Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1997-07-22
2002-09-10
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S530000, C382S162000
Reexamination Certificate
active
06449060
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and method and, more particularly, to an image processing apparatus and method for performing color processing of an input image signal.
An example of a conventional color image processing apparatus will be described below with reference to
FIG. 12
taking color image processing in a color copying machine as an example. In
FIG. 12
, reference numeral
101
denotes a color image input unit such as an image reader unit of a color copying machine. The color image input unit outputs three color-separated signals R
1
, G
1
, and B
1
which are obtained by color-separating each pixel of a color image into R, G, and B components. The three color-separated signals R
1
, G
1
, and B
1
are input to an achromatic color/chromatic color determination unit
1201
, which determines if the pixel of interest is a monochrome pixel (achromatic color) or a color pixel (chromatic color), and outputs a determination signal KC.
The signal G
1
of the three color-separated signals is input to a character/halftone image determination unit
111
, which determines if the pixel of interest corresponds to a line image such as a character or a thin line or a continuous-gradation image (halftone image) such as a picture image or a printed image, and outputs a character/halftone image determination signal TI. The character/halftone image determination signal TI is input to a spatial filter coefficient storage unit
112
, which selects character spatial filter coefficients
1301
shown in
FIG. 13
when the pixel of interest corresponds to a character signal, or selects halftone image spatial filter coefficients
1302
shown in
FIG. 13
when the pixel of interest corresponds to a halftone image signal.
Conventional spatial filter processing such as edge emphasis and the like will be explained below.
FIG. 13
shows an example of the 5×5 pixel character spatial filter coefficients
1301
, and the halftone image spatial filter coefficients
1302
. The character spatial filter coefficients
1301
are determined to effect stronger edge emphasis than the coefficients
1302
for a halftone image.
The character or halftone image spatial filter coefficients Kij selected in accordance with the character/halftone image determination signal TI are set in edge emphasis units
103
-R,
103
-G, and
103
-B to respectively edge-emphasize the three color-separated signals R
1
, G
1
, and B
1
, thus outputting signals R
2
, G
2
, and B
2
.
FIG. 14
shows an example of the edge emphasis unit
103
-R. A dotted frame
1401
represents a data delay circuit in the edge emphasis unit
103
-R. The signal R input to the edge emphasis unit
103
-R is input to line memories
801
,
802
,
803
, and
804
that store image data for four lines. Image data for a total of five lines, i.e., the stored image data for four lines and image data of the line of interest, are input to flip-flops in units of lines to extract five successive pixel data (Xj1 to Xj5).
The signals R for 5 lines×5 pixels, i.e., a total of 25 signals R (Xij: 1≦i≦5) are multiplied by spatial filter coefficients (aij: 1≦i≦5, 1≦j≦5) indicated by a dotted frame
1403
and corresponding to pixel positions by an edge emphasis arithmetic circuit indicated by a dotted frame
1402
, and the products are added to each other. These spatial filter coefficients are supplied from the spatial filter storage unit.
Such calculations require 25 multipliers (
1404
to
1428
) for 25 pixels, and 24 adders (
1429
to
1452
) of the products.
The conventional spatial filter processing for the signal R has been described. The same applies to signals G and B. Consequently, the processing circuit for all the signals R, G, and B requires a circuit scale: line memories for 12 lines (4 lines×3 colors), 75 multipliers (25×3 colors), and 72 adders (24×3 colors).
The three edge-emphasized color-separated signals R
2
, G
2
, and B
2
shown in
FIG. 12
are input to a luminance/density conversion unit
106
, and are converted into density signals C
1
, M
1
, and Y
1
by, e.g., log conversion. The density signals C
1
, M
1
, and Y
1
are input to a color correction unit
107
to be subjected to color processing such as generation of a black signal K, undercolor removal (UCR), color correction, and the like, thus outputting density signals C
2
, M
2
, Y
2
, and K
2
.
The color correction unit
107
sets the density signals C
2
, M
2
, and Y
2
at C
2
=M
2
=Y
2
=0 in accordance with the determination signal KC as the determination result of the achromatic color/chromatic color determination unit
1201
when the pixel of interest is an achromatic pixel, thereby converting the pixel of interest into a pixel defined by black color alone. Reference numeral
110
denotes a color image output unit which comprises an image recording apparatus such as an electrophotographic or ink-jet printer.
When the color image output unit is, e.g., a binary printer, the density signals C
2
, M
2
, Y
2
, and K
2
are converted into binary pixel signals C
3
, M
3
, Y
3
, and K
3
by a binarization unit
108
.
On the other hand, when the resolution of the image input from the color image input unit
101
is different from that of the image to be output from the color image output unit
110
, the binary pixel signals C
3
, M
3
, Y
3
, and K
3
are subjected to resolution conversion processing by a smoothing/resolution conversion unit
109
to be converted into signals C
4
, M
4
, Y
4
, and K
4
. Especially, when the resolution of the color image output unit
110
is higher than that of the color image input unit
101
, smoothing processing for smoothly interpolating edge portions of the image is performed, and the processing result is printed by the color image output unit
110
.
However, as described above, the conventional image edge emphasis requires identical arrangements in units of signals to process the signals R (
103
-R), G (
103
-G), and B (
103
-B). Especially, in order to perform two-dimensional plane spatial filtering processing of the above-mentioned 5×5 pixel size for an image signal from the image reader unit of the color copying machine using a CCD line image sensor as the image input unit, many line memories, multipliers, and adders are required, as described above, resulting in high cost.
In terms of image quality, since the above-mentioned color correction unit
107
sets the density signals C
2
, M
2
, and Y
2
to be C
2
=M
2
=Y
2
=0 in accordance with the determination result of the achromatic color/chromatic color determination unit
1201
when the pixel of interest is an achromatic pixel, so as to convert the pixel of interest into a pixel defined by black color alone, the densities obtained by the signals C
2
, M
2
, and Y
2
are lost, resulting in a low density.
In general, in a color image processing apparatus, especially, in a color copying machine, when an image corresponding to a monochrome original is to be formed and output, the image is copied using four colors, i.e., C (cyan), M (magenta), Y (yellow), and K (black). However, in the case of a laser beam printer, in consideration of the service life of a drum and consumption of toner, the image corresponding to the monochrome original is preferably copied using black color alone. The same applies to a copying machine that incorporates an ink-jet printer.
For this reason, the copying machine is required to have a processing unit for determining if the input original is a color or monochrome original. Conventionally, such processing is realized by simple evaluation, i.e., by summing up the color pixels of an input original and performing simple statistical processing of the sum or comparing the sum with a threshold value or a slice level.
However, when color pixel determination is done based on color components (in this case, R, G, and B luminance values) in units of pixels in an original input device, if the reading elements for the individual color components c
Aoyagi Takeshi
Kawai Takashi
Matsuya Akihiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Rogers Scott
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