JPH06181521A - Image forming device - Google Patents

Abstract

PURPOSE:To finely constitute both the gradations of a photograph and to smooth characters by setting up one threshold level for picture density in the picture elements of an area recognized as a binary image. CONSTITUTION:Picture information read out by a scanner part 1 is inputted to a picture processing part 2 as analog data. The processings of A/D conversion, peak detection, pattern/character separation, the error dispersion of a binary photographic picture, gamma correction, and so on, are then performed. Processed binary data and multilevel data are inputted to a recording control part 3 and a communication control part 4, the data of the control part 3 are printed out by a plotter part 5 and the data of the control part 4 are transferred to a line. A pattern/picture separating part in the processing part 2 converts picture elements in an area detected as a picture into a many-valued signal by a gamma curve. Since black and white judgement is executed in high and low peak light quantity parts, the gradation property can be held, the generation of void on a black solid part in a binary part or the staining of a white ground can be prevented and the boundary of a line is smoothed by preventing it from being rugged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
More specifically, it can be applied to image forming apparatuses such as fax machines, scanners, and digital copiers. In particular, it is possible to obtain good gradation of a photographic image and smoothness of character portions, and a good image with less noise. And an image forming apparatus capable of obtaining the above.

[0002]

2. Description of the Related Art Conventionally, there is an image forming apparatus reported in, for example, Japanese Patent Application Laid-Open No. 2-210966, in which an image signal including a specifying signal for specifying different image forming conditions depending on the characteristics of an image is used. An image forming apparatus which receives and forms an image in accordance with the image forming condition, and a discriminating means for discriminating between a halftone image area and a character and thin line image area, and the character and thin line image area. The image signal of the highlight portion is shifted to the dark side to reproduce the edge-enhanced gradation, and the first image forming means for linear gradation reproduction to the halftone image area. The second image forming means is provided, and linear gradation reproduction is performed with respect to a halftone image area, so that a stable image is output without degrading the image quality of a document in which a character image and a photographic image are mixed. I am trying to do it.

A conventional image area separation method for binary images has been reported in, for example, Japanese Patent Laid-Open No. 3-57083, in which a simple binary area and a pseudo halftone area are used. In a mixed image, the matrix of mxn pixels is used as a reference pixel to separate the regions on a pixel-by-pixel basis.

[0004]

By the way, in recent years, multi-valued facsimile images and widespread use of digital copying machines have been rapidly advancing along with the progress of image processing technology and the increase in memory capacity. In order to obtain a good image quality of a gradation image such as, for example, multi-value processing with fine resolution is performed.

However, when the above-described multi-value processing is performed on a character image, the lines are smoothed but the background is not uniform, or noise, vibration of the document or the like causes background stains on a white background portion or black solid portions. There was a blank spot.
Therefore, there is a problem that it is difficult to obtain beautiful gradation of a photographic image and smoothness of a character portion, and it is difficult to obtain a good image with less noise. Note that the conventional multi-value processing method will be specifically described in comparison with the embodiment in the embodiments described later.

Therefore, an object of the present invention is to provide an image forming apparatus capable of sufficiently obtaining the gradation of a photographic image and the smoothness of a character portion and obtaining a good image with less noise. There is.

[0007]

The invention according to claim 1 is
Means for reading image information in a dot matrix form and recording it in a dot matrix form, means for discriminating whether the read image is a binary image or a halftone image (pictogram separating means), multi-value reading and In an image forming apparatus having a unit for performing multi-valued recording, a) For a pixel in a region recognized as a binary image, an image processing unit of a reading unit sets one image density threshold level, and A value which is set to any value of black and white based on the level, and when the value is recognized as a multi-valued image, the value is set without setting a threshold level, and the value is transferred to a recording system, a communication line or a storage device; ) All pages are set to binary or multi-valued manually or by a condition judgment mechanism, and when the binary is set, the threshold level in the item a) is applied to all pages. Means, c) means for transferring the input data as binary data to a recording system, a communication system or a storage device when the binary value is set in the item b), and d) the a). Set the threshold level of the item to a level at which the background white background does not cause dirt due to noise or other disturbances.When the light intensity is higher than that level, the data is uniformly set to white, and when the light intensity is below the threshold level. Is provided with means for making multi-valued data.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, means for setting the threshold level of the above item d) in the range of 50% or more and 87.5% or less of the peak light amount is provided. It is a thing. The invention according to claim 3 is the same as the invention according to claim 1 or 2,
Two threshold levels are set, and one threshold level is defined as the above d) and claim 2, and the other threshold level is a level at which a solid black portion does not cause white spots due to disturbance such as noise. And a means for uniformly setting the data to black when the amount of light is smaller than that level is provided.

The invention according to claim 4 is characterized in that, in the invention according to claim 3, means for setting the threshold level of the other one in the range of 12.5% to 25% of the peak light amount is provided. It is a thing.

[0010]

According to the present invention, a) In the pixel of the area recognized as a binary image, the image processing section of the reading section sets one threshold level of image density, and based on the level, any one of black and white is selected. When it is recognized that the image is a multi-valued image, the value is set without setting a threshold level, and the value is transferred to a recording system, a communication line or a storage device, and b) manually or by a condition judging mechanism. All pages are set to binary or multi-valued, and when the binary is set, the threshold level in the item a) is applied to all pages,
c) When the binary value is set in the item b), the image processing unit transfers the input data as binary data to a recording system, a communication system or a storage device, and d) the threshold level in the item a) is transferred. Set the background white background to a level that will not cause background stains due to noise or other disturbances, and if the amount of light is higher than that level, set the data uniformly to white,
When the light quantity is below the threshold level, multi-valued data is used. Therefore, the black and white judgment can be made more effectively than the case of making the black and white judgment by the conventional binary threshold, so that the background stain due to the disturbance such as noise on the white background is prevented. You can

In the present invention, it is preferable to set the threshold level of the above item d) to 50% or more and 87.5% or less of the peak light amount. In this case, it is possible to more effectively determine black and white. It is possible to effectively prevent the background stain from being caused by a disturbance such as noise on a white background. In the present invention, two threshold levels of the item a) are set, and one threshold level is set as the item d) and the claim 2, and the other threshold level is set such that the black solid part indicates noise or the like. It is preferable to set to a level that does not cause white spots due to disturbance, and to set the data uniformly to black when the amount of light is less than that level.
In this case, in addition to the effect of the first aspect, it is possible to prevent white spots from occurring in the solid black portion due to a disturbance such as noise, as compared with the related art.

In the present invention, it is preferable that the threshold level of the other one is 12.5% or more and 25% or less of the peak light amount. In this case, it is possible to more effectively make a black and white judgment, which is more effective. Therefore, it is possible to prevent white spots from occurring in a solid black portion due to disturbance such as noise.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the arrangement of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a scanner unit, and image information read by the scanner unit 1 is input to the image processing unit 2 as analog data. The image processing unit 2 performs A / D conversion processing, peak detection processing, pictogram separation processing, error diffusion processing in the case of a binary photographic image, and γ correction processing. Next, the binary data and multi-valued data processed by the image processing unit 2 are input to the recording control unit 3 and the communication control unit 4, the data of the recording control unit 3 is printed by the plotter unit 5, and the data of the communication control unit 4 is printed. The data is transferred to the line. Reference numerals 6 and 7 are a CPU unit and an operation unit, respectively.

Next, the multi-value processing of this embodiment will be described in comparison with the conventional multi-value processing. First, conventional multi-value processing will be described. Conventionally, in the case of multi-valued processing, FIG.
Quantize analog data based on the γ curve of
In the case of a binary value, black and white is judged based on the threshold level of image density shown in FIG. 2 and transferred to the next recording control unit 3 or communication control unit 4. However, in the conventional multi-valued processing, as described above, the determination of black and white is likely to be ambiguous particularly in a portion where the peak light amount is high and in a portion where the peak light amount is low, and a white background has a background stain or a black solid portion has a white spot. It was not possible to obtain a smooth image due to the jagged edges of the lines.

On the other hand, in this embodiment, the image processing unit 2
In the pictographic character separation unit, the pixels in the area detected as a picture (gradation image) are multivalued based on the γ curve in FIG.
Next, the pixels in the area detected as a character are based on the γ curve clamped based on the threshold 1 in the low light amount portion or the threshold 2 in the high light amount portion in FIG. 4, or based on the threshold 1 and the threshold 2 Multi-valued based on the clamped γ curve. As a result, in the present embodiment, it is possible to more effectively determine black and white in a portion having a high peak light amount and in a portion having a low peak light amount, so that it is possible to maintain gradation in a picture portion and a binary value. In this case, it is possible to prevent white spots in a solid black portion and a background stain on a white background from occurring, and it is possible to obtain a smooth image by eliminating the jaggedness at the line boundary.

The level of Threshold 1 is set between 50% and 87.5% of the peak light amount from the experimental value, and the light amount above that is set to white (here, 256 in 256 gradations),
The level of Threshold 2 was set between 12.5% and 25% of the peak light intensity, and below that, black (φ in 256 gradations) was set. Within this level range, the noise can be made stronger and the smoothness of characters can be further improved.

By the way, in the binary transmission mode such as the G3 mode transmission of the facsimile, the image processing unit 2 does not apply the multi-valued mode, selects the binary mode, and the data is passed through the communication control unit 4. Go out to the line. Then, switching of these and the like is performed by the judgment / command of the CPU section 6.

[0018]

According to the present invention, the gradation of a photographic image and the smoothness of a character portion can be sufficiently obtained, and an excellent image with less noise can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention.

[FIG. 2] Multivalued data according to Comparative Example 1 and γ in light intensity
It is a figure which shows a curve and a binary threshold.

FIG. 3 is a diagram showing a multi-valued data and a γ curve in a light amount according to an embodiment of the present invention.

FIG. 4 is a diagram showing threshold 1 and threshold 2 in multivalued data and light amount according to an embodiment of the present invention.

[Explanation of symbols]

 1 Scanner Section 2 Image Processing Section 3 Recording Control Section 4 Communication Control Section 5 Plotter Section 6 CPU Section 7 Operation Section

Claims (4)

[Claims] 1. Reading image information in a dot matrix form,
An image forming apparatus comprising: a unit for recording in a dot matrix form; a unit for determining whether a read image is a binary image or a halftone image; and a unit for performing multi-value reading and multi-value recording, a) In the pixels in the area recognized as a binary image,
In the image processing unit of the reading unit, one threshold level of image density is set, and either one of black and white is set based on the level, and when the image is recognized as a multi-valued image, the threshold level is not set. A means for setting a value and transferring it to a recording system, a communication line or a storage device; and b) manually or by a condition judging mechanism to set all pages to binary or multi-valued, and when the binary is set, (a) means for applying the threshold level to all pages, and (c) when a binary value is set in (b), the image processing unit records the input data as binary data in a recording system, a communication system, or a storage system. A) means for transferring to the device, and d) setting the threshold level in the above item a) to a level at which the background white background does not cause soiling due to disturbance, and when the amount of light is higher than that level. The image forming apparatus is set to white, when the light quantity is below the threshold level is characterized by providing a means for the multi-valued data of data as. 2. The image forming apparatus according to claim 1, further comprising means for setting the threshold level in the item d) in a range of 50% or more and 87.5% or less of the peak light amount. 3. The two threshold levels of the a) are set, one of the threshold levels is set as the d) and the other of the threshold levels, and the other one of the threshold levels is blank due to a disturbance in a black solid portion. 3. The image forming apparatus according to claim 1, further comprising means for setting a level that does not cause the occurrence of blackout and setting the data uniformly to be black when the light amount is lower than the level. 4. The image forming apparatus according to claim 3, further comprising means for setting the other threshold level within a range of 12.5% to 25% of a peak light amount.