Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-06-02
2002-01-22
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S521000, C358S534000, C358S523000
Reexamination Certificate
active
06341019
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for processing an image, including the process of converting the image to an n-level image, and also to a recording medium.
2. Description of the Related Art
A color copying machine is known which makes a copy of an original document using four color component signals C (cyan), M (magenta), Y (yellow), and Bk (black) in the form of two-level signals generated from a digital image signal of the document.
FIG. 2
is a schematic diagram illustrating such a type of color copying machine. In
FIG. 2
, an image scanner
201
reads image data from a document and performs digital signal processing on the image data. In accordance with the document image data obtained via the image scanner
201
, a printer
202
outputs a full-color image on paper.
In the image scanner
201
, a document
204
is placed on a document glass plate (hereinafter referred to as a platen)
203
, and a mirror-surface pressure plate
200
is placed on the document
204
. The document
204
is illuminated by lamps
205
. Light reflected from the document
204
is directed by mirrors
206
,
207
, and
208
to a lens
209
which in turn focuses the light onto a three-line solid state image sensor (hereinafter referred to as a CCD)
210
so that an image of the document
204
is formed on the CCD
210
. A full-color image signal including red (R), green (G), and blue (B) components is generated by the CCD
210
and sent to a signal processor
211
. The lamps
205
and the mirror
206
are moved at a speed v and the mirrors
207
and
208
at a speed v/2 in a direction perpendicular to the direction of electric scanning performed by the line sensor thereby scanning (secondary-scanning) the whole surface of the document. The image of the document
204
obtained by the scanning has a resolution of 400 dpi (dots per inch) in both primary and secondary scanning directions.
The signal processor
211
performs an electronic process on the image signal obtained by the scanning so as to decompose the image signal into magenta (M), cyan (C), yellow (Y), and black (Bk) components. The resultant color component signals are sent to the printer
202
. The respective color component signals M, C, Y, and Bk are converted to two-level signals having a value of either 0 or 1 by means of a known binarization technique such as an error diffusion method. When the document is scanned by the image scanner
201
, one of color component signals M, C, Y, and Bk is generated and sent to the printer
202
. Thus, the document must be scanned four times to obtain a printed image.
In the error diffusion method, as disclosed for example in a paper titled “An adaptive algorithm for the spatial gray scale” (R. Floyd and L. Steinberg, SID 75 Digest, pp.36-67), multilevel image data of a pixel of interest is converted to two-level data (representing either a black or white level), and the error of the two-level data relative to the original multilevel image data is weighted according to a predefined rule. The error is diffused by adding the weighted error to the data of pixels neighboring of the pixel of interest. In this method, the original multilevel image data can be converted to two-level data while preserving the density of the original image. The conversion to two-level data is performed independently for each of color component signals M, C, Y, and Bk.
The image signal including the color component signals M, C, Y, and Bk transmitted from the image scanner
201
is applied to a laser driver
212
. In response to the image signal, the laser driver
212
drives a semiconductor laser
213
so that the optical output of the semiconductor laser
213
is modulated in accordance with the color component signals. When the image signal has a value equal to 0 the laser is not turned on, but the laser is turned on when the image signal has a value equal to 1. Thus, two-level image data is written on a photosensitive drum
217
depending on whether the image signal is equal to 0 or 1. The laser beam scans the photosensitive drum
217
via a polygon mirror
214
, an f-
2
lens
215
, and a mirror
216
. As in the reading operation, the writing operation is also performed so that the written image has a resolution of 400 dpi (dots per inch) in both primary and secondary scanning directions.
There is also provided a rotating developing device
218
including a magenta developing unit
219
, a cyan developing unit
220
, a yellow developing unit
221
, and a black developing unit
222
. The four developing units alternately come into contact with the photosensitive drum
217
. The electrostatic latent image formed on the photosensitive drum is developed with toner. In the developing process, toner is put on those pixels which are exposed to the laser beam, while no toner is put on those pixels which are not exposed to the laser beam. Thus, a toner image corresponding to the two-level image data written on the drum is created.
Paper is fed from a paper cassette
224
or
225
toward a transfer drum
223
. The paper is wound around the transfer drum
223
, and the image developed on the photosensitive drum
217
is transferred to the paper.
The image transfer is performed successively for four colors M, C, Y, and Bk. The paper is then passed through a fixing unit
226
so as to fix the toner to the paper. The paper is then fed out.
In the color copying machine constructed in the above-described manner, the image signal which has been converted to two-level signal for each color component may be temporarily stored in a buffer memory so that the image may be printed at a desired arbitrary time after completion of the image reading process. This makes it possible to print an image for example after performing 90°-rotation on the image data stored in the buffer memory, or print a composite image by combining a plurality of pages into one page.
However, when the printed image has a density higher or lower than the expected density, or when the color of the printed image is different from the expected color, it is difficult to make a correction because the image signal has already been quantized to two levels, that is, either a white or black level, for each color component.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for processing an image in such a manner that excellent color reproduction is achieved regardless of whether the image is reproduced from m-level data or n-level data (where m and n are integer).
It is another object of the present invention to provide a method for processing an image, in which a desired color correction may be made on n-level data.
According to one aspect of the present invention, there is provided a method of processing an image, having first and second modes, wherein in the first mode m-level color data is converted to n (n<m)-level color data, and wherein in the second mode n-level color data is first converted to m-level color data and further converted to n-level color data.
According to another aspect of the present invention, there is provided a method of processing an image, including the steps of: mannually inputting correction information, setting a look-up table associated with conversion to m-level data in accordance with the correction information, and converting n (n<m)-level data to m-level data using the set look-up table.
These and other features and objects will become apparent from the following detailed description in conjunction with the accompanying drawings.
REFERENCES:
patent: 4926268 (1990-05-01), Kawamura et al.
patent: 5031179 (1991-07-01), Yoshida et al.
patent: 5245354 (1993-09-01), Ono et al.
patent: 5282059 (1994-01-01), Fukushima et al.
patent: 5313286 (1994-05-01), Sugiura et al.
patent: 5315415 (1994-05-01), Kawai et al.
patent: 5488672 (1996-01-01), Mita
patent: 5760922 (1998-06-01), Kojima
“An Adaptive Algorithm For the Spatial Grey Scale” R. Floyd et al. SID 75 Digest, pp. 36-67.
Fitzpatrick ,Cella, Harper & Scinto
Rogers Scott
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