JP5454368B2 - Image forming apparatus, image processing method, and program - Google Patents

Description

  The present invention relates to an image forming apparatus, an image processing method, and a program.

  Conventionally, based on an input digital image signal, an electrostatic latent image is formed on a photosensitive drum by an LED head writing optical system in which a plurality of light emitting diode elements (hereinafter referred to as LEDs) are arranged in a line. There is an image forming apparatus that forms an image by transferring and fixing a toner image formed by attaching toner to the electrostatic latent image onto a recording medium such as paper.

  In this image forming apparatus, it is known that when an image is formed on one side, the recording medium contracts due to thermal contraction due to fixing processing. The reduction rate of the image size due to this heat shrinkage is usually a small value of 0.5% or less, and is fine at the pixel unit level in the main scanning direction.

  For this reason, in the above-described image forming apparatus, it has been necessary to perform a minute scaling process in units of pixels in accordance with usage conditions. In particular, when image formation is performed on both sides, it is necessary to perform fine scaling processing as a measure against thermal shrinkage, and to form an image by reducing the image on the back side with respect to the front surface.

  Therefore, for example, as a minute enlargement process, as shown in FIG. 14A, conventionally, a technique for performing minute enlargement by interpolating signal values from adjacent pixels at a predetermined pixel interval to generate additional pixels. It has been known. As a minute reduction process, as shown in FIG. 14B, a technique for performing minute reduction by thinning out pixels at a predetermined pixel interval is known.

  Also, as shown in FIGS. 15A and 15B, there is a technique for preventing a position where a pixel is added or deleted from appearing linear by randomizing a position where a pixel is added or deleted. Are known.

  Further, for example, in Patent Document 1, when forming a reduced image by thinning out pixels with an image forming apparatus having an LED head writing optical system, not only thinning out pixels but also adjusting adjacent pixels to halftones. A technique for improving reproducibility is disclosed.

  Further, for example, in Patent Document 2, the average of pixels adjacent in the main scanning direction is calculated, and the number of pixels is increased / decreased by outputting the calculation result and multi-value data of adjacent pixels according to the conversion density. Techniques to do this are disclosed.

JP 2004-207950 A JP-A-10-28223

  By the way, in an image forming apparatus provided with LED head writing optical systems arranged in a line shape, a writing element is driven based on a multi-value digital image signal that is image information, so that the multi-value digital image signal can be driven. In this configuration, pixels with high density are formed on a recording medium to form an image. For this reason, it is impossible to adjust the pixel width as in the case of writing with a laser, and minute scaling can be performed only by adding or deleting pixels.

  However, the technique described in FIGS. 14A and 14B has a problem that the position where the pixel is added or deleted appears to be linear. In the techniques described in FIGS. 15A and 15B, it can be avoided that the positions where the pixels are added or deleted appear to be linear, but a specific pattern may appear, and the entire image is cluttered. There was a problem that the image became noisy.

  In addition, in the technique described in Patent Document 1, since it is fixedly adjusted to the halftone of adjacent pixels, sufficient reproducibility cannot be obtained when an image is formed with a minute magnification.

  An object of the present invention is to provide an image with good reproducibility that suppresses the occurrence of noise and image roughness even when a scaling process is performed.

In order to solve the above-mentioned problem, the invention described in claim 1
In an image forming apparatus that forms an image based on an input multi-value digital image signal,
A scaling processing unit for performing scaling processing on the input multi-value digital image signal in units of scanning lines, and dividing the pixel signal value of each pixel of the input multi-value digital image signal according to a scaling factor A scaling unit that adds or deletes pixels by sequentially shifting a part of the divided pixel signal values to adjacent pixels in a certain direction, and generates an image corresponding to the scaling factor. .

The invention according to claim 2 is the invention according to claim 1,
A correction processing unit is provided for correcting the level of the pixel signal value of each pixel that has been increased or decreased by shifting a part of the divided pixel signal value.

The invention according to claim 3 is the invention according to claim 1 or 2,
An image forming unit that forms an image by electrophotography based on the input multi-value digital image signal,
The image forming unit includes a print head that forms a latent image on a photosensitive member by causing an exposure element to emit light based on the scaled image.

The invention according to claim 4
An image processing method for performing image processing on an input multi-value digital image signal in units of scanning lines,
Dividing the pixel signal value of each pixel of the input multi-valued digital image signal by the number of divisions according to the scaling factor;
Adding or deleting pixels by sequentially shifting a part of the divided pixel signal values to adjacent pixels in a certain direction, and generating an image according to the scaling factor;
including.

The program of the invention described in claim 5 is:
A computer that processes an input multi-value digital image signal in units of scanning lines,
The pixel signal value of each pixel of the input multi-value digital image signal is divided by the number of divisions according to the scaling factor, and a part of the divided pixel signal value is sequentially shifted to adjacent pixels in a certain direction. A scaling process unit that adds or deletes pixels and generates an image according to the scaling ratio,
To function as.

  According to the present invention, it is possible to provide an image with good reproducibility that suppresses the occurrence of noise and image roughness even when scaling processing is performed.

1 is a block diagram illustrating a functional configuration of an image forming apparatus in the present embodiment. It is a figure which shows the principal part structure of the image processing part of FIG. FIG. 2 is a diagram illustrating a cross-sectional configuration of an image forming unit in FIG. 1. It is a figure which shows the principal part structure of the writing unit of FIG. It is a flowchart which shows the scaling process performed by the scaling process part of FIG. It is a flowchart which shows the expansion process performed in step T3 of FIG. It is a figure which shows typically the processing content of the expansion process of FIG. It is a flowchart which shows the reduction process performed in step T4 of FIG. It is a figure which shows typically the processing content of the reduction process of FIG. It is a flowchart which shows the expansion process B in 2nd Embodiment. It is a flowchart which shows the 2nd expansion process performed by step A103 of FIG. It is a figure which shows typically the processing content of the 2nd expansion process of FIG. It is a figure which shows the process direction of a scaling process. (A) is a figure which shows typically the content of the expansion process in a prior art, (b) is a figure which shows typically the content of the reduction process in a prior art. (A) is a figure which shows typically the content of the other expansion process in a prior art, (b) is a figure which shows typically the content of the other reduction process in a prior art.

[First Embodiment]
The first embodiment of the present invention will be described below in detail with reference to the drawings.
First, the configuration will be described.

  FIG. 1 shows an example of the internal configuration of the image forming apparatus 1 in the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a CPU 101, an operation display unit 102, an image reading unit 103, an image processing unit 104, an image forming unit 105, a RAM 106, a storage unit 107, a communication control unit 108, and the like. Each part is connected by a bus 109.

  A CPU (Central Processing Unit) reads out a system program and various processing programs stored in the storage unit 107 by operating the operation display unit 102 and expands them in a RAM. According to the expanded programs, each unit of the image forming apparatus 1 Centralized control of operation.

  The operation display unit 102 includes an LCD (Liquid Crystal Display), and displays various screens such as various operation screens and status displays in accordance with instructions of display signals input from the CPU 101. The LCD display screen is covered with a pressure-sensitive (resistive film pressure) touch panel configured with transparent electrodes arranged in a grid, and the XY coordinates of the force point pressed with a finger or a touch pen are expressed as voltage values. The detected position signal is output to the CPU 101 as an operation signal.

  For example, the operation display unit 102 is configured to be able to input an image scaling factor X (enlargement ratio, reduction ratio). The scaling factor X is set to adjust a subtle difference in the size of the image formed on the front surface and the back surface due to, for example, heat shrinkage at the time of fixing, and is mainly from an enlargement ratio of 1% to a reduction ratio. It is set in the range of 1%. The set scaling factor X is output to the CPU 101 and stored in the storage unit 107 by the CPU 101.

  The image reading unit 103 includes a light source, a mirror, a CCD (Charge Coupled Device), an A / D converter, a shading correction circuit, and the like. The image reading unit 103 forms an image of the reflected light of the light scanned from the light source to the original, photoelectrically converts it to obtain an analog image signal, and performs A / D conversion and shading correction on the analog signal to obtain R, G , B color components are converted into digital image signals and output to the image processing unit 104 in units of scanning lines.

As shown in FIG. 2, the image processing unit 104 includes a color conversion unit 141, a scaling processing unit 142, an image memory 143, and the like.
The color conversion unit 141 converts the image signals of R, G, and B color components into multi-value digital image signals Dy, Dm, Dc, and Dk of each color of Y, M, C, and K using a three-dimensional color information conversion table. Color conversion processing is performed and the image is temporarily stored in the input image memory 143a of the image memory 143.
The scaling processing unit 142 performs scaling processing on the multi-value digital image signals Dy, Dm, Dc, Dk stored in the input image memory 143a, and multi-value digital image signals Dy ′, Dm ′, Dc ′, Dk ′. Is output to the image forming unit 105. Specifically, the multi-value digital image signal Dy ′ is supplied to the LED print head 401Y (see FIG. 4) of the writing unit 40Y in units of scanning lines and in units of pixels. Similarly, the multi-value digital image signal Dm ′ is supplied to the LED print head 401M of the writing unit 40M in units of scanning lines and pixels. Similarly, the multi-value digital image signal Dc ′ is supplied to the LED print head 401C of the writing unit 40C in units of scanning lines and pixels. Similarly, the multi-value digital image signal Dk ′ is supplied to the LED print head 401K of the writing unit 40K in units of scanning lines and in units of pixels.
In the present embodiment, the color conversion unit 141 and the scaling processing unit 142 are realized by software processing in cooperation with the CPU 101 and the color conversion processing program and the scaling processing program stored in the storage unit 107, respectively. However, it may be realized by dedicated hardware.

The image forming unit 105 forms and outputs a toner image on the transfer paper by an electrophotographic process based on the multi-value digital image signals Dy ′, Dm ′, Dc ′, and Dk ′ input from the image processing unit 104.
FIG. 3 shows a main configuration of the image forming unit 105. As shown in FIG. 3, the image forming unit 105 forms toner images of Y, M, C, and K, and writing units 40Y, 40M, 40C, and 40K that write the latent image of the image on the photosensitive drum. Photoconductor units 50Y, 50M, 50C, and 50K, and an intermediate transfer belt 56 as an intermediate transfer member that conveys a toner image formed by the photoconductor units 50Y, 50M, 50C, and 50K to transfer paper so that the roller 57 is rotatable. The transfer sheet is transferred to the secondary transfer roller 59 in synchronization with the toner image formed on the intermediate transfer belt 56, and the toner image formed on the intermediate transfer belt 56 is transferred to the transfer sheet 2 The image forming apparatus includes a next transfer roller 59, a fixing unit 60 for fixing the toner image on the transfer paper, and a paper discharge roller 61 for discharging the transfer paper.

  As shown in FIG. 4, the writing unit 40Y includes an LED print head 401Y, a gradient index rod lens 402Y, a drive circuit (not shown), and the like. The LED print head 401Y is disposed so as to face the photosensitive drum 51Y of the photosensitive unit 50Y. The LED print head 401Y has a plurality of LED elements 41Y arranged in a line in the direction perpendicular to the rotation direction (sub-scanning direction) of the photosensitive drum 51Y, that is, the main scanning direction. The LED print head 401Y causes the LED elements 41Y for one line to emit light at a time based on the multi-value digital image signal Dy ′ for one line supplied from the scaling unit 142, and this light is emitted to the photosensitive drum. By irradiating 51Y, a latent image is written line by line on the surface of the photosensitive drum 51Y. The writing units 40M, 40C, and 40K have the same configuration.

  The photoreceptor unit 50Y includes a photoreceptor drum 51Y, a developing device 52Y, a charger 53Y, a cleaner 54Y, and a primary transfer roller 55Y. The same applies to the photoreceptor units 50M, 50C, and 50K.

  Here, image formation in the image forming unit 105 will be described. First, in the photoreceptor unit 50Y, the photoreceptor drum 51Y rotates and the surface thereof is charged by the charger 53Y. In the charged portion, a latent image based on the multi-value digital image signal Dy ′ is written by the light emission of the LED element group 41Y of the writing unit 40Y. When yellow toner is attached to the latent image portion by the developing device 52Y, a yellow toner image is formed. This toner image is transferred to the intermediate transfer belt 56 by the pressure contact of the primary transfer roller 55Y (primary transfer). The toner image is a yellow image corresponding to the image data to be output. The toner that has not been transferred is removed by the cleaner 54Y.

  Similarly, for the photoconductor units 50M, 50C, and 50K, magenta toner images, cyan toner images, and black toner images are similarly formed and transferred. The intermediate transfer belt 56 is also rotated by the rotation of the roller 57, the primary transfer rollers 55Y, 55M, 55C, and 55K, and the secondary transfer roller 59, and the YMCK toner images are sequentially superimposed and transferred on the intermediate transfer belt 56. The Further, the transfer paper is conveyed one by one from one of the paper feed trays 66A to 66C by rotation of any of the paper feed rollers 68A to 68C, and is conveyed to the secondary transfer roller 59 by rotation of the registration roller 58.

  When the transfer paper passes through the pressure contact portion of the secondary transfer roller 59, the YMCK toner image on the intermediate transfer belt 56 is transferred to the transfer paper (secondary transfer). The transfer paper on which the YMCK toner image is transferred passes through the fixing unit 60. By the pressurization and heating of the fixing unit 60, the YMCK toner image is fixed on the transfer paper, and a color toner image is formed. The transfer paper on which the image has been formed is discharged by a paper discharge roller 61.

  After the image is formed on the transfer paper, the toner attached on the intermediate transfer belt 56 is removed by the belt cleaning 62. Further, a positive polarity current and a negative polarity current are alternately switched from a power source (not shown) to the secondary transfer roller 59 and allowed to flow for a predetermined time, whereby the toner attached to the secondary transfer roller 59 is applied to the intermediate transfer belt 56. After the transfer, the secondary transfer roller 59 is cleaned.

  Each unit of the image forming unit 105 described above is driven via various motors (not shown) under the control of the CPU 101, and the operation timing of each unit is controlled by the CPU 101.

  Returning to FIG. 1, the RAM 106 is a temporary storage area for programs, input or output data, parameters, and the like read from the storage unit 107 in various processes controlled by the CPU 101.

  The storage unit 107 is configured by a nonvolatile semiconductor memory or the like, and includes a system program corresponding to the image forming apparatus 1 and various processing programs for controlling the operation of the image forming apparatus 1 that can be executed on the system program. A scaling process program and the like are stored. The program is stored in the form of computer-readable program code, and the CPU 101 sequentially executes operations according to the program code. The storage unit 107 stores a setting value (for example, a scaling factor X (enlargement rate or reduction rate)) input from the operation display unit 102 in accordance with an instruction from the CPU 101.

  The communication control unit 108 includes a LAN adapter, a router, and the like, and performs data transmission / reception with each device such as an external information terminal via a communication line such as a LAN (Local Area Network).

Next, the scaling process executed by the scaling process unit 142 will be described in detail.
The scaling processing unit 142 performs scaling processing shown in FIG. 5 using each of the digital image signals Dy, Dm, Dc, and Dk for one line as input images. This scaling process is a process that mainly performs minute scaling in pixel units.
In the scaling process, as shown in FIGS. 7 and 9, the pixel signal value (referred to as pixel level) of each pixel of the input image is divided by the division number N (10 in FIGS. 7 and 9) corresponding to the scaling factor X. A process of dividing and sequentially shifting a part of the divided pixel level to a pixel (adjacent pixel) adjacent to a certain direction is performed from the first pixel that is one end of the input image toward the other end. When a part of the pixel level divided in this way is shifted to the adjacent pixel, one pixel is added or deleted at a period corresponding to the number of divisions, and when the other end is reached, the approximate magnification X is met. An output image is obtained.

  First, the scaling factor X (enlargement rate or reduction rate) stored in the storage unit 107 is acquired (step T1), and it is determined whether the acquired scaling factor X is an enlargement rate or a reduction rate ( Step T2). If it is determined that the enlargement rate is reached (step T2: YES), enlargement processing is executed (step T3). If it is determined that the reduction rate is reached (step T2; NO), reduction processing is executed (step T4).

FIG. 6 is a flowchart showing the enlargement process executed by the scaling unit 142 in step T3.
In the enlargement process, a loop process (steps T103 to T110) is performed for each predetermined number of pixels (K) according to the division number N calculated based on the scaling factor X, and the pixel level is sequentially applied to pixels adjacent in a certain direction. Is added (shifted). When the pixel level to be shifted becomes one pixel, exception processing for adding an additional pixel is performed (steps T112 to T116). Then, the next loop is executed. This process is executed while sequentially moving the target pixel P from one end to the other end of the input image. Hereinafter, the flow of the enlargement process will be described in detail.

First, the division number N at the pixel level is calculated based on the obtained scaling factor X (step T101). Specifically, it is calculated by (Equation 1).
N = 100 / X (Formula 1)
(Expression 1) is a calculation expression for obtaining N so that the enlargement of the scaling factor X can be performed when one pixel is added for every N pixel periods of the division number. For example, when 10% enlargement is performed, if 1 pixel is added at a cycle of 100/10 = 10 pixels, the enlargement can be 10%.

  Next, initial setting of each value used in the scaling process is performed (step T102). That is, 1 is set to the variable Y of the temporary memory 143b, 0 is set to the variable M and the shift amount Ps, and N is set to the variable K.

  Next, it is determined whether or not there is an unprocessed pixel on the same line of the input image stored in the input image memory 143a. If it is determined that there is an unprocessed pixel (step T103; YES), An unprocessed pixel (a pixel at the start point at the start of processing) adjacent to the pixel processed as the target pixel P is set as the target pixel P, and the pixel level Pi (input pixel level Pi) is an image. It is read from the input image memory 143a of the memory 143 (step T104).

  Next, the shift amount Ps is read from the temporary memory 143b (step T105), the shift amount Ps is added to the input pixel level Pi of the target pixel P, and a pixel level after shifting (referred to as an intermediate generation pixel level) Pr is obtained. (Step T106). The intermediate generation pixel level Pr is stored in the temporary memory 143b.

Next, the intermediate generation pixel level Pr is read from the temporary memory area 143b, and the output pixel level Po of the target pixel P is calculated by the following (Equation 2) (step T107).
Po = Pr × {(N−1) / (N + M)} (Formula 2)
The calculated output pixel level Po is stored at a predetermined address in the output image memory 143c (step T108). The predetermined address is an address next to the address at which the pixel level is stored immediately before.

Next, the pixel level to be shifted from the target pixel P to the pixel adjacent to the processing direction, that is, the shift amount Ps is calculated by the following (Equation 3) (step T109).
Ps = Pr × {Y / (N + M)} (Formula 3)
The calculated shift amount Ps is stored in the temporary memory 143b.

  Next, the variable K is decremented by 1, and the variables Y and M are incremented by 1 (step T110). Then, it is determined whether or not K = 0 (step T111). If it is determined that K is not 0 (step T111; NO), the process returns to step T103.

If it is determined that K = 0 (step T111; YES), the shift amount Ps is read from the temporary memory 143b (step T112). Since the shift amount Ps read out here corresponds to the pixel level of one pixel of the input image, the output pixel level Po of the pixel to be added is calculated by the following (Equation 4) (step T113).
Po = Ps × {(N−1) / N} (Formula 4)
The calculated output pixel level Po is stored at a predetermined address in the output image memory 143c as the output pixel level Po of the additional pixel (step T114). The predetermined address is an address next to the address at which the pixel level is stored immediately before.

  Next, a shift amount Ps = Ps × (1 / N) for shifting from the additional pixel to the pixel adjacent to the processing direction is calculated and stored in the temporary memory 143b (step T115). Then, variable Y = 2, variable M = 1, and variable K = N−1 are set (step T116), and the process returns to step T103.

  If it is determined in step T103 that there is no unprocessed pixel on the same line of the input image (step T103; NO), level correction according to the magnification X is performed (step T116). In the enlargement process, enlargement can be performed while maintaining the continuity of the image between adjacent pixels, but the range of the output pixel level Po (the range of possible minimum value to maximum value) is the range of the pixel level Pi of the input image. It becomes lower according to the magnification X. For example, in the 10% enlargement process, the output pixel level Po is reduced to 90% compared to the input pixel level Pi. Therefore, by performing level correction according to the variable magnification X, the reduced amount of the pixel level is restored. Specifically, the output pixel level Po of each pixel is multiplied by {N / (N−1)}.

In general, since the enlargement ratio is 1% or less in a scaling process as a measure against heat shrinkage, the correction amount is also 1% or less. Therefore, in this case, since the influence on the image quality is small, there is often no need to perform level correction depending on the use of the printed matter. Therefore, the operation display unit 102 may be configured to allow the user to set whether or not level correction is performed.
When the level correction ends, the enlargement process ends.

FIG. 7 is a diagram schematically showing an enlargement process when the scaling factor X (enlargement ratio) is 10% and the number of pixels in one line is 100. In the description of FIG. 7, description will be made assuming that the nth pixel is Pn, the input pixel level of the nth pixel is Pin, the intermediate generation pixel level is Prn, and the output pixel level is Pon.
If the number of pixels in one line is 100 and the scaling factor is 10%, adding pixels in a cycle of 10 pixels results in a 10% enlargement, so the number of divisions is 10.
First, the input pixel level Pi1 of the first pixel P1 is divided, and 1/10 thereof is shifted to the second pixel P2. The output pixel level Po1 of the first pixel P1 is converted to 9/10 obtained by subtracting the shift amount from the input pixel level Pi1.
When the shift amount 1/10 from the first pixel P1 is added, the pixel level of the second pixel P2 becomes Pi2 + Pi1 × 1/10 (intermediate generation pixel level Pr2). Since this intermediate generation pixel level Pr2 receives the pixel level of 1/10 from the first pixel P1, the number of divisions is 11, and Pr2 × 9/11 is the output pixel level Po2 of the second pixel P2. . Thereby, the range of the pixel level (range of possible minimum value to maximum value) can be made uniform between the pixels. The level of Pr2 × 2/11 minutes is shifted to the third pixel.
When the above processing is performed while sequentially shifting the target pixel to the next, the shift amount Pr10 × 10/19 from the tenth pixel P10 becomes one pixel. Therefore, the Pr10 × 10/19 pixel is added to the 10 + 1st. The addition of the 10 + 1st pixel completes 10% zooming.
Next, the input image level Pi10 + 1 of the 10th + 1 pixel is divided by 10, and 1/10 thereof is shifted to the 11th pixel P11. The output pixel level Po11 of the eleventh pixel P11 is converted to 9/10 obtained by subtracting the shift amount from the input pixel level Pi11.
Hereinafter, when the above process is repeated until the other end of the input image is reached, an output image enlarged by about 10% in the scanning line direction is obtained.

  In the enlargement process, the pixel level is divided by the number of divisions corresponding to the scaling factor X, and a part of the divided pixel level is shifted to the adjacent pixel in a certain direction, whereby the pixel period corresponding to the scaling factor X To generate an additional pixel, and the input image is enlarged at a scaling factor X substantially designated by the additional pixel. Therefore, since the data can be scaled while ensuring the continuity of data between adjacent pixels, it is possible to output a highly reproducible image that suppresses the occurrence of patterns, noise, and image roughness at additional locations. Is possible.

FIG. 8 is a flowchart showing the reduction processing executed by the scaling processing unit 142 in step T4 of FIG.
In the reduction process, a loop process (steps T203 to T210) is performed for each predetermined number of pixels (K) corresponding to the division number N calculated based on the scaling factor X, and the pixels adjacent to the fixed direction side in order. To shift a part of the pixel level. When the shift amount becomes one pixel, the shift source pixel is deleted (step T212). Then, the next loop is executed. This process is executed while sequentially moving the target pixel from one end of the input image toward the other end. Hereinafter, the flow of the reduction process will be described in detail.

First, the division number N at the pixel level is calculated based on the obtained scaling factor X (step T201). Specifically, it is calculated by the following (Formula 11).
N = 100 / X (Formula 11)
According to (Equation 11), N can be calculated so that the scaling factor X can be reduced when one pixel is deleted for every N pixel periods of the division number. For example, when 10% reduction is performed, if 1 pixel is added in a cycle of 100/10 = 10 pixels, the reduction can be performed by 10%.

  Next, initialization of variables used in the reduction process is performed (step T202). Specifically, 1 is set to the variable Y, 2 is set to the variable M, and N−1 is set to the variable K.

  Next, it is determined whether or not there is an unprocessed pixel on the same line of the input image stored in the input image memory 143a. If it is determined that there is an unprocessed pixel (step T203; YES), immediately before An unprocessed pixel (a pixel at the start point at the start of processing) adjacent to the processing direction of the target pixel P processed in step S3 is set as the target pixel P, and the pixel level (input pixel level Pi) is set in the image memory 143. It is read from the input image memory 143a (step T204).

Next, the intermediate generation pixel level Pr of the target pixel P is calculated by (Equation 12) (step T205).
Pr = Pi × {(N−Y) / N} (Formula 12)
The intermediate generation pixel level Pr is stored in the temporary memory 143b.

Next, the pixel level Pi + of the pixel P + adjacent to the pixel of interest P (pixel adjacent to the processing direction, referred to as adjacent pixel P +) is read from the input image memory 143a of the image memory 143 (step T206). Then, a pixel level shift amount Ps from the adjacent pixel P + to the target pixel P is calculated by the following (formula 13) (step T207).
Ps = (Pi +) × (M / N) (Formula 13)
The calculated shift amount Ps is stored in the temporary memory 143b.

Next, the intermediate generation pixel level Pr and the shift amount Ps are read from the temporary memory 143b, and the output pixel level Po of the target pixel P is calculated by the following (Equation 14) (step T208).
Po = Pr + Ps (Formula 14)
The calculated output pixel level Po is stored at a predetermined address in the output image memory 143c (step T209). The predetermined address is an address next to the address at which the pixel level is stored immediately before.

  Next, the variable K is decremented by 1, and the variables Y and M are incremented by 1 (step T210). Then, it is determined whether or not K = 0 (step T211). If it is determined that K = 0 (step T211; YES), the adjacent pixel P + is deleted (step T212). Here, when K = 0 in the determination in step T211, the shift amount Ps calculated in step T207 corresponds to one pixel of the adjacent pixel P +. That is, the pixel level Pi + of the adjacent pixel P + is all shifted to the target pixel P. Therefore, the pixel of the adjacent pixel P + is deleted. After deletion, the process returns to step T202.

On the other hand, if it is determined in step T211 that K = 0 is not satisfied (step T211; NO), the process proceeds to step T203, and the processes in steps T203 to T211 are repeatedly executed. If it is determined in step T203 that there is no unprocessed pixel on the same line of the input image (step T203; NO), level correction according to the scaling factor X is performed (step T204). In the above-described reduction process, the image can be reduced while maintaining the continuity of the image between adjacent pixels, but the range of the output pixel level Po is higher than the range of the input pixel level Pi according to the scaling factor X. For example, in the reduction process of 10%, it increases to 110%. Therefore, the increase in the pixel level is restored by performing level correction according to the magnification X. Specifically, the output pixel level Po of each pixel is multiplied by N / (N + 1). Further, since there is no pixel level to be shifted for the last pixel (terminal pixel) to be processed, a necessary level shift is supplemented.
In general, since a reduction ratio is 1% or less in a scaling process as a measure against heat shrinkage, the correction amount is also 1% or less. Therefore, in this case, since the influence on the image quality is slight, depending on the use of the printed matter, it is often unnecessary to perform level correction except for the end pixel. Therefore, the operation display unit 102 may be configured to allow the user to set whether or not level correction is performed.
When the level correction ends, the reduction process ends.

FIG. 9 is a diagram schematically showing an enlargement process when the scaling factor X (reduction ratio) is 10% and the number of pixels in one line is 100. In the description of FIG. 9, description will be made assuming that the nth pixel is Pn, the input pixel level of the nth pixel is Pin, the intermediate generation pixel level is Prn, and the output pixel level is Pon.
If the number of pixels in one line is 100 and the scaling factor is 10%, the number of divisions is set to 10 because if the pixels are deleted in a cycle of 10 pixels, the reduction is 10%.
First, the input pixel level Pi1 of the first pixel P1 is divided by the division number 10, and the shift amount from the second pixel P2 (input pixel level Pi2 × 2/10 of the second pixel P2) is added to 9/10 thereof. Is done. The pixel level obtained by adding the shift amount from the second pixel P2 is set as the output pixel level Po1 of the first pixel P1.
Since the pixel level of the second pixel P2 is shifted 2/10 to the first pixel P1, it becomes Pi2 × 8/10 (intermediate generation pixel level Pr2). A shift amount from the third pixel P3 (input pixel level Pi3 × 3/10 of the third pixel P3) is added to the intermediate generation pixel level Pr2 to obtain an output pixel level Po2 of the second pixel.
When the above processing is performed while sequentially shifting the target pixel to the next, the tenth pixel P10 is shifted to 10/10 of the tenth pixel P10, that is, all pixel levels. Therefore, the tenth pixel P10 is deleted. This deletion of the tenth pixel completes the 10% reduction.
When the above process is repeated until the other end of the input image is reached, an output image reduced by 10% in the scanning line direction is obtained.

In the reduction process, the pixel level is divided by the number of divisions corresponding to the scaling factor X, and a part of the divided pixel level is sequentially shifted to the adjacent pixel in a certain direction. If this is repeated, a pixel whose shift amount to the adjacent pixel is one pixel appears for each division number. Therefore, by deleting this pixel, the input image can be reduced at the scaling factor X. In this reduction process, data continuity between adjacent pixels is ensured by shifting a part of the divided pixel level to a neighboring pixel in a certain direction. Since the pixel level of the pixel to be deleted has been shifted to the adjacent pixel, it is possible to output an image with good reproducibility that suppresses the generation of patterns, noise, and image roughness due to deletion.
It should be noted that the pixel level is not shifted between one adjacent pixel of the deleted pixel and the other adjacent pixel, but the pixel level of the deleted pixel is shifted to one adjacent pixel. Therefore, the continuity of data with the other adjacent pixel is maintained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
Since the configuration of the image forming apparatus 1 in the second embodiment is the same as that of the first embodiment, the description is incorporated herein.

  In the second embodiment, the enlargement processing flow is different among the scaling processing executed in the scaling processing unit 142 of the image processing unit 104. Here, in the enlargement process (referred to as the first enlargement process) described in the first embodiment, an error occurs in the magnification. This error is not a problem if the enlargement ratio is very small, but if the enlargement ratio exceeds a certain level, the error cannot be ignored. Therefore, in the second embodiment, when the scaling factor X is equal to or greater than a predetermined threshold value (here, 1%), processing different from the enlargement processing of the first embodiment (second processing) (Enlargement process) is executed, and an output image with no error in enlargement ratio is generated.

FIG. 10 shows a flowchart of the enlargement process (referred to as enlargement process B) in the scaling processing unit 142 in the second embodiment.
First, it is determined whether or not the scaling factor X (enlargement ratio) is 1% or more (step A101). If it is determined that the scaling factor X is not 1% or more (step A101; NO), the first enlargement process is executed (step A102). Since the first enlargement process is the same as that described with reference to FIG. 6 in the first embodiment, the description is incorporated. If it is determined that the magnification X is 1% or more (step A101; YES), the second enlargement process is executed (step A102).

FIG. 11 shows a flowchart of the second enlargement process. Hereinafter, the second enlargement process will be described.
In the second enlargement process, a loop process (steps T303 to T310) is performed for each pixel number (K) of the division number N calculated based on the scaling factor X, and the pixel level is sequentially applied to pixels adjacent in a certain direction. Some are shifted. When the number of pixels to be shifted becomes one pixel, exception processing for adding additional pixels is performed (steps T312 to T314). Then, the next loop is executed. This process is executed while sequentially moving the target pixel from one end of the input image toward the other end. Hereinafter, the flow of the second enlargement process will be described in detail.

First, the division number N at the pixel level is calculated based on the obtained scaling factor X (step T301). Specifically, it is calculated by (Equation 21).
N = 100 / X (Formula 21)
According to (Equation 21), N can be calculated so that the enlargement of the scaling factor X can be performed when one pixel is added for each pixel period of the division number N. For example, when 10% enlargement is performed, if 1 pixel is added at a cycle of 100/10 = 10 pixels, the enlargement can be 10%.

  Next, initial setting of each value used in the enlargement process is performed (step T302). That is, 1 is set to the variable Y of the temporary memory 143b, 0 is set to the variable M, N is set to the variable K, and 0 is set to the shift amount Ps.

  Next, it is determined whether or not there is an unprocessed pixel on the same line of the input image stored in the input image memory 143a. If it is determined that there is an unprocessed pixel (step T303; YES), An unprocessed pixel (a pixel at the processing start point) adjacent to the processing direction side of the pixel processed as the target pixel P is set as the target pixel P, and the pixel level Pi (input pixel level Pi) is stored in the image memory 143. It is read from the input image memory 143a (step T304).

  Next, the shift amount Ps is read from the temporary memory 143b (step T305), the shift amount Ps is added to the input pixel level Pi of the target pixel P, and a pixel level after shifting (referred to as an intermediate generation pixel level) Pr is obtained. (Step T306). The intermediate generation pixel level Pr is stored in the temporary memory 143b.

Next, the intermediate generation pixel level Pr is read from the temporary memory 143b, and the output pixel level Po of the target pixel P is calculated by the following (Equation 22) (step T307).
Po = Pr × {(N−1) / (N + M)} (Formula 22)
The calculated output pixel level Po is stored at a predetermined address in the output image memory 143c (step T308). The predetermined address is an address next to the address at which the pixel level is stored immediately before.

Next, the pixel level to be shifted from the target image P to the pixel adjacent to the processing direction, that is, the shift amount Ps is calculated by the following (Equation 23) (step T309).
Ps = Pr × {Y / (N + M)} (Formula 23)
The calculated shift amount Ps is stored in the temporary memory 143b.

  Next, the variable K is decremented by 1, and the variables Y and M are incremented by 1 (step T310). Then, it is determined whether or not K = 0 (step T311). If it is determined that K = 0 is not satisfied (step T311; NO), the process returns to step T302.

If it is determined that K = 0 (step T311; YES), the shift amount Ps is read from the temporary memory 143b (step T312), and the output pixel level Po of the pixel to be added is calculated by the following (Equation 24). (Step T313).
Po = Ps × {(N−1) / N} (Formula 24)
The calculated output pixel level Po is stored at a predetermined address in the output image memory 143c as the output pixel level of the additional pixel (step T314), and the process returns to step T302. The predetermined address is an address next to the address at which the pixel level is stored immediately before.

When the processing up to the other pixel of the input image is completed and it is determined in step T303 that there are no unprocessed pixels on the same line (step T303; NO), level correction according to the magnification X is performed. (Step T315). Here, in the above-described second enlargement process, the range of the output pixel level is lower than the range of the input pixel level according to the scaling factor X. For example, in the enlargement process of 10%, it decreases to 90%. Therefore, the reduction of the pixel level is restored by performing level correction according to the magnification X. Specifically, the output pixel level of each pixel is multiplied by N / (N−1).
When the level correction ends, the second enlargement process ends.

FIG. 12 is a diagram schematically illustrating a second enlargement process when the scaling factor X is 10% and the number of pixels in the main scanning direction is 100. In the description of FIG. 11, description will be made assuming that the nth pixel is Pn, the input pixel level of the nth pixel is Pin, the intermediate generation pixel level is Prn, and the output pixel level is Pon.
When the number of pixels in one line is 100 and the scaling factor X is 10%, if an additional pixel appears in a 10-pixel cycle, the enlargement process is 10%, and the division number N is set to 10.
First, the input pixel level Pi1 of the first pixel P1 is divided by the division number 10, and 1/10 of the input pixel level Pi1 is shifted to the second pixel P2. The output pixel level Po1 of the first pixel P1 is converted to 9/10 obtained by subtracting the shift amount from the input pixel level Pi1.
When the shift amount 1/10 from the first pixel P1 is added, the pixel level of the second pixel P2 becomes Pi2 + Pi1 × 1/10 (intermediate generation pixel level Pr2). Since this intermediate generation pixel level Pr2 receives the pixel level of 1/10 from the first pixel P1, the number of divisions is 11, and Pr2 × 9/11 is the output pixel level Po2 of the second pixel P2. . Thereby, the range of the pixel level (range of possible minimum value to maximum value) can be made uniform between the pixels. The level of Pr2 × 2/11 minutes is shifted to the third pixel.
When the above processing is performed while sequentially shifting the target pixel to the next, the shift amount Pr10 × 10/19 becomes one pixel in the tenth pixel P10. Therefore, the Pr10 × 10/19 pixel is added to the 10 + 1st. The addition of the 10 + 1st pixel completes 10% zooming.
Thereafter, when the above process is repeated from the eleventh pixel P1 until the other end of the input image is reached, an output image enlarged by 10% in the scanning line direction is obtained.

  In the second enlargement process, enlargement can be performed without error of the variable magnification X. Here, in the second enlargement process, the pixel level is not shifted from the additional pixel to the adjacent pixel. However, since the additional pixel is the pixel whose pixel level to be shifted to the pixel adjacent to the processing direction side is the smallest (that is, it hardly affects the generation of the next additional pixel), the influence on the image quality is minimized. It is done.

  As described above, according to the image forming apparatus 1 in the first and second embodiments, the scaling processing unit 142 determines the pixel level of each pixel of the input multi-value digital image signal according to the scaling factor. The number of divisions is divided, and a part of the divided pixel signal values is sequentially shifted to adjacent pixels in a fixed direction, whereby pixels are added or deleted, and an image corresponding to the scaling factor is generated.

  Therefore, since it is possible to perform scaling while ensuring the continuity of data between adjacent pixels, it is possible to provide a highly reproducible image with reduced noise and image roughness even when scaling is performed. Can do.

  In addition, the range of the input pixel level and the output pixel level can be made uniform by correcting the pixel level of each pixel that has been increased or decreased due to a partial shift of the divided pixel level.

  In particular, in an LED print head type image forming apparatus that writes to a photoconductor for each pixel, noise and image roughness due to scaling processing are problems. It is possible to output a scaled image without roughness.

  Note that the descriptions in the first and second embodiments show a preferred example of the image forming apparatus 1 according to the present invention, and the present invention is not limited to this.

  For example, in the enlargement process and the reduction process, as shown in FIGS. 13A and 13B, any one end of the input image may be set as the start point of the process. Further, as shown in FIG. 13C, the processing can be started from an arbitrary pixel as long as the processing proceeds toward the edge of the image. However, as shown in FIG. 13 (d), if processing is started from both ends, the continuity of data is not maintained between the end points of both processing, and there may be a difference in pixel level, which is not preferable. .

  In the above description, an example in which a non-volatile memory, a hard disk, or the like is used as a computer-readable medium of the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also applied as a medium for providing program data according to the present invention via a communication line.

  In addition, the detailed configuration and detailed operation of each device can be changed as appropriate without departing from the spirit of the present invention.

1 Image forming apparatus 101 CPU
102 Operation Display Unit 103 Image Reading Unit 104 Image Processing Unit 141 Color Conversion Unit 142 Scaling Processing Unit 143 Image Memory 143a Input Image Memory 143b Temporary Memory 143c Output Image Memory

Claims (5)

In an image forming apparatus that forms an image based on an input multi-value digital image signal,
A scaling processing unit for performing scaling processing on the input multi-value digital image signal in units of scanning lines, and dividing the pixel signal value of each pixel of the input multi-value digital image signal according to a scaling factor A scaling unit that adds or deletes pixels by sequentially shifting a part of the divided pixel signal values to adjacent pixels in a certain direction, and generates an image according to the scaling factor. Image forming apparatus.   The image forming apparatus according to claim 1, further comprising: a correction processing unit that corrects a level of a pixel signal value of each pixel that is increased or decreased due to a partial shift of the divided pixel signal value. An image forming unit that forms an image by electrophotography based on the input multi-value digital image signal,
The image forming apparatus according to claim 1, wherein the image forming unit includes a print head that forms a latent image on a photosensitive member by causing an exposure element to emit light based on the scaled image. An image processing method for performing image processing on an input multi-value digital image signal in units of scanning lines,
Dividing the pixel signal value of each pixel of the input multi-valued digital image signal by the number of divisions according to the scaling factor;
Adding or deleting pixels by sequentially shifting a part of the divided pixel signal values to adjacent pixels in a certain direction, and generating an image according to the scaling factor;
An image processing method including: A computer that processes an input multi-value digital image signal in units of scanning lines,
The pixel signal value of each pixel of the input multi-value digital image signal is divided by the number of divisions according to the scaling factor, and a part of the divided pixel signal value is sequentially shifted to adjacent pixels in a certain direction. A scaling process unit that adds or deletes pixels and generates an image according to the scaling ratio,
Program to function as.

Images