Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
2000-02-11
2004-06-15
Rogers, Scott (Department: 2626)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S462000, C382S176000, C382S205000
Reexamination Certificate
active
06750984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus such as a copying machine or a facsimile apparatus, and more particularly to an image processing apparatus which, when processing a color image, can apply to each different kind of image region, an optimum process according to characteristics of the image region.
2. Description of the Related Art
When reproducing color images using a color digital copying machine, color facsimile apparatus or the like, a color discrimination process is performed and, in non-colored image regions is used only black ink or black toner so as to form images of good image quality. In colored image regions are used inks or toners of three primary colors, cyan (C), magenta (M), and yellow (Y) to form color images. Black images could also be formed using all the three primary color inks or toners, but since registration errors tend to occur when overlaying colors one on top of another, causing problems such as colored tinges at black edges. Accordingly in the case of forming characters, the quality of images of characters would degrade. A color discrimination process thus becomes necessary to discriminate between non-colored and colored regions. Furthermore, using only black ink or black toner for non-colored regions has the effect of reducing the amount of use of the inks or toners of the three primary colors.
The color discrimination process is performed using an output from an image reading input apparatus such as a scanner. This kind of input apparatus contains an imaging device such as CCD (charged coupled device) and reads an image as a collection of pixels. In an imaging device such as a CCD, a plurality of light receiving elements are arranged to correspond with pixels. However, because of variations in characteristics such as sensitivity among the plurality of light receiving elements, pixel displacements may occur among inputs corresponding to the respective colors. If such pixel displacements occur, an input condition in which red (R), green (G), and blue (B) are equal in density cannot be obtained; as a result, with a pixel-by-pixel color discrimination process, when an image of a non-colored region is input, the region may often be judged erroneously as being a colored region.
Japanese Unexamined Patent Publication JP-A 5-41796 (1993) discloses a technique for correcting pixel displacements by applying smoothing prior to the color discrimination process. The color discrimination is accomplished by obtaining a maximum value and a minimum value of the density of each color and by comparing the two values to determine through binarization whether the color is achromatic or not. To discriminate a character region, photographic region, halftoned region, etc., a mask region is set and the image density within the mask region is binarized; then, using as an address signal the binarized image density of the pixels contained within the mask, a search is made through a lookup table and data prestored in the lookup table is evaluated as a characteristic value.
If a smoothing process is applied prior to the color discrimination process in order to prevent pixel displacements of RGB inputs, etc. caused by variations within an input apparatus, as practiced in the prior art of JP-A 5-41796, since such a process is not appropriate as a process for correcting pixel displacements, an erroneous discrimination may result. More specifically, a process based only on the maximum and minimum values cannot provide a sufficient number of parameters to achieve accurate color discrimination, and the possibility of erroneously judging a colored region as being a non-colored region or a non-colored region as being a colored region cannot be eliminated. Furthermore, though provisions are made to discriminate character regions, photographic regions, halftoned regions, etc. using a lookup table, it is extraordinary difficult to create a lookup table which can yield good discrimination results, and also, information is not easily obtainable on how the lookup table is to be corrected when there occur many errors in discrimination results. Moreover, when the process is performed using only the smoothing technique, not only pixel displacements but also the differences in color originally present in the original document are all absorbed, and such a process is therefore not effective in color discrimination.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image processing apparatus capable of accurately discriminating image region characteristics of an image region of an input to the apparatus, including a discrimination process of characters, photographs or half tone dots and a color discrimination process, regardless of whether the input to the apparatus contains pixel displacements, noise, etc.
The present invention provides an image processing apparatus which carries out a process of discriminating characteristics of a region including an object pixel in order to optimally process an original document which may contain a mixture of different kinds of image regions including characters, photographs and halftone regions, according to characteristics of each image region, comprising:
a mask setting circuit for setting within the region including the object pixel a mask of a predetermined shape so as to contain therein the object pixel;
a sub-region mask generation circuit for generating sub-region masks, each smaller than the mask set by the mask setting circuit, sequentially in different positions within the mask set by the mask setting circuit, to obtain a sum of pixel densities within each of the sub-region masks;
a parameter calculation circuit for calculating a parameter within the mask, using the sum of pixel densities obtained by the sub-region mask generation circuit;
multi-valuing means for performing a multi-valuing process using the parameter calculated by the parameter calculation circuit;
characteristic signal generating means for generating from distribution of multi-valued data generated by the multi-valuing means, within the mask, a characteristic signal represented by the multi-valued data; and
region discriminating means for discriminating the characteristics of the region, based on the characteristic signal supplied from the characteristic signal generating means.
According to the invention, for the original document containing a mixture of characters, photographs, halftone dots, etc., the process of discriminating character regions, photograph regions and halftone regions is performed in order to process the document optimally in accordance with the characteristics of the respective image regions. The mask setting circuit sets a mask containing an object pixel. The mask has a predetermined shape, for example, a shape consisting of m×n pixels. The sub-region mask generation circuit generates sub-region masks, each consisting of u×v pixels, wherein m≧u and n≧v, and having a shape smaller than that of the mask set by the mask setting circuit, by sequentially setting the sub-region masks in different positions within the mask, and obtains the sum of pixel densities within each of the sub-region masks. The parameter calculation circuit calculates a parameter within the mask, using the sum of pixel densities obtained by the sub-region mask generation circuit. The multi-valuing means performs the multi-valuing process using the parameter calculated by the parameter calculation circuit. From the distribution of the multi-valued data generated by the multi-valuing means, within the mask, the characteristic signal generating means generates a characteristic signal representing a characteristic amount expressed by the multi-valued data. The region discriminating means discriminates the characteristics of the region, based on the characteristic signal supplied from the characteristic signal generating means. For example, by performing a process of obtaining the sum of pixel densities set by the mask setting circuit within the mask, the characteristics
Adachi Yasushi
Kanata Toshihiro
Conlin David G.
Edwards & Angell
Rogers Scott
Sharp Kabushiki Kaisha
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