JPH04316273A - Picture processor - Google Patents

Abstract

PURPOSE:To suppress the extent of noise of a black component due to ground color eliminating processing propagated to another color. CONSTITUTION:Document reflected light is separated into three colors R, G, and B to generate a picture signal by a sensor 1 consisting of a photoelectric conversion element like a CCD and a color filter, and this signal is quantized to an 8-bit signal by an A/D conversion part 2. The shading due to a light source or the like is corrected by a shading correction part 3 in the next stage, and the quantized digital signal is converted to C, M, and Y signals for recording by a next logarithmic transformation part 4. C, M, and Y signals are inputted to a black extracting part 5 to obtain a common component and are smoothed by a noise eliminating part 6 and are inputted to a masking UCR part 7. The masking UCR part 7 performs color correction and foundation removal by the black signal which has the noise eliminated and C, M, and Y signals from the logarithmic transformation part 4. C, M, Y, and K signals obtained as the result are subjected to prescribed processings with respect to each color by a gamma correction part 8 and a half-tone processing part 9 and are sent to a recorder 10, and an image faithful to data of C, M, Y, and K is reproduced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to color copying machines, etc.
The present invention relates to an image processing apparatus that generates C, M, Y, and K four color signals for recording from three B color signals and reproduces an image, and particularly relates to an image processing apparatus that generates a black signal and performs background removal (UCR). It is something.

0002

[Prior Art] Conventionally, cyan (C), magenta (M),
The so-called UCR (background removal) process, which generates a black signal from the yellow (Y) three color signals and subtracts the amount equivalent to the black signal from the C, M, and Y signals, is calculated according to the following formula. Ru. K=f(min(C'M'Y')) C=C'-
gc (K) M=M'-gm (K)

...(1) Y=Y'-gy (K) Here, min(C'M'Y') is the minimum value in the C'M'Y' signal, and the black signal K is determined according to this value. The functions gc and gm are generated and further correspond to the value of K.
, gy, the background is removed from the C'M'Y' signal.

0003

However, in the above-mentioned conventional background removal calculation, the K signal is C'M'
The noise component contained in the Y' signal is transformed by the function f, and this noise component is further propagated to the C'M'Y' signal. For example, the noise component in the C' signal after UCR processing is in addition to the component originally included in the C' signal.
Since the generation of gc (K) is added, there is a problem that image quality inevitably deteriorates when recording only one color after color separation into four colors.

[0004] The present invention has been made in view of the above points, and an object thereof is to provide an image processing apparatus that suppresses deterioration in image quality due to noise propagation during UCR processing.

[0005]

[Means for Solving the Problems] The present invention has the following configuration as a means for solving the above-mentioned problems. That is, a means for extracting a black component from the three-color image signal of cyan, magenta, and yellow of an input image, and a means for smoothing the black component of the pixel of interest and pixels adjacent to the pixel of interest based on the extracted black component. and means for generating four color signals of cyan, magenta, yellow, and black by removing the undercolor based on the smoothed black component.

[0006]

[Operation] The above configuration functions to suppress the amount of noise in the black component caused by the undercolor removal process that propagates to other colors.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention. In the figure, a sensor 1 is composed of, for example, a photoelectric conversion element such as a CCD and a color filter, and converts the reflected light of the original into R, R,
An image signal is generated by color separation into three colors, G and B. and,
The signal is quantized by the A/D converter 2 into an 8-bit signal. The quantized digital signal is corrected for unevenness caused by the light source, sensor, and optical system in the next-stage shading correction section 3, and then converted into density data in the logarithmic conversion section 4, i.e.,
It is converted into C, M, and Y signals for recording.

The C, M, and Y signals are input to a black extraction section 5 to find a common component, smoothed two-dimensionally by a noise removal section 6 to be described later, and input to a masking UCR section 7. In the masking UCR unit 7, color correction and background removal are performed using the noise-removed black signal and the C, M, and Y signals from the logarithmic conversion unit 4, and four colors of C, M, Y, and K are used for recording. I get a signal. These four color signals are further subjected to predetermined processing for each color in a γ correction section 8 and a halftone processing section 9 according to the recording device 10 to reproduce an image faithful to the C, M, Y, and K data. possible. <Description of Noise Removal UCR> Next, the noise removal UCR in this embodiment will be described in detail.

In FIG. 2, the minimum value detection section 51 is composed of a plurality of comparators (not shown), and
A min(C'M'Y') signal is output based on the 'M'Y' signal. This min(C'M'Y') signal is delayed and held one line at a time using memories 60-1 and 60-2, and both are smoothed by a noise removal section 61 to obtain a black component K'1.

On the other hand, the signal smoothed by the noise removal unit 61 is converted into data in a non-linear system using a non-linear conversion unit 62 composed of, for example, ROM or RAM, and the black component K'
It is output as 2. This conversion can be done by e.g.
K'2 = (K'1)n

(2) However, when n=1 to 2, a signal with so-called "black" emphasized is obtained. Therefore, here, the black component K used for masking UCR is
'1, K'2, high frequency noise is suppressed by using two-dimensional smoothing means in the noise removal section 61.

The black components K'1 and K'2 are stored in the memory 60-3 with respect to the input C'M'Y' signal.
It is input to the masking UCR section together with the C'M'Y' signal delayed and held by one line. The masking UCR used in this example follows the following formula (3). That is,

0012
]

[Math 3]

For example, if we rewrite only the M signal component using the above equation (3), we get M=A1 C'+A2 M'+A3 Y'+A4
K'1 +A5 K'2 (4), and the coefficients A4 and A5 of the black components K'1 and K'2 generally have negative values. Note that if the noise line segments included in the black components K'1 and K'2 are ΔK'1 and ΔK'2, the above equation (4
), the M signal is A4 ΔK'1 + A5 ΔK'2
However, according to this embodiment, ΔK'1 and ΔK'2 themselves are noise suppressed. <Description of Noise Removal> Next, noise removal in this embodiment will be described.

FIG. 3 is a detailed block diagram of the noise removal section 61 shown in FIG. 2. In the same figure, flip-flops (F/F) 611-1, 611-2, 611-3, 61
1-4 delay and hold the min (C'M'Y') signal, which has been delayed and held one line at a time in the above-mentioned memory, for each pixel. Therefore, the position of the pixel of interest is set to F/F611-3.
If the output position is (a in FIG. 3), F/F611-1 input end image b, F/F611-2 output end image c, F/F61
The 1-4 input end image d and the F/F 611-5 output end image e are pixels diagonally adjacent to the pixel of interest a. Therefore, the signal obtained by multiplying the target pixel signal a by 4 using the multiplier 614,
The black component K'1 is obtained by calculating the above pixel signals other than a in an adder 613 according to the following equation (5).

K′1 = (4a+b+c+d+e)/8
...(5) As explained above, according to this embodiment, the noise suppression means is used to remove the noise component from the CMY color components to generate the black signal, and then the UCR for generating the black signal is performed. By performing this, it is possible to prevent the noise caused by the UCR processing from propagating to other colors, and it is possible to improve the quality of the output image.

It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. Therefore, modifications of the embodiment will be described below. <Modification 1> FIG. 4 is a block diagram showing a modification of the noise removal section 6 for removing noise. In this modification, the same components as those of the noise removal section shown in FIG. 3 according to the above embodiment are given the same numbers, and detailed explanation thereof will be omitted.

In this modification, the Laplacian calculation unit 612 first calculates the pixel b, c, d, and e adjacent to the pixel a
is used to find the edge amount lp in the image according to the following equation (6). That is, lp=4a-(b+c+d+e)
…(6
) However, when |lp|≧K, |lp|=k (
(k is a constant) Then, smoothing is performed according to the following equation depending on the magnitude of |pl|.

[0018]

[Math. 7]

That is, the adder 613 calculates (b+c+d+e) used in the above equation (6), and the mixer 615 calculates the equation (7) according to the Laplacian |lp|. According to this modification, whereas in the above-described embodiment, the noise removal unit uniformly smoothes regardless of the image, smoothing is performed when the pixel of interest corresponds to an edge part of an image in a character or line drawing. By weakening the degree of noise, noise can be removed without losing edge information in the image. <Modification 2> FIG. 5 is a block diagram showing a modification of the above-described noise suppression UCR. In this modification, the same components as in the block diagram for explaining the noise suppression UCR according to the above embodiment shown in FIG. 2 are given the same numbers, and detailed explanation thereof will be omitted.

In the modification shown in FIG. 5, K'1 and K'2 from which noise has been removed are used as the black components used for UCR, and the K' and K'2 signals which are not smoothed are used to generate the black signal. Equation (8) below is an arithmetic expression for masking UCR according to this modification.

[0021]

[Math. 8]

According to this modification, whereas all the black components generated in the above embodiment are smoothed for noise suppression, the black components before noise removal, that is, mi
By outputting the n(C'M'Y') signal as K' and using the other components K'1 and K'2 together for masking UCR, the generated black signal K is able to eliminate the blurring of the image that occurs. This makes it possible to prevent noise from occurring in the K component due to UCR and to suppress propagation of noise.

Further, the noise suppression means is not limited to the smoothing means shown in the above embodiments, but may be used, for example, by means such as Hadamard transform cosine transform which decomposes image data into frequency components. The concentration data may be restored after suppressing the components. Furthermore, when performing nonlinear UCR, noise suppression means may be provided for each component after each nonlinear transformation.

The present invention may be applied to a system made up of a plurality of devices, or to an apparatus made up of one device. It goes without saying that the present invention can also be applied to cases where the present invention is achieved by supplying a program to a system or device.

[0025]

[Effects of the Invention] As explained above, according to the present invention,
By performing smoothing using the black component generated from the CMY color components to remove noise components and then performing UCR to generate a black signal, it is possible to prevent the noise caused by UCR processing from propagating to other colors, resulting in high image quality. This has the effect of making it possible to improve the

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an image processing device according to an embodiment of the present invention;

FIG. 2 is a block diagram showing the noise removal UCR in the embodiment,

FIG. 3 is a detailed block diagram of the noise removal unit 61 according to the embodiment;

FIG. 4 is a block diagram showing a modification of the noise removal section 6 for noise removal;

FIG. 5 is a block diagram showing a modified example of noise suppression UCR.

[Explanation of symbols]

1 Sensor 2 A/D conversion section 3 Shading correction section 4 Logarithmic conversion section 5 Black extraction part 6 Noise removal section 7 Masking UCR section 8 γ correction section 9 Halftone processing section 10 Recording device

Claims (1)

[Claims] 1. A means for extracting a black component from a three-color image signal of cyan, magenta, and yellow of an input image, and a means for extracting a black component of a pixel of interest and a pixel adjacent to the pixel of interest based on the extracted black component. An image processing device comprising a smoothing means and a means for generating four color signals of cyan, magenta, yellow, and black by removing the undercolor based on the smoothed black component. .