JP2021048578A - Image processing apparatus, image processing method, and program - Google Patents

Abstract

To prevent a deterioration in image quality due to magnification varying processing.SOLUTION: An image processing apparatus of an embodiment provides an apparatus that processes image data for forming an image on a surface of a photoreceptor by using a plurality of light emitting devices arranged along a main scanning direction of the photoreceptor. The image processing apparatus has: specification means that, based on an image magnification for varying a magnification in a main scanning direction of an image that is formed from image data by inserting or deleting pixels into or from the image data, specifies a reference section for determining first and second insertion/withdrawal positions at which the insertion or deletion of the pixels is performed; first determination means that determines the first insertion/withdrawal position based on the reference section specified by the specification means; second determination means that determines the second insertion/withdrawal position based on the first insertion/withdrawal position; and magnification varying means that varies the magnification of the image by inserting the pixels into or deleting the pixels from the image data based on the first and second insertion/withdrawal positions.SELECTED DRAWING: Figure 7

Description

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

In a tandem color image forming apparatus, as an exposure means provided for each color and forming an electrostatic latent image on the outer peripheral surface of a photoconductor, a plurality of LED arrays in which a large number of LEDs (Light Emitting Diodes) are arranged in an array are provided. Equipped line heads are known. In the line head, the LED array thermally expands due to the heat generated by the LED array itself and the drive IC, and the heat from the fixing device arranged around the line head, and the LED array shifts to the exposure position in the main scanning direction (LED arrangement direction). May occur, and the magnification in the main scanning direction may change for each color. This causes a relative positional shift and eventually a color shift when the toner images of each color such as yellow, magenta, cyan, and black are superimposed and transferred.

Patent Document 1 describes by executing an insertion process / thinning process (hereinafter, the insertion process and the thinning process are collectively referred to as an insertion / extraction process) in which one pixel randomly selected for a predetermined number of pixels is inserted or thinned out. , Discloses a method for enlarging and reducing printed image information.

An image forming apparatus equipped with a line head in which a large number of LEDs are arranged in a line shape as a writing optical system drives the LEDs based on a multi-valued digital image signal and records pixels having a density corresponding to the signal. It is configured to be formed on a medium. In an image forming apparatus having such a configuration, the pixel width cannot be adjusted unlike an image forming apparatus equipped with a laser as a writing optical system. It is executed in units of LEDs.

Japanese Unexamined Patent Publication No. 2012-124584

However, if the insertion / removal process is executed at a resolution corresponding to the LED arrangement interval, a visible step may occur in the image formed on the recording medium. On the other hand, if the insertion / extraction process is executed at a resolution higher than the resolution corresponding to the LED arrangement interval, the phase of the image deviates from the phase of the LED arrangement, and the image quality deteriorates. Such a problem may occur not only when an LED is used as a light emitting element of a line head but also when an organic EL (Electro Luminescence) element is used.

The present invention provides a technique for suppressing deterioration of image quality due to scaling processing.

The image processing apparatus according to one aspect of the present invention uses a plurality of light emitting elements arranged along the main scanning direction of the photoconductor to process image data for forming an image on the surface of the photoconductor. The apparatus is based on the scaling factor of an image in which the image formed from the image data is scaled in the main scanning direction by inserting or deleting the pixels in the image data. Based on the specific means for specifying the reference section L for determining the first insertion / extraction position and the second insertion / removal position for inserting or deleting the pixel, and the reference section L specified by the specific means. A first determining means for determining the first insertion / extraction position and a second determining means for determining the second insertion / extraction position based on the first insertion / extraction position determined by the first determining means. And a scaling means for scaling the image by inserting or deleting pixels in the image data based on the first insertion / extraction position and the second insertion / extraction position. It is characterized by.

According to the present invention, deterioration of image quality due to scaling processing can be suppressed.

It is a block diagram which shows the structural example of the image forming apparatus. It is sectional drawing of the image forming apparatus. It is a figure which shows the structural example of the LED line head part. It is a figure which shows the arrangement example of the LED chip and LED. It is a flowchart which shows the flow of a variable magnification process. It is a flowchart which shows the flow of the insertion / removal position determination processing. It is a flowchart which shows the flow of the insertion / removal position determination processing. It is explanatory drawing of the insertion / removal position. It is explanatory drawing of the variable magnification processing. It is explanatory drawing of the variable magnification processing. It is explanatory drawing of the insertion / removal process. It is explanatory drawing of the variable magnification processing. It is explanatory drawing of the insertion / removal process. It is explanatory drawing of the variable magnification processing. It is a flowchart which shows the flow of the insertion / removal position determination processing. It is explanatory drawing of the insertion / removal position. It is explanatory drawing of the variable magnification processing. It is explanatory drawing of the variable magnification processing. It is a figure which shows the potential distribution of the electrostatic latent image formed on the photoconductor drum.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following embodiments do not limit the present invention, and not all combinations of features described in the present embodiment are essential for the means for solving the present invention. In addition, various embodiments that do not deviate from the gist of the present invention are also included in the present invention, and some of the following embodiments can be appropriately combined. The same configuration will be described with the same reference numerals.

<< Embodiment 1 >>
FIG. 1 is a block diagram showing a configuration example related to creating an electrostatic latent image of the electrophotographic color image forming apparatus according to the present embodiment. The color image forming apparatus includes an image forming unit 101 and an image processing unit 102. The image processing unit 102 generates bitmap image information. The image forming unit 101 has a plurality of colors (for example, cyan / magenta / yellow / black; hereinafter referred to as C / M / Y / K) on the recording medium based on the bitmap image information generated by the image processing unit 102. An image is formed by superimposing the toner images of.

<Structure of image forming apparatus>
FIG. 2 is a cross-sectional view of a tandem color image forming apparatus using an intermediate transfer body, which is an example of an electrophotographic image forming apparatus. The operation of the image forming unit 101 in the electrophotographic color image forming apparatus will be described with reference to FIG. In the drawings, the members provided for each color are shown by adding an alpha bed (C / M / Y / K) indicating each color to the end of the code, but the description is given without particularly distinguishing the colors. In this case, the alphabet at the end of the code shall be omitted for explanation.

The image forming unit 101 drives the exposure light according to the exposure time based on the data processed by the image processing unit 102 to form an electrostatic latent image, and further develops the electrostatic latent image to produce a monochromatic toner image. Form. The monochromatic toner images are superposed to form a multicolor toner image, and the multicolor toner image is transferred to the recording medium 11 shown in FIG. 2 to fix the multicolor toner image on the recording medium.

Next, the configuration of the image forming unit 101 will be described in more detail with reference to FIG. The injection charger 23 is for uniformly charging the surface of the photoconductor 22 to a predetermined potential for each color in the order of Y, M, C, and K, and includes a sleeve 23S.

The photoconductor 22 rotates by transmitting the driving force of a drive motor (not shown). A drive motor (not shown) rotates the photoconductor 22 in the counterclockwise direction in FIG. 2 in response to the image forming operation. The exposure means is configured to form an electrostatic latent image by irradiating the photoconductor 22 with exposure light from the LED line head portion 24 and selectively exposing the surface of the photoconductor 22. The exposure means can control the exposure time of the LED line head unit 24 by a light emitting element such as an LED by the PWM unit 113 shown in FIG.

The developing means includes a developing device 26 for visualizing the electrostatic latent image with toner. The developer 26 is provided with a sleeve 26S. Each developer 26 is removable. A monochromatic toner image is developed on the photoconductor 22 by the developer 26.

The intermediate transfer member 28 rotates clockwise in FIG. 2 to receive a monochromatic toner image from the photoconductor 22. A monochromatic toner image is transferred to the intermediate transfer body 28 as the photoconductor 22 and the primary transfer roller 27 located opposite to the photoconductor 22 rotate. By applying an appropriate bias voltage to the primary transfer roller 27 and making a difference between the rotation speed of the photoconductor 22 and the rotation speed of the intermediate transfer body 28, the monochromatic toner image is efficiently transferred onto the intermediate transfer body 28. This is called primary transcription.

Further, the monochromatic toner image for each station of CMYK is superposed on the intermediate transfer body 28. The superimposed multicolor toner image is conveyed to the secondary transfer roller 29 as the intermediate transfer body 28 rotates. Further, the recording medium 11 is sandwiched and conveyed from the paper feed tray 21a or the paper feed tray 21b to the secondary transfer roller 29, and the multicolor toner image on the intermediate transfer body 28 is transferred to the recording medium 11 such as paper. At this time, by applying an appropriate bias voltage to the secondary transfer roller 29, the toner image is electrostatically transferred. This is called secondary transcription. The secondary transfer roller 29 comes into contact with the recording medium 11 at the position 29a while transferring the multicolor toner image onto the recording medium 11, and is separated from the position 29b after the printing process.

The fixing device 31 applies a fixing roller 32 for heating the recording medium 11 and a fixing roller 32 for pressing the recording medium 11 against the fixing roller 32 in order to melt and fix the multicolor toner image transferred to the recording medium 11 on the recording medium 11. A pressure roller 33 is provided. The fixing roller 32 and the pressure roller 33 are formed in a hollow shape, and heaters 34 and 35 are built in, respectively. The fixing device 31 conveys the recording medium 11 holding the multicolor toner image by the fixing roller 32 and the pressure roller 33, and applies heat and pressure to fix the toner on the recording medium 11.

The recording medium 11 after the toner is fixed is then discharged to a paper discharge tray (not shown) by a discharge roller (not shown), and the image forming operation is completed. The cleaning means 30 cleans the toner remaining on the intermediate transfer body 28, and the waste toner remaining after transferring the four-color multicolor toner image formed on the intermediate transfer body 28 to the recording medium 11 is used. , Stored in a cleaner container.

<Configuration of LED line head>
Next, the configuration of the LED line head portion included as a unit of the writing optical system in the color image forming apparatus will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing a configuration example of the LED line head unit 24. FIG. 4 is a diagram showing an arrangement example of the LED chip and the LED.

The LED line head portion 24 is arranged so as to face the peripheral surface of the photoconductor 22. The LED line head portion 24 includes a printed circuit board 40, a plurality of LED chips 42 mounted on the surface of the printed circuit board 40 and arranged along the main scanning direction in the rotation axis direction of the photoconductor 22, and a lens array 41. Have. The printed circuit board 40 is formed with a circuit (not shown) for supplying various signals for controlling the drive of the LED line head unit 24.

As shown in FIG. 4, each LED chip 42 is configured by arranging a large number (for example, 512) of LEDs 43 having the same size in a line along the main scanning direction at equal intervals. That is, the LED 43, which is a plurality of light emitting elements, is arranged along the rotation axis direction of the photoconductor 22. The plurality of LED chips 42 are overlapped in a direction along the main scanning direction, for example, a row of light emitting elements arranged in one row and an LED 43 at an end in the main scanning direction are overlapped in a sub-scanning direction orthogonal to the main scanning direction. It may be a row of light emitting elements having a staggered arrangement of two rows. In FIG. 4, the plurality of LED chips 42 are arranged in a state in which two LEDs 43 at the ends in the main scanning direction overlap each other in the sub scanning direction. As the LED chip 42, for example, a self-scanning LED (SLED: Self-scanning LED) array chip is used, but the LED chip 42 is not limited thereto. The LED chip 42 can also be a light emitting element array in which light emitting elements such as LEDs and organic EL elements are arranged in a direction along the main scanning direction.

The lens array 41 is a device that is arranged between the LED chip 42 and the photoconductor 22 and functions as an imaging lens. In the lens array 41, LED refractive index distribution type rod lenses 41a are arranged at a pitch corresponding to each pixel according to the resolution, for example, and the light beam emitted from each LED 43 is imaged on the photoconductor 22. ..

As described above, the LED line head portion 24 has a large number of LEDs 43 arranged in the main scanning direction. In each LED 43, the distance between the centers of adjacent LEDs in the direction along the main scanning direction is set to about 21.15 μm. Therefore, the LED line head unit 24 has an output resolution (first resolution) of 1200 dpi (dot per inch) in the main scanning direction.

<Variable magnification processing in the main scanning direction>
Next, the scaling process in the main scanning direction of the LED line head unit 24 will be described.

The printed circuit board 40 thermally expands due to the heat generated by the LED chip 42 and the drive IC (not shown) and the heat from the fixing device, etc., causing a positional shift in the main scanning direction, and the main scanning direction (the arrangement direction of the LEDs 43 of the LED chip 42). ) May change for each color. In order to suppress the deterioration of image quality due to the change in the magnification in the main scanning direction, it is necessary to correct the change in the magnification in the main scanning direction.

Hereinafter, the correction of the change in the magnification in the main scanning direction is simply referred to as “magnification processing”.

<Processing details of image processing unit 102>
Next, the processing of the image processing unit 102 in the color image forming apparatus will be described in detail with reference to FIG.

The image processing unit 102 includes an image generation unit 104, a color conversion processing unit 105, a storage unit 106, an enlargement processing unit 107, an HT processing unit 108, a scaling processing unit 109, a main scanning resolution conversion unit 110, a storage unit 111, and a PWM unit. It has 113, a CPU 201, a RAM 202, and a ROM 203. Each component of the image processing unit 102 is connected to each other by an internal bus 204, which is a system bus connecting the units.

The CPU (Central Processing Unit) 201 controls the entire image processing unit 102 using programs and data stored in the RAM 202 and the ROM 203.

The RAM (Random Access Memory) 202 includes a work area used by the CPU 201 to execute various processes.

The ROM (Read Only Memory) 203 stores programs and data for causing the CPU 201 to execute various processes described later, setting data of the image processing unit 102, and the like.

Part or all of each of the parts 104 to 111 and 113 of the image processing unit 102 shown in FIG. 1 can be realized by dedicated hardware. Alternatively, a part or all of the parts 104 to 111 and 113 can be realized by the CPU 201 expanding the program stored in the ROM 203 into the RAM 202 and executing the program.

The image generation unit 104 generates raster image data that can be printed based on print data received from a computer device (not shown) or the like, and outputs it as RGB data for each pixel. The image generation unit 104 has a reading device provided inside the color image forming device instead of the image data received from a computer device or the like, and reads the surface of the recording medium by the reading device inside the color image forming device. The configuration may be such that the obtained image data is handled. The reading device is, for example, a device including a CCD (Chaerged Couple Device) or a CIS (Control Image sensor), and may be a device having a processing unit that performs predetermined image processing on the read image data. .. Further, the reading device may not be configured inside the color image forming device, but may be configured to receive data from a reading device outside the color image forming device via an interface (not shown). In the present embodiment, the case where the resolution of the image data is 600 dpi × 600 dpi will be described as an example. However, the resolution of the image data is not limited to this, and the resolution of the image data may be 1200 dpi × 1200 dpi or 2400 dpi × 2400 dpi.

The color conversion processing unit 105 converts the RGB data into CMYK data according to the toner color of the image forming unit 101, and stores the CMYK data in the storage unit 106.

The storage unit 106 is a first storage unit included in the image processing unit 102, and temporarily stores raster image data to be printed. The storage unit 106 may be used as a page memory for storing image data for one page, or may be used as a band memory for storing data for a plurality of lines. The data stored in the storage unit 106 is read from the storage unit 106 in page units or line units in accordance with instructions from the enlargement processing unit 107, the HT processing unit 108, the scaling processing unit 109, and the main scanning resolution conversion unit 110. It is taken out and processed by each processing unit.

The enlargement processing unit 107 simply enlarges the CMYK data of 600 dpi × 600 dpi to the CMYK data of 2400 dpi × 2400 dpi. The enlargement processing unit 107 executes, for example, a process of simply enlarging CMYK data having a resolution of 600 dpi × 600 dpi and 8 bits (256 gradations) into CMYK data having a resolution of 2400 dpi × 2400 dpi and 8 bits (256 gradations). To do.

The HT processing unit 108 performs a half toning process on the image data of each color (for example, an 8-bit 256 gradation image) enlarged by the enlargement processing unit 107, and sets the input gradation to a pseudo intermediate as represented by the dither method. Conversion to a key (for example, two gradations) expression is performed. For example, the HT processing unit 108 executes half toning processing on CMYK data having a resolution of 2400 dpi × 2400 dpi and 8 bits (256 gradations), and has a resolution of 2400 dpi × 2400 dpi and 1 bit (2 gradations). Convert to the data of.

The scaling processing unit 109 executes scaling processing on the input image data according to the scaling factor to be corrected. The scaling process executed here is the above-mentioned correction process for changing the magnification in the main scanning direction. Details will be described later. The scaling processing unit 109 executes the scaling processing at least between 99.00% and 101.00%. The magnification is 100.00% to 101.00%. The reduction ratio is 99.00% to 100.00%. Both the enlargement ratio and the reduction ratio can be set in increments of 0.01%, for example.

The main scanning resolution conversion unit (hereinafter referred to as resolution conversion unit) 110 corresponds to the resolution (2400 dpi) in the main scanning direction of the image data input from the scaling processing unit 109 to the arrangement interval of the LEDs 43 of the LED line head unit 24. Convert to resolution (1200 dpi). At this time, the resolution in the main scanning direction is 2400 dpi, and the resolution in the main scanning direction is 1200 dpi, and the 1-pixel data of 2 bits (4 gradations) is generated from the 2-pixel data of 1 bit (2 gradations). For example, when both pixels are white, the resolution conversion unit 110 converts the pixel value of one pixel data of 1200 dpi to 0. When even one of the two pixels has a black pixel, the resolution conversion unit 110 converts the pixel value of one pixel data of 1200 dpi to 1. When both of the two pixels are black pixels, the pixel value of the 1200 dpi 1-pixel data is converted to 2. The conversion method is not limited to this, and the average or the logical sum with the adjacent pixels may be derived and converted into the derived result.

The storage unit 111 is a second storage unit included in the image processing unit 102, and stores image data that has undergone resolution conversion processing in the main scanning direction by the resolution conversion unit 110.

The pulse width modulation (PWM) unit 113 converts the image data for each color read from the storage unit 111 into a signal indicating the exposure time of the LED line head unit 24 corresponding to each color. The exposure time signal, which is the converted image data generated by the PWM unit 113, is output to the LED line head unit 24 of the image forming unit 101 corresponding to each color of CMYK.

The LED line head unit 24 causes the LED 43 to emit light based on the pulse width-modulated exposure time signal, and exposes the photoconductor 22 to light.

The temperature sensor 116 measures the temperature inside the LED line head portion 24 or in the vicinity of the LED line head portion 24. As the temperature sensor 116, for example, a thermistor is used. The measurement data obtained by the measurement by the temperature sensor 116 is output to the image processing unit 102 as analog data. In the image processing unit 102, the measurement data is A / D converted, and as a result of the conversion, the temperature inside the LED line head unit 24 is recognized as digital data (hereinafter, also referred to as temperature data). The image processing unit 102 derives the variable magnification based on the temperature data. The details of the method for deriving the variable magnification will be described later.

In the present embodiment, the variable magnification is derived from the temperature data based on the measurement data obtained by the temperature sensor, but the method for deriving the variable magnification is not limited to this. For example, a correction patch may be output from the image forming apparatus 101, the amount of deviation between colors may be measured by the output patch, and the variable magnification may be derived based on the measurement result.

<Driving method of variable magnification>
Next, a method of deriving the variable magnification from the temperature data will be described.

First, it is assumed that the maximum paper size that can be printed by the image forming apparatus of the present embodiment is A3 (297 mm × 420 mm), and the maximum length in the main scanning direction is 297 mm. In the present embodiment, it is assumed that even if the maximum paper size A3 is passed through, the back side and the front side are each outside the 16.5 mm image area. That is, it is assumed that the length in the main scanning direction in which the pattern can be created is 330 mm.

When the printed circuit board 40 of the LED line head portion 24 is glass epoxy, which is a general substrate material, the coefficient of linear expansion of the glass epoxy is about 20 [10 ^-6 / ° C]. In this embodiment, a case where the coefficient of linear expansion α is 20 × 10 ^-6 / ° C. will be described as an example.

The amount of thermal expansion of the printed circuit board 40 can be derived based on the following equation (1), which is a relational expression between the coefficient of linear expansion, the amount of temperature change, and the length. As an example, when the length of the printed circuit board 40 is 330 mm and the temperature rises by 20 ° C., the formula (1) can be expressed as the following formula (2).
Thermal expansion = linear expansion coefficient x temperature change x length (mm) x μm conversion ... (1)
Coefficient of thermal expansion = (20 x 10 ^-6 ) x 20 x 330 x 10 ³ ... (2)
= 132 μm

Based on the above formula (2), 132 μm is derived as the amount of thermal expansion of the printed circuit board 40.

The coefficient of expansion can be derived based on the following equation (3), which is a relational expression between the amount of thermal expansion and the length of the substrate. When the amount of thermal expansion is 132 × 10 ^-6 and the length of the substrate is 330, the equation (3) can be expressed as the following equation (4).
Expansion rate = (thermal expansion amount / substrate length) x 100 ... (3)
Expansion rate = (132 x 10 ^-6/330 ) x 100 ... (4)
= 0.04 (%)

Based on the above formula (4), 0.04% is derived as the thermal expansion coefficient of the printed circuit board 40.

Therefore, since the expansion coefficient when the temperature rises by 20 ° C. is 0.04%, it is necessary to correct it at a variable magnification of 0.04%.

The CPU 201 derives the expansion coefficient (variable magnification) based on the temperature data, and notifies the variable magnification processing unit 109 of the variable magnification.

<Flowchart of variable magnification processing>
FIG. 5 is a flowchart showing the flow of the scaling process in the present embodiment. The process shown in FIG. 5 is realized by the CPU 201 reading the control program stored in the ROM 203, expanding it into the RAM 202, and executing this by the CPU 201. Alternatively, some or all of the functions of the steps in FIG. 5 may be realized by hardware such as an ASIC or an electronic circuit. It is assumed that the storage unit 106 stores the data after the HT processing obtained by the HT processing unit 108. The symbol "S" in the description of each process means that it is a step in the flowchart (the same applies in the present specification). Hereinafter, a description will be given with reference to FIGS. 1 and 5.

First, in S501, the scaling processing unit 109 executes the parameter initialization processing. The parameter initialization process resets the parameters xi, yi, xo, and yo that represent the coordinate positions of the halftone image before and after the scaling process, and sets each of the parameters xi, yi, xo, and yo to 0. is there. The parameter xo represents the coordinate position in the main scanning direction in the halftone image plane after the scaling process, and is expressed as the main scanning position xo in the following description. The parameter yo is the same as the parameter xo, and the parameter yo represents the coordinate position in the sub-scanning direction in the halftone image plane after the scaling process, and is expressed as the sub-scanning position yo in the following description. To. The parameter xi represents the coordinate position in the main scanning direction in the halftone image plane before the scaling process, and is expressed as the main scanning position xi in the following description. The parameter yi is the same as the parameter xi, and the parameter yi represents the coordinate position in the sub-scanning direction in the halftone image plane before the scaling process, and is expressed as the sub-scanning position y in the following description. Will be done. Further, the scaling processing unit 109 determines the output size in the main scanning direction (also referred to as the main scanning output size) derived by the CPU 201 based on the input image data and the variable magnification with respect to the image data for one page to be processed. get. The variable magnification processing unit 109 acquires the output size in the sub-scanning direction (also referred to as the sub-scanning output size) derived from the input image data by the CPU 201.

In S502, the scaling processing unit 109 executes the insertion / removal position determination process. The details of the insertion / removal position determination process will be described with reference to FIGS. 6, 7, and 8. The detailed flow of the insertion / removal position determination process in S502 is shown in FIG. 6 for a comparative example and in FIG. 7 for the present embodiment. By executing the insertion / removal position determination process, the insertion / extraction position in the line of interest is determined.

<Flowchart of insertion / removal position determination process of comparative example>
Subsequently, the details of the insertion / removal position determination process (S502) of the comparative example will be described with reference to FIGS. 6 and 8. FIG. 6 is a flowchart showing the flow of the insertion / removal position determination process of the comparative example. FIG. 8 is an explanatory diagram of an insertion / extraction position to be an insertion / extraction process, which is determined by the insertion / extraction position determination process. FIG. 8A is an explanatory diagram of the insertion / extraction position determined by the insertion / extraction position determination process of the comparative example. In the insertion / extraction position determination process of the comparative example, all the insertion / extraction positions are determined by the same method regardless of the odd-numbered and even-numbered insertion / extraction positions. In FIG. 8A, the coordinates painted with diagonal lines represent the insertion / extraction positions. Note that FIG. 8B is an explanatory diagram of the insertion / extraction position determined by the insertion / extraction position determination process of the present embodiment. The details of the insertion / removal position determination process of this embodiment will be described later.

First, in S601, the scaling processing unit 109 derives the insertion / extraction cycle L and the number of insertion / extraction IN based on the scaling set by the notification from the CPU 201. The insertion / extraction period L indicates a section that serves as a reference for determining the insertion / extraction coordinates described later. The insertion / removal period L can be derived based on the following equation (5), which is a relational expression with the magnification. Here, a case where the correction of the magnification of 10% is performed will be described. When the magnification is 0.1, the equation (5) can be expressed as the following equation (6).
Insertion / extraction cycle L = 1 / magnification ・ ・ ・ (5)
Insertion / extraction cycle L = 1 / 0.1 ... (6)
= 10 (pixels)

Based on the above equation (6), 10 pixels are derived as the insertion / extraction period L.

Next, the scaling processing unit 109 derives the number of insertions / extractions IN by using the insertion / extraction period L derived based on the above equation (5) and the number of pixels in the main scanning direction in the image data for one page to be processed. To do. The number of insertions / extractions IN can be derived based on the following equation (7), which is a relational expression between the insertion / extraction period and the number of pixels in the main scanning direction. Here, as shown in FIG. 8A, in the comparative example, a case where the number of pixels in the main scanning direction is 48 pixels will be described. When the number of pixels in the main scanning direction is 48 and the insertion / extraction period L is 10 (pixels), the equation (7) can be expressed as the following equation (8).
Number of insertions / extractions IN = number of pixels in the main scanning direction / insertion / extraction period L ... (7)
Number of insertions and removals IN = 48/10 ・ ・ ・ (8)
= 4 (times)

Based on the above equation (8), 4 times are derived as the number of insertions / removals IN. That is, when the insertion / extraction period L is 10 (pixels), the insertion / extraction process is executed four times for an image having 48 pixels in the main scanning direction.

In S602, the scaling processing unit 109 initializes the parameter i. This parameter i is a number assigned to the insertion / extraction position in order from the upstream side (left side in FIG. 8A) in the main scanning direction. That is, the parameter i = 1 indicates the first insertion / extraction position from the upstream side in the main scanning direction, and the parameters i = 2, ..., N are the first, ..., (N-1) th insertion / extraction processing, respectively. Indicates the second, ..., Nth insertion / extraction positions from the upstream side in the main scanning direction. n is a natural number. The nth position, which is the last insertion / extraction position in the main scanning direction, corresponds to the number of insertions / extractions IN derived in S601.

In S603, the scaling processing unit 109 determines the basic insertion / extraction coordinates basepos [i], which are the coordinates that serve as the reference for the insertion / extraction coordinates. The basic insertion / extraction coordinates basepos [i] are determined by multiplying the insertion / extraction period L by (i-1) and adding the insertion / extraction start coordinates ST indicating the insertion / extraction start position in the main scanning direction set in advance. That is, the basic insertion / extraction coordinates basepos [i] can be derived based on the following equation (9), which is a relational expression between the insertion / extraction period L, (i-1), and the insertion / extraction start coordinate ST. When the parameter i is 1 and the insertion / extraction start coordinate ST is 3, the equation (9) can be expressed as the following equation (10).
basepos [i] = (insertion / extraction period L × (i-1)) + insertion / extraction start coordinates ST ・ ・ ・ (9)
basepos [1] = (10 x (1-1)) +3 ... (10)
= 3

Based on the above equation (10), 3 is derived as the basic hot-swap coordinates basepos [1] when the parameter i is 1.

As shown in FIG. 8A, the basic hot-swap coordinate basepos [1] is set to 3.

In S604, the scaling processing unit 109 generates a random number random [i] corresponding to the parameter i. As a method for generating a random number sequence, a known method such as the Box-Muller method may be used. The method for generating the random number sequence of the scaling processing unit 109 is not limited to the comparative example.

In S605, the scaling processing unit 109 derives the insertion / extraction coordinates fixpos [i] corresponding to the parameter i based on the basic insertion / extraction coordinates basepos [i] determined in S603 and the random number land [i] generated in S604. .. The insertion / extraction coordinates fixpos [i] are derived by adding the random number random [i] to the basic insertion / extraction coordinates basepos [i]. That is, the insertion / extraction coordinates fixpos [i] can be derived based on the following equation (11), which is a relational expression between the basic insertion / extraction coordinates basepos [i] and the random number random [i]. When the basic hot-swap coordinates basepos [1] are 3 and the random [1] is 3, the equation (11) can be expressed as the following equation (12).
Insertion / extraction coordinates fixpos [i] = basepos [i] + land [i] ... (11)
Insertion / extraction coordinates fixpos [1] = basepos [1] + land [1] ... (12)
= 3 +3
= 6

Based on the above equation (12), 6 is derived as the insertion / extraction coordinates fixpos [1].

Therefore, as shown in FIG. 8A, the insertion / extraction coordinate fixpos [1] is set to 6.

In S606, the scaling processing unit 109 determines whether the parameter i is equal to the number of insertions / extractions IN. When the variable magnification processing unit 109 obtains a determination result that the parameter i is not equal to the number of insertion / extraction IN (NO in S606), the variable magnification processing unit 109 determines that there is an insertion / extraction coordinate fixpos [i] for which the insertion / extraction coordinate has not yet been determined. , The process shifts to S607. In S607, the process of adding 1 to the parameter i is executed. After executing the addition process, the variable magnification processing unit 109 shifts the process to S603. In S603, the scaling processing unit 109 executes a derivation process of the insertion / extraction position corresponding to the parameter after the addition processing, following the insertion / extraction position corresponding to the parameter before the addition processing. On the other hand, when the variable magnification processing unit 109 obtains a determination result that the parameter i is equal to the number of insertion / extraction times IN (YES in S606), the scaling processing unit 109 determines that all the insertion / extraction coordinates fixpos [i] have been determined, and performs this flow. finish. That is, the scaling processing unit 109 executes a series of processes (S603 to S607) for deriving the insertion / extraction coordinates fixpos [i] corresponding to each parameter i until the parameter i becomes equal to the number of insertion / extraction times IN.

In this way, the basic insertion / extraction coordinates basepos [i] and the insertion / extraction coordinates fixpos [i] are derived in the order of the numbers indicated by the parameters i from the first to the nth corresponding to the number of insertions / extractions IN.

The case where the parameter i is 2 in the process of S603 described above will be described. When the parameter i is 2 and the insertion / extraction start coordinate ST is 3, the equation (9) can be expressed as the following equation (13).
basepos [2] = (10 x (2-1)) +3 ... (13)
= 13

Based on the above equation (13), 13 is derived as the basic hot-swap coordinates basepos [2] when the parameter i is 2.

As shown in FIG. 8A, the basic hot-swap coordinates basepos [2] are set to 13.

The case where the parameters i are 2, 3 and 4 in the process of S605 described above will be described. When the basic hot-swap coordinates basepos [2] are 13 and the random [2] is 5, the equation (11) can be expressed as the following equation (14).
Insertion / extraction coordinates fixpos [2] = basepos [2] + land [2] ... (14)
= 13 + 5
= 18

Based on the above equation (14), 18 is derived as the second hot-swap coordinate fixpos [2].

Next, when the basic insertion / extraction coordinates basepos [3] are 23 and the random [3] is 1, the equation (11) can be expressed as the following equation (15).
Insertion / extraction coordinates fixpos [3] = basepos [3] + land [3] ... (15)
= 23 + 1
= 24

Based on the above equation (15), 24 is derived as the third hot-swap coordinate fixpos [3].

Next, when the basic hot-swap coordinates basepos [4] are 33 and the random [4] is 5, the equation (11) can be expressed as the following equation (16).
Hot-swap coordinates fixpos [4] = basepos [4] + land [4] ... (16)
= 33 +5
= 38

Based on the above equation (16), 38 is derived as the fourth hot-swap coordinate fixpos [4].

Therefore, as shown in FIG. 8A, fixpos [2] is set to 18, fixpos [3] is set to 24, and fixpos [4] is set to 38.

<Flowchart of insertion / removal position determination process of this embodiment>
Subsequently, the details of the insertion / removal position determination process (S502) of the present embodiment will be described with reference to FIGS. 7 and 8 (b). FIG. 7 is a flowchart showing the flow of the insertion / removal position determination process of the present embodiment. In FIG. 8B, the coordinates painted with diagonal lines represent the insertion / extraction positions.

In the present embodiment, if the insertion / removal process is executed at the same resolution as the resolution corresponding to the LED arrangement interval, the problem that a step is generated in the resolution conversion process is solved. Further, if the insertion / extraction process is executed at a resolution higher than the resolution corresponding to the LED arrangement interval, the problem that the phase of the image deviates from the phase of the LED arrangement is also solved. Therefore, in the present embodiment, by making the even-numbered insertion / extraction position as close as possible to the previous odd-numbered insertion / extraction position, the LED can be corrected locally with a high resolution, and the LED can be used in a broad sense. The insertion / extraction process is performed at the same resolution as the resolution corresponding to the arrangement interval.

First, in S701, the scaling processing unit 109 derives the insertion / extraction cycle L and the number of insertion / extraction IN based on the scaling set by the notification from the CPU 201. The insertion / extraction period L indicates a section that serves as a reference for determining the insertion / extraction coordinates described later. That is, the insertion / removal cycle L can be said to be the reference section L. The insertion / extraction period L can be derived based on the following equation (17), which is a relational expression with the magnification, as in the case of the comparative example. Here, a case where the correction of the magnification of 10% is performed will be described. When the magnification is 0.1, the equation (17) can be expressed as the following equation (18).
Insertion / extraction cycle L = 1 / magnification ・ ・ ・ (17)
Insertion / extraction cycle L = 1 / 0.1 ... (18)
= 10 (pixels)

Based on the above equation (18), 10 pixels are derived as the insertion / extraction period L. It can be said that 10 pixels are specified as the reference interval L by performing the calculation of the equation (18). That is, when the correction of the magnification of 10% is executed, the insertion / extraction process is executed once every 10 pixels.

Next, the scaling processing unit 109 derives the number of insertions / extractions IN by using the insertion / extraction period L derived based on the above equation (18) and the number of pixels in the main scanning direction in the image data for one page to be processed. To do. The number of insertions / extractions IN can be derived based on the following equation (19), which is a relational expression between the insertion / extraction period and the number of pixels in the main scanning direction. Here, as shown in FIG. 8B, in the present embodiment, a case where the number of main scanning pixels is 48 pixels will be described. When the number of pixels in the main scanning direction is 48 and the insertion / extraction period L is 10 (pixels), the equation (19) can be expressed as the following equation (20).

Number of insertions / extractions IN = number of pixels in the main scanning direction / insertion / extraction period L ... (19)
= 48/10 ・ ・ ・ (20)
= 4 (times)

Based on the above equation (20), 4 times are derived as the number of insertions / removals IN.

In S702, the scaling processing unit 109 initializes the parameter i. Parameter i is a number assigned to the insertion / extraction position in order from the upstream side (left side in FIG. 8B) in the main scanning direction. That is, the parameter i = 1 indicates the first insertion / extraction position from the upstream side in the main scanning direction, and the parameters i = 2, ..., N are the first, ..., (N-1) th insertion / extraction processing, respectively. Indicates the second, ..., Nth insertion / extraction positions from the upstream side in the main scanning direction. n is a natural number. The nth position, which is the last insertion / extraction position in the main scanning direction, corresponds to the number of insertions / extractions IN derived in S701.

In S703, the scaling processing unit 109 determines the basic insertion / extraction coordinates basepos [i], which are the coordinates that serve as the reference for the insertion / extraction coordinates. The basic insertion / extraction coordinates basepos [i] are determined by multiplying the insertion / extraction period L by (i-1) and adding the insertion / extraction start coordinates ST indicating the insertion / extraction start coordinates in the main scanning direction set in advance. That is, the basic insertion / extraction coordinates basepos [i] can be derived based on the following equation (21), which is a relational expression between the insertion / extraction period L, (i-1), and the insertion / extraction start coordinate ST. When the parameter i is 1 and the insertion / extraction start coordinate ST is 3, the equation (21) can be expressed as the following equation (22).
basepos [i] = (insertion / extraction period L × (i-1)) + insertion / extraction start coordinates ST ... (21)
basepos [1] = (10 x (1-1)) +3 ... (22)
= 3

Based on the above equation (22), 3 is derived as the basic hot-swap coordinates basepos [1] when the parameter i is 1.

As shown in FIG. 8B, the basic hot-swap coordinate basepos [1] is set to 3.

In S704, the scaling processing unit 109 determines whether the parameter i is an odd number of reference positions. This is because the method of deriving the hot-swap coordinate fixpos [i] differs depending on whether the parameter i is an odd number or an even number that is not the reference position. When the determination result that the parameter i is odd is obtained, the odd-numbered insertion / extraction coordinates fixpos [i] are derived by adding the random number random [i] to the basic insertion / extraction coordinates basepos [i]. On the other hand, when the determination result that the parameter i is an even number is obtained, the offset value offset, which is a predetermined offset value, is added to the odd-numbered insertion / extraction coordinates fixpos [i-1], which is the previous insertion / extraction coordinates. , The even-numbered insertion / extraction coordinates fixpos [i] are derived.

Therefore, when the variable magnification processing unit 109 obtains a determination result that the parameter i is an odd number (YES in S704), the scaling processing unit 109 shifts the processing to S705. When the variable magnification processing unit 109 obtains a determination result that the parameter i is an even number and not an odd number (NO in S704), the variable magnification processing unit 109 shifts the processing to S707.

In S705, the scaling processing unit 109 generates a random number random [i] corresponding to the parameter i. As a method for generating a random number sequence, a known method such as the Box-Muller method may be used. The method for generating a random number sequence of the scaling processing unit 109 does not limit the present embodiment. The random number land [i] corresponding to the parameter i is, for example, any of 0 to 63 with 63 as the maximum value when the random number is about 100 pixels in the main scanning direction and the variable magnification is ± 1%. A number is generated. Further, when the number of pixels is 48 in the main scanning direction and the variable magnification is 10% as shown in FIG. 8B, a numerical value not exceeding the insertion / extraction period L is generated as the random number rank [i] corresponding to the parameter i. Will be done.

In S706, the scaling processing unit 109 derives the insertion / extraction coordinates fixpos [i] corresponding to the parameter i based on the basic insertion / extraction coordinates basepos [i] determined in S703 and the random number land [i] generated in S705. .. The insertion / extraction coordinates fixpos [i] are derived by adding the random number random [i] to the basic insertion / extraction coordinates basepos [i]. That is, the insertion / extraction coordinates fixpos [i] can be derived based on the following equation (23), which is a relational expression between the basic insertion / extraction coordinates basepos [i] and the random number random [i]. When the basic insertion / extraction coordinates basepos [1] are 3 and the random number random [1] is 3, the equation (23) can be expressed as the following equation (24).
Insertion / extraction coordinates fixpos [i] = basepos [i] + land [i] ... (23)
Insertion / extraction coordinates fixpos [1] = basepos [1] + land [1] ... (24)
= 3 +3
= 6

Based on the above equation (24), 6 is derived as the insertion / extraction coordinates fixpos [1].

Therefore, as shown in FIG. 8B, the insertion / extraction coordinate fixpos [1] is 6.

In S707, the scaling processing unit 109 is an even number based on the odd-numbered insertion / extraction coordinates fixpos [i-1] immediately before the main insertion / extraction coordinates fixpos [i] and the offset value offset. Derivation of the insertion / extraction coordinates fixpos [i] of. The even-numbered insertion / extraction coordinates fixpos [i] are derived by adding the offset value offset, which is a predetermined offset value, to the previous odd-numbered insertion / extraction coordinates fixpos [i-1]. That is, the even-numbered hot-swap coordinate fixpos [i] is the relational expression between the previous odd-numbered hot-swap coordinate fixpos [i-1] and the preset offset value offset (25). Can be derived based on. When the first hot-swap coordinate fixpos [1] immediately before the second hot-swap coordinate fixpos [2] is 6 and the offset is 2, the equation (25) is as shown in the following equation (26). Can be represented.
Insertion / extraction coordinates fixpos [i] = fixpos [i-1] + offset ... (25)
Hot-swap coordinates fixpos [2] = fixpos [2-1] +2 ... (26)
= 6 + 2
= 8

Based on the above equation (26), 8 is derived as the second insertion / extraction coordinate fixpos [2].

Therefore, as shown in FIG. 8B, the second insertion / extraction coordinate fixpos [2] is 8. In the method of the insertion / extraction position determination processing of the comparative example described above, as shown in FIG. 8A, it can be seen that the insertion / extraction positions are arranged at a certain distance. On the other hand, in the method of the insertion / extraction position determination processing of the present embodiment, as shown in FIG. 8B, it can be seen that the even-numbered insertion / extraction positions are arranged at positions close to the odd-numbered insertion / extraction positions. As a result, while locally realizing high-resolution insertion / extraction, scaling processing is realized at the LED arrangement interval in the big picture. The size of the offset value, which is the offset value described above, is sufficiently small that even if the offset value is deviated, the unevenness of the density is not noticeable and cannot be visually recognized, and may be, for example, 10 pixels or less.

In S708, the scaling processing unit 109 determines whether the parameter i is equal to the number of insertions / extractions IN. When the variable magnification processing unit 109 obtains a determination result that the parameter i is not equal to the number of insertion / extraction IN (NO in S708), the variable magnification processing unit 109 determines that there is an insertion / extraction coordinate fixpos [i] for which the insertion / extraction coordinate has not yet been determined. , The process shifts to S709. In S709, the process of adding 1 to the parameter i is executed. After executing the addition process, the variable magnification processing unit 109 shifts the process to S703. In S703, the scaling processing unit 109 executes a derivation process of the insertion / extraction position corresponding to the parameter after the addition processing, following the insertion / extraction position corresponding to the parameter before the addition processing. On the other hand, when the variable magnification processing unit 109 obtains a determination result that the parameter i is equal to the number of insertion / extraction times IN (YES in S708), the scaling processing unit 109 determines that all the insertion / extraction coordinates fixpos [i] have been determined, and performs this flow. finish. That is, the scaling processing unit 109 executes a series of processes (S703 to S709) for deriving the insertion / extraction coordinates fixpos [i] corresponding to each parameter i until the parameter i becomes equal to the number of insertion / extraction times IN.

In this way, the basic insertion / extraction coordinates basepos [i] and the insertion / extraction coordinates fixpos [i] are derived in the order of the numbers indicated by the parameters i from the first to the nth corresponding to the number of insertions / extractions IN.

The case where the parameter i is 3 in the process of S706 described above will be described. When the basic insertion / extraction coordinates basepos [3] are 23 and the random [3] is 1, the above equation (23) can be expressed as the following equation (27). The basic insertion / extraction coordinates basepos [3] are derived by substituting 10 for the insertion / extraction period L, 3 for i, and 3 for the insertion / extraction start coordinate ST in the above equation (21).
Insertion / extraction coordinates fixpos [3] = basepos [3] + land [3] ... (27)
= 23 + 1
= 24

Based on the above equation (27), 24 is derived as the third hot-swap coordinate fixpos [3].

Therefore, as shown in FIG. 8B, the third insertion / extraction coordinate fixpos [3] is 24.

The case where the parameter is 4 in the process of S707 described above will be described. When the third hot-swap coordinate fixpos [3] is 24 and the offset is 2, the equation (25) can be expressed as the following equation (28).
Hot-swap coordinates fixpos [4] = fixpos [4-1] +2 ... (28)
= 24 + 2
= 26

Based on the above equation (28), 26 is derived as the fourth hot-swap coordinate fixpos [4].

Therefore, as shown in FIG. 8B, the fourth insertion / extraction coordinate fixpos [4] is 26.

Here, it returns to the explanation of the flowchart of the scaling process of FIG.

In S503, the scaling processing unit 109 determines whether or not the coordinate xi of the pixel of interest is equal to the hot-swap coordinate fixpos [i] in order to execute the hot-swap process at the hot-swap position derived in S502. When the determination result that the coordinate xi of the pixel of interest and the insertion / extraction coordinate fixpos [i] are equal (YES in S503) is obtained (YES in S503), the process shifts to S504 in order to execute the insertion / extraction process. When it is determined that the coordinates xi of the pixel of interest and the values of the insertion / extraction coordinates fixpos [i] are not equal (NO in S503), the process shifts to S505 in order to execute the transfer process.

In S504, the scaling processing unit 109 executes the insertion / extraction process. When the variable magnification is larger than 100.00%, the variable magnification processing unit 109 executes the pixel insertion process. When the scaling factor is smaller than 100.00%, the scaling factor 109 executes pixel thinning processing.

In the pixel insertion process, the pixel value of the pixel of the coordinate xi input to the scaling processing unit 109 is output from the scaling processing unit 109, which corresponds to the pixel of the input coordinate xi, and the output coordinate xo. The process of outputting to the pixel of the coordinates obtained by adding 1 to is executed. That is, since one pixel is added by executing the pixel insertion process once, the pixel is enlarged by one pixel on the downstream side in the main scanning direction.

In the pixel thinning process, the pixel value of the coordinate xi input to the scaling processing unit 109 is deleted without being output. That is, by executing the pixel thinning process once, one pixel is deleted, so that the pixel is reduced by one pixel on the upstream side in the main scanning direction.

In S505, the scaling processing unit 109 executes the transfer processing. In the transfer process, a process of outputting the pixel value of the pixel of the coordinate xi input to the scaling processing unit 109 to the pixel of the coordinate xo output from the scaling processing unit 109 corresponding to the pixel of the input coordinate xi is executed. To.

In S506, the scaling processing unit 109 determines whether or not the output coordinate xo is larger than the output size in the main scanning direction acquired in S501. When the determination result that the output coordinate xo is larger than the output size in the main scanning direction is obtained (YES in S506), it is determined that the processing in the main scanning direction is completed, and the processing is shifted to S508. When it is determined that the output coordinate xo is not larger than the output size in the main scanning direction and the output coordinate xo is equal to or less than the output size in the main scanning direction (NO in S506), the process shifts to S507.

In S507, the scaling processing unit 109 executes update processing on the input coordinate xi and the output coordinate xo as shown below. In the update process of the input coordinate xi, 1 is added to the input coordinate xi, so that the coordinate of the pixel of interest becomes the coordinate of the pixel shifted by one pixel to the downstream side in the main scanning direction. In the update process of the output coordinate xo, the process corresponding to the process content of the previous stage of S506 is executed. That is, when the scaling processing unit 109 executes the enlargement processing in the insertion / extraction processing of S504, 2 is added to the output coordinates xo, so that the pixels of the attention coordinates are advanced by two pixels downstream in the main scanning direction. It becomes a pixel. This is because the scaling processing unit 109 outputs two pixels to the resolution conversion unit 110 by executing the enlargement processing. When the reduction processing is executed in the insertion / extraction processing of S504, the scaling processing unit 109 shifts the processing to S502 without updating the pixels of the output coordinates xo. This is because even if the scaling processing unit 109 executes the reduction processing, nothing is output to the resolution conversion unit 110. When the variable magnification processing unit 109 executes the transfer processing of S505, 1 is added to the output coordinate xo, so that the coordinate of the attention coordinate becomes a pixel advanced by one pixel to the downstream side in the main scanning direction. This is because the scaling processing unit 109 executes the transfer processing to output one pixel to the resolution conversion unit 110. The variable magnification processing unit 109 executes the above-described update processing of the input coordinate xi and the update processing of the output coordinate xo as necessary, and then shifts the processing to S503.

In S508, the scaling processing unit 109 determines whether or not the output coordinate yo is larger than the output size in the sub-scanning direction acquired in S501. When the determination result that the output coordinate yo is equal to or less than the output size in the sub-scanning direction is obtained (NO in S508), the process shifts to S509.

In S509, the scaling processing unit 109 executes update processing for the input coordinate yi and the output coordinate yo as shown below. In the update process of the input coordinate y and the output coordinate yo, 1 is added to each of the input coordinate y and the output coordinate yo, so that the line of interest is shifted by one line to the downstream side in the sub-scanning direction. The variable magnification processing unit 109 executes the update processing of the input coordinate yi and the output coordinate yo, and then shifts the processing to S502. In S502, the insertion / extraction position determination process is performed on the line after the update process following the line before the update process.

On the other hand, when the determination result that the output coordinate yo is larger than the output size in the sub-scanning direction is obtained (YES in S508), it is determined that the processing in the sub-scanning direction is completed, and the processing is terminated.

<Details of scaling processing when pixels are thinned out>
The details of the scaling process when the pixels are thinned out by the scaling processing unit 109 will be described with reference to FIG. 9.

9 (a), 9 (d), and 9 (g) are explanatory views when the insertion / removal process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements.

9 (b), (e), and (h) are explanatory views when the insertion / removal process is executed at a resolution (2400 dpi) higher than the resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements.

9 (c), (f), and (i) are explanatory views when the insertion / extraction process is executed by the method of the present embodiment.

9 (a), (b), and (c) show images input to the scaling processing unit 109 before the insertion / extraction process is applied. The pixels painted with diagonal lines indicate the pixels at the insertion / extraction position.

9 (d), (e), and (f) are images output from the scaling processing unit 109 with respect to the insertion / extraction positions shown in FIGS. 9 (a), (b), and (c). The image after applying the pixel thinning process of the insertion / extraction process is shown.

In FIGS. 9 (g), 9 (h), and (i), the resolution conversion unit 110 has a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements in the main scanning direction with respect to the image after the insertion / extraction process is applied. The image after performing the resolution conversion process is shown. The images after the insertion / extraction process is applied are the images shown in FIGS. 9 (d), (e), and (f). When both of the two pixels are black pixels, the pixel value of the pixel after the resolution conversion is 2. When one of the two pixels is a white pixel and the other is a black pixel, the pixel value of the pixel after resolution conversion is 1. When both of the two pixels are white pixels, the pixel value of the pixel after the resolution conversion is set to 0.

<In the case of 1200 dpi>
First, using FIGS. 9A, 9D, and 9G, when the insertion / extraction process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, the state of the insertion / extraction process and the main scanning direction. The state of the resolution conversion process will be described.

FIG. 9D is a diagram showing a state in which the image is reduced by deleting the pixels painted with diagonal lines shown in FIG. 9A. The pixel 901 shown in FIG. 9A is a pixel to be thinned out (deleted). When the pixel 901 is deleted, the pixel 902 shown in FIG. 9A moves to the left, which is the upstream side in the main scanning direction, and becomes the pixel 903, as shown in FIG. 9D.

Next, the pixel 905 shown in FIG. 9 (g) is converted from the pixels 903 and the pixel 904 shown in FIG. 9 (d). Since both the pixel 903 and the pixel 904 are black pixels, the pixel value of the pixel 905 is 2.

When the insertion / removal process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, it can be seen that a large step is generated between the pixels 906 and the pixels 907 as shown in FIG. 9 (g).

<In the case of 2400 dpi>
Next, when the insertion / removal process is executed at a resolution (2400 dpi) higher than the resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements using FIGS. 9 (b), (e), and (h), the insertion / removal process is performed. The state and the state of the resolution conversion process in the main scanning direction will be described.

FIG. 9 (e) is a diagram showing a state in which the image is reduced by deleting the pixels painted with the diagonal lines shown in FIG. 9 (b). The pixel 908 shown in FIG. 9B is a pixel to be thinned out (deleted). When the pixel 908 is deleted, the pixel 909 and the pixel 910 shown in FIG. 9B move to the left, which is the upstream side in the main scanning direction, as shown in FIG. 9E, and the pixel 911 and the pixel 912 move to the left. It becomes.

Next, the pixel 913 shown in FIG. 9 (h) is converted from the pixels 911 and the pixel 912 shown in FIG. 9 (e). Since the pixel 911 is a white pixel and the pixel 912 is a black pixel, the pixel value of the pixel 913 is 1.

When the insertion / extraction process is executed at a resolution (2400 dpi) higher than the resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, the line width of the thin line changes before and after the insertion / removal position as shown in FIG. 9 (h). I understand. This is due to the fact that the phase of the light emitting element is deviated.

<In the case of this embodiment>
Finally, using FIGS. 9 (c), (f), and (i), when the insertion / extraction process is executed by the method of the present embodiment, the state of the insertion / extraction process and the state of the resolution conversion process in the main scanning direction. Will be described.

FIG. 9 (f) is a diagram showing a state in which the image is reduced by deleting the pixels painted with the diagonal lines shown in FIG. 9 (c). Pixels 914 and 915 shown in FIG. 9C are pixels to be thinned out (deleted). When the pixels 914 and 915 are deleted, as shown in FIG. 9 (f), the pixels 916 and 917 shown in FIG. 9 (c) move to the left, which is the upstream side in the main scanning direction, and become the pixels 918. It becomes pixel 919.

Next, the pixel 920 shown in FIG. 9 (i) is converted from the pixels 918 and the pixel 919 shown in FIG. 9 (f). Since both the pixel 918 and the pixel 919 are black pixels, the pixel value of the pixel 920 is 2.

When the insertion / extraction process is executed by the method of the present embodiment, as shown in FIG. 9 (i), it can be seen that the line width of the thin line does not change before and after the insertion / extraction position. Further, since the insertion / extraction process is locally performed between the pixels 921 and the pixels 922 at a resolution of 2400 dpi, it can be seen that the step is smoother than in the case of FIG. 9 (g). Further, since the pixel value of the pixel 921 is 1, and the amount of light emitted from the LED corresponding to the pixel 921 is 50% of the case where the pixel value is 2, a smoothing effect can be obtained and the step becomes inconspicuous.

<Details of scaling processing when pixels are inserted>
The details of the scaling process when the pixel is inserted by the scaling processing unit 109 will be described with reference to FIG. 10.

10 (a), (d), and (g) are explanatory views when the insertion / removal process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements.

10 (b), (e), and (h) are explanatory views when the insertion / removal process is executed at a resolution (2400 dpi) higher than the resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements.

10 (c), (f), and (i) are explanatory views when the insertion / extraction process is executed by the method of the present embodiment.

10 (a), (b), and (c) show images input to the scaling processing unit 109 before the insertion / extraction process is applied. The pixels surrounded by the broken line indicate the pixels at the insertion / extraction position.

10 (d), (e), and (f) are images output from the scaling processing unit 109 with respect to the insertion / extraction positions shown in FIGS. 10 (a), (b), and (c). The image after applying the pixel insertion process among the insertion / extraction processes is shown. The pixel surrounded by the broken line indicates the pixel at the insertion / extraction position, and the pixel surrounded by the alternate long and short dash line indicates the inserted pixel.

In FIGS. 10 (g), (h), and (i), the resolution conversion unit 110 has a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements in the main scanning direction with respect to the image after the insertion / extraction process is applied. The image after performing the resolution conversion process is shown. The images after the insertion / extraction process is applied are the images shown in FIGS. 10 (d), (e), and (f). When both of the two pixels are black pixels, the pixel value of the pixel after the resolution conversion is 2. When one of the two pixels is a white pixel and the other is a black pixel, the pixel value of the pixel after resolution conversion is 1. When both of the two pixels are white pixels, the pixel value of the pixel after the resolution conversion is set to 0.

<In the case of 1200 dpi>
First, using FIGS. 10A, 10D, and 10G, when the insertion / extraction process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, the state of the insertion / extraction process and the main scanning direction. The state of the resolution conversion process will be described.

FIG. 10 (d) is a diagram showing a state in which the image is enlarged by inserting the pixel surrounded by the broken line shown in FIG. 10 (a). The pixel 1001 shown in FIG. 10A is a pixel to be inserted. When the pixel 1001 is inserted, the pixel 1002 shown in FIG. 10A moves to the right, which is the downstream side in the main scanning direction, and becomes the pixel 1003, as shown in FIG. 10D.

Next, the pixel 1005 shown in FIG. 10 (g) is converted from the pixels 1003 and the pixel 1004 shown in FIG. 10 (d). Since both the pixel 1003 and the pixel 1004 are black pixels, the pixel value of the pixel 1005 is 2.

When the insertion / removal process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, it can be seen that a large step is generated between the pixels 1006 and the pixels 1007 as shown in FIG. 10 (g).

<In the case of 2400 dpi>
Next, when the insertion / removal process is executed at a resolution (2400 dpi) higher than the resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements using FIGS. 10 (b), (e), and (h), the insertion / removal process is performed. The state and the state of the resolution conversion process in the main scanning direction will be described.

FIG. 10 (e) is a diagram showing a state in which the image is enlarged by inserting the pixel surrounded by the broken line shown in FIG. 10 (b). Pixel 1008 shown in FIG. 10B is a pixel to be inserted. When the pixel 1008 is inserted, the pixel 1009 and the pixel 1010 shown in FIG. 10B move to the right, which is the downstream side in the main scanning direction, as shown in FIG. 10E, and the pixel 1011 and the pixel 1012 are moved. It becomes.

Next, the pixel 1013 shown in FIG. 10 (h) is converted from the pixel 1011 and the pixel 1012 shown in FIG. 10 (e). Since the pixel 1011 is a white pixel and the pixel 1012 is a black pixel, the pixel value of the pixel 1013 is 1.

When the insertion / extraction process is executed at a resolution (2400 dpi) higher than the resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, the line width of the thin line changes before and after the insertion / removal position as shown in FIG. 10 (h). I understand. This is due to the fact that the phase of the light emitting element is deviated.

<In the case of this embodiment>
Finally, using FIGS. 10 (c), (f), and (i), when the insertion / extraction process is executed by the method of the present embodiment, the state of the insertion / extraction process and the state of the resolution conversion process in the main scanning direction. Will be described.

FIG. 10 (f) is a diagram showing a state in which the image is enlarged by inserting the pixel surrounded by the broken line shown in FIG. 10 (c). Pixels 1014 and 1015 shown in FIG. 10C are pixels to be inserted. When the pixels 1014 and 1015 are inserted, as shown in FIG. 10 (f), the pixels 1016 and 1017 shown in FIG. 10 (c) move to the right, which is the downstream side in the main scanning direction, and become the pixels 1018. It becomes pixel 1019.

Next, the pixel 1020 shown in FIG. 10 (i) is converted from the pixels 1018 and the pixel 1019 shown in FIG. 10 (f). Since both the pixel 1018 and the pixel 1019 are black pixels, the pixel value of the pixel 1020 is 2.

When the insertion / extraction process is executed by the method of the present embodiment, as shown in FIG. 10 (i), it can be seen that the line width of the thin line does not change before and after the insertion / extraction position. Further, since the insertion / extraction process is locally performed between the pixels 1021 and the pixels 1022 at a resolution of 2400 dpi, it can be seen that the step is smoother than in the case of FIG. 10 (g). Further, since the pixel value of the pixel 1021 is 1, and the amount of light emitted from the LED corresponding to the pixel 1021 is 50% of the case where the pixel value is 2, a smoothing effect can be obtained and the step becomes inconspicuous.

As described above, when the insertion / removal process is executed at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements, a visible step may occur. Further, if the insertion / extraction process is executed at a resolution (2400 dpi) higher than the arrangement interval (1200 dpi) of the light emitting elements, the phase of the image may shift and the line width such as thin lines may become non-uniform. On the other hand, in the present embodiment, the even (2n) th insertion / extraction position (n is a natural number) is set to a position closer to the odd (2n-1) th insertion / extraction position, which is one smaller than the even number. As a result, while performing the insertion / extraction process by adjusting the phase of the image to the resolution corresponding to the arrangement interval of the light emitting elements in a broad sense, the insertion / removal process is locally executed at a resolution higher than the resolution corresponding to the arrangement interval of the light emitting elements. By doing so, it is possible to reduce the step due to the insertion / extraction process.

In the present embodiment, the resolution of the insertion / removal process is not limited to twice the resolution corresponding to the arrangement interval of the light emitting elements. If the resolution is 2 × N times (N is an integer) corresponding to the arrangement interval of the light emitting elements, the phases can be matched, so 4800 dpi or 9600 dpi may be used. In that case, the insertion / removal position of (2 × N-1) may be arranged closer to the insertion / removal position which is the reference position. For example, if the resolution is 9600 dpi, which is 6 times the resolution corresponding to the arrangement interval of the light emitting elements, the five insertion / extraction positions from fixpos [i + 1] to fixpos [i + 5] should be arranged close to the fixpos [i]. become. In this case, the size of the offset value, which is the offset value, is sufficiently small that even if the offset value is deviated, the unevenness of the density is not noticeable and cannot be visually recognized. May be 50 pixels or less. Further, in this case, it is also possible to set the insertion / extraction coordinates fixpos [i + 2] instead of the insertion / extraction coordinates fixpos [i] of the pixel as the reference position, and set the insertion / extraction coordinates before and after the fixpos [i + 2] as follows. Regarding fixpos [i] and fixpos [i + 1], let them be fixpos [i + 2] -2 x offset and fixpos [i + 2] -offset. Regarding fixpos [i + 3], fixpos [i + 4], and fixpos [i + 5], let them be fixpos [i + 2] + offset, fixpos [i + 2] + 2 × offset, and fixpos [i + 2] + 3 × offset. In S704 of FIG. 7, "is i an odd number?" Is changed to "is the remainder obtained by dividing i by 6?". When the remainder is 2, a random number random [i + 2] is generated in S705, and a fixpos [i + 2] serving as a reference position is derived in S706. If the remainder is other than 2 which is not the reference position, the insertion / extraction coordinates are derived in S707. In this way, the insertion / removal position that serves as the reference position can be set to a position other than the first.

<< Embodiment 2 >>
In this embodiment, only the processing different from that of the first embodiment will be described. In the first embodiment, a method of simply deleting and inserting pixels during the insertion / removal process has been described. In the present embodiment, a method of executing the insertion / extraction process while interpolating from adjacent pixels during the insertion / extraction process will be described. That is, in the present embodiment, in S504 of FIG. 5, which shows the flow of the scaling process, the insertion / extraction process is executed while performing the interpolation process. The interpolation target may be pixels adjacent to the pixels to be inserted / removed on the upstream side in the main scanning direction or the downstream side in the main scanning direction. The interpolation target may be pixels adjacent to each other on the side having a large size from the pixel to be inserted / removed to the pixel having the same pixel value as the pixel to be inserted / removed in the main scanning direction.

<Overview of pixel thinning processing including interpolation processing>
The outline of the pixel thinning process including the interpolation process (hereinafter, referred to as the pixel thinning process of the present embodiment) among the insertion / extraction processes of the present embodiment will be described with reference to FIG. FIG. 11 is an explanatory diagram of the pixel thinning process of the present embodiment. In FIG. 11, the upper side shows an image of the state before the pixel thinning process of the present embodiment is performed, and the lower side shows an image of the state after the pixel thinning process of the present embodiment is performed. In FIG. 11, each frame shows each pixel.

As shown on the upper side of FIG. 11, before the pixel thinning process of the present embodiment is performed, pixel A, pixel B, pixel C, pixel D, pixel E, pixel F, and pixels are viewed from the upstream side in the main scanning direction. It is assumed that they are arranged in the order of G. It is assumed that the pixels C and E are set as the pixels to be processed for pixel thinning in the present embodiment. Pixels that are adjacent on the upstream side or downstream side in the main scanning direction and whose size up to the pixel that has the same pixel value as the pixel value of the pixel thinning processing target pixel is larger are the pixels to be interpolated. Suppose it is set as. Here, it is assumed that the pixel to be interpolated with respect to the pixel C to be thinned out is set to the pixel B. Therefore, when the pixel C is deleted by the pixel thinning process in the insertion / extraction process, the scaling processing unit 109 executes an interpolation process using the pixel B to generate the pixel B'. As the pixel value of the pixel B', for example, the sum of the pixel value of the pixel B and the pixel value of the pixel C is used. Further, it is assumed that the pixel to be interpolated with respect to the pixel E to be thinned out is set to the pixel F. Therefore, when the pixel E is deleted by the pixel thinning process in the insertion / extraction process, the scaling processing unit 109 executes an interpolation process using the pixel F to generate the pixel F'. As the pixel value of the pixel F', for example, the sum of the pixel value of the pixel E and the pixel value of the pixel F is used.

Therefore, when the scaling processing unit 109 performs the pixel thinning process of the present embodiment on the image shown on the upper side of FIG. 11, as a processing result, as shown on the lower side of FIG. 11, from the upstream side in the main scanning direction. , Pixel A, Pixel B', Pixel D, Pixel F', and Pixel G are output.

In the present embodiment, the pixel data before the scaling process is a value of 1 bit (0 to 1). The pixel data after the scaling process has a value of 2 bits (0 to 2). If the pixel value is 1, the pixel that is not the target of the pixel thinning process outputs 2 as the pixel value of the pixel data after the scaling process. If the pixel value is 0, the pixel that is not the target of the insertion / extraction process outputs 0 as the pixel value of the pixel data after the scaling process. For the pixel to be interpolated, the pixel value of the pixel data to be output is determined by adding two pixels. For example, when the pixel value of pixel B is 1 and the pixel value of pixel C is 0, the two pixels are added and the pixel value of pixel B'is 1.

<Details of scaling processing when pixels are thinned out while interpolating>
The details of the scaling process when the pixels are thinned out while interpolating by the scaling processing unit 109 will be described with reference to FIG. FIG. 12 is an explanatory diagram when the insertion / extraction process is executed by the method of the present embodiment.

FIG. 12A is a diagram showing an example of an image before applying the insertion / extraction process of the present embodiment. FIG. 12A shows an image input to the scaling processing unit 109 before the insertion / extraction process is applied. The pixels painted with diagonal lines indicate the pixels at the insertion / extraction position.

FIG. 12B is a diagram showing an example of an image after applying the insertion / extraction process of the present embodiment. In FIG. 12B, the image output from the scaling processing unit 109 is subjected to pixel thinning processing while interpolating in the insertion / extraction processing with respect to the insertion / extraction position shown in FIG. 12A. The image after application is shown.

FIG. 12C is a diagram showing an example of an image after performing the resolution conversion process in the main scanning direction. In FIG. 12 (c), with respect to the image after the insertion / extraction process shown in FIG. 12 (b), the resolution conversion unit 110 has a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements in the main scanning direction. The image after performing the resolution conversion process is shown.

In the first embodiment, the values that can be obtained after the scaling process are 0, 1, and 2, so the image format after the scaling process is 2400 dpi × 2400 dpi × 1 bit. In the present embodiment, since the values that can be obtained by executing the scaling process while interpolating are 0, 1, and 2, the image format after the scaling process is 2400 dpi × 2400 dpi × 2 bit. Further, in the first embodiment, since the values that can be obtained after the resolution conversion process in the main scanning direction are 0, 1, and 2, the image format after the resolution conversion process in the main scanning direction is 1200 dpi × 2400 dpi × 2 bit. It was. In the present embodiment, the values that can be obtained by performing the scaling process while interpolating are 0, 1, 2, and 4, so that the image format after the resolution conversion process in the main scanning direction is 1200 dpi × 2400 dpi × 3 bit. It becomes.

Subsequently, when the pixel thinning process of the present embodiment is performed using FIGS. 12A, 12B, and 12C, the state before and after the pixel thinning process of the present embodiment and the state in the main scanning direction. The state after the resolution conversion process will be described.

FIG. 12B shows how the image is reduced by performing the pixel thinning process on the pixels painted with the diagonal lines in FIG. 12A. The pixel 1201 shown in FIG. 12A is a pixel to be thinned out. At this time, the pixel 1201 is deleted by using the pixel 1201 and the pixel 1202. Since the pixel value of the pixel 1201 is 1 and the pixel value of the pixel 1202 is 0, the pixel value of the pixel 1205 becomes 1 by thinning out the pixels while interpolating, which is the pixel thinning process of the present embodiment.

Similarly, pixel 1203 and pixel 1204 are used to delete pixel 1204. Since the pixel value of the pixel 1203 is 0 and the pixel value of the pixel 1204 is 1, the pixel value of the pixel 1206 becomes 1 by the pixel thinning process of the present embodiment.

Next, when the resolution conversion process is executed on the image shown in FIG. 12B in the main scanning direction, the image shown in FIG. 12C is obtained. Pixel 1208 is converted from pixel 1205 and pixel 1207. Since the pixel value of the pixel 1205 is 1 and the pixel value of the pixel 1207 is 0, the pixel value of the pixel 1208 is 1 which is the sum of the pixel value of the pixel 1205 and the pixel value of the pixel 1207.

By executing the resolution conversion process in the main scanning direction on the image data obtained by the pixel thinning process of the present embodiment, the converted image data shown in FIG. 12 (c) can be obtained in FIG. 9 (i). It can be seen that the step due to the scaling process is smoother than in the case.

<Overview of pixel insertion processing including interpolation processing>
The outline of the pixel insertion process (hereinafter, referred to as the pixel insertion process of the present embodiment) including the interpolation process among the insertion / extraction processes of the present embodiment will be described with reference to FIG. FIG. 13 is an explanatory diagram of the pixel insertion process of the present embodiment. In FIG. 13, the upper side shows an image of the state before the pixel insertion process of the present embodiment is performed, and the lower side shows an image of the state after the pixel insertion process of the present embodiment is performed. In FIG. 13, each frame shows each pixel.

As shown on the upper side of FIG. 13, before performing the pixel insertion process of the present embodiment, pixel A, pixel B, pixel C, pixel D, pixel E, pixel F, and pixels are viewed from the upstream side in the main scanning direction. It is assumed that they are arranged in the order of G. It is assumed that the pixel C and the pixel E are set to the pixels to be processed for pixel insertion in the present embodiment. Pixels that are adjacent on the upstream side or downstream side in the main scanning direction and whose size up to the pixel that has the same pixel value as the pixel value of the pixel insertion processing target pixel is larger are the pixels to be interpolated. Suppose it is set as. Here, it is assumed that the pixel to be interpolated with respect to the pixel C to be inserted is set to the pixel B. Therefore, when the pixel C is inserted by the pixel insertion process in the insertion / extraction process, the scaling processing unit 109 executes an interpolation process using the pixel B to generate the pixel C'. As the pixel value of the pixel C', for example, the sum of the pixel value of the pixel B and the pixel value of the pixel C is used. Further, it is assumed that the pixel to be interpolated with respect to the pixel E to be inserted is set to the pixel F. Therefore, when the pixel E is inserted by the pixel insertion process in the insertion / extraction process, the scaling processing unit 109 executes an interpolation process using the pixel F to generate the pixel E'. As the pixel value of the pixel E', for example, the sum of the pixel value of the pixel E and the pixel value of the pixel F is used.

Therefore, when the pixel insertion processing of the present embodiment is performed on the image shown on the upper side of FIG. 13, the scaling processing unit 109 outputs the processing result shown below. That is, as a processing result, the scaling processing unit 109 has pixel A, pixel B, pixel C', pixel C, pixel D, pixel E, and pixels from the upstream side in the main scanning direction as shown in the lower side of FIG. An image that becomes E', pixel F, and pixel G is output.

In the present embodiment, the pixel data before the scaling process is a value of 1 bit (0 to 1). The pixel data after the scaling process has a value of 2 bits (0 to 2). If the pixel value is 1, the pixel that is not the target of the pixel insertion process outputs 2 as the pixel value of the pixel data after the scaling process. If the pixel value is 0, the pixel that is not the target of the insertion / extraction process outputs 0 as the pixel value of the pixel data after the scaling process. For the pixel to be interpolated, the pixel value of the pixel data to be output is determined by adding two pixels. For example, when the pixel value of the pixel B is 1 and the pixel value of the pixel C is 0, the two pixels are added and the pixel value of the pixel C'is 1.

<Details of scaling processing when pixels are inserted while interpolating>
The details of the scaling process when pixels are inserted while interpolating by the scaling processing unit 109 will be described with reference to FIG. FIG. 14 is an explanatory diagram when the insertion / extraction process is executed by the method of the present embodiment.

FIG. 14A is a diagram showing an example of an image before applying the insertion / extraction process of the present embodiment. FIG. 14A shows an image input to the scaling processing unit 109 before the insertion / extraction process is applied. The pixels painted with diagonal lines indicate the pixels at the insertion / extraction position.

FIG. 14B is a diagram showing an example of an image after applying the insertion / extraction process of the present embodiment. In FIG. 14B, the image output from the scaling processing unit 109 is subjected to the pixel insertion processing while interpolating in the insertion / extraction processing with respect to the insertion / extraction position shown in FIG. 14A. The image after application is shown.

FIG. 14C is a diagram showing an example of an image after performing the resolution conversion process in the main scanning direction. In FIG. 14 (c), with respect to the image after the insertion / extraction process shown in FIG. 14 (b), the resolution conversion unit 110 has a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements in the main scanning direction. The image after performing the resolution conversion process is shown.

In the first embodiment, the values that can be obtained after the scaling process are 0, 1, and 2, so the image format after the scaling process is 2400 dpi × 2400 dpi × 1 bit. In the present embodiment, since the values that can be obtained by executing the scaling process while interpolating are 0, 1, and 2, the image format after the scaling process is 2400 dpi × 2400 dpi × 2 bit. Further, in the first embodiment, since the values that can be obtained after the resolution conversion process in the main scanning direction are 0, 1, and 2, the image format after the resolution conversion process in the main scanning direction is 1200 dpi × 2400 dpi × 2 bit. It was. In the present embodiment, the values that can be obtained by performing the scaling process while interpolating are 0, 1, 2, and 4, so that the image format after the resolution conversion process in the main scanning direction is 1200 dpi × 2400 dpi × 3 bit. It becomes.

Subsequently, when the pixel insertion processing of the present embodiment is performed using FIGS. 14A, 14B, and 14C, the state before and after the pixel insertion processing of the present embodiment and the state in the main scanning direction. The state after the resolution conversion process will be described.

FIG. 14 (b) shows how the image is enlarged by performing the pixel insertion process on the pixels painted with the diagonal lines in FIG. 14 (a). The pixel 1401 shown in FIG. 14A is a pixel to be inserted. At this time, the pixel 1401 is inserted using the pixel 1401 and the pixel 1402. Since the pixel value of the pixel 1401 is 1 and the pixel value of the pixel 1402 is 0, the pixel value of the pixel 1405 becomes 1 by inserting the pixels while interpolating, which is the pixel insertion process of the present embodiment. ..

Similarly, pixel 1404 is inserted using pixel 1403 and pixel 1404. Since the pixel value of the pixel 1403 is 0 and the pixel value of the pixel 1404 is 1, the pixel value of the pixel 1406 becomes 2 by the pixel insertion process of the present embodiment.

Next, when the resolution conversion process is executed on the image shown in FIG. 14 (b) in the main scanning direction, the image is shown in FIG. 14 (c). Pixel 1408 is converted from pixel 1405 and pixel 1407. Since the pixel value of the pixel 1405 is 2 and the pixel value of the pixel 1407 is 0, the pixel value of the pixel 1408 is 2 which is the sum of the pixel value of the pixel 1405 and the pixel value of the pixel 1407.

By executing the resolution conversion process in the main scanning direction on the image data obtained by the pixel insertion process of the present embodiment, the converted image data shown in FIG. 14 (c) can be obtained in FIG. 10 (i). It can be seen that the step due to the scaling process is smoother than in the case.

As described above, if the insertion / extraction process is performed while interpolating from adjacent pixels during the insertion / extraction process, it is possible to further smooth the step due to the scaling process.

<< Embodiment 3 >>
In this embodiment, only the processes different from those of the first and second embodiments will be described. In the first embodiment, a method of determining the odd-numbered and even-numbered insertion / extraction positions in the main scanning direction has been described. Further, in the second embodiment, a method of smoothing the connection of steps by executing the insertion / extraction process while interpolating from adjacent pixels during the insertion / extraction process has been described. In the present embodiment, the insertion / extraction positions in the main scanning direction on the n + 2m line and the nth line are set to the same position, and the insertion / extraction section is provided in the sub-scanning direction to reduce the step due to the insertion / extraction process. At this time, the larger m is, the smoother the insertion / removal process becomes possible.

<Flowchart of insertion / removal position determination process>
The details of the insertion / removal position determination process (S502) in the present embodiment will be described with reference to FIGS. 15 and 16. FIG. 15 is a flowchart showing the flow of the insertion / removal position determination process of the present embodiment. Here, the description will be focused on the points different from those of FIG. 7 (Embodiment 1). Specifically, the repetition counter determination processing S1505 and S1514, the repetition pixel number determination processing S1508, the insertion / extraction position derivation processing S1509 and S1510, and the repetition counter derivation (determination) processing S1515 and S1516 will be described. Note that S1501-S1503 is the same as S701-S703, S1506-S1507 is the same as S705-S706, and S1511-S1513 is the same as S707-S709, and detailed description thereof will be omitted. In the present embodiment (FIG. 16), the image has a main scanning pixel number of 48 pixels, the insertion / extraction cycle L is 10 (pixels), the number of insertion / extraction IN is 4, and the insertion / extraction start coordinate ST is 3. The case where the basic insertion / extraction coordinates basepos [1] when the parameter i is 1 is 3 will be described. In the present embodiment, the basic hot-swap coordinates basepos [i] of the first embodiment are described as the basic hot-swap coordinates basepos [i] [yi].

When the processes from S1501 to S1503 are executed to determine the basic hot-swap coordinate basepos [i] which is the reference coordinate of the hot-swap coordinate, in S1504, the variable magnification processing unit 109 has the parameter i which is an odd number of the reference position. Determine if. This is because the method of deriving the insertion / extraction coordinates fixpos [i] [yi] is changed depending on whether the parameter i is an odd number or the parameter i is an even number that is not the reference position.

Therefore, when the determination result that the parameter i is an odd number is obtained (YES in S1504), the scaling processing unit 109 shifts the processing to S1505. On the other hand, when the determination result that the parameter i is an even number and not an odd number is obtained (NO in S1504), the scaling processing unit 109 shifts the processing to S1511.

In S1505, the scaling processing unit 109 determines whether or not the repetition counter repeat_ct [i] is 0. This is to change the derivation method of the insertion / extraction coordinates fixpos [i] [yi] depending on whether the repetition counter repeat_ct [i] is 0 or not. The number of repeated pixels repeat_pix is a preset unit and is a unit indicating an insertion / extraction section in the sub-scanning direction. The number of repeating pixels repeat_pix is the first insertion / removal position and the main scan at the third insertion / removal position next to the first insertion / removal position and the position next to the third insertion / removal position in the direction orthogonal to the scaling direction. It can also be said to be a unit indicating an insertion / extraction section in which the same position in the direction is determined as the fourth insertion / extraction position. In the present embodiment, the insertion / extraction coordinates are skipped by one line in the sub-scanning direction and are the same in the main scanning direction in a predetermined unit (8 pixels in FIG. 16) in the sub-scanning direction. The above-mentioned predetermined unit is set with reference to the number of repeating pixels repeat_pix. Then, the repetition is controlled by using the repetition counter repeat_ct [i]. The number of repeated pixels repeat_pix is set to 8 or more. This is because the processing is performed at 2400 dpi in a pseudo manner in the section where the insertion / extraction position is repeated by skipping one line. If this section is too short (the number of repeated pixels repeat_pix is 1 or 2), a step of 1200 dpi will be visually recognized. According to the results of the experiment, it has been confirmed that when the width of the repeating section is about 88 μm or more, it becomes difficult to visually recognize the step of the thin line. That is, it is desirable that 8 pixels or more are set at 2400 dpi. However, if this repeating section continues for a long section such as 20 cm, it will be visually recognized as a streak, so it is desirable to set it to an appropriate length. That is, it is desirable that less than 18182 pixels are set at 2400 dpi.

When the repeat counter repeat_ct [i] is 0, it serves as a reference for the insertion / extraction position. When the determination result that the repetition counter repeat_ct [i] is 0 is obtained (YES in S1505), the scaling processing unit 109 shifts the processing to S1506. On the other hand, when the determination result that the repetition counter repeat_ct [i] is not 0 is obtained (NO in S1505), the scaling processing unit 109 shifts the processing to S1508.

When the process of S1506 is executed and a random number random [i] is generated as in S705, in S1507, the scaling processing unit 109 derives the hot-swap coordinates fixpos [i] [yi] as follows. That is, the scaling processing unit 109 derives the hot-swap coordinates fixpos [i] [yi] based on the following equation (29) in which the sub-scanning direction [y] is added to the above equation (23) used in S706. .. When the basic hot-swap coordinates basepos [1] are 3 and the random number random [1] is 3, the equation (29) can be expressed as the following equation (30).
Hot-swap coordinates fixpos [i] [yi] = basepos [i] [yi] + land [i] ... (29)
Hot-swap coordinates fixpos [1] [0] = basepos [1] + land [1]
... (30)
= 3 +3
= 6

Based on the above equation (30), 6 is derived as the insertion / extraction coordinates fixpos [1] [0].

Therefore, as shown in FIG. 16, the insertion / extraction coordinates fixpos [1] [0] are 6.

In S1508, the scaling processing unit 109 determines whether or not the repetition counter repeat_ct [i] is an even number. This is to change the derivation method of the insertion / extraction coordinates fixpos [i] [yi] depending on whether the repetition counter repeat_ct [i] is an even number or not.

When the repeat counter repeat_ct [i] is an odd number and a determination result of not being an even number is obtained (NO in S1508), the scaling processing unit 109 shifts the processing to S1510. On the other hand, when the determination result that the repetition counter repeat_ct [i] is an even number is obtained (YES in S1508), the scaling processing unit 109 shifts the processing to S1509.

In S1509, the scaling processing unit 109 derives the odd-numbered coordinates fixpos [i] by substituting the insertion / extraction coordinates fixpos [i] [y-2], which are the insertion / extraction coordinates two lines before. That is, the insertion / extraction coordinates fixpos [i] [yi] can be derived based on the following equation (31).
Insertion / extraction coordinates fixpos [i] [yi] = fixpos [i] [y-2] ... (31)
Insertion / extraction coordinates fixpos [1] [2] = fixpos [1] [2-2] ... (32)
= Fixpos [1] [0]
= 6

Based on the above equation (32), 6 is derived as the insertion / extraction coordinates fixpos [1] [2].

In S1510, the scaling processing unit 109 is based on the insertion / extraction coordinates fixpos [i] [y-1] one line before the main insertion / extraction coordinates fixpos [i] [yi] and shift_pix which is a predetermined offset value. , The insertion / extraction coordinates fixpos [i] [yi] are derived. In S1510, odd-numbered hot-swap coordinates fixpos [i] [yi] are derived. The insertion / extraction coordinates fixpos [i] [yi] add shift_pix, which is a predetermined offset value, to the odd-numbered insertion / extraction coordinates fixpos [i] [y-1], which are the previous insertion / extraction coordinates one line before. It is derived by. That is, the insertion / extraction coordinates fixpos [i] [yi] are the relational expressions between the insertion / extraction coordinates fixpos [i] [y-1] one line before and the preset offset value shift_pix (33). Can be derived based on. When the first hot-swap coordinate fixpos [1] immediately before the second hot-swap coordinate fixpos [2] is 6 and shift_pix is 2, the equation (33) is as shown in the following equation (34). Can be represented.
Hot-swap coordinates fixpos [i] [yi] = fixpos [i] [y-1] + shift_pix ... (33)
Hot-swap coordinates fixpos [1] [1] = fixpos [1] [0] +6
... (34)
= 6 + 6
= 12

Based on the above equation (34), 12 is derived as the insertion / extraction coordinates fixpos [1] [1].

In S1511, the scaling processing unit 109 adds the sub-scanning direction [yi] to the above-mentioned equation (25) used in S707, and based on the following equation (35), the even-numbered hot-swap coordinates fixpos [i] [yi] ] Is derived. When the first insertion / extraction coordinates fixpos [1] [0] immediately before the second insertion / extraction coordinates fixpos [2] [0] of the first line are 6 and the offset is 2, the equation (35) is , Can be expressed as the following equation (36).
Insertion / extraction coordinates fixpos [i] [yi] = fixpos [i-1] [yi] + offset ... (35)
Insertion / extraction coordinates fixpos [2] [0] = fixpos [2-1] [0] +2 ... (36)
= 6 + 2
= 8

Based on the above equation (36), 8 is derived as the second insertion / extraction coordinates fixpos [2] [0] of the first line.

In S1512, the scaling processing unit 109 determines whether the parameter i is equal to the number of insertions / extractions IN. When the determination result that the parameter i is not equal to the number of insertion / extraction IN is obtained (NO in S1512), the scaling processing unit 109 determines the insertion / extraction coordinates fixpos [i] [yi] in the line of interest. ] Exists, and the process shifts to S1513. In S1513, the scaling processing unit 109 executes a process of adding 1 to the parameter i. After executing the addition process, the variable magnification processing unit 109 shifts the process to S1503. In S1503, the scaling processing unit 109 executes a derivation process of the insertion / extraction position corresponding to the parameter after the addition processing, following the insertion / extraction position corresponding to the parameter before the addition processing. On the other hand, when the determination result that the parameter i is equal to the number of insertion / extraction IN is obtained (YES in S1512), the scaling processing unit 109 determines that all the insertion / extraction coordinates fixpos [i] have been determined in the line of interest. ,finish. That is, the scaling processing unit 109 executes a series of processes (S1503 to S1513) for deriving the insertion / extraction coordinates fixpos [i] corresponding to each parameter i until the parameter i becomes equal to the number of insertion / extraction times IN.

In S1514, the scaling processing unit 109 determines whether or not the repetition counter repeat_ct [i] is equal to the number of repetition pixels repeat_pix. When the determination result that the repetition counter repeat_ct [i] is equal to the number of repetition pixels repeat_pix is obtained (YES in S1514), the scaling processing unit 109 shifts the processing to S1515. On the other hand, when the determination result that the repetition counter repeat_ct [i] is not equal to the number of repetition pixels repeat_pix is obtained (NO in S1514), the scaling processing unit 109 shifts the processing to S1516.

In S1515, the scaling processing unit 109 initializes the repetition counter repeat_ct [i] by substituting 0 for the repetition counter repeat_ct [i]. The variable magnification processing unit 109 ends this flow after the initialization processing of the repeat counter repeat_ct [i].

In S1516, the scaling processing unit 109 updates the repetition counter repeat_ct [i] by adding 1 to the repetition counter repeat_ct [i]. The variable magnification processing unit 109 ends this flow after the repetitive counter repeat_ct [i] is updated.

The repeat counter repeat_ct [i] described above is a counter in the sub-scanning direction. When the value of the repeat counter repeat_ct [i] is 0, the insertion / extraction position is derived based on the equation (29) of S1507. When the value of the repeat counter repeat_ct [i] is not 0 and is even, the insertion / extraction position is derived based on the equation (31) of S1509. When the value of the repetition counter repeat_ct [i] is not 0 and is an odd number, the insertion / extraction position is derived based on the equation (33) of S1510.

<Details of scaling processing>
The details of the scaling process when the pixels are thinned out by the scaling processing unit 109 will be described with reference to FIG. 17 (a), (c), and (e) are explanatory views when the insertion / removal process is executed by the method of the first embodiment described above. 17 (b), (d), and (f) are explanatory views when the insertion / extraction process is executed by the method of the present embodiment (embodiment 3).

17 (a) and 17 (b) show images input to the scaling processing unit 109 before the insertion / extraction process is applied. The pixels painted with diagonal lines indicate the pixels at the insertion / extraction position.

17 (c) and 17 (d) are images output from the scaling processing unit 109, and the pixels in the insertion / extraction process are thinned out with respect to the insertion / extraction positions shown in FIGS. 17 (a) and 17 (b). The image after applying the processing is shown.

In FIGS. 17 (e) and 17 (f), the resolution conversion unit 110 performs resolution conversion processing in the main scanning direction at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements with respect to the image after the insertion / extraction processing is applied. The image after executing is shown. In FIGS. 17A to 17F, the horizontal direction indicates the main scanning direction and the vertical direction indicates the sub-scanning direction.

(In the case of Embodiment 1)
A state of the insertion / extraction process and a state of the resolution conversion process in the main scanning direction when the insertion / extraction process is executed by the method of the first embodiment will be described with reference to FIGS. 17 (a), (c), and (e). To do.

FIG. 17 (c) is a diagram showing a state in which the image is reduced by deleting the pixels painted with the diagonal lines shown in FIG. 17 (a). Pixels 1701 and 1702 shown in FIG. 17A are pixels to be thinned out (deleted). When the pixels 1701 and 1702 are deleted, as shown in FIG. 17 (c), the pixels 1703 and 1704 shown in FIG. 17 (a) move to the left, which is the upstream side in the main scanning direction, and become the pixels 1705. The number of pixels is 1706.

Next, the pixel 1707 shown in FIG. 17 (e) is converted from the pixels 1705 and the pixel 1706 shown in FIG. 17 (c). Since both the pixel 1705 and the pixel 1706 are black pixels, the pixel value of the pixel 1707 is 2.

(In the case of Embodiment 3)
A state of the insertion / extraction process and a state of the resolution conversion process in the main scanning direction when the insertion / extraction process is executed by the method of the third embodiment using FIGS. 17 (b), (d), (f) and FIG. Will be described.

FIG. 17D is a diagram showing a state in which the image is reduced by deleting the pixels painted with diagonal lines shown in FIG. 17B. Pixels 1708 and 1709 shown in FIG. 17B are pixels to be thinned out (deleted). When the pixels 1708 and 1709 are deleted, as shown in FIG. 17 (d), the pixels 1710 and 1711 shown in FIG. 17 (b) move to the left, which is the upstream side in the main scanning direction, and become the pixels 1712. It becomes pixel 1713.

FIG. 19 is a diagram showing the potential distribution of the electrostatic latent image formed on the photoconductor drum. In FIG. 19, the horizontal direction indicates the main scanning direction, and the vertical direction indicates the sub-scanning direction.

FIG. 19A is a diagram showing the potential distribution of the electrostatic latent image formed on the photoconductor drum based on the image data shown in FIG. 17E.

FIG. 19 (b) is a diagram showing the potential distribution of the electrostatic latent image formed on the photoconductor drum based on the image data shown in FIG. 17 (f).

Next, the pixel 1714 shown in FIG. 17 (f) is converted from the pixel 1712 and the pixel 1713 shown in FIG. 17 (d). Since both the pixel 1712 and the pixel 1713 are black pixels, the pixel value of the pixel 1714 is 2.

When the insertion / extraction process is executed by the method of the first embodiment, it can be seen that a step is generated in the thin line as shown in FIG. 19 (a). When the insertion / extraction process is executed by the method of the third embodiment, as shown in FIG. 19B, the thin line can be arranged at the position of 2400 dpi between the phases of 1200 dpi at the place where the insertion / extraction position is repeated across the thin line. You can see that. A place where the insertion / extraction position is repeated across the thin line can be said to be a place where the insertion / removal position is repeated on the upstream side and the downstream side in the main scanning direction across the thin line. As a result, the width of the step is reduced from 1200 dpi to 2400 dpi, and the insertion / removal process is repeated with a constant width (a predetermined size in the sub-scanning direction), so that the step can be reduced.

<Details of scaling processing when pixels are inserted>
The details of the scaling process when the pixel is inserted by the scaling processing unit 109 will be described with reference to FIGS. 18 and 19. 18 (a), (c), and (e) are explanatory views when the insertion / extraction process is executed by the method of the first embodiment. 18 (b), (d), and (f) are explanatory views when the insertion / extraction process is executed by the method of the present embodiment (embodiment 3).

18 (a) and 18 (b) show images input to the scaling processing unit 109 before the insertion / extraction process is applied. The pixels surrounded by the broken line indicate the pixels at the insertion / extraction position.

18 (c) and 18 (d) are images output from the scaling processing unit 109, and the pixel insertion process of the insertion / extraction processes is performed with respect to the insertion / extraction positions shown in FIGS. 18 (a) and 18 (b). The image after applying is shown. The pixel surrounded by the broken line indicates the pixel at the insertion / extraction position, and the pixel surrounded by the alternate long and short dash line indicates the inserted pixel.

In FIGS. 18 (e) and 18 (f), the resolution conversion unit 110 performs resolution conversion processing in the main scanning direction at a resolution (1200 dpi) corresponding to the arrangement interval of the light emitting elements with respect to the image after the insertion / extraction processing is applied. The image after executing is shown.

FIG. 19 (c) is a diagram showing the potential distribution of the electrostatic latent image formed on the photoconductor drum based on the image data shown in FIG. 18 (e). FIG. 19 (d) is a diagram showing the potential distribution of the electrostatic latent image formed on the photoconductor drum based on the image data shown in FIG. 18 (f).

(In the case of Embodiment 1)
A state of the insertion / extraction process and a state of the resolution conversion process in the main scanning direction when the insertion / extraction process is executed by the method of the first embodiment will be described with reference to FIGS. 18 (a), (c), and (e). To do.

FIG. 18 (c) is a diagram showing a state in which the image is enlarged by inserting the pixel surrounded by the broken line shown in FIG. 18 (a). Pixels 1801 and 1802 shown in FIG. 18A are pixels to be inserted. When the pixels 1801 and 1802 are inserted, as shown in FIG. 18 (c), the pixels 1803 and 1804 shown in FIG. 18 (a) move to the right, which is the downstream side in the main scanning direction, and become the pixels 1805. The number of pixels is 1806.

Next, the pixel 1807 shown in FIG. 18 (e) is converted from the pixels 1805 and the pixel 1806 shown in FIG. 18 (c). Since both the pixel 1805 and the pixel 1806 are black pixels, the pixel value of the pixel 1807 is 2.

(In the case of Embodiment 3)
A state of the insertion / extraction process and a state of the resolution conversion process in the main scanning direction when the insertion / extraction process is executed by the method of the third embodiment will be described with reference to FIGS. 18 (b), (d), and (f). To do.

FIG. 18D is a diagram showing a state in which the image is enlarged by inserting the pixel surrounded by the broken line shown in FIG. 18B. Pixels 1808 and 1809 shown in FIG. 18B are pixels to be inserted. When the pixels 1808 and 1809 are inserted, as shown in FIG. 18 (d), the pixels 1810 and 1811 shown in FIG. 18 (b) move to the right, which is the downstream side in the main scanning direction, and become the pixels 1812. It becomes pixel 1813.

Next, the pixel 1814 shown in FIG. 18 (f) is converted from the pixel 1812 and the pixel 1813 shown in FIG. 18 (d). Since both the pixel 1812 and the pixel 1813 are black pixels, the pixel value of the pixel 1814 is 2.

When the insertion / extraction process is executed by the method of the first embodiment, it can be seen that a step is generated in the thin line as shown in FIG. 19 (c). When the insertion / extraction process is executed by the method of the third embodiment, as shown in FIG. 19D, the thin line can be arranged at the position of 2400 dpi between the phases of 1200 dpi at the place where the insertion / extraction position is repeated across the thin line. You can see that. A place where the insertion / extraction position is repeated across the thin line can be said to be a place where the insertion / removal position is repeated on the upstream side and the downstream side in the main scanning direction across the thin line. As a result, the width of the step is reduced from 1200 dpi to 2400 dpi, and the insertion / removal process is repeated with a constant width (a predetermined size in the sub-scanning direction), so that the step can be reduced.

As described above, according to the present embodiment, it is possible to reduce the step due to the insertion / removal process in the human visual range and make the connection of the steps smoother.

[Other Embodiments]
In the first embodiment, the insertion / extraction position determination process for determining the even-numbered insertion / extraction coordinates fixpos [2n] following the odd-numbered number based on the odd-numbered insertion / extraction coordinates fixpos [2n-1] (n is a natural number). explained. For example, the insertion / extraction position of the first pixel is fixed, the insertion / extraction position of the second pixel corresponds to the odd number based on the explanation of FIG. 7, and the insertion / extraction position of the third pixel is the even number of the explanation of FIG. It is also possible to perform the insertion / extraction position determination process for determining the insertion / extraction coordinates in correspondence with. It is also possible to perform the insertion / extraction position determination process for determining the odd-numbered insertion / extraction coordinates fixpos [2n-1] before the even-numbered number based on the even-numbered insertion / extraction coordinates fixpos [2n] (n is a natural number). Is. That is, it is also possible to perform the insertion / extraction position determination process of deriving the insertion / extraction positions of two consecutive pixels and determining the insertion / extraction coordinates as follows. The sum of the basic insertion / extraction coordinates basepos [i] and the random number random [i] is derived to determine the insertion / extraction position fixpos [i] of one pixel. Then, the sum or difference between the insertion / extraction coordinates fixpos [i] and the offset value offset is derived to determine the insertion / extraction position fixpos [i ± 1] of the other pixel.

In the second embodiment, the interpolation processing when the two pixels to be inserted / removed are close to each other in the main scanning direction has been described. When the three pixels to be inserted / removed are close to each other in the main scanning direction and the adjacent pixels to be inserted / removed have the same size, the following processing can be executed. That is, among the three pixels of the insertion / extraction processing target adjacent in the main scanning direction, the pixel adjacent to the central pixel on the upstream side or the downstream side in the main scanning direction can be used as the pixel to be interpolated to perform the interpolation processing.

Further, when the four pixels of the insertion / extraction processing target are close to each other in the main scanning direction and the sizes of the adjacent pixels of the insertion / extraction processing target are the same, the following processing can be executed. That is, the interpolation processing can be performed by using the pixels adjacent to the upstream two pixels in the main scanning direction as the pixels to be interpolated from the four pixels to be inserted and removed that are adjacent to each other in the main scanning direction. Of the four pixels to be inserted and removed that are adjacent in the main scanning direction, the pixels that are adjacent to the downstream two pixels in the main scanning direction can be used as the pixels to be interpolated.

By executing such an interpolation process, it is possible to further smooth the step due to the scaling process.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

S501 Insertion / removal position determination process S701 Reference section identification process S706 First insertion / removal position determination process S707 Second insertion / removal position determination process

Claims (19)

An image processing device that processes image data for forming an image on the surface of the photoconductor using a plurality of light emitting elements arranged along the main scanning direction of the photoconductor.
By inserting or deleting pixels in the image data, the pixels are inserted or the pixels are inserted or deleted based on the scaling factor of the image in which the image formed from the image data is scaled in the main scanning direction. A specific means for specifying the reference section L for determining the first insertion / extraction position and the second insertion / extraction position for deleting the image, and
Based on the reference section L specified by the specific means, the first determination means for determining the first insertion / removal position and the first determination means.
Based on the first insertion / removal position determined by the first determination means, the second determination means for determining the second insertion / extraction position and the second determination means.
A scaling means for scaling the image by inserting or deleting pixels in the image data based on the first insertion / extraction position and the second insertion / extraction position.
An image processing device characterized by having. The image processing apparatus according to claim 1, wherein the second determination means determines the second insertion / extraction position based on the first insertion / extraction position and a preset offset value. .. The image processing apparatus according to claim 2, wherein the second determination means determines the second insertion / extraction position by adding the offset value to the first insertion / extraction position. The first determination means is characterized in that the first insertion / extraction position is determined based on the reference section L, a preset insertion / extraction start position, and a preset random number. The image processing apparatus according to any one of 3 to 3. The first determination means determines the first insertion / extraction position by adding the insertion / extraction start position and the random number to the reference interval L × N (N is an integer). Item 4. The image processing apparatus according to item 4. It has a determination means for determining whether to determine the insertion / extraction position for inserting or deleting the pixel by using the first determination means or the second determination means.
When the determination means determines that the insertion / removal position is the reference position, the first determination means determines the first insertion / extraction position at the insertion / extraction position.
The fifth aspect of claim 5, wherein when the determination means determines that the insertion / removal position is not the reference position, the second determination means determines the second insertion / removal position at the insertion / extraction position. Image processing equipment. The image processing apparatus according to claim 6, wherein the reference position is m (m is a natural number) × N. The image processing apparatus according to claim 6, wherein the reference position is an odd number or an even number. Further, it has a setting means for setting pixels adjacent to the first insertion / extraction position and the second insertion / extraction position on the upstream side or the downstream side in the main scanning direction as interpolation targets.
The scaling means inserts the pixel or deletes the pixel with respect to the first insertion / extraction position and the second insertion / extraction position while interpolating using the pixel to be interpolated set by the setting means. The image processing apparatus according to any one of claims 1 to 8, wherein the image processing apparatus is to be performed. The setting means is characterized in that the pixel to be interpolated is set based on the size up to the pixel showing the same pixel value as the pixel value of the pixel at the first insertion / extraction position or the second insertion / extraction position. The image processing apparatus according to claim 9. The interpolation is characterized in that the pixel values of the pixels to be interpolated are added to the pixel values of the pixels at the first insertion / extraction position and the pixel values of the pixels at the second insertion / extraction position, respectively. Item 9. The image processing apparatus according to Item 9. A third determining means for determining a third insertion / extraction position next to the first insertion / extraction position in a direction orthogonal to the scaling direction,
A fourth position that is next to the third insertion / extraction position in a direction orthogonal to the scaling direction and is the same as the first insertion / extraction position in the main scanning direction as the fourth insertion / extraction position. Determining means and
The image processing apparatus according to any one of claims 1 to 11, wherein the image processing apparatus has. The image processing apparatus according to claim 12, wherein the fourth determination means performs a process of determining the fourth insertion / extraction position a predetermined number of times. When the number of times the fourth insertion / removal position is determined is less than the predetermined first number of times, the fourth determination means places the fourth insertion / removal position at the same position in the main scanning direction as the first insertion / removal position. The image processing apparatus according to claim 12, wherein the insertion / removal position is determined. When the fourth insertion / removal position is determined more times than the predetermined first number of times, the fourth determination means places the fourth insertion / removal position at a different position in the main scanning direction from the first insertion / extraction position. The image processing apparatus according to claim 12, wherein the insertion / removal position of the image processing apparatus is determined. Based on image data for each color, which is provided with a writing unit containing a plurality of light emitting elements arranged along the main scanning direction of the photoconductor for each color and scaled at the first resolution. An image forming apparatus that superimposes images to form a color image.
The image processing apparatus according to any one of claims 1 to 15, which processes the input image data.
A conversion means for converting the resolution from the first resolution to the second resolution, and
An image forming apparatus characterized by having. The image forming apparatus according to claim 16, wherein the first resolution is N (N: integer) times the second resolution. An image processing method for processing image data for forming an image on the surface of the photoconductor using a plurality of light emitting elements arranged along the main scanning direction of the photoconductor.
By inserting or deleting pixels in the image data, the pixels are inserted or the pixels are inserted or deleted based on the scaling factor of the image in which the image formed from the image data is scaled in the main scanning direction. A specific step to specify the reference section for specifying the first insertion / removal position and the second insertion / removal position to delete the
Based on the reference section specified in the specific step, the first determination step for determining the first insertion / removal position and the first determination step.
Based on the first insertion / removal position determined in the first determination step, the second determination step for determining the second insertion / extraction position and the second determination step.
A scaling step of scaling the image by inserting or deleting pixels in the image data based on the first insertion / extraction position and the second insertion / extraction position.
An image processing method characterized by having. A program for causing a computer to execute the image processing method according to claim 18.

Images