Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-10-27
2001-05-22
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S451000, C358S462000, C382S266000
Reexamination Certificate
active
06236466
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing system, and more particularly, to a system and method for converting a gray-level image into a binary image.
2. Description of the Prior Art
Many image-processing devices need to convert gray-level images into binary images. Line-art/bi-level conversion method and half-tone conversion method are the most commonly used two conversion methods. The line-art/bi-level method uses a gray-level threshold value between 0 and 255 to convert a gray-level pixel. A gray-level pixel with a value greater than the threshold is converted into 1, otherwise it is converted into 0. The converted binary image usually shows a character of strong contrast. Such a conversion method is ideal for text image conversion since the edges of text data usually show strong contrast character, but it is inappropriate for converting graphic images because graphic images usually have a lot of continuous gray-level variations.
The half-tone conversion method includes dither method, error diffusion method, and correlative density assignment of adjacent pixels (CAPIX). The half-tone conversion method can effectively reflect continuous variations of gray levels and can thus be adequately used to convert graphic images. However, in converting text images it will blur the edges of text data and thus should be avoided.
Text and graphic images need to use different conversion methods for converting each of them into a binary image. But since the prior art image conversion method can only be used to convert a complete image each time, a user must make a decision to select a single conversion method which is suitable for converting one type of images even though the image to be converted may contain both types of images.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide an image processing system which can convert both types of images so that the above mentioned problem can be solved.
In a preferred embodiment, the present invention comprises an image processing method for converting a gray-level image into a binary image by using an image processing system, the gray-level image comprising a plurality of gray-level pixels arranged in a matrix format, the binary image comprising the same number of binary pixels arranged in the same manner as the gray-level image, the image processing system comprising a memory for storing programs and the gray-level and binary images, and a processor for executing the programs stored in the memory, the image processing method comprising the following steps:
(1) examining the gray-level pixels of the gray-level image so as to locate and define gray-level pixels with boundary characteristics as boundary points according to a predetermined boundary determination method, and defining gray-level pixels next to each of the boundary points as neighboring points according to a predetermined neighboring point determination method; and
(2) converting each of the boundary points and neighboring points of the gray-level image into a corresponding binary pixel according to a first pixel conversion method, and converting each of the gray-level pixels other than the boundary points and neighboring points in the gray-level image into a corresponding binary pixel according to a second pixel conversion method to generate the binary image.
It is an advantage of the present invention that the image processing system assigns an edge-closeness parameter to each of the gray-level pixels in a gray-level image to identify two types of gray-level pixels. The two types of gray-level pixels are then separately converted by using two different image conversion methods. Furthermore, the image processing method can intensify the boundary image by adjusting the maximum value of the edge-closeness parameter thus increasing the flexibility of using the image processing system.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.
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patent: 5784488 (1998-07-01), Kuwata
patent: 5815606 (1998-09-01), Baker et al.
patent: 5970178 (1999-10-01), Lin
Acer Peripherals Inc.
Hsu Winston
Rogers Scott
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