JP2918367B2 - Semiconductor integrated circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit device for image processing control capable of outputting a halftone binary signal by pseudo-halftoning an image signal obtained by imaging a subject.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of an image reading control LSI used for a conventional facsimile disclosed on pages 4-92 and 4-93 of "'91 Mitsubishi Semiconductor Digital ASSP Data Book". It is a block diagram.

As shown in FIG. 1, first, an image signal S0 obtained by imaging a document as a subject is converted into a γ correction circuit
It is taken in. The γ correction circuit 1 performs γ correction based on the γ value of the image signal S0 and outputs a corrected image signal S1 to the non-uniformity correction circuit 2. The γ value is a value determined from the γ characteristic of an image sensor in a facsimile, the sensitivity of the human eye, the recording density of a printer, and the like.Generally, logarithmic correction is used, and a white image in a black image is determined based on the γ value. Be emphasized.

[0006] The non-uniformity correction circuit 2 generates a correction image signal S
1 from the corrected image signal S1, the light source drops at both ends of the illumination light source, the peripheral image dimming of a lens used for condensing the light obtained from the illumination light source on the image sensor, and the correction image signal due to the characteristic variation of the image sensor. S1
To correct the non-uniformity of the signal level of the
2 is output to the resolution compensation circuit 3.

[0005] The resolution compensating circuit 3 outputs the corrected image signal S
2 and fetches the corrected image signal S3 from the corrected image signal S2 by compensating for the MTF (Modulation Transfer Function) characteristics of the photoelectric conversion signal based on the resolution of the lens and the sensitivity distribution of the image sensor.
To the image area separation circuit 4, the systematic dither circuit 5, the error diffusion circuit 6, and the simple binarization circuit 7.

[0006] The image area separating circuit 4 outputs a corrected image signal S3.
From the image information obtained from the corrected image signal S3, the character portion and the grayscale image portion are determined so that the image is optimally binarized in the entire reading area of the document, and the simple black and white binarization is performed for the character portion. An output port 8 outputs a separation control signal S4 for separating and controlling a black and white binarized image region to be converted into a grayscale image region to be binarized for a grayscale image portion. Further, when the separation control signal S4 is determined to be a grayscale image area, the first grayscale binarized signal S5 output from the systematic dither circuit 5 and the error diffusion circuit 7 are output based on the external signal SS. One of the two grayscale binarized signals S6 is designated.

The systematic dither circuit 5 takes in the corrected image signal S3, regards the screen as a set of n × n pixel matrices, generates different thresholds for each coordinate based on only the coordinate information in the matrix, and generates these thresholds. A first grayscale binarized signal S5 obtained by comparing each pixel signal with each pixel signal obtained from the corrected image signal S3 is output to an output port 8
Output to

The error diffusion circuit 6 outputs the corrected image signal S3
And sequentially paying attention to the pixel signals obtained from the corrected image signal S3, adding an error obtained by weighting and averaging the error between the read density and the display density of the reference pixel with the distance to the pixel of interest and comparing the error with the fixed threshold The obtained second grayscale binarized signal S6 is output to the output port 8.

The simple binarizing circuit 7 sequentially detects the background level and the character level, generates a fixed threshold value suitable for the document (image), and converts this threshold value and the pixel signal obtained from the corrected image signal S3. The simple binary signal S7 obtained by the comparison is output to the output port 8.

The output port 8 outputs one of the first gray-scale binary signal S5, the second gray-scale binary signal S6 and the simple binary signal S7 based on the separation control signal S4. The signal is output as a value signal S8.

[0011]

The conventional image processing control LSI is constructed as described above, and includes an image area separation circuit 4, an organized dither circuit 5, an error diffusion circuit 6, and a simple binarization circuit 7. And the same corrected image signal S3 subjected to γ correction and resolution compensation under the same conditions, respectively.
Therefore, it is not possible to apply the optimum correction image signal S3 for the operation of each of the circuits 4 to 7 to each of the circuits 4 to 7, so that each of the circuits 4 to 7 outputs the optimum control signal or the binarized signal. As a result, there is a problem that a binarized signal capable of pseudo halftoning cannot be output with good reproducibility.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor integrated circuit device for image processing control capable of outputting a binary signal which can be pseudo-halftoned with good reproducibility. Aim.

[0013]

SUMMARY OF THE INVENTION A semiconductor integrated circuit device according to the present invention has a first feature that emphasizes reproducibility of an image signal.
First resolution compensation means and the pixels the image signal in the weaker than the first resolution compensation strength second resolution compensation strength for outputting a first correction image signal and the resolution compensation pixel resolution compensation strength of Second resolution compensating means for performing a resolution compensation in units and outputting a second corrected image signal;
The image signal is resolution-compensated on a pixel- by- pixel basis with a third resolution compensation intensity higher than the first resolution compensation intensity.
A third resolution compensating means for outputting a corrected image signal, a halftone binarizing means for pseudo-halftoning the second corrected image signal to output a grayscale binarized signal, and the third corrected image signal Is compared with a fixed threshold value to output a simple binarized signal expressing black and white, and, based on the first corrected image signal, the grayscale binarized signal and the simple binarized signal An image area control unit that outputs an image area control signal indicating one of them, and, according to the instruction of the image area control signal, one of the grayscale binarized signal and the simple binarized signal is output binary. And output means for outputting the converted signal.

[0014]

According to the present invention, the first, second and third resolution compensating means provide first, second and third corrections to the image area control means, the shading binarizing means and the simple binarizing means, respectively. An image signal is provided.

Since the first corrected image signal is subjected to the resolution compensation with the first resolution compensation strength that emphasizes reproducibility, the image area control means can output an image area control signal giving an appropriate instruction. Since the second corrected image signal is subjected to resolution compensation in which the resolution compensation intensity is made weaker than the first resolution compensation intensity and is suitable for pseudo halftoning, it is necessary to output a grayscale binarized signal having good reproducibility. Can be. Further, since the third corrected image signal is subjected to resolution compensation under the third resolution compensation condition in which the resolution compensation strength is increased and is suitable for monochrome simple binarization, a simple binary signal with good reproducibility is output. can do.

[0016]

FIG. 1 is a block diagram showing the configuration of an image reading control LSI according to an embodiment of the present invention.

As shown in FIG. 1, first, an image signal S00 obtained by imaging a document as a subject is taken in.
The non-uniformity of the signal level of the image signal S00 is corrected, and the corrected image signal S11 is output to the first, second, and third resolution compensation circuits 12, 13, and 14 in common.

The first resolution compensation circuit 12 compensates the resolution of the corrected image signal S11 with the first resolution compensation intensity, and outputs the first corrected image signal S12 to the image area separation circuit 15. The first resolution compensation strength is a level that faithfully reproduces an image captured by the image sensor.

The second resolution compensation circuit 13 performs resolution compensation on the corrected image signal S11 with the second resolution compensation intensity, and outputs the second corrected image signal S13 to the γ correction circuit 16 and the systematic dither circuit 17. The second resolution compensation intensity is a relatively weak level at which the gray level binarization process is easily performed.

The third resolution compensation circuit 14 performs resolution compensation on the corrected image signal S11 with a third resolution compensation intensity, and outputs the third corrected image signal S14 to the simple binarization circuit 18. The third resolution compensation strength is a relatively strong level at which simple binarization processing is easily performed.

The pixel information X 'after the resolution compensation is expressed by the following (I)
Determined by the formula.

X ′ = X + α ((X−B) + (X−D)) β ((X−A) + (X−C)) (I) In the formula (I), X is a resolution compensation target. Pixel information, A,
C is pixel information above and below (sub-scanning direction) the pixel X;
D is pixel information on the left and right (main scanning direction) of the pixel X, α,
β is a main scanning compensation coefficient and a sub-scanning compensation coefficient, respectively.
The magnitude of the values of α and β indicates the magnitude of the resolution compensation strength.

A compensation coefficient α indicating the first resolution compensation strength
1, β1 is appropriately determined in consideration of the resolution of a lens for condensing light on the image sensor, the MTF characteristic of a photoelectric conversion signal based on the sensitivity distribution of the image sensor, and the like so that the image captured by the image sensor is faithfully reproduced. Value is determined.

The compensation coefficients α2 and β2 indicating the second resolution compensation strength are calculated by taking into account the halftone processing.
Compensation coefficients α3 and β3, which are smaller than 1, β1 and indicate the third resolution compensation strength, are larger than compensation coefficients α1 and β1 in consideration of simple binarization.

The gamma correction circuit 16 performs gamma correction on the second correction image signal S13 to obtain a fourth correction image signal S1.
6 is output to the error diffusion circuit 19.

The image area separating circuit 15 takes in the first corrected image signal S12 and, based on the image information obtained from the corrected image signal S12, converts the image data in the entire reading area of the original into a character portion so as to optimally binarize the image. The output port 20 outputs a separation control signal S15 for controlling the separation into a black and white binarized image area for simple black and white binarization for a character part and a gray and white image area for binarization for a shaded image part. Output to If the separation control signal S15 is determined to be a grayscale image area, the systematic dither circuit 17
And a second gray-scaled binary signal S19 output from the error diffusion circuit 19.
, One of the grayscale binarized signals is indicated.

The systematic dither circuit 17 takes in the second corrected image signal S13, regards the screen as a set of (dither) matrices of n × n pixels, and sets a different threshold value for each coordinate based only on the coordinate information in the matrix. Then, each of these threshold values is compared with each of the pixel signals obtained from the second corrected image signal S13, and the first grayscale binarized signal S17 is output to the output port 20.

The error diffusion circuit 6 takes in the fourth corrected image signal S16, sequentially focuses on the pixel signals obtained from the corrected image signal S16, and determines the error between the read density of the reference pixel and the display density by the distance from the target pixel. The weighted and averaged error is added to the target pixel and compared with a fixed threshold value, and a second grayscale binarized signal S19 is output to the output port 20.

The simple binarizing circuit 18 sequentially detects the background level and the character level, generates a fixed threshold value suitable for the document (image), and outputs the threshold value and the pixel signal obtained from the third corrected image signal S14. By comparing them with each other, a simple binary signal S18 is output to the output port 20.

The output port 20 outputs one of the first grayscale binarized signal S17, the second grayscale binarized signal S19, and the simple binarized signal S18 based on the separation control signal S15. The signal is output as a value signal S20.

The resolution of the first corrected image signal S12 taken into the image area separation circuit 15 is compensated by the first resolution compensation circuit 12 with the first resolution compensation intensity having good reproducibility. A good separation control signal S15 can be output.

The second input to the systematic dither circuit 17
Are both the second corrected image signal S12 and the fourth corrected image signal S16 taken into the error diffusion circuit 19.
Of the resolution compensation by the resolution compensation circuit 13
Since the resolution is compensated with the second resolution compensation intensity weaker than the resolution compensation intensity of the first and second halftones, the first and second grayscale binarized signals S17 and S19 subjected to the halftone binarization process with high accuracy are output. can do.

It is desirable to perform the γ correction by the γ correction circuit 16 when performing the shading binarization processing (pseudo halftoning processing), but the systematic dither circuit 17 sets the threshold value to be written in the dither matrix. Since the γ correction can be performed internally by appropriately setting, in this embodiment, the signal obtained by performing the γ correction only on the fourth correction image signal S16 captured by the error diffusion circuit 19 is used.

The third correction image signal S14 taken into the simple binarization circuit 18 is converted to a third resolution compensation circuit 14
Accordingly, since the resolution is compensated by the third resolution compensation intensity in which the resolution compensation intensity is higher than the first resolution compensation intensity, it is possible to output an accurate simple binary signal S18.

As described above, the image processing control LS of this embodiment is
I is the first, second and third resolution compensation circuits 12 and 13 for the image area separation processing, the gray level binarization processing and the simple binarization processing, respectively, from the captured corrected image signal S11.
And 14 are provided independently, so that each resolution compensating circuit 12
By changing the resolution compensation intensity between １４14 and １４14, the image area separation processing, the shading binarization processing, and the simple binarization processing can be optimally performed.

Also, since the gamma correction circuit 16 is provided only in the preceding stage of the error diffusion circuit 19 which originally requires gamma correction, the first correction image signal S12 captured by the image area separation circuit 15
In addition, the third correction image signal S14 captured by the simple binarization circuit 18 is a signal obtained by uniformly correcting the image of the entire area without performing γ correction, so that the image area separation processing and the simple binary Conversion processing can be performed.

As a result, the binarized signal capable of pseudo halftoning can be output with good reproducibility as the output binarized signal S20 from the output port 20.

[0038]

As described above, according to the present invention, the first and second signals, which are independent signals, are provided to the image area control means, the gray level binarization means, and the simple binarization means, respectively.
And first, second and third resolution compensating means for outputting the first, second and third corrected image signals. The first, second and third corrected image signals are respectively imaged by changing the respective resolution compensation intensities. Since the signals are suitable for the range control process, the gray level binarization process, and the simple binarization process, a binarized signal capable of pseudo halftoning can be output with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image reading control LSI according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional image reading control LSI.

[Explanation of symbols]

 Reference Signs List 11 Non-uniformity correction circuit 12 First resolution compensation circuit 13 Second resolution compensation circuit 14 Third resolution compensation circuit 15 Image area separation circuit 16 γ correction circuit 17 Systematic dither circuit 18 Simple binarization circuit 19 Error diffusion circuit 20 output port

Claims (1)

(57) [Claims] And 1. A first resolution compensation means for outputting a first correction image signal and the resolution compensation for each pixel in the first resolution compensation strength with an emphasis on the image signal reproduction, the said image signal first Resolution compensation is performed on a pixel- by- pixel basis with a second resolution compensation intensity weaker than the first resolution compensation intensity.
A second resolution compensating means for outputting a corrected image signal, and a third resolution compensating means for compensating the image signal with a third resolution compensating intensity higher than the first resolution compensating intensity in pixel units .
A third resolution compensating means for outputting a corrected image signal of the following; a halftone binarizing means for outputting a halftoned signal by pseudo-halftoning the second corrected image signal; and a third corrected image signal. Is compared with a fixed threshold value to output a simple binarization signal expressing black and white, and based on the first correction image signal, the gray level binarization signal and the simple binarization signal An image area control means for outputting an image area control signal indicating one of them, according to an instruction of the image area control signal, one of the gray level binarization signal and the simple binarization signal is output binary. A semiconductor integrated circuit device comprising: an output unit configured to output an integrated signal.