JP2002094776A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that applies background color to an original image, in such a way that a border between a blank and the original image cannot be recognized when copying the original image onto a recording sheet, independently of the state of the background color of the original image. SOLUTION: Upon the receipt of an image signal (step S1), a printer control section checks whether a background setting button on an operation panel 15 has been depressed, and when the button has been depressed ('YES' in step S2), the printer control section checks the image signal and a copy mode (paper designation and magnification or the like), to check whether there is a blank. If there is any blank ('YES' in step S3), the printer control section detects a background (step S4), and if the printer control section detects the background ('YES' in step S5), the printer control section detects the tendency of the background color (step S6). Then the printer control section sets the background color to the blank (step S7) in accordance with the tendency of the background color and drives a semiconductor laser driver, to form an image (step S8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for forming an image on a recording sheet, and more particularly, to an image forming apparatus for forming an image on a margin of a recording sheet.

[0002]

2. Description of the Related Art For example, when a document image is copied on a recording sheet using a copying machine as an image forming apparatus, if the recording sheet is larger than the document image or the document image and the recording sheet have different shapes. However, a blank portion where the original image is not copied occurs on the recording sheet, and the appearance is poor. For example,
When a postcard is read by a scanner as a manuscript image and copied on A4 paper, the postcard and A4 paper have different aspect ratios.
No matter how the magnification is adjusted, a margin will remain after copying. On the other hand, it is possible to eliminate the margin by using roll paper for the recording sheet, but it is difficult to separate the copied portion with roll paper, and it takes time to separate.

[0003] Techniques for improving the appearance of margins include:
Japanese Patent Laying-Open No. 10-191024 has been proposed. This publication discloses an image processing apparatus having background color setting means for setting the background color of an inlay image and a base image to the same background color. According to the image processing device,
The background color of the inlaid image can be detected and the background color of the inlaid image can be set in the background of the base image. Accordingly, if the inlaid image is regarded as a document image and the base image is regarded as a recording sheet, the background color of the document image can be set in a blank portion that would have occurred on the recording sheet by using the image processing apparatus.

[0004]

SUMMARY OF THE INVENTION However, the image processing apparatus disclosed in the above-mentioned publication discloses a method in which the difference between the frequency of the most frequent value and the frequency of another density is equal to or more than a predetermined value in the density histogram of the fitted image. , The density of the most frequent value is used as the background color, so that the background color may not be detected in some cases. As described in the above publication, when the background color of the document is not uniform, the background color cannot be detected, and in that case, the background color cannot be set as the background of the base image. .

[0005] Even if the background color can be detected,
If a specific density value is set in the margin when the background color is not uniform, the boundary between the portion where the document image is copied on the recording sheet and the other portion will be visible. FIG. 10 is a diagram showing a change in density value when a specific density value is set in a margin when copying a document image having a non-uniform background color. In FIG. 10, the density of the background of the document image has a constant inclination. Such inclination of the background color is a phenomenon that often appears in a photographic image, such as when the image is taken with illumination from the lateral direction. On the other hand, if a specific density value is set in the blank portion, the density will be significantly changed at the boundary between the document image and the blank portion. Such a boundary gives an unnatural impression and has a problem that the appearance is poor.

According to the present invention, there is provided an image forming apparatus for applying a background color so that a border between a blank portion and a document image is not recognized when the document image is copied onto a recording sheet regardless of the state of the background color of the document image. The purpose is to provide.

[0007]

In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus for copying an original image on a recording sheet, and detects a background portion of the original image to be copied. Background detecting means, a tendency detecting means for detecting a tendency of the pixel density to change in the background portion detected by the background detecting means, and the tendency detecting means for detecting the tendency in an area around the area where the original image is copied on the recording sheet. An image forming means for forming a background equivalent image according to the tendency detected by the means. By doing so, the tendency of the density change of the background portion of the document image can be set in the blank portion, so that the border portion between the blank portion of the recording sheet and the document image can not be recognized, and it is natural and has a good appearance. An image can be formed.

Further, the trend detecting means detects a density gradient of the background portion in a predetermined direction, and the image forming means forms a background-equivalent image to be formed in a region other than a region where a document image of a recording sheet is copied. An image is formed such that the density gradient in the predetermined direction matches the density gradient detected by the trend detecting means. A mode selection unit for selecting one of a mode in which an image is formed in an area other than the area where the original image of the recording sheet is copied and a mode in which no image is formed in the area; The trend is detected only when a mode for forming an image is selected, and the image forming means forms the image only when a mode for forming an image in the area is selected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below with reference to the drawings. (Embodiment) FIG. 1 is a schematic sectional view of an image forming apparatus (hereinafter simply referred to as "copier") according to the present embodiment. This copying machine is a so-called tandem-type color copying machine that forms a color image by multiply transferring images formed on a plurality of image forming units arranged along a transfer belt.

The copying machine 1 is roughly divided into an image reader 2 for reading a document image and a printer 3 for reproducing an image read by the image reader 2. The image reader unit 2 scans a document on the platen glass 14 to read R, G, and B electrical signals, and reads the electrical signals obtained thereby to perform processing such as conversion into gradation data. It comprises a signal processing unit 13. Scanner 8
Is driven by the scan motor 16 to move in the direction of arrow A when reading the original, and scans the original on the platen glass 14 while irradiating the original with the exposure lamp 12.
The reflected light of the irradiation light from the document surface is condensed by the rod lens array 10 and photoelectrically converted by the contact type CCD color image sensor 11 to become R, G and B electric signals. The read signal processing unit 13 converts this electric signal into 8-bit grayscale data of yellow (Y), magenta (M), cyan (C), and black (K).

The printer unit 3 includes a printer control unit 4, a laser optical system 5, an image forming system 6, and a transport system 7.
The printer control unit 4 generates laser diode drive signals for each gradation data of each color based on the signal output from the read signal processing unit 13, and the drive signals of the corresponding printer heads 17C to 17K of the laser optical system 5 are generated by the respective drive signals. The laser diode emits light. The photosensitive drums 20C to 20 which are rotated and driven by the laser beam generated thereby.
K is exposed and scanned.

The photosensitive drums 20C to 20K are uniformly charged by charging chargers 17C to 17K. An electrostatic latent image is formed by the exposure, and the developing units 21C to 21K.
K supplies toner of each color of cyan, magenta, yellow, and black to each of the photosensitive drums 20C to 20K to visualize the toner. On the other hand, the paper cassette 27 or 28
Is fed by a transfer belt 25 which is stretched by a driving roller 24 and a driven roller 26 and is rotated at a constant speed, with a timing, and is conveyed to the photosensitive drums 20C to 20K. The formed toner images of each color are sequentially transferred so as to be superimposed on the recording sheet by receiving transfer electric fields from the transfer brushes 24C to 24K. The recording sheet to which the toner image has been transferred is separated from the transfer belt 25 and fixed by the fixing device 25, and thereafter, the recording sheet is discharged onto the discharge tray 23.

An operation panel 15 is provided at an easy-to-operate position on the front of the image reader unit 2. The operation panel includes keys for inputting various copy modes, and a display unit for displaying settings and the like. Next, the configuration of a control system installed inside the copying machine 1 will be described with reference to the block diagram of FIG.

FIG. 2 is a block diagram showing a functional configuration of a control system installed in the copying machine 1. As shown in FIG. This control system
An image reader control unit 28 for controlling the operation of the image reader unit 2, a read signal processing unit 13 for performing necessary correction processing on the image data obtained by the image reader control unit 28, and a printer control for controlling the operation of the printer unit 3. It comprises a unit 4 and the like. The image reader control unit 28 includes a position detection sensor 9 that indicates the position of the document on the platen glass 14.
The lighting of the exposure lamp 12 is controlled by the position signal from
Further, it controls a scan motor driver 29 that drives the scan motor 16 to cause the scanner 8 to scan the document image. The image signal read through the CCD color image sensor 11 by this scanning operation is subjected to gradation data conversion, shading correction, and the like by the read signal processing unit 13.

In this embodiment, the printer control unit 4
It also controls the overall timing, controls the semiconductor laser driver 30, drives the semiconductor lasers 31C to 31K in each of the printer heads 17C to 17K based on the image signals processed by the read signal processing unit 13, and controls the photoconductor. The drums 20 </ b> C to 20 </ b> K are exposed and scanned, and the operations of the image forming system 6 and the transport system 7 are uniformly controlled via the copy control unit 32 while taking timing.

Next, the operation of the printer control unit 4 will be described with reference to a flowchart. Copier 1
When the start button on the operation panel 15 is pressed,
The image reader control unit 28 drives the scan motor 16 and the like to scan the original image on the platen glass 14. The image signal thus obtained is read by the read signal processing unit 13.
And sends it to the printer control unit 4. FIG. 3 is a flowchart showing the operation of the printer control unit 4. Upon receiving the image signal from the read signal processing unit 13 (step S1), the printer control unit 4 checks whether the background setting button of the operation panel 15 has been pressed, and if not pressed (NO in step S2), Proceeding to step S6, the semiconductor laser driver is driven to execute a normal copying operation. If the background setting button has been pressed (YES in step S2), the image signal and the copy mode (paper designation, magnification, etc.) are checked to see if there is a margin. If there is no margin (NO in step S3), the process proceeds to step S6. If there is a margin (YE in step S3)
S), background detection is performed (step S4). If the background cannot be detected (NO in step S5), a normal copying operation is performed. If the background can be detected (Y in step S5)
ES), the tendency of the background color is detected (step S6). Next, after setting the background color in the margin according to the detected tendency of the background color (step S7), the semiconductor laser driver is driven to form an image (step S8).

Regarding the background detection in step S4,
The copying machine 1 discriminates between them by utilizing the fact that the density differs between the foreground and the background. FIG. 4 is an example of a density histogram of a document image. Because the foreground and background have different densities,
The histogram of the foreground part and the histogram of the background part exist separately. In addition, the background color takes similar density values, so the histogram existence range is narrow and the frequency value is large, but the foreground color takes various density values, so the histogram existence range is wide and the frequency The value is also small. Focusing on such features, the copying machine 1 determines the density range of the background portion, and specifies a pixel having a density value in the density range as a background pixel. FIG. 5 is a flowchart showing the background detection processing of the copying machine 1. The copying machine 1 first creates a density histogram from document image data (step S
9) The density histogram is divided into a plurality of histogram clusters using a known clustering algorithm (step S10). Next, the frequency, that is, the number of pixels belonging to the cluster, is obtained for each cluster (step S1).
1) If there is a cluster having the highest frequency (YES in step S12), the cluster is regarded as a cluster of the background color (step S13). If there are a plurality of clusters having the highest frequency (NO in step S12),
It is determined that the background cannot be detected, and the process ends. FIG.
FIG. 4 is a diagram illustrating an example of a density histogram. In the density histogram of FIG. 6, the histogram is divided into five clusters 33 to 37. These clusters 33-37
Among them, the cluster 33 having the largest frequency is set as the cluster of the background color.

Next, the detection of the tendency of the background color in step S6 and the setting of the background color in step S7 will be described in detail. FIG.
FIG. 4 is a diagram showing a recording sheet and a document image copied thereon. In FIG. 7, a document image 42 is copied on a recording sheet 38. There are margins 39 to 47 around the copied document image 42. The printer control unit 4 sets the margins to left and right margins 41 and 46, and upper and lower margins 39 and 4.
A background color is set for each of the four types of four and four corner margins 40, 43, 45, and 47 by different methods.

First, for the left and right margin portions 41 and 46,
The printer control unit 4 sets the background color as follows. The original image data read by the copying machine 1 is a one-dimensional array of density values (hereinafter, simply referred to as a "density value sequence") for one scanning line. The printer control unit 4 performs the processing in step S
The trend detection is performed on the pixels belonging to the background color cluster detected in step 4. FIG. 8 is a graph showing the position and density value of a pixel for which a trend is to be detected for one scanning line. In FIG. 8, the pixels to be subjected to the trend detection are:
A density value sequence 50 is formed, and the printer control unit 4 obtains a straight line 49 indicating the tendency of the background color from the density value sequence 50 by using the least square method. The straight line 49 is extended to portions 48 and 51 corresponding to the left and right margins, and the left and right margins 4 are extended.
The density of the background color to be set to 1, 46 is determined. For the upper and lower margin portions 39 and 44, the printer control unit forms a density value sequence in the sub-scanning direction, and obtains a straight line representing the tendency of the background color from the density value sequence by using the least square method. Like the left and right margins 41 and 46, this straight line is extended to the margin, and the background color to be set in the margin is determined.

For the four corner margins 40, 43, 45, and 47, the background color to be set is determined using the background colors of the upper, lower, left, and right margins determined as described above. Hereinafter, a description will be given taking the four corner margins 40 as an example. FIG. 9 is a diagram showing a portion including four corner blank portions 40 of the recording sheet 38. In the figure, a pixel 52 is a pixel included in the four corner margins 40, a pixel 53 is a pixel included in the left and right margins 41, a pixel 54 is a pixel included in the upper and lower margins 39, and the density of the pixels 53 and 54 is A ₁ and A ₂ have already been determined by the above method. The pixel 52 and the pixel 5
The distance of 3 is D ₁ , and the distance between pixel 52 and pixel 54 is D ₂ . At this time, the density A of the pixel 52 is determined using the following equation.

A = (A ₁ D ₂ + A ₂ D ₁ ) / (D ₁ + D ₂ ) That is, the density of the pixels 53 and 54 is proportionally distributed according to the distance to obtain the density of the pixel 52. If the display panel is provided in the copying machine 1 and the background cannot be detected (step S5).
Otherwise, if a background-equivalent image cannot be formed in the margin even though the background setting button has been pressed on the operation panel 15, that effect may be displayed on the display panel.

As described above, the tendency of the background color is determined based on the density value sequence in the main scanning direction and the sub-scanning direction, the background color of the upper, lower, left and right margins is determined, and then the distance from the determined background color is determined. The process of determining the background color of the remaining blank portion by proportional distribution based on the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) provides a background color of the original image. The background color of the margin is determined according to the tendency described above, and the background color is set in the margin.

Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be made. (Modification) In the above embodiment, the tendency of the background color is obtained by using the least squares method. However, the effect of the present invention can be obtained by obtaining the tendency of the background color by another method.
For example, a curve approximating the density value sequence may be obtained from the density value sequence using a Lagrangian polynomial or a spline function, and the extension may be used as the background color of the margin.

In the above description, the background color of the margin is determined by a one-dimensional approximation method, but a two-dimensional approximation method may be used. For example, if an original image is FFT (Fa
St Fourier Transform) may be used to obtain a spatial frequency by Fourier expansion, and the background color of the margin may be determined based on the frequency. In this way, even if the background of the document image does not have a density gradient when the background of the document image is averaged like a striped pattern, a background equivalent image can be formed in a margin according to such a tendency of the background color. .

The method of detecting the background color is not limited to the above-described method, and the effect of the present invention can be obtained by using any of a number of known techniques relating to discrimination between the background and the foreground in an image. Further, in the above description, the case where the present invention is applied to a copying machine that reads an image from a document and copies the image is described. For example, when receiving image data from a terminal such as a personal computer and printing the image data, The invention may be applied to form an image in a margin.

[0026]

As described above, according to the present invention,
Since the background color of the document image is detected to determine the background color to be set in the margin, the background color can be set in the margin so that the boundary between the document image and the margin is not visible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a functional configuration of a control system installed inside the copying machine 1;

FIG. 3 is a flowchart showing an operation of the printer control unit 4;

FIG. 4 is a view exemplifying a density histogram of a document image;

FIG. 5 is a flowchart showing a background detection process of the copying machine 1;

FIG. 6 is a diagram illustrating an example of a density histogram of a document image;

FIG. 7 is a diagram illustrating a recording sheet and a document image copied on the recording sheet.

FIG. 8 is a graph showing the position and density value of a pixel for which a trend is to be detected for one scanning line.

FIG. 9 is a diagram showing a portion including four corner blank portions 40 of the recording sheet 38;

FIG. 10 is a diagram illustrating a change in density value when a background color is applied to a blank portion according to the related art when a document image having a non-uniform background color is copied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 2 Image reader part 3 Printer part 4 Printer control part 5 Laser optical system 6 Imaging system 7 Transport system 8 Scanner 9 Position detection sensor 10 Rod lens array 11 CCD color image sensor 12 Exposure lamp 13 Reading signal processing part 14 Platen Glass 15 Operation panel 16 Scan motor 17C-17K Printer head 18C-18K Charger 19C-19K Static eliminator 20C-20K Photoconductor drum

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironobu Nakata 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Hiroyasu Ito Azuchi, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Co., Ltd. (13) Kaoru Tada 2-3-13-Azuchicho, Chuo-ku, Osaka-shi, Osaka Prefecture Osaka International Building Minolta Co., Ltd. F-term (reference) 2H027 DB01 FA30 FD01 5B047 AA01 BA02 BB02 CA05 CB09 CB13 DA03 5C076 AA11 AA13 AA27 AA37 BA02 BA06 CA09

Claims (3)

[Claims] 1. An image forming apparatus for copying an original image on a recording sheet, comprising: a background detecting means for detecting a background portion of the original image to be copied; and a density of pixels in the background portion detected by the background detecting means. A tendency detecting means for detecting a tendency of change of the document image, and an image forming means for forming a background equivalent image in an area around an area where a document image is copied on a recording sheet in accordance with the tendency detected by the tendency detecting means. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the tendency detecting unit detects a density gradient of the background portion in a predetermined direction, and the image forming unit detects a background-equivalent image to be formed in a region other than a region where a document image of a recording sheet is copied. 2. The image forming apparatus according to claim 1, wherein the image is formed such that a density gradient in the predetermined direction coincides with a density gradient detected by the trend detecting unit. 3. A mode selecting means for selecting one of a mode in which an image is formed in an area other than an area where a document image of a recording sheet is copied and a mode in which an image is not formed in the area, wherein the tendency detecting means comprises: Detecting the tendency only when a mode for forming an image in the area is selected; and forming the image only when the mode for forming an image in the area is selected. The image forming apparatus according to claim 1.