiko Epson Corporation
Sughrue & Mion, PLLC
Wallerson Mark
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