JPH0681251B2 - Image processing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing device in a facsimile, a digital copier or the like.

2. Description of the Related Art Conventionally, there are various states of original images to be read (characters, photographs, etc.), and it is impossible to obtain a good image by the same processing for all these original images. Therefore, the operator determines the state of the original image, and obtains the state of the original image to adjust the image processing.

Problems to be Solved by the Invention However, the above-described configuration has a problem in that the operator makes a wrong decision and the adjustment operation is troublesome, and good image processing cannot be executed due to an incorrect adjustment.

The present invention has been made in view of the above points, and provides image processing for performing image conversion suitable for the state of a document image to be read.

Means for Solving the Problems In order to solve the above problems, the image processing apparatus of the present invention is
The peak value of each line in the sub-scanning direction (direction in which the image sensor moves) of the original to be read is detected, a histogram is formed based on this, the average and variance are obtained, and the state of the original image is judged from the variance value. The image conversion is performed according to the type of original image.

Operation The present invention has the above-mentioned configuration to provide means for detecting the state of the document image to be read, and to automatically perform the optimum image processing operation on the document image according to the detection result. This makes it possible to eliminate erroneous judgments and eliminate troublesome adjustment operations.

Embodiment An image processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a block diagram for implementing the present invention.

The image sensor 1, which is an image sensor, reads each line of a document image, and the image signal a read by the sensor 1 is
It is converted into a digital signal by the A / D converter 2. The image signal b converted into the digital signal is corrected to the image signal c through the shading correction circuit 3. The shading correction circuit 3 is a circuit for correcting unevenness in illuminance of a document illumination light source and sensitivity variation of the sensor 1. The image signal output from the shading correction circuit 3 is input to the gamma correction circuit 4 and the peak detection circuit 8, respectively. The gamma correction circuit 4 is a circuit that converts a luminance signal into a density signal, and the image signal d converted here is input to the binarization processing circuit 5 as a density signal. The peak detection circuit 8 is a circuit that detects the maximum value of the image signal c sequentially sent from the shading correction circuit 3. The maximum value obtained here is input to the control unit 9 as a signal i. Binarization processing circuit 5, control unit 9
Will be described later. The signals e, f and g processed by the binarization processing circuit 5 are input to the selector 6 as the signal i processed by the control unit 9. The signal e input to the selector 6,
For f and g, one of the three processed signals is selected according to the signal i, and is output to the printer 7 as the signal h.

FIG. 2 shows a specific example of the binarization processing circuit 5. The binarization processing circuit 5 includes a dither processing 201 and an error diffusion processing circuit 202 and 2
It is composed of a value processing 203. The dither processing 201 is an image processing circuit most suitable for an image in which the input image signal d has gradation characteristics such as a photographic original. The binarization processing 203 is an image processing circuit most suitable for an image in which an input image signal does not have gradation such as a character original. The error diffusion processing circuit 202 is an image processing circuit which is most suitable for an original document in which the input signal d is a mixture of characters and photographs. The signals e, f, and g are output through the three processing circuits.

FIG. 3 shows a specific example of the control unit 9. Control unit 9 is CPU3
01, I / O 302, I / O 304, and RAM 303. I / O302
Takes in the signal j sent from the peak detector circuit 8,
The CPU 301 forms a histogram in the RAM 303 based on the signal j.

FIG. 4 shows a histogram of a character original. The original image is processed as shown in the block diagram of FIG.
The histogram formed in the RAM 303 is a feature of the background portion of the text original image. Average of original image from this histogram
Wp and variance S can be obtained.

FIG. 5 shows a histogram of a mixed original of characters and photographs. Similar to FIG. 4, this histogram is a feature of the background portion of a mixed original image of characters and photographs.

FIG. 6 shows a histogram of a photographic original. Similar to FIG. 4, this histogram is a feature of the background portion of the photographic document image.

By detecting the maximum value of the signal sent from the shading correction circuit 3 as described above, the luminance level distribution of the background portion of the original image can be obtained. As shown in FIG. 1, when the document image is read by the sensor 1, a signal is sent to the control unit 9 through the A / D conversion 2, shading correction 3 and peak detection circuit 8 lines in the pre-scan at the time of pre-scan. The control unit 9 can form a histogram and obtain the variance S from the average Wp. The value of the variance S is small in the histogram shown in FIG. 4, and the variance is large in the histogram shown in FIG. 5, and the type of the document image can be discriminated by the value of the variance S.

Therefore, the value of this variance S is used as a parameter in equation (1),
The control unit 9 is equipped with the algorithms shown in (2) and (3).

If S <α, the manuscript image is a character manuscript (1) If α ≦ S ≦ β, the manuscript image is a mixed manuscript of characters and photographs (2) If S> β, the manuscript image is a photo manuscript (3) α <β, and α and β are empirical values.

The control unit 9 discriminates the type of the original image and outputs the processing circuit selection signal i to the selector 6, whereby the optimum image processing according to the original image can be performed.

Furthermore, in the present embodiment, the black-and-white image processing apparatus has been described, but the present invention can be similarly applied to, for example, a color image processing apparatus. At that time, a luminance signal is generated from the output signals R, G, B of the sensor 1 by using the following equation.

[Max (R, G, B) + Min (R, G, B)] / 2 (4) Effects of the Invention As described above, according to the present invention, the maximum value of the image brightness level of the original image is line by line. A histogram can be formed based on the detected maximum value and the average and the variance can be obtained. The type of the original image can be discriminated by the value of this dispersion, and the dither processing capable of gradation processing is executed for the photo original, the binary processing is executed for the text original, and the photograph and character mixed original is executed. In that case, the error diffusion process can be automatically executed, so that the troublesome adjustment operation of the operator can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram of an image processing apparatus in an embodiment of the present invention, FIG. 2 is an internal configuration diagram of the binarization processing circuit of FIG. 1,
FIG. 3 is an internal block diagram of the control unit in FIG. 1, FIG. 4 is a histogram in the case of a character original formed on the RAM 303 in FIG. 3, and FIG. 5 is formed on the RAM 303 in FIG. Histogram for mixed text and photo manuscript, Fig. 6 shows RAM3 in Fig. 3
It is a histogram in the case of the photographic manuscript configured on 03. 1 ... Sensor, 2 ... A / D converter, 3 ... Shading correction circuit, 4 ... Gamma correction circuit, 5 ... Binarization processing circuit, 6 ... Selector, 7 ... Printer, 8 ... Peak detector circuit, 9 ... Control unit, 201 ... Dither processing circuit, 2
02 ... Error diffusion processing circuit, 203 ... Binary processing circuit, 301 ...
… CPU, 302 …… I / O, 303 …… RAM, 304 …… I / O.

Claims (1)

[Claims] 1. A peak detecting means for detecting a peak value of an image signal of an original image read by an image pickup device, a histogram converting means for forming a histogram based on the image signal detected by the peak detecting means, and a histogram converting means. An image including an original background distribution unit for obtaining an average and a variance by means, and an image conversion unit for discriminating the type of the original by the original background distribution unit and executing image processing corresponding to the type of the original image. Processing equipment.