Image analysis – Color image processing – Image segmentation using color
Reexamination Certificate
1997-03-27
2001-03-06
Au, Amelia (Department: 2723)
Image analysis
Color image processing
Image segmentation using color
C382S167000, C358S521000, C358S522000, C358S534000
Reexamination Certificate
active
06198841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital color image processor.
2. Description of Prior Art
In a digital color image processor, black characters in a document are usually discriminated to improve reproducibility of black characters. Characters (edges) are discriminated from achromatic image portions in a document by detecting an edge portion and an achromatic portion in the document. Various techniques are proposed for discriminating an achromatic image, and they discriminate an achromatic portion according to color data, that is, red (R), green (G) and blue (B) data. For example, in a technique, a difference of the maximum from the minimum of R, G and B color data, is used as chroma data. A portion having a larger difference is decided to be a color image, while a portion having a lower difference is decided to be an achromatic image.
It is also known to discriminate a dot area in a document and prevents Moire phenomenon by using the discrimination. In the discrimination, isolated dots isolated are detected from the gradation distribution of color data, and a dot area is detected according to the number of the dots in a unit pixel matrix.
On the other hand, in such an image processor, image forming mode such as the magnification or the density of an output image is changed automatically or manually by a user. The magnification can be changed by controlling resolution of color data. The density can be changed by controlling gradation characteristic such as background level.
When the gradation characteristic is changed for density control, the chroma data and the edge level are affected. For example, when the image reading conditions are set so as to remove the background of a document, it becomes difficult to decide an edge of a character having a low density. Further, when an image is reduced by changing magnification, a character having many lines therein is erroneously decided as dots. Thus, the quality of image reproduction is deteriorated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image processor which improves the quality of a reproduced image surely by controlling image forming conditions when an image forming mode is set.
In one aspect of the invention, an image processor comprises an image scanner, and color data are obtained by reading a color image with a color image sensor. A specification device is provided to specify an image forming mode of the color image, and the image forming mode is changed according to the specified image forming mode when the color data is processed. The color data is changed according the image forming mode, and an area in the color data is discriminated for image processing of the color data with a reference value changed according to the image forming mode. Then, the color data is corrected according to the discrimination. For example, a gradation characteristic such as background level is specified as the image forming mode related to density, and a black portion in the color data is discriminated with the reference value changed according to the background level. In another example, magnification is specified as the image forming mode, and a dot area in the color data is discriminated with the reference value changed according to the magnification.
An advantage of the present invention is that a black portion in a color data can be discriminated surely when a gradation characteristic is changed.
Another advantage of the present invention is that a dot area in a color data can be discriminated surely even when magnification of the image is changed.
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U.S. application No. 08/611,754, Co-pending.
U.S. application No. 08/747,827, Co-pending.
Hirota Yoshihiko
Toyama Katsuhisa
Au Amelia
McDermott & Will & Emery
Minolta Co. , Ltd.
Wu Jingge
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