JP2009177314A - Image forming apparatus, image forming method, and program - Google Patents

Abstract

The tracking signal is not affected by smoothing even if there is a tracking signal in the vicinity of the edge, and the tracking signal can be detected stably. Even if there is a tracking signal in the vicinity of the edge, the edge can be normally detected. Image forming apparatus in which smoothing is performed and edge jaggies are not noticeable.
An information addition processing unit that adds an additional signal, which is information for specifying a device to an input image signal, to an image corresponding to the input image signal, and smoothing processing of an edge of the image corresponding to the input image signal And a smoothing processing unit 209 that performs the processing, and the smoothing processing unit 209 does not perform the smoothing processing on the image signal of the pixel in the region to which the additional signal is added by the information addition processing unit 206, and the additional signal is not added. Smoothing processing is performed on the signal.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus, an image forming method, and a program, and more particularly to an image forming apparatus that forms an image based on an image signal.

  In recent years, image forming apparatuses such as color printers and color copiers have been able to form high-quality images due to improved performance. Under such circumstances, it is becoming possible to form images similar to banknotes, banknotes, securities, etc., and problems such as counterfeiting of banknotes, securities, etc. and copyright infringement will increase in the future. It is possible.

  As a countermeasure against these problems, for example, an additional signal (tracking signal) indicating information for identifying the device such as the serial number of the image forming apparatus is added to the formed color image so that it is difficult for human eyes to identify. A method has been proposed (see, for example, Patent Document 1).

  Usually, this additional signal is added to the entire image. In addition, when a dot pattern is added to a color image composed of yellow, magenta, cyan, and black planes in order to make it difficult for human eyes to identify, it is usually added only to the yellow plane.

  By performing the above addition, when an image that should be prohibited from image formation or a copy image that should be prohibited from copying appears, an additional signal is extracted from these images and additional information is restored. By doing so, it is possible to specify the device on which these images are formed.

  Conventionally, an additional signal is added after halftone processing, that is, halftone processing, is performed on an input image signal. However, when an additional signal is added after halftone processing, there are the following problems.

1) Depending on the positional relationship between the halftone halftone dot and the additional signal, it may be difficult to identify the additional signal, or the image quality may be deteriorated. 2) Identification of the additional signal depending on the density of the image or the number of halftone lines. 3) Since it is difficult to finely control the dot size due to electrophotographic characteristics, the intensity of the additional signal cannot be finely adjusted.

Therefore, it is considered to add an additional signal before halftone processing. By adding or subtracting predetermined data in a certain area in the original image data by adding an additional signal before the halftone process, for the above 1) and 2), a halftone dot and an additional signal The relationship is stable regardless of density or halftone type. For this reason, it is not difficult to identify the additional signal or the image quality is not deteriorated. For 3), it is possible to finely adjust the strength of the additional signal by adjusting the amount of addition or subtraction.
Japanese Patent Laid-Open No. 06-113107

  While performing the above halftone processing, smoothing is performed to smooth out the edges of characters and graphics in the image by eliminating jaggy (jagged edges that appear when characters and graphics are represented by bitmaps). The process called is performed. This smoothing process is usually performed after the halftone process. Therefore, if the additional signal is added before the halftone process, the smoothing process is performed after the additional signal is added. However, when the smoothing process is performed after the additional signal is added, if the additional signal is present near the edge of the image, the additional signal is affected by the smoothing process, and the additional signal is changed, thereby making it difficult to detect the additional signal. There is a case. On the other hand, there is an additional signal in the vicinity of the edge, so that smoothing does not function, and there is a problem that jaggy is conspicuous without performing smoothing that should be applied to the edge.

  The present invention has been made paying attention to the above points, and even if there is a tracking signal in the vicinity of the edge of the image, the tracking signal can be stably detected without being affected by the smoothing processing. It is an object to provide an image forming apparatus, an image forming method, and a program. It is another object of the present invention to provide an image forming apparatus, an image forming method, and a program in which smoothing processing of an edge of an image is normally performed even if there is a tracking signal in the vicinity of the edge of the image, and edge jaggies are not noticeable. To do.

  In order to solve the above problems, an image forming apparatus of the present invention has the following configuration.

  (1) Tracking signal adding means for adding a tracking signal, which is information for specifying a device to an input image signal, to an image corresponding to the input image signal; and corresponding to the input image signal Smoothing processing means for performing smoothing processing of an edge of an image, and without performing the smoothing processing by the smoothing processing means on the image signal of the pixel in the region to which the tracking signal is added by the tracking signal adding means, An image forming apparatus that performs the smoothing process on an image signal to which no tracking signal is added.

  (2) First tracking signal addition for outputting a non-superimposed signal that does not add the first tracking signal together with a superimposed signal to which the first tracking signal, which is information for specifying a device, is added to the input image signal Means, a first halftone processing means for performing halftone processing on the superimposed signal and the non-superimposed signal output by the first tracking signal adding means, and the first halftone processing means. A second tracking signal generating means for comparing the superimposed signal that has undergone halftone processing and the non-superimposed signal, and generating a second tracking signal based on a result of the comparison, and the input image signal A second halftone processing unit that performs halftone processing on the image, a smoothing processing unit that performs a smoothing process on the image signal subjected to the halftone processing by the second halftone processing unit, and the smoothing processing unit. The An image forming apparatus comprising: a second tracking signal adding unit that adds the second tracking signal generated by the second tracking signal generating unit to the image signal subjected to the aging process. .

  According to the present invention, even if a tracking signal is present in the vicinity of the edge of the image, the tracking signal is not affected by the smoothing process, and the tracking signal can be detected stably. Further, even if there is a tracking signal in the vicinity of the edge of the image, the edge smoothing process is normally performed, and the edge jaggy does not stand out.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 shows an example of an electrophotographic color image forming apparatus to which the present invention is applied.

  FIG. 1 is a configuration diagram showing an image forming unit of a tandem color image forming apparatus employing an intermediate transfer belt 27 as an intermediate transfer member.

<Operation of Image Forming Unit>
The operation of the image forming unit in the electrophotographic color image forming apparatus will be described with reference to FIG. The color image forming apparatus first forms an electrostatic latent image with exposure light that is turned on based on an exposure time converted from input image data (hereinafter referred to as input image data). Is developed to form a single color toner image. The single-color toner images are superimposed to form a multi-color toner image, the multi-color toner image is transferred to the transfer material 11, and the multi-color toner image on the transfer material 11 is fixed. The image forming unit that performs such an operation is configured as follows. First, a paper feed unit 21 (paper feed cassette 21a, manual feed tray 21b) is provided. Next, photosensitive drums 22Y, 22M, 22C, and 22K, which are photoconductors for each station arranged in parallel for development colors, injection chargers 23Y, 23M, 23C, and 23K as primary charging means, and toner cartridges 25Y, 25M, 25C, and 25K. Consists of. Further, the image forming apparatus includes developing devices 26Y, 26M, 26C, and 26K as developing means, an intermediate transfer belt 27, a transfer roller 28, and a fixing unit 30.

  The photosensitive drums 22Y, 22M, 22C, and 22K are configured by applying an organic optical transmission layer to the outer periphery of an aluminum cylinder, and rotate by receiving a driving force of a driving motor (not shown). The drive motor rotates the photosensitive drums 22Y, 22M, 22C, and 22K in the counterclockwise direction according to the image forming operation.

  As primary charging means, four injection chargers 23Y, 23M, 23C, and 23K for charging the photosensitive drums of yellow (Y), magenta (M), cyan (C), and black (K) for each station. It is the structure provided with. Each injection charger is provided with sleeves 23YS, 23MS, 23CS, and 23KS.

  Exposure light to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the scanner units 24Y, 24M, 24C, and 24K, and the electrostatic latent images are selectively exposed by exposing the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. An image is formed.

  As developing means, in order to visualize the electrostatic latent image, four developing units 26Y, 26M, and 26C for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station. , 26K. Each developing device is provided with sleeves 26YS, 26MS, 26CS, and 26KS. Each developing device is detachably attached.

  The intermediate transfer belt 27 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, rotates clockwise when forming a color image, rotates with the rotation of the photosensitive drums 22Y, 22M, 22C, and 22K, and is monochromatic. A toner image is superimposed and transferred. Thereafter, a transfer roller 28 (to be described later) comes into contact with the intermediate transfer belt 27 to sandwich and transfer the transfer material 11, and the multicolor toner image on the intermediate transfer belt 27 is transferred to the transfer material 11.

  While transferring the multicolor toner image onto the transfer material 11, the transfer roller 28 contacts the transfer material 11 at the position 28a, and the image forming process on the transfer material 11 is finished, that is, the printing is finished. After that, it is separated to the position 28b.

  The fixing unit 30 melts and fixes the transferred multi-color toner image while conveying the transfer material 11, and as shown in FIG. 1, the fixing roller 31 for heating the transfer material 11 and the transfer material 11 are fixed to the fixing roller. A pressure roller 32 is provided for pressure contact with 31. The fixing roller 31 and the pressure roller 32 are formed in a hollow shape, and heaters 33 and 34 are incorporated therein. That is, the transfer material 11 holding the multicolor toner image is conveyed by the fixing roller 31 and the pressure roller 32, and heat and pressure are applied to fix the toner on the surface.

  After the toner image is fixed, the transfer material 11 is discharged to a discharge tray (not shown) by a discharge roller (not shown) and the image forming operation is finished.

  A cleaning device 29 serving as a cleaning unit cleans the toner remaining on the intermediate transfer belt 27, and after the four-color multicolor toner image formed on the intermediate transfer belt 27 is transferred to the transfer material 11. Waste toner is stored in a cleaner container.

<Signal Processing Flow of Image Forming Apparatus>
Next, the flow of signal processing in this embodiment will be described with reference to the block diagram of FIG. When a print command is received from an application (not shown), a page description language is transmitted from the driver 201 and input to the printer 212. When outputting a bitmap image, the page description language includes bitmap data.

  The following processing units are arranged in the printer 212. First, a decoder 202, a band memory A 203, a band memory B 204, a color conversion processing unit 205, an information addition processing unit 206 (tracking signal addition means), and a γ correction unit 207 are arranged. Further, a halftone processing unit 208 (halftone processing unit) and a smoothing processing unit 209 (smoothing processing unit) are arranged. The input page description language is interpreted by the decoder 202 and converted to RGB 8-bit image data. RGB image data is input to the band memory. The band memory is composed of two memories, a band memory A 203 and a band memory B 204, and one memory can store image data for several lines. First, the image data of the image area corresponding to the first predetermined number of lines is expanded in the band memory A 203, and the image data of the image area corresponding to the next predetermined number of lines is expanded in the band memory B 204. From 203, RGB image data is output. Further, while the image data of the image area for the next predetermined number of lines is expanded in the band memory A 203, the RGB image data is output from the band memory B 204, and so on alternately to the two band memories. Image data is developed and output. The RGB image data output from the band memory is input in parallel to the color conversion processing unit 205, subjected to predetermined color conversion processing and UCR (Under Color Removal) processing, and Y, M, C, It is converted into a K image signal. As described above, the color electrophotographic printer of this embodiment forms an image for each screen of each of the Y, M, C, and K colors. That is, yellow, magenta, cyan, and black planes are formed. For this reason, the color conversion processing unit 205 performs the following in the order of planes, that is, data for one screen of Y, data for one screen of M, data for one screen of C, and data for one screen of K. Image signals corresponding to the planes are output with a time difference.

  Next, information is added only to the yellow plane by the information addition processing unit 206, correction is performed by the γ correction unit 207 so that the output density curve is optimized, and the halftone processing unit 208 performs halftone processing by systematic dithering. Processing is performed. For the magenta, cyan, and black planes, no information is added by the information addition processing unit 206, and correction is performed by the γ correction unit 207 so that the output density curve is optimized, and the halftone processing unit 208. The halftone processing is performed by the systematic dither method. The image signal corresponding to each plane output from the halftone processing unit 208 is subjected to smoothing processing by the smoothing processing unit 209. After that, pulse width modulation is applied by a PWM (Pulse Width Modulation) processing unit 210, D / A (digital / analog) conversion is performed, and then input to the laser driving unit 211 to form an image. Further, additional position information 213 (described later) is input from the information addition processing unit 206 to the smoothing processing unit 209.

<Adding method of additional signal>
Next, a method for adding information in this embodiment will be described. In this embodiment, information is added by performing an operation on yellow pixel data.

  FIG. 16 shows a basic additional form (hereinafter referred to as an additional pattern) of an additional signal on an image.

  Positions indicated by black circles (0, 0) to (4, 4) in FIG. 16 are referred to as additional positions. The additional positions are arranged at intervals of Tx (for example, 20 dots) in the X direction and Ty (for example, 20 dots) in the Y direction. Each additional position represents 1-bit information. When it is 1, an additional signal is added, and when it is 0, no additional signal is added. Further, two additional signals are added at a predetermined interval in order to indicate the start position of the additional pattern at the position (0, 0) (upper left in FIG. 16). Since the two additional signals for indicating the start position of the additional pattern in FIG. 16 are fixedly assigned 1, the entire additional pattern can be represented by 24-bit information instead of 25 bits. The additional pattern shown is repeated for the entire image. Therefore, in the image of one page A4, an additional signal is added over the entire image by the additional pattern of FIG.

  FIG. 4 is a diagram for explaining what the additional signal is specifically. It is a yellow dot of 3 pixels × 3 pixels, and by adding these, + α (predetermined value) can be added to the density. Note that 3 pixels × 3 pixels is an example of the additional signal, and may be 2 pixels × 2 pixels or 4 pixels × 4 pixels. If applicable as an additional signal, it can be expanded to m pixels × n pixels. In the following description, a typical case of 3 pixels × 3 pixels will be described. Further, the shaded portion in the figure represents the pixel to which the density is added, and the white portion represents the surrounding pixel. Hereinafter, an area (region) to which the dot density is added is referred to as an additional signal area.

  Here, the relationship between FIG. 4 and FIG. 16 will be described. For the additional position to which 1 bit to which the additional signal is added in FIG. 16 is assigned, the additional position and the upper left of the portion shown by the shaded area in FIG. Match. That is, when a plurality of 1 bits to which the additional signal is added are assigned to the additional positions in FIG. 16, a plurality of yellow 3 pixel × 3 pixel dot patterns as shown in FIG. 4 are superimposed. It will be.

<Information addition processing>
Next, information addition processing in the information addition processing unit 206 in the present embodiment for adding the additional pattern to the image will be described.

  FIG. 3 is a block diagram of the information addition processing unit 206. The ROM 301 contains an individual ID of the image forming apparatus. The CPU 302 receives a 24-bit individual ID from the ROM 301 during image formation and stores it in the RAM 303. The stored individual ID data is scrambled by replacing the position of each bit according to a predetermined rule, and further converted into ON / OFF information of each additional position according to a predetermined rule (encryption rule). And stored in the additional position information storage unit 304. The CPU 302 determines a position (addition signal area) to which an additional signal in the image is added according to the ON / OFF information of each additional position in the additional position information storage unit 304, and sends the coordinate information of the additional signal area to the addition designation processing unit 708. Enter. Note that the coordinate information of the additional signal area indicates the coordinate information of each of the nine dots in the shaded portion shown in FIG.

  The main scanning counter 305 performs a counting operation in accordance with the clock signal VCLK in the main scanning direction of the image signal, and notifies the additional designation processing unit 307 of the count number in the main scanning direction. The sub-scanning counter 306 performs a counting operation according to the sub-scanning direction clock signal LCLK, and notifies the additional designation processing unit 307 of the count number in the sub-scanning direction. The coordinates of the dot being drawn can be specified by the count number in the main scanning direction and the count number in the sub-scanning direction. Only when the color designation signal notified from the CPU 302 designates yellow, the additional designation processing unit 307 counts the count in the main scanning direction and the sub-scanning direction and the coordinates of the additional signal area input from the additional position information storage unit 304. Browse information. If the coordinates indicated by the count number in the main scanning direction and the count number in the sub-scanning direction coincide with the coordinates of the additional signal area, the additional designation signal is turned on, and the additional signal (tracking signal) generated by the additional signal generation unit 308 Is input to the signal conversion unit 309.

  When the additional designation signal is on, the signal conversion unit 309 superimposes the input additional signal on the image signal corresponding to the input yellow plane. At the same time, the additional position information storage unit 304 outputs the coordinate information of the additional signal area to the smoothing processing unit 209 as additional position information 213.

<Halftone processing>
Next, halftone processing in the halftone processing unit 208 in this embodiment will be described.

  Since the halftone processing in this embodiment is performed by a systematic dither method, the halftone processing unit 208 stores a dither matrix.

  FIG. 5A shows the dither matrix of this embodiment. Each cell number in the figure represents a threshold value, and the threshold value of each cell is compared with the input image signal. If the input image signal ≧ the threshold value, the output is ON, and if the input image data <the threshold value, the output = Turn off. The dither matrix shown in FIG. 5A is repeated in the image as shown in FIG. 5B, and the input image signal is compared with the threshold value. FIG. 6 shows how dots are formed as a result of processing a uniform input image signal with an input value of 4 using the dither matrix of FIG. One square in FIG. 6 represents one pixel of the image forming apparatus. Since cells whose threshold values are 1 to 4 are turned on, halftone dots are formed in the hatched portions.

  The additional signal added by the information addition processing unit 206 is also subjected to halftone processing by the halftone processing unit 208 being subjected to halftone processing.

  Here, FIG. 7 shows a state in which, for example, α = 5 and the additional signal added to the area of input image data = 0 is subjected to halftone processing. In the figure, the number of each cell indicates the threshold value of the dither matrix. A 3 × 3 thick frame portion in the figure is an area to which an additional signal is added (an area to which a tracking signal is added), and the pixel value is 5 in the pixels in this area. The pixel value 5 is compared with the threshold value, and the pixels having the threshold value of 5 or less are turned on. Therefore, the pixels indicated by diagonal lines in the drawing are turned on as a result of the halftone process. FIGS. 7A, 7B, and 7C show examples in which the positional relationship between the additional signal and the dither matrix is different. When added to the position of FIG. 7A, the additional signal becomes 2 × 2 dots by halftone processing, and when added to the position of FIG. 7B, it becomes a dot of area 5, and FIG. ) Is formed by dispersed dots having areas 1 and 2. As described above, the shape of the additional signal after halftone processing changes depending on the positional relationship between the dither matrix and the additional signal.

<Smoothing process>
Next, the smoothing process in the smoothing processing unit 209 will be described.

  FIG. 8 is a diagram illustrating patterns 1a to 16a used for pattern matching of the smoothing process and results 1b to 16b of the smoothing process in the present embodiment. In this embodiment, 3 × 3 window processing is performed on the input image signal. That is, pattern matching is performed on the 3 × 3 area around the pixel of interest, and when the pattern in the 3 × 3 area matches any of the patterns 1a to 16a in FIG. 8, attention is paid to 1b to 16b. Change pixels to half dots. That is, the target pixel is set to be in the middle in the 3 × 3 area. Note that if the target pixel is at the edge of the image, exceptional processing is performed. The half dots in which the diagonal lines 1b to 16b in the figure are changed are shown. The above processing is performed on all pixels in the image. FIG. 9 shows the result of such smoothing processing performed on the edge portion of the image. For example, when an image as shown in FIG. 9A is input, as a result of performing the above smoothing process, half dots as shown by diagonal lines are formed as shown in FIG. 9B, and the edge smoothing process is performed. Is called.

<Smoothing Process Flowchart Considering Additional Signal>
In this embodiment, the smoothing process is not performed for the area to which the additional signal is added. The operation of the smoothing processing unit 209 in the present embodiment will be described with reference to the smoothing processing flowchart shown in FIG. When the smoothing process is started (step 1001, indicated as S1001 in the figure), it is determined whether or not the pixel (target pixel) is within the additional signal area based on the additional position information 213 that is the coordinates of the input additional signal area. (Step 1002). If it is within the additional signal area, the process proceeds to the next pixel without executing the smoothing process (step 1004). On the other hand, if the pixel is not in the additional signal area, the smoothing process described in FIG. 8 is performed (step 1003), and the process proceeds to the next pixel (step 1004). This operation is sequentially executed for all the pixels in the image.

  The difference in how much the dot detection difficulty of the additional signal is different between the conventional smoothing process and the process of this embodiment when there is an additional signal near the edge of the image character or graphic will be described.

<Conventional smoothing process>
FIG. 11A shows the input image signal of the edge portion of the same image as FIG. 9, and the thick frame portion of the figure is an area where an additional signal is added to this input image signal. +5 (= + α) is added to the input image signal. When the result of addition is 12 or more, it is 12. FIG. 11B shows the image signal after the addition signal is added. Further, the dither matrix in this area is as shown in FIG. 11C, and the result of performing halftone processing on the image signal in FIG. 11B is FIG. 11D. The shaded dots in the figure indicate the dots resulting from the halftone processing of the additional signal. When the smoothing process shown in FIG. 8 is performed on this image signal, the result is as shown in FIG. 11E, and one of the dots of the additional signal is changed to a half dot (in FIG. Half-dot part). As a result, it becomes difficult to detect the dots of the additional signal.

<When smoothing processing of the present invention is performed>
Next, the case where the smoothing process of the present invention is performed on the same input image signal will be described. The flow of processing up to halftone processing is the same as in the prior art (same as in FIGS. 11A to 11C), and the image subjected to halftone processing is as shown in FIG. In this embodiment, since the pixels in the area (additional signal area) to which the additional signal indicated by the thick frame in FIG. 12A is added are not smoothed, the result of the smoothing process is as shown in FIG. become. For this reason, the dots of the additional signal indicated by shading are held as they are without being smoothed, and the dots of the additional signal can be detected.

  With the above configuration, the present invention can be effectively implemented. As described above, according to the present embodiment, even if there is an additional signal in the vicinity of the image character or graphic edge, the additional signal is not affected by the smoothing process, and the additional signal can be detected stably. Become.

  In this embodiment, the systematic dither method is used as the halftone processing. However, the present invention can be effectively implemented using other halftone processing methods such as error diffusion.

  Next, a second embodiment using the present invention will be described. In this embodiment, similarly to the first embodiment, a color image forming apparatus using an electrophotographic method is used.

  The configuration of the color image forming apparatus of the present embodiment and the form of the additional signal are the same as those of the first embodiment, and will be described below using the same reference numerals. The signal flow up to the color conversion processing unit 205 and after the PWM processing unit 210 in this embodiment is the same as that in the first embodiment. The flow of signals after the color conversion processing in this embodiment and before the PWM processing is shown in the block diagram of FIG.

  The color-converted image signal of each plane is subjected to density correction by a γ correction unit 1301, subjected to halftone processing by a halftone processing unit 1302 (second halftone processing unit), and then subjected to a smoothing processing unit 1303 (smoothing processing unit). ). The smoothing processing unit 1303 performs smoothing processing in the same manner as in FIG.

  On the other hand, the color-converted image signal of each plane is input to a first signal conversion unit 1304 (first tracking signal addition means), and the first signal conversion unit 1304 generates the first signal generated by the first additional signal generation unit 1310. One additional signal (first tracking signal) is superimposed on the image signal to output a superimposed image signal. At the same time, the first signal converter 1304 outputs a non-superimposed image signal that does not superimpose the first additional signal on the image signal. Here, the first additional signal is the same signal as the additional signal of the first embodiment shown in FIG.

  The superimposed image signal on which the additional signal output from the first signal conversion unit 1304 is superimposed and the non-superimposed non-superimposed image signal are subjected to density correction by the γ correction unit 1305, respectively. Then, halftone processing is performed by the halftone processing unit 1306 (first halftone processing unit), and the result is input to the comparison processing unit 1307 (second tracking signal generation unit). The comparison processing unit 1307 compares the superimposed image signal and the non-superimposed image signal, extracts the difference between the two, and stores the difference as a second additional signal (second tracking signal) in the second additional signal storage unit 1308.

  The main scanning counter 1311 performs a counting operation according to the clock signal VCLK in the main scanning direction of the image signal, and notifies the additional designation processing unit 1313 of the count number in the main scanning direction. The sub-scanning counter 1312 performs a counting operation in accordance with the sub-scanning direction clock signal LCLK and notifies the additional designation processing unit 1313 of the count number in the sub-scanning direction. The additional designation processing unit 1313 receives the additional signal input from the count number in the main scanning direction and the sub-scanning direction and the additional position information storage unit 1314 only when the color designation signal notified from the CPU (not shown) designates yellow. Refer to the coordinate information of the area. Then, when the position to which the dot is to be added, that is, the coordinates indicated by the count number in the main scanning direction and the count number in the sub-scanning direction coincide with the coordinates of the additional signal area, the addition designation signal is turned on. Then, the second additional signal stored in the second additional signal storage unit 1308 is called and input to the second signal conversion unit 1309 (second tracking signal adding means).

  When the additional designation signal is on, the second signal conversion unit 1309 superimposes the input second additional signal on the image signal corresponding to the yellow plane smoothed by the smoothing processing unit 1303.

  The difference between the conventional smoothing process and the smoothing process of this embodiment when there is an additional signal in the vicinity of the image character or graphic edge will be described.

<Conventional smoothing process>
FIG. 14A shows an input image signal at an edge portion of the same input image as in the first embodiment, and a thick frame portion of the drawing is an additional signal in which an additional signal is added to the input image signal. This area is a region in which +5 (= + α) is added to the input image signal. The dither matrix in this area is as shown in FIG. 14C, and FIG. 14D shows the result of performing halftone processing on the image signal in FIG. 14B. The shaded dots in the figure indicate the dots resulting from the halftone processing of the additional signal. The smoothing process shown in FIG. 8 is performed on this image. Then, the pattern shape of the edge of the image in the vicinity of the additional signal area does not match any of 1a to 16a in FIG. 8, and the smoothing process is not performed in the vicinity of the additional signal area as shown in FIG. )). Therefore, the smoothing process for the edge of the image does not function normally due to the presence of the additional signal, the jaggy of the edge becomes noticeable, and the image quality deteriorates.

<When smoothing processing of the present invention is performed>
Next, the case where the smoothing process of the present embodiment is performed on the same input image signal will be described. As for the first additional signal, +5 is added to the image signal in the additional signal area as described above. First, a first additional signal is added to the image signal by the first signal conversion unit 1304 and output (superimposed image signal). At the same time, a signal to which the first additional signal is not added is output (non-superimposed image signal). FIGS. 15A and 15B show the results of performing γ correction on the superimposed image signal and the non-superimposed image signal by the γ correction unit 1305 and performing the halftone processing by the halftone processing unit 1306. The comparison processing unit 1307 compares the image signals of FIG. 15A (superimposed image signal) and FIG. 15B (non-superimposed signal), and the extracted second additional signal is the thick frame in FIG. 15C. It looks like the dot shown in.

  On the other hand, as a result of performing γ correction and halftone processing by the γ correction unit 1301 and halftone processing unit 1302 on the input image signal and then performing smoothing processing by the smoothing processing unit 1303, the result is as shown in FIG. When the second additional signal (FIG. 15C) is added to the image signal by the second signal conversion unit 1309, an image as shown in FIG. 15E is obtained. As can be seen from FIG. 15 (E), smoothing processing is normally performed on the edge portion of the image, and the additional signal is also normally added, so that the additional signal can be detected while maintaining the image quality of the edge. It becomes possible. Further, as can be seen from FIG. 15E, in the present embodiment, dots other than the additional signal are half-dotted by the smoothing process, so that detection of the dot of the additional signal is further easier than in the first embodiment.

  As described above, according to the present embodiment, even if there is an additional signal in the vicinity of the image character or graphic edge, the additional signal is not affected by the smoothing process, and the additional signal can be detected stably. Become. Further, even if there is an additional signal in the vicinity of the edge of the image, smoothing processing of the edge of the image is normally performed, and the jaggy of the edge does not stand out. With the above configuration, the present invention can be effectively implemented.

<Other examples>
Note that the present invention can be applied to a system (for example, a copier, a facsimile machine, etc.) consisting of a single device even if it is applied to a system composed of a plurality of devices (eg, a host computer, interface device, reader, printer, etc.). You may apply. Another object of the present invention is to supply a recording medium recording a program code for realizing the functions of the above-described embodiments to a system or apparatus, and the computer of the system or apparatus reads and executes the program code stored in the storage medium. Is also achieved. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention.

  Further, according to the present invention, the operating system (OS) running on the computer performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized by the processing. This is also included. Furthermore, the present invention is also applied to the case where the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. In that case, the CPU of the function expansion card or function expansion unit performs part or all of the actual processing based on the written program code instruction, and the functions of the above-described embodiments are realized by the processing. .

1 is a configuration diagram illustrating an image forming unit of a color image forming apparatus according to Embodiments 1 and 2 of the present invention. FIG. It is a block diagram explaining the flow of the signal processing of the color image forming apparatus in Example 1 of this invention. It is a block diagram which shows the structure of the information addition process part in Example 1 of this invention. It is a figure which shows the additional signal in Example 1, 2 of this invention. (A) is a figure which shows the dither matrix in Example 1, 2, and (B) is a figure which shows the repetition of a dither matrix. FIG. 6 is a diagram illustrating a result of performing halftone processing with a dither matrix in FIG. 5 on a uniform input image signal having an input value of 4; It is a figure which shows a mode that the halftone process was applied to the additional signal, (A), (B), (C) is a figure which shows that a result changes with the positional relationship of an additional signal and a dither matrix. It is a figure which shows the pattern used for the pattern matching of the smoothing process in Example 1, 2 of this invention, and the result of having performed the smoothing process. 5A and 5B are diagrams illustrating smoothing processing according to the first and second embodiments of the present invention, where FIG. 5A is a diagram illustrating an input image, and FIG. 5B is a diagram illustrating a result of edge smoothing performed by forming half dots. is there. It is a flowchart which shows the flow of the smoothing process in Example 1 of this invention. FIGS. 9A and 9B are diagrams illustrating conventional smoothing processing, where FIG. 9A is a diagram illustrating an input image signal of the same image as FIG. 9A, FIG. 9B is a diagram illustrating an image signal after addition of an additional signal, and FIG. The figure which shows a matrix, (D) is a figure which shows the result of having performed the halftone process with respect to the image signal of (B), (E) is one dot of the additional signal changed into a half dot as a result of performing the smoothing process It is a figure which shows having done. 5A and 5B are diagrams illustrating a smoothing process in Embodiment 1 of the present invention, in which FIG. 5A is a diagram illustrating an image that has been subjected to halftone processing, and FIG. It is a figure which shows being hold | maintained. It is a block diagram explaining the flow of the signal processing of the color image forming apparatus in Example 2 of this invention. FIGS. 9A and 9B are diagrams illustrating conventional smoothing processing, where FIG. 9A is a diagram illustrating an input image signal of the same image as FIG. 9A, FIG. 9B is a diagram illustrating an image signal after addition of an additional signal, and FIG. The figure which shows a matrix, (D) is a figure which shows the result of having performed the halftone process with respect to the image signal of (B), (E) is a figure which shows that smoothing does not function even if it performs a smoothing process. 5A and 5B are diagrams illustrating smoothing processing according to the second embodiment of the present invention, in which FIG. 5A illustrates an image to which a first additional signal is added, FIG. 5B illustrates an image to which a first additional signal is not added, and FIG. Is a diagram showing the second additional signal, (D) is a diagram showing the result of performing γ correction, halftone processing, and smoothing processing on the input image signal, and (E) is a second addition to the image signal of (D). It is a figure which shows the image to which the signal was added. It is a figure which shows the form of the additional pattern in Example 1, 2 of this invention.

Explanation of symbols

11 Transfer Material 21a Paper Feed Cassette 21b Manual Tray 22Y, 22M, 22C, 22K Photosensitive Drum (Photoconductor)
23Y, 23M, 23C, 23K Injection charger (primary charging means)
24Y, 24M, 24C, 24K Scanner 25Y, 25M, 25C, 25K Toner cartridge 26Y, 26M, 26C, 26K Developer (Developing means)
27 Intermediate transfer belt (intermediate transfer member)
28 Transfer roller 29 Cleaning device (cleaning means)
30 Fixing section 31 Fixing roller 32 Pressure roller 33, 34 Heater 201 Driver 202 Decoder 203 Band memory A
204 band memory B
205 Color conversion processing unit 206 Information addition processing unit (tracking signal addition means)
207 γ correction unit 208 Halftone processing unit (halftone processing means)
209 Smoothing processing unit (smoothing processing means)
210 PWM processing unit 211 Laser driving unit 212 Printer

Claims (10)

A tracking signal adding means for adding a tracking signal, which is information for specifying a device to the input image signal, to an image corresponding to the input image signal;
Smoothing processing means for performing smoothing processing of an edge of an image corresponding to the input image signal;
Have
The smoothing processing by the smoothing processing unit is not performed on the image signal of the pixel to which the tracking signal is added by the tracking signal adding unit, and the smoothing processing is performed on the image signal to which the tracking signal is not added. An image forming apparatus. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the tracking signal adding unit adds a tracking signal by adding a predetermined yellow density to an area of m pixels × n pixels. The image forming apparatus according to claim 1,
Halftone processing means for performing halftone processing on the input image signal;
The tracking signal adding means adds the tracking signal before the halftone processing by the halftone processing means is performed on the image signal,
The image forming apparatus according to claim 1, wherein the smoothing processing unit performs the smoothing process on the image signal on which the halftone process is performed after the halftone process is performed by the halftone processing unit. First tracking signal adding means for outputting a non-superimposed signal that does not add the first tracking signal together with a superimposed signal to which the first tracking signal, which is information for specifying a device, is specified with respect to the input image signal;
First halftone processing means for performing halftone processing on the superimposed signal and the non-superimposed signal output by the first tracking signal adding means;
Second tracking signal generation means for comparing the superimposition signal subjected to halftone processing by the first halftone processing means with the non-superimposition signal and generating a second tracking signal based on the comparison result When,
Second halftone processing means for performing halftone processing on the input image signal;
Smoothing processing means for performing smoothing processing on the image signal subjected to halftone processing by the second halftone processing means;
Second tracking signal adding means for adding the second tracking signal generated by the second tracking signal generating means to the image signal subjected to smoothing processing by the smoothing processing means;
An image forming apparatus comprising: A tracking signal adding step of adding a tracking signal, which is information for specifying a device to the input image signal, to an image corresponding to the input image signal;
A smoothing process step for performing a smoothing process on an edge of an image corresponding to the input image signal;
Have
The smoothing process is not performed on the image signal of the pixel in the region to which the tracking signal is added in the tracking signal adding step, and the smoothing process is performed on the image signal to which the tracking signal is not added. An image forming method characterized by comprising: The image forming method according to claim 5.
In the image forming method, the tracking signal adding step adds a tracking signal by adding a predetermined density of yellow to an area of m pixels × n pixels. The image forming method according to claim 5.
A halftone processing step for performing halftone processing on the input image signal;
The tracking signal adding step adds the tracking signal before the halftone processing by the halftone processing step is performed on the image signal,
In the image forming method, the smoothing processing step performs the smoothing processing on the image signal on which the halftone processing is performed after the halftone processing is performed in the halftone processing step. A first tracking signal adding step for outputting a non-superimposed signal that does not add the first tracking signal together with a superimposed signal to which the first tracking signal, which is information for specifying a device, is specified with respect to the input image signal;
A first halftone processing step of performing halftone processing on the superimposed signal output by the first tracking signal adding step and the non-superimposed signal;
A second tracking signal generation step of comparing the superimposition signal that has been subjected to halftone processing in the first halftone processing step with the non-superimposition signal and generating a second tracking signal based on the comparison result When,
A second halftone processing step for performing halftone processing on the input image signal;
A smoothing process step of performing a smoothing process on the image signal subjected to the halftone process in the second halftone process step;
A second tracking signal adding step of adding the second tracking signal generated by the second tracking signal generating step to the image signal subjected to the smoothing processing by the smoothing processing step;
An image forming method comprising: A tracking signal adding step of adding a tracking signal, which is information for specifying a device to the input image signal, to an image corresponding to the input image signal;
A smoothing process step for performing a smoothing process on an edge of an image corresponding to the input image signal;
A program for causing a computer to execute
The smoothing process is not performed on the image signal of the pixel in the region to which the tracking signal is added in the tracking signal adding step, and the smoothing process is performed on the image signal to which the tracking signal is not added. A program characterized by being performed. A first tracking signal adding step for outputting a non-superimposed signal that does not add the first tracking signal together with a superimposed signal to which the first tracking signal, which is information for specifying a device, is specified with respect to the input image signal;
A first halftone processing step of performing halftone processing on the superimposed signal output by the first tracking signal adding step and the non-superimposed signal;
A second tracking signal generation step of comparing the superimposition signal that has been subjected to halftone processing in the first halftone processing step with the non-superimposition signal and generating a second tracking signal based on the comparison result When,
A second halftone processing step for performing halftone processing on the input image signal;
A smoothing process step of performing a smoothing process on the image signal subjected to the halftone process in the second halftone process step;
A second tracking signal adding step of adding the second tracking signal generated by the second tracking signal generating step to the image signal subjected to the smoothing processing by the smoothing processing step;
A program that causes a computer to execute.

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