JP2009223237A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device and an image processing method that can suppress scattering of toner and ensure image sharpness. <P>SOLUTION: The image processing apparatus 1000 includes: a density change degree detecting means 1310 for detecting the degree of a change in the density value of a target pixel of image data; and a density determining means 1414 for setting, if the degree of change in the density value is equal to or greater than a prescribed threshold, the density value of the target pixel to a first output density value for suppressing scattering of toner, which may be caused during the printing of the target pixel onto recording paper. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method applied to a printing machine using an electrophotographic system, an inkjet system, a thermal system, and the like.

  In recent years, printers such as laser printers, color laser printers, ink jet printers, and color ink jet printers have become widespread, and the development of printers that meet all user needs has become important in order to win competition among companies. ing. One such user requirement is that images can be drawn sharply on recording paper. Such sharpness is generally evaluated based on how steep the density change is at the boundary between the background and the line when, for example, a line is drawn on a recording sheet.

  Normally, in a printer using toner as a color material, the toner output to draw a line may scatter to the background, particularly near the boundary between the background and the line, resulting in a steep change in density. Will be lost. Such toner scattering (hereinafter referred to as toner scattering) has a sharper change in density, and becomes more noticeable as the amount of toner increases.

  As an apparatus for suppressing such toner scattering, for example, as disclosed in Patent Document 1, an inner edge vicinity region that is inside the edge of the input color image data and adjacent to the edge region is extracted. An image processing apparatus that reduces the toner density in a region near the inner edge is known. Also, as disclosed in Patent Document 2, there is known an image processing apparatus that reduces the density of an image corresponding to the density at which toner scattering occurs.

JP 2004-253979 A Japanese Patent Laid-Open No. 10-69131

  However, in the apparatus disclosed in Patent Document 1, the toner density is reduced only in the area near the inner edge, and the toner scattering generated from the edge area cannot be sufficiently suppressed. It cannot be answered.

  Further, the apparatus disclosed in Patent Document 2 simply reduces the toner application amount at a location where it is determined that the toner application amount is large, and this also sufficiently satisfies the increasing user demand. Absent.

  The present invention has been made in view of the above, and an object thereof is to provide an image processing apparatus and an image processing method capable of suppressing toner scattering and ensuring the sharpness of an image.

  In order to solve the above-described problems and achieve the object, an image processing apparatus according to an aspect of the present invention includes an image data receiving unit that receives predetermined image data including a plurality of pixels, and the plurality of pixels. A density value acquiring unit that acquires the respective density values, a target pixel selecting unit that selects at least one of the plurality of pixels as a target pixel, and a magnitude of a change in the density value of the target pixel in the image data And a density change amount detecting means for detecting the density, and if the magnitude of the change in density value of the target pixel is equal to or greater than a predetermined density change amount threshold, the density value of the target pixel is recorded on the recording paper. A density determination unit that sets a first output density value that suppresses toner scattering that occurs during printing, and a density change amount of the pixel of interest is equal to or greater than the density change amount threshold; The first output density value set by the fixing means is output, and when the magnitude of the density value change of the target pixel is less than the density change amount threshold, the attention value acquired by the density value acquisition means Density output means for outputting the density value of the pixel.

  An image processing method according to another aspect of the present invention includes an image data receiving unit that receives predetermined color image data including a plurality of pixels, and the density value of each of the plurality of pixels for each color component. A density value acquiring unit to acquire; a target pixel selecting unit that selects at least one of the plurality of pixels as a target pixel; and a magnitude of a change in density value of an arbitrary color component of the target pixel in the color image data A density change amount detecting means for detecting the density; a density sum calculating means for calculating a density sum based on the acquired density value of each color component of the target pixel; and a change in the density value of the arbitrary color component of the target pixel. Is larger than a predetermined density change amount threshold value and the density sum is equal to or larger than a predetermined density sum threshold value, the density value of the arbitrary color component of the target pixel is set to the recording paper. In Density determining means for setting the first output density value to suppress toner scattering that occurs during printing, and the magnitude of the change in the density value of the arbitrary color component of the pixel of interest is greater than or equal to the density change amount threshold value. When the density sum is equal to or greater than the density sum threshold, the first output density value set by the density determination unit is output, and the density value of the arbitrary color component of the target pixel is changed. Is equal to or larger than the density change amount threshold value and the density sum is less than the density sum threshold value, the density value of the arbitrary color component of the target pixel acquired by the density value acquisition unit is obtained. Density output means for outputting.

  An image processing method according to still another aspect of the present invention includes an image data receiving step for receiving predetermined image data including a plurality of pixels, and a density value for acquiring each density value of the plurality of pixels. An acquisition step; a target pixel selection step of selecting at least one of the plurality of pixels as a target pixel; and a density change amount detection step of detecting a magnitude of a change in density value of the target pixel in the image data; When the magnitude of change in the density value of the pixel of interest is equal to or greater than a predetermined density change amount threshold, the density value of the pixel of interest is suppressed from toner scattering that occurs when the pixel of interest is printed on recording paper. A density determination step to be set to the first output density value to be set, and if the magnitude of the density value change of the pixel of interest is equal to or greater than the density change amount threshold, the density output step The first output density value set in step S3 is output, and when the magnitude of change in the density value of the target pixel is less than the density change amount threshold, the target pixel acquired in the density value acquisition step And a density output step for outputting the density value.

  An image processing method according to still another aspect of the present invention includes an image data receiving step for receiving predetermined color image data composed of a plurality of pixels, and the density values of the plurality of pixels for each color component. A density value acquisition step to be acquired, a target pixel selection step for selecting at least one of the plurality of pixels as a target pixel, and a change in density value of an arbitrary color component of the target pixel in the color image data. A density change amount detecting step for detecting a magnitude; a magnitude of a change in density value of the arbitrary color component of the target pixel is equal to or greater than a predetermined density change amount threshold value; and the density sum is a predetermined density sum threshold value In the case described above, the density value of the arbitrary color component of the target pixel is set to the first output density value that suppresses toner scattering that occurs when the target pixel is printed on recording paper. Density determination step, and when the magnitude of change in the density value of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, and the density sum is equal to or greater than the density sum threshold, the density The first output density value set in the determining step is output, the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, and the density sum is A density output step of outputting a density value of the arbitrary color component of the target pixel acquired in the density value acquisition step when the density value is less than the density sum threshold value.

  According to the present invention, since the output density value is set based on the magnitude of the change in density value of the color image data, it is possible to effectively suppress toner scattering.

  Exemplary embodiments of an image processing apparatus and an image processing method according to the present invention are explained in detail below with reference to the accompanying drawings. The present invention is not limited to these embodiments, and various modified embodiments are possible without departing from the spirit of the present invention.

(First embodiment)
An image processing apparatus according to a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, as an example to which the image processing apparatus is applied, a digital color printing machine (hereinafter simply referred to as a printing machine) that performs printing using a subtractive color mixing method of CMYK (cyan, magenta, yellow, black). ).

  FIG. 1 is a block diagram schematically showing the configuration of an image processing apparatus 1000 applied to a printing press. An image processing apparatus 1000 illustrated in FIG. 1 includes an image data receiving unit 1100 that receives predetermined color image data, an image processing unit 1200 that performs normal image processing (described later) on the received color image data, To the color image data that has been subjected to image processing, a toner scattering reduction process, which will be described later, is performed to reduce toner scattering (hereinafter referred to as toner scattering) that occurs when the color image data is printed on recording paper. A toner scattering reduction unit 1300 and an image data output unit 1500 that outputs color image data subjected to normal image processing and toner scattering reduction processing are provided.

  The image data receiving unit 1100 receives color image data page by page. Here, the color image data is an instruction for drawing characters, images, and the like from the user via a personal computer or the like.

  The image processing unit 1200 performs image processing (hereinafter referred to as normal image processing) necessary for printing color image data. Specifically, the image processing unit 1200 includes a color conversion unit that converts color image data expressed in RGB (red, green, blue) into color image data expressed in CMYK, and converted color image data. Normal image processing is executed by a rendering unit that arranges characters and graphics included in the image, and a halftone processing unit that reduces the number of gradation levels of the rendered color image data.

  In the following description, it is assumed that the above-described halftone processing unit drops the density value of each color component of the pixels constituting the received color image data to a binary value (for example, 0 or 255). Normally, the number of gradations of color image data is changed to a value that can be processed by an engine (not shown) that receives color image data output from the image processing apparatus 1000. In the present embodiment, it is assumed that the image processing apparatus 1000 outputs color image data to an engine (not shown) that can process color image data expressed in 65,536 colors at maximum. Accordingly, the density value of each color component of each pixel constituting the color image data output from the image processing apparatus 100 is 16 density values (0, 17, 34, 51, 68, 85, 102, 119, 136, 153). , 170, 187, 204, 221, 238, 255). For this reason, the halftone processing unit drops the density value of each color component to one of 16 values, and further reduces it to 2 values for the sake of simplicity of explanation.

  The image data output unit 1500 accumulates each color density value that has undergone normal image processing and toner scattering reduction processing, reconstructs color image data, and outputs the color image data to an engine (not shown).

  The configuration of the toner scattering reduction unit 1300 and its internal processing will be specifically described below. FIG. 2 is a block diagram schematically showing the configuration of the toner scattering reduction unit 1300. A toner scattering reduction unit 1300 shown in FIG. 2 outputs a density value of each pixel constituting the color image data received from the image processing unit 1200 to a different output destination for each color component, and will be described later. A cyan buffer 1302, a magenta buffer 1303, a yellow buffer 1304, and a black buffer 1305; a cyan operation unit 1310, a magenta operation unit 1330, a yellow operation unit 1350, and a black operation unit 1370, which will be described later; and a cyan density control unit 1410, which will be described later. A magenta density control unit 1430, a yellow density control unit 1450, and a black density control unit 1470. The processing in each color buffer, each color calculation unit, and each color density control unit has the same function and / or configuration except that it processes density values of different color components. Therefore, in the following description, only the configuration and / or function of the cyan buffer 1302, the cyan calculation unit 1310, and the cyan density control unit 1410 will be described, and the description of the other configuration and / or function will be omitted. .

  The cyan buffer 1302 receives the density value of the cyan color component (hereinafter referred to as cyan density) output from the density value acquisition unit 1301. The cyan buffer 1302 waits for the output of the next received color image data until the cyan calculation unit 1310 and the cyan density control unit 1410 provided downstream in the data transfer direction complete predetermined processing. In other words, the cyan buffer 1302 holds the next received color image data until the toner scattering reduction process described later is completed for all the pixels constituting the previously received color image data.

  FIG. 3 is a block diagram showing the configuration of the cyan calculation unit 1310. 3 includes a cyan density storage unit 1311, a filter A value calculation unit 1312, a filter B value calculation unit 1313, a filter C value calculation unit 1314, a filter D value calculation unit 1315, a density A change amount A calculation unit 1316, a density change amount B calculation unit 1317, a density change amount C calculation unit 1318, a density change amount D calculation unit 1319, and a cyan density change amount selection unit 1320 are provided.

A cyan density accumulation unit 1311 accumulates the cyan density of pixels constituting color image data for one page of recording paper. The filter while selecting each pixel stored as a sequential pixel of interest T, area of 7 × 7 pixels square centering on the target pixel T cyan density of pixels included in (hereinafter, referred to as selection area T _R) The A value calculation unit 1312 to the filter D value calculation unit 1315 are output. Further, the cyan density storage unit 1311 outputs the cyan density (hereinafter referred to as input cyan density) of the selected target pixel T to the cyan density control unit 1410. As the selection area T _R, not limited to the 7 × 7 pixel square area, for example 25 × 25 pixels square area or the like may be optionally selected size.

  FIG. 4 is a schematic diagram showing the cyan density of the color image data of the cyan color component accumulated in the cyan density accumulation unit 1311. As shown in FIG. 4, the color image data of the cyan component is composed of n × m pixels, and each pixel has a binary cyan density (0 or 255). It should be noted that the cyan density of the pixel having a value of 0 is the lowest (light) and corresponds to, for example, the background portion of the color image data of the cyan component, and the cyan density of the pixel having a value of 255 is the highest (dark). ), Corresponding to, for example, a line portion of the color image data of the cyan component.

Next, internal processing of the filter A value calculation unit 1312 to the filter D value calculation unit 1315 will be described. 5A to 5D are schematic diagrams illustrating filters A to D included in the filter A value calculation unit 1312 to the filter D value calculation unit 1315. FIG. Filter A~D are those having a predetermined filter settings such as -1, 0, or 1, and their filter setting value is given to each pixel included in the selection area T _R. The filter A~D is selected magnitude of the change in density value in the region T _R (hereinafter, referred to as concentration variation) are those used to determine the vertical direction, the horizontal direction of the respective selected area T _R , And are used to determine the amount of density change in the upper left-lower right direction and lower left-upper right direction.

Filter A value calculation unit 1312 integrates a cyan density of each pixel included in the selection area T _R, a filter A set value associated with each pixel. Specifically, the filter A value calculating unit 1312, a filter A shown in FIGS. 5 (a) superimposed in the selection area T _R shown in FIG. 4, integrated numerical each other at the same position, shown in FIG. 6 The filter A value to be calculated is calculated. Note that the filter value calculation processing by the filter B value calculation unit 1313 to the filter D value calculation unit 1315 also uses a filter (see FIGS. 5B to 5D) different from the filter A, respectively. Since the same processing as that of the filter A value calculation unit 1312 is performed, the description thereof is omitted.

Next, the internal processing of the density change amount A calculation unit 1316 to the density change amount D calculation unit 1319 will be described. The density change amount A calculation unit 1316 calculates the absolute value of the filter A value input from the filter A value calculation unit 1312. Specifically, the density change amount A calculation unit 1316 adds the filter A values of the respective pixels shown in FIG. 6 and calculates the absolute value of the addition result. Note that the cyan density change amount calculation processing by the density change amount B calculation unit 1317 to the density change amount D calculation unit 1319 is the same as the cyan density change amount A calculation process by the density change amount A calculation unit 1316. Result of the processing by the density change amount A calculator 1316～ density change amount D calculation section 1319, the selection area T _R in FIG. 4, for example, each concentration variation 0,3570,2550, and 2550 are calculated.

The cyan density change amount selection unit 1320 compares the calculated density change amounts A to D and outputs the maximum value as the cyan density change amount of the target pixel T. Specifically, the selection region T _R in FIG. 4, for example, cyan density change amount selector 1320 compares the concentration variation 0,3570,2550 described above, and 2550 to each other, the concentration change with them largest value The amount 3570 is output as the cyan density change amount.

  Hereinafter, the processing of the cyan calculation unit 1310 for the target pixel T will be described in more detail. FIG. 7 is a flowchart showing the internal processing of the cyan calculation unit 1310.

  The cyan density accumulation unit 1311 accumulates the cyan density of the pixels constituting the received color image data (step S101). Then, the cyan density storage unit 1311 determines whether or not the cyan density storage of all the pixels constituting the color image data has been completed (step S102). As a result, when the cyan density accumulation is not completed (No at Step S102), Step S101 is repeated until the cyan density accumulation is completed. On the other hand, when the accumulation of the cyan density has been completed (step S102-Yes), any pixel that constitutes the color image data and has not been selected as the target pixel T is selected as the target pixel T ( Step S103).

Next, the cyan density accumulation unit 1311 determines whether it is possible to select a 7 × 7 pixel square area centered on the selected target pixel T (hereinafter referred to as a selection area) (step S104). ). For example, when the pixel A shown in FIG. 4 is selected as the target pixel T, the pixel A belongs to the area near the page end of the color image data, and therefore the selection area T around the pixel A cannot be selected. Therefore, the toner scattering reduction process for the pixel A cannot be performed. Thus, the cyan density storage unit 1311, when it is not possible to select a selection region T _R with respect to the target pixel T (step S104-No), a predetermined signal to be described later with respect to the cyan density control unit 1410 (hereinafter , Referred to as an exception signal) (step S105), and notifies the cyan density control unit 1410 that the toner scattering reduction process for the pixel of interest T cannot be performed.

On the other hand, cyan density storage unit 1311, when it was possible to select the selected area (step S104-Yes), selects the region as a selected region T _R (step S106). Next, the filter A value calculator 1312～ filter D value calculating unit 1315 calculates the filter A value-filter D values of the respective selected area T _R (step S107), density variation A calculator 1316～ concentration variation The D calculation unit 1319 calculates the density change amount A to the density change amount D, respectively (step S108). Thereafter, the cyan density change amount selection unit 1320 compares the calculated density change amounts A to D with each other, and selects the density change amount having the largest value among them as the cyan density change amount (step S109). ), And outputs the selected cyan density change amount to the cyan density controller 1410 (step S110). Further, the cyan density storage unit 1311 outputs the input cyan density of the selected target pixel T to the cyan density control unit 1410 (step S111). Next, the cyan density storage unit 1311 determines whether or not all the pixels constituting the color image data have been selected as the target pixel T (step S112). If not selected (step S112-No), Steps S103 to S111 are repeated. On the other hand, if it is selected (step S112—Yes), the processing by the cyan calculation unit 1310 is completed.

  Next, the configuration of the cyan density control unit 1410 and its internal processing will be described. FIG. 8 is a block diagram showing the configuration of the cyan density control unit 1410. The cyan density control unit 1410 illustrated in FIG. 8 includes a cyan density receiving unit 1411 that receives the input cyan density of the target pixel T, a cyan density change amount receiving unit 1412 that receives the cyan density change amount of the target pixel T, and an exception. An exception signal receiving unit 1413 for receiving a signal, a cyan density determining unit 1414 for setting a cyan density (hereinafter referred to as an output cyan density) suitable for suppressing toner scattering based on an input cyan density and a cyan density change amount; A cyan density output unit 1415 for outputting the set output cyan density.

  FIG. 9 is a flowchart showing internal processing of the cyan density control unit 1410. First, the cyan density receiving unit 1411 receives the input cyan density of the target pixel T output from the cyan density storage unit 1311 (step S121). Also, the cyan density change amount receiving unit 1412 receives the cyan density change amount output from the cyan density change amount selecting unit 1320, and the exception signal receiving unit 1413 is the cyan density change amount output from the cyan density accumulation unit 1311. Is received (step S122). As will be described later, when the cyan density change receiving unit 1412 receives the cyan density change, the exception signal receiving unit 1413 does not receive the exception signal, and the cyan density change receiving unit 1412 receives the cyan density change. Is not received, the exception signal receiver 1413 receives an exception signal. Next, the cyan density determination unit 1414 determines whether an exception signal has been received (step S123). As a result, when the cyan density determination unit 1414 determines that an exception signal has been received (step S123-Yes), the input cyan density of the pixel of interest T received by the cyan density reception unit 1411 is set as the output cyan density (step step). If it is determined that an exception signal has not been received (S124) (step S123-No), the process of step S125 described later is executed.

Note that the exception signal referred to here, there is outputted from the cyan density storage unit 1311 when it is not possible to select the selected region T _R centering on the target pixel T, a color image data page This is output when toner scattering reduction processing is performed on pixels belonging to the edge vicinity region (hereinafter referred to as page edge vicinity pixels). As described above, cyan calculating unit 1310, for example, if you select a page end neighboring pixels, such as pixel A shown in FIG. 4, by selecting the selection area T _R centered on the pixel A toner scattering reduction processing Can not do. Therefore, in the present embodiment, when a pixel near the page edge is selected as the target pixel T, an exception signal is generated to notify the cyan density control unit 1410 that the toner scattering reduction process cannot be performed. When the cyan density control unit 1410 receives such an exception signal, the cyan density control unit 1410 outputs the input cyan density received by the cyan density receiving unit 1411 as it is. Note that since toner scattering reduction processing is not performed on pixels near the page edge, toner scattering that may occur at pixels near the page edge cannot be suppressed at present. However, before the image processing unit 1200 generates color image data in a region wider than the image range to be printed in advance and the image processing apparatus 1000 performs actual output with a configuration not shown, the color image data outside the image range to be printed Is deleted.

Note that this embodiment is not limited to this, and it is also possible to perform different toner scattering reduction processing for pixels near the page edge. For example, toner scattering in a region near the page edge can be reduced by performing toner scattering reduction processing using a filter that can perform appropriate toner scattering reduction processing on pixels near the page edge. Further, it is also possible to reduce toner scattering by setting the cyan density of the pixels missing in the selection area T _R around the page near-edge pixel virtually.

  When the cyan density determination unit 1414 determines that an exception signal has not been received (step S123-No), the cyan density change amount received by the cyan density change amount reception unit 1412 is a cyan density change threshold (here, 1530). It is determined whether or not the above is satisfied (step S125). As a result, when the cyan density output unit 1415 determines that the cyan density change amount is less than the cyan density change threshold 1530 (No in step S125), the cyan density output unit 1415 sets the input cyan density as the output cyan density (step S124). . On the other hand, when the cyan density determination unit 1414 determines that the cyan density change amount is equal to or greater than the cyan density change threshold 1530 (step S125—Yes), the output cyan density is one of the 16 density values described above. 170 is set (step S126). Then, the cyan density output unit 1415 outputs the set output cyan density (step S127). Thereby, the processing by the cyan density determination unit 1410 is completed.

  As described above, in the image processing apparatus 1000 according to the present embodiment, when it is determined that toner scattering may occur because the density change is steep, the output density of the selected pixel T is a predetermined value lower than the input density. Set the density. As a result, it is possible to reduce the density change at a portion where the density change where toner scattering is likely to occur is steep, and to suppress the occurrence of toner scattering.

  Hereinafter, the input cyan density and the output cyan density will be described with reference to FIGS. FIG. 10 is a graph showing pixels for one line in the x-axis direction of FIG. 4 and their input cyan densities. FIG. 11 is a graph showing pixels for one line and their cyan density change amount. Further, FIG. 12 is a graph showing pixels for one line and output cyan density.

  When the toner scattering reduction unit 1300 receives the input cyan density shown in FIG. 10, for example, the cyan calculation unit 1310 calculates the cyan density change amount shown in FIG. In addition, the area | region of ab shown in FIG. 10 shows the line drawn by a cyan color, and another area | region shows a background. At such boundary portions a and b between the line and the background, the amount of change in cyan density is steep, and therefore toner scattering is likely to occur. Such steepness of the change in the cyan density is calculated as a cyan density change amount by the cyan computing unit 1310 as shown in FIG. Then, the cyan density control unit 1410 sets the cyan density to a predetermined value based on the calculated density change amount so that the density change is smooth in the vicinity of the boundary portions a and b. As a result, the output density is as shown in FIG. 12, and an output density capable of suppressing toner scattering can be acquired.

  In this embodiment, the cyan density change amount threshold value in the cyan density determination unit 1414 is set to 1530, but it may be set lower than 1530, for example. As a result, even a slight density change can be a target of toner scattering reduction processing. On the other hand, there is a possibility that such a slight density change may not cause toner scattering, and by setting the threshold value low, the cyan density is set over almost the entire area of the received color image data. There is also a risk that the color image data will be excessively falsified. Therefore, it is preferable to set a boundary value that causes toner scattering and that does not detract from the received color image data.

  In the present embodiment, when the cyan density change amount is equal to or greater than the cyan density change threshold 1530, the output cyan density is output as 170. However, any value that can suppress toner scattering is used. Any value may be used. In the present embodiment, the density value of each color needs to be expressed by any one of 16 values for engine performance. Therefore, when setting the output cyan density to a value other than 16 values, for example, It is necessary to replace the output density with one of the 16 values by using an arbitrary method such as replacement with the closest value among the 16 values.

In this embodiment, the toner scattering reduction process is performed using the filters shown in FIGS. 5A to 5D. However, it is possible to use different filters. For example, the filter setting value can be set to a value other than that shown in FIGS. It is also possible to change the arrangement, and furthermore, by using five or more filters, density change amounts in directions other than the vertical direction, the horizontal direction, the upper left-lower left direction, and the lower left-upper right direction are calculated. It is also possible. In other words, it is possible to use a calculation if possible, any filter density variation in the selection area T _R.

  In the present embodiment, color image data expressed in CMYK is targeted for toner scattering reduction processing, but monochrome image data may also be targeted. In this case, for example, when it is assumed that the background is white, the toner scattering reduction process can be realized by using only the configuration of the black calculation unit or the like that processes the black density.

  In this embodiment, the pixel of interest T is sequentially selected after the cyan density storage unit 1311 temporarily stores all the pixels constituting the color image data for one page of recording paper. However, the present embodiment is not limited to this. For example, the toner scattering reduction process may be performed at the time when the cyan density of the pixels included in the 7 × 7 pixel square region centered on the target pixel T is accumulated.

(Second Embodiment)
Next, an image processing apparatus and an image processing method according to the second embodiment will be described. Also in this embodiment, a printing machine is illustrated as an example to which the image processing apparatus is applied. The image processing apparatus according to the second embodiment is different from the image processing apparatus according to the first embodiment only in the internal processing of the cyan density determination unit. However, in the following description, the cyan density determination unit according to the present embodiment. The same reference numerals as those in the cyan density determination unit of the first embodiment are used. In addition, the other component which attached | subjected the same name and code | symbol has the structure and function similar to 1st Embodiment, unless it mentions in particular below.

  The internal processing of the cyan density control unit 1410 according to this embodiment will be described below. FIG. 13 is a flowchart showing the internal processing of the cyan density control unit 1410. As illustrated in FIG. 13, the cyan density receiving unit 1411, the cyan density change amount receiving unit 1412, the exception signal receiving unit 1413, and the cyan density determining unit 1414 are similar to step S <b> 121 in the first embodiment. ˜S125 is executed. Next, when the cyan density determination unit 1414 determines that the cyan density change amount is equal to or greater than the cyan density change amount threshold (Yes in step S125), the cyan density determination unit 1414 determines whether the input cyan density is equal to or higher than the cyan density upper limit 170. (Step S211). As a result, when the cyan density determination unit 1414 determines that the input cyan density is less than the cyan density upper limit 170 (No in step S211), the cyan density determination unit 1414 sets the input cyan density as the output cyan density (step S124). On the other hand, when the cyan density determination unit 1414 determines that the input cyan density is equal to or higher than the cyan density upper limit 170 (step S211—Yes), the cyan density determination unit 1414 sets a predetermined cyan density value 170 as the output cyan density (step S212). Then, the cyan density output unit 1415 outputs the set output cyan density (step S127). Thereby, the internal processing of the cyan density control unit 1410 according to the present embodiment is completed. The internal processes of the other color density control units are the same as the internal processes of the cyan density control unit 1410, and thus the description thereof is omitted.

  As described above, in this embodiment, when it is determined that the cyan density change amount is equal to or greater than the cyan density change amount threshold value, it is further determined whether or not the input cyan density is equal to or greater than a predetermined cyan density upper limit value. To set the output cyan density. Normally, even if the density change is steep, toner scattering does not occur in a region where the density is relatively low. Therefore, in this embodiment, the toner scattering reduction process is not performed for such an area. For example, as shown in FIG. 14, the cyan density determination unit 1414 of the present embodiment sets the output cyan density after further making a determination based on the input cyan density, so that the input cyan density is relatively low. The output cyan density of the pixels belonging to the lower regions a ′ to a and regions b to b ″ in FIG. 14 is not changed. This allows output color image data that is more faithful to the received color image data. It becomes possible to form.

  When the cyan density determination unit 1414 determines that the input cyan density is less than the cyan density upper limit 170, the cyan density determination unit 1414 further determines whether or not the input cyan density is equal to or lower than the cyan density lower limit (here, 85 is exemplified). Thus, the output cyan density may be determined. Specifically, for example, as illustrated in FIG. 15, when the cyan density determination unit 1414 determines that the cyan density is less than the cyan density upper limit 170 (step S <b> 211 -No), the input cyan density further becomes the cyan density. It is determined whether or not the lower limit value is 85 or less (step S213). As a result, when it is determined that the input cyan density exceeds the cyan density lower limit value 85 (step S213-No), the input cyan density is set to the output cyan density (step S124), while the input cyan density is the cyan density. When it is determined that the lower limit value is 85 or less (step S213-Yes), the output cyan density is set as 85 (step S214). Then, the cyan density output unit 1415 outputs the set output cyan density (step S127).

  As described above, by further determining whether or not the input cyan density is equal to or lower than the cyan density lower limit value, the output cyan density can be slightly increased in a region where the input density is relatively low. As shown in FIG. 16, the density change can be made smoother in the vicinity of the boundaries a and b.

  In the present embodiment, the cyan density upper limit value is set to 170, but when the cyan density change amount is equal to or greater than the cyan density change quantity 1530, a boundary value that determines whether toner scattering occurs or not is used. Any one may be used if present. The cyan density lower limit value is set to 85. If the cyan density change amount is equal to or greater than the cyan density change quantity 1530, any value can be used as long as the output density density change can be made smoother. The value of may be used. Furthermore, any value can be used in place of the output cyan densities 170 and 85 as long as the toner scattering can be suppressed under the above conditions.

(Third embodiment)
Next, an image processing apparatus and an image processing method according to the third embodiment will be described. Also in this embodiment, a printing machine is illustrated as an example to which the image processing apparatus is applied. The image processing apparatus according to the third embodiment differs from the image processing apparatuses according to the first and second embodiments only in the internal processing of the cyan density determination unit, but in the following description, the cyan processing according to the present embodiment is performed. For the density determination unit, the same reference numerals as those of the cyan density determination unit of the first and second embodiments are used. In addition, the other component which attached | subjected the same name and code | symbol has the structure and function similar to 1st and 2nd embodiment unless it mentions in particular below.

  FIG. 17 is a flowchart showing toner scattering reduction processing according to the present embodiment. In addition, since the process from step S121 to step S125 is the same as the process of 1st Embodiment, the description is abbreviate | omitted. If the cyan density determining unit 1414 determines that the cyan density change amount is equal to or greater than the cyan density change threshold 1530 (Yes in step S125), the cyan density determining unit 1414 determines whether the input cyan density is equal to or greater than the cyan density upper limit value 153. (Step S311). As a result, when the cyan density determination unit 1414 determines that the input cyan density is equal to or higher than the cyan density upper limit value 153 (step S311-Yes), the cyan density change coefficient A described later is acquired (step S312), and also described later. The output cyan density is calculated based on the equation (1) (step S313), and the calculated output cyan density is converted into a predetermined value to be described later (step S314). Thereafter, the cyan density output unit 1415 outputs the converted output cyan density (step S315).

  On the other hand, when the cyan density determination unit 1413 determines that the input cyan density is less than the cyan density upper limit value (here, 153 is exemplified) (step S311-No), the input cyan density is the cyan density lower limit value (here Then, 102 is exemplified) or not (step S316). As a result, when the cyan density determination unit 1414 determines that the input cyan density exceeds 102 (step S316-No), the input cyan density is set as the output cyan density (step S124), and the cyan density output unit 1415 The set output cyan density is output (step S127). On the other hand, if the cyan density determination unit 1414 determines that the input cyan density is equal to or lower than the cyan density lower limit value 102 (step S316-Yes), the cyan density change coefficient B is acquired (step S317), which will be described later, and will be described later. The output cyan density is calculated based on the equation (2) (step S318). Then, the process of step S314 and step S315 is performed. Thereby, the processing of the cyan density control unit 1410 is completed.

  Below, the process of step S312, step S313, and step S314 is demonstrated more concretely. In step S312, the cyan density determination unit 1414 determines a density change coefficient A. The density change coefficient A is obtained as a function of the cyan density change amount calculated by the cyan calculation unit 1310, and is obtained based on the relationship shown in FIG. 18, for example. The cyan density determination unit 1414 stores the relationship between the cyan density change amount and the density change coefficient A in advance. As shown in FIG. 18, the density change coefficient A has a value from 0 to 1, and increases as the cyan density change amount increases.

In step S313, the cyan density determination unit 1414 calculates an output cyan density based on the following equation (1).
Output cyan density = 255− (input cyan density−conversion lower limit) × density change coefficient A (1)
As the conversion lower limit value in the above formula (1), it is preferable to use the cyan density upper limit value 153 used in step S311.

  After calculating the output cyan density based on the output cyan density calculation processing, the cyan density determination unit 1414 converts the calculated output cyan density into a value closer to any of the 16 values that can be received by the engine (step S314).

  Next, the processing of steps S317 and S318 will be described more specifically. The cyan density determination unit 1414 determines the density change coefficient B in step S317. The density change coefficient B is obtained as a function of the cyan density change amount calculated by the cyan calculation unit 1310, and is acquired based on, for example, the relationship shown in FIG. The cyan density determination unit 1414 stores such a relationship between the cyan density change amount and the density change coefficient B in advance. As shown in FIG. 19, the density change coefficient B has a value from 0 to 1, and increases as the cyan density change amount increases.

In step S318, the cyan density determination unit 1414 calculates an output cyan density based on the following equation (2).
Output cyan density = (conversion upper limit value−input cyan density) × density change coefficient B (2)
Note that it is preferable to use the cyan density lower limit 102 used in step S316 as the conversion upper limit in the above formula (2).

  As described above, in the toner scatter reduction processing according to the present embodiment, the output density of the pixel whose density change is steep to some extent and whose input density is relatively high is reduced as the density change amount increases. . Thereby, it is possible to efficiently reduce toner scattering. Further, although the density change is steep, the output density of the pixel having a relatively low input density is increased as the density change amount increases. As a result, the density change can be made smooth, and the toner scattering can be efficiently reduced. Specifically, as shown in FIG. 20, for example, by performing the toner scattering reduction process according to the present embodiment on the input cyan density shown in FIG. 10, the output cyan density particularly near the boundaries a and b. Becomes smoother. Thereby, it is possible to more effectively reduce toner scattering.

  In this embodiment, the upper limit of cyan density is set to 153. However, when the cyan density change amount is equal to or greater than the cyan density change quantity 1530, the cyan density is determined to determine whether toner scattering occurs. Any value may be used as long as it is a boundary value. The cyan density lower limit value is set to 102. If the cyan density change amount is equal to or greater than the cyan density change quantity 1530, any value can be used as long as the output density density change can be made smoother. The value of may be used.

  Further, in the present embodiment, the cyan density change amount A is acquired based on the relationship shown in FIG. 18, but the cyan density change amount is not less than the cyan density change threshold 1530 and the input cyan density is cyan density. When the upper limit value is 153 or more, it is possible to use an arbitrary function that reduces the output cyan density as the cyan density change amount increases. Further, in the present embodiment, the cyan density change amount B is acquired based on the relationship shown in FIG. 19, but the cyan density change amount is not less than the cyan density change amount threshold 1530 and the input cyan density is cyan density. When the lower limit value is 102 or less, it is possible to use an arbitrary function that increases the output cyan density as the cyan density change amount increases.

(Fourth embodiment)
Next, an image processing apparatus and an image processing method according to the fourth embodiment will be described. Also in this embodiment, a printing machine is illustrated as an example to which the image processing apparatus is applied. In the image processing apparatus according to the fourth embodiment, the toner scattering reduction unit further includes a density sum calculation unit, and the internal processing of the cyan density determination unit includes the image processing apparatuses according to the first to third embodiments. And different. Therefore, components having the same names and symbols have the same structures and functions as those of the first to third embodiments unless otherwise specified below.

  FIG. 21 is a block diagram showing a configuration of the toner scattering reduction unit 4300 according to the present embodiment. In addition to the configuration shown in FIG. 2, the toner scattering reduction unit 4300 shown in FIG. 21 calculates density sums connected to each of the cyan calculation unit 1310, magenta calculation unit 1330, yellow calculation unit 1350, and black calculation unit 1370. Part 4305 is provided.

  The density sum calculator 4305 calculates the input cyan density, input magenta density, input yellow density, and input black density output from each of the cyan calculator 1310, magenta calculator 1330, yellow calculator 1350, and black calculator 1370. Add up to calculate the sum of their densities. The calculated density sum is output to each of the cyan density control unit 4410, the magenta density control unit 4430, the yellow density control unit 4450, and the black density control unit 4470.

  Next, the configuration and processing of the cyan density control unit 4410 according to this embodiment will be described. The configuration of magenta density control unit 4430, yellow density control unit 4450, and black density control unit 4470 and their processing are the same as the configuration and processing of cyan density control unit 4410. Omitted. The cyan density control unit 4410 shown in FIG. 22 receives the density sum output from the cyan density receiving unit 1411, the cyan density change amount receiving unit 1412, the exception signal receiving unit 1413, and the density sum calculating unit 4305. A sum receiving unit 4411; a cyan density determining unit 4412 for setting an output cyan density based on a cyan density change amount or exception signal; an input cyan density; and a cyan density sum; and a cyan density output unit 4413 for outputting an output cyan density. And comprising.

  FIG. 23 is a flowchart showing the internal processing of the cyan density control unit 4410. As shown in FIG. 23, the density sum receiving unit 4411 receives the density sum of each color density of the target pixel T output from the density sum calculating unit 4305 after the processing of step S121 and step S122 is executed (step S121). S411). Thereafter, the processes of steps S123 to S125 are performed. When the cyan density determination unit 4412 determines that the cyan density change amount is equal to or greater than the cyan density change threshold 1530 (Yes in step S125), the density sum received by the density sum reception unit 4411 is the density sum threshold. (Here, 511 is exemplified) It is determined whether or not (step S412). As a result, when the density sum is less than the cyan density sum threshold 511 (step S412-No), the cyan density determination unit 4412 sets the input cyan density as the output cyan density (step S124), and the density sum is the density sum. When the threshold value is 511 or more (step S412-Yes), the processing of step S311 to step S318 is performed. Thereby, the processing of the cyan density control unit 4410 is completed.

  As described above, in this embodiment, in addition to the toner scattering reduction process in the fourth embodiment, an output cyan density calculation process is performed based on the sum of the color densities of the pixel of interest T. As a result, since the output density of the pixel having a low density sum and toner scattering is not changed, it is possible to print an image that is as faithful as the received color image data.

  In this embodiment, the cyan density sum reception process in step S411 is performed immediately after step S122, and the determination process based on the cyan density sum in step S412 is performed immediately after step S125. The process may be performed at any timing as long as it is before the process of step S412, and the process of step S412 may be performed at any timing as long as it is after the process of step S411.

  In this embodiment, the density sum reception process (step S411) and the density sum determination process (step S412) are incorporated in the toner scattering reduction process according to the fourth embodiment. Alternatively, these processes may be incorporated into any of the toner scattering reduction processes according to the third embodiment. These also make it possible to print an image that is as faithful as the received color image data.

  In this embodiment, 511 is set as the density sum threshold value, but any value can be used as long as the value indicates a boundary value as to whether or not toner scattering occurs.

(Fifth embodiment)
Next, an image processing apparatus and an image processing method according to the fifth embodiment will be described. Also in this embodiment, a printing machine is illustrated as an example to which the image processing apparatus is applied. The image processing apparatus according to the fifth embodiment is different from the image processing apparatus according to the fourth embodiment only in the internal processing of the cyan density determination unit, but in the following description, the cyan density determination unit is described in the fourth implementation. The same reference numeral as that of the cyan density determination unit of the form is used. In addition, the other component which attached | subjected the same name and code | symbol has a structure and a function similar to 1st-4th embodiment unless it mentions in particular below.

  FIG. 24 is a flowchart showing internal processing of the cyan density control unit 4410 according to this embodiment. In addition, since the process of step S121, step S122, step S411, step S123, step 124, step S125, and step S127 is the same as that of 4th Embodiment, the description is abbreviate | omitted below.

  If the cyan density determination unit 4412 determines that the cyan density change amount is equal to or greater than the cyan density change threshold value 1530 in the process of step S125, is the density sum equal to or greater than the density sum threshold value (here, 341 is exemplified)? It is determined whether or not (step S511). As a result, when it is determined that the density sum is less than 341 (step S511-No), the cyan density determination unit 4412 sets the input cyan density as the output cyan density. On the other hand, when the cyan density determination unit 4412 determines that the density sum is 341 or more (step S511-Yes), the cyan density determination unit 4412 performs the process of step S311.

  As a result, when the cyan density determination unit 4412 determines that the input cyan density is equal to or higher than the cyan density upper limit value 153 (step S311-Yes), it acquires cyan density change coefficients A and C described later (step S512). An output cyan density is calculated based on equation (3) described later (step S513). And the process of step S314 and step S315 is performed. Thereby, the processing of the cyan density control unit 4410 is completed.

If the cyan density determination unit 4412 determines that the input cyan density is greater than or equal to the cyan density threshold value 153 in step S311, the cyan density determination unit 4412 calculates the output cyan density based on the following equation (3).
Output cyan density = 255− (input cyan density−conversion lower limit) × density change coefficient A × density change coefficient C (3)
Here, the conversion lower limit value preferably has the same value as the cyan density upper limit value 153 in Step S512. The density change coefficient A shown in FIG. 18 is used.

  The density change coefficient C is obtained as a function of the density sum calculated by the density sum calculation unit 4305 and is acquired based on the relationship shown in FIG. 25, for example. Note that the cyan density determination unit 4412 stores the relationship between the density sum and the density change coefficient C in advance. As shown in FIG. 25, the density change coefficient C has a value between 0 and 1, and the density change coefficient C is 0 in the area where the density sum is relatively low, and the density sum increases in the predetermined area. Accordingly, the density change coefficient C increases, and the density change coefficient C becomes 1 in a region where the density sum is relatively high.

  As described above, according to the present embodiment, the density sum is obtained even for a pixel having a sharp density change and a high input density by performing a process for determining whether to perform the toner scattering reduction process based on the density sum. The toner scattering reduction process is not performed for low pixels, and the output density of a pixel with a higher density sum can be made higher than that of a pixel with a lower density sum even for a pixel with a high density sum. As a result, toner scattering can be effectively suppressed.

In this embodiment, the output cyan density is calculated using the density change coefficients A and C. However, the output cyan density is calculated without using the density change coefficient A, for example, as in the following equation (4). You may do it.
Output cyan density = 255− (input cyan density−conversion lower limit) × density change coefficient C (4)
This also makes it possible to reduce the output cyan density as the density sum increases for pixels having a sharp density change and a high density value, effectively suppressing toner scattering. Can do.

  In this embodiment, 341 is set as the density sum threshold value. However, in the case where the cyan density change amount is the cyan density change threshold value 1530 or more and the input cyan density is the cyan density upper limit value 153 or more. Any density sum threshold value can be used as long as it is a density sum indicating a boundary value as to whether or not toner scattering occurs.

  In this embodiment, the cyan density change amount C is acquired based on the relationship shown in FIG. 25. However, the cyan density change quantity is not less than the cyan density change threshold 1530 and the input cyan density is cyan density. When the upper limit value is 153 or more, it is possible to use an arbitrary function that reduces the output cyan density as the cyan density change amount increases.

  As described above, the image processing apparatus and the image processing method according to the present invention are useful when used for laser printers, digital copying machines, color laser printers, and digital color copying machines.

It is a block diagram which shows the structure of an image processing apparatus roughly. FIG. 3 is a block diagram schematically illustrating a configuration of a toner scattering reduction unit. It is a block diagram which shows the structure of a cyan calculating part roughly. It is the schematic which shows the cyan density | concentration of all the pixels which comprise the received color image data. It is the schematic which shows the filter A-the filter D used for a filter value calculation process. It is the schematic which shows the filter A value calculated using the filter A. It is a flowchart which shows the internal process of a cyan calculating part. It is a block diagram which shows roughly the structure of a cyan density | concentration control part. It is a flowchart which shows the internal process of the cyan density | concentration determination part concerning 1st Embodiment. 6 is a graph showing an input cyan density for one line of color image data. It is a graph which shows the cyan density change amount for one line of color image data. 6 is a graph showing an output cyan density for one line of color image data. It is a flowchart which shows the internal process of the cyan density | concentration determination part concerning 2nd Embodiment. 6 is a graph showing an output cyan density for one line of color image data. It is a flowchart which shows the modification of the internal process of the cyan density | concentration determination part concerning 2nd Embodiment. 6 is a graph showing an output cyan density for one line of color image data. It is a flowchart which shows the internal process of the cyan density | concentration determination part concerning 3rd Embodiment. 5 is a graph showing a relationship between a cyan density change amount and a density change coefficient A. 6 is a graph showing a relationship between a cyan density change amount and a density change coefficient B. 6 is a graph showing an output cyan density for one line of color image data. It is a block diagram which shows roughly the structure of the toner scattering reduction part concerning 4th Embodiment. It is a block diagram which shows roughly the structure of the cyan density | concentration control part concerning 4th Embodiment. It is a flowchart which shows the internal process of the cyan density | concentration determination part concerning 4th Embodiment. It is a flowchart which shows the internal process of the cyan density | concentration determination part concerning 5th Embodiment. It is a graph which shows the relationship between density sum and density change coefficient C.

Explanation of symbols

1000 Image Processing Device 1100 Image Data Receiving Unit 1200 Image Processing Units 1300 and 4300 Toner Scatter Reduction Unit 1301 Density Value Acquisition Unit 1302 Cyan Buffer 1303 Magenta Buffer 1304 Yellow Buffer 1305 Black Buffer 1310 Cyan Operation Unit 1311 Cyan Density Storage Unit 1312 to 1315 Filter A value calculation unit to filter D value calculation unit 1316 to 1319 Density change amount A calculation unit to density change amount D calculation unit 1320 Cyan density change amount selection unit 1330 Magenta calculation unit 1350 Yellow calculation unit 1370 Black calculation units 1410 and 4410 Cyan density Control unit 1411 Cyan density receiving unit 1412 Cyan density change amount receiving unit 1413 Exception signal receiving units 1414 and 4412 Cyan density determining units 1415 and 4413 Cyan density output unit 1430, 430 magenta density control unit 1450,4450 yellow density control unit 1470,4470 black concentration controller 1500 image data output section 4305 density sum calculating section 4411 density sum receiving section T target pixel T _R selected area A pixel

Claims (20)

Image data receiving means for receiving predetermined image data composed of a plurality of pixels;
Density value acquisition means for acquiring the density value of each of the plurality of pixels;
Pixel-of-interest selecting means for selecting at least one of the plurality of pixels as a pixel of interest;
A density change amount detecting means for detecting a magnitude of a change in density value of the target pixel in the image data;
When the magnitude of the change in the density value of the target pixel is equal to or greater than a predetermined density change amount threshold, the density value of the target pixel suppresses toner scattering that occurs when the target pixel is printed on recording paper. Density determining means for setting the first output density value;
When the magnitude of the change in the density value of the target pixel is equal to or greater than the density change amount threshold, the first output density value set by the density determination unit is output, and the change in the density value of the target pixel Density output means for outputting the density value of the pixel of interest acquired by the density value acquisition means,
An image processing apparatus comprising:   The density change amount detecting means detects a magnitude of a change in density value of the target pixel by obtaining a difference between a density value of a peripheral pixel adjacent to the target pixel and a density value of the target pixel. The image processing apparatus according to claim 1. A region selection means for selecting a predetermined range including the target pixel as a selection region;
2. The image according to claim 1, wherein the density change amount detection unit detects a magnitude of a change in density value of a pixel included in the selection region as a magnitude of a change in density value of the target pixel. Processing equipment.   The density determination unit is configured so that when the magnitude of the density value change of the target pixel is equal to or greater than the density change amount threshold value and the density value of the target pixel is within a predetermined density value range, The image processing apparatus according to claim 1, wherein a density value is set to the first output density value.   The density determination unit is configured so that when the magnitude of the density value change of the target pixel is equal to or greater than the density change amount threshold value and the density value of the target pixel is equal to or greater than a predetermined density upper limit value, The image processing apparatus according to claim 1, wherein a density value is set to the first output density value equal to or lower than the density value.   The density determination unit is configured so that when the magnitude of the density value change of the target pixel is equal to or greater than the density change amount threshold value and the density value of the target pixel is equal to or greater than a predetermined density upper limit value, The density value is set to the first output density value equal to or lower than the density value, the magnitude of the density value change of the pixel of interest is greater than or equal to the density change amount threshold value, and the density value of the pixel of interest is a predetermined value 5. The image processing apparatus according to claim 4, wherein if the density value is equal to or lower than a density lower limit value, the density value of the target pixel is set to the first output density value equal to or higher than the density value.   The density determination unit determines the density of the target pixel when the magnitude of the density value change of the target pixel is equal to or greater than the density change amount threshold value and the density value of the target pixel is within the density value range. The image processing apparatus according to claim 4, wherein the first output density value is set based on a magnitude of a change in value.   The density determination means determines the density of the target pixel when the magnitude of the density value change of the target pixel is equal to or greater than the density change amount threshold value and the density value of the target pixel is equal to or greater than the density upper limit value. The first output density value is set so as to decrease as the magnitude of change in value increases, the magnitude of change in density value of the target pixel is equal to or greater than the density change amount threshold, and the target pixel The first output density value is set to increase as the magnitude of the change in the density value of the pixel of interest increases when the density value is less than or equal to the lower limit density value. 6. The image processing apparatus according to 6. Image data receiving means for receiving predetermined color image data composed of a plurality of pixels;
Density value acquisition means for acquiring the density value of each of the plurality of pixels for each color component;
Pixel-of-interest selecting means for selecting at least one of the plurality of pixels as a pixel of interest;
A density change amount detecting means for detecting a magnitude of a change in density value of an arbitrary color component of the target pixel in the color image data;
A density sum calculation means for calculating a density sum based on the acquired density values of the respective color components of the target pixel;
When the magnitude of change in the density value of the arbitrary color component of the target pixel is equal to or greater than a predetermined density change amount threshold and the density sum is equal to or greater than the predetermined density sum threshold, the arbitrary of the target pixel Density determining means for setting the density value of the color component to a first output density value for suppressing toner scattering that occurs when the target pixel is printed on recording paper;
When the magnitude of the change in the density value of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold and the density sum is equal to or greater than the density sum threshold, the density determination unit sets the density value. The first output density value is output, the magnitude of change in the density value of the arbitrary color component of the target pixel is greater than or equal to the density change amount threshold value, and the density sum is less than the density sum threshold value. A density output unit that outputs a density value of the arbitrary color component of the target pixel acquired by the density value acquisition unit;
An image processing apparatus comprising:   The density change amount detecting means obtains a difference between a density value of the arbitrary color component of a peripheral pixel adjacent to the target pixel and a density value of the arbitrary color component of the target pixel, thereby calculating the difference of the target pixel. The image processing apparatus according to claim 9, wherein a magnitude of a change in density value of an arbitrary color component is detected. A region selection means for selecting a predetermined range including the target pixel as a selection region;
The density change amount detection means detects the magnitude of the change in the density value of the arbitrary color component of the pixel included in the selection area as the magnitude of the change in the density value of the arbitrary color component of the target pixel. The image processing apparatus according to claim 9.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel The density value of the arbitrary color component of the target pixel is set as the first output density value when the density value of the arbitrary color component is within a predetermined density value range. The image processing apparatus according to any one of 9 to 11.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel When the density value of the arbitrary color component is equal to or higher than a predetermined density upper limit value, the density value of the arbitrary color component of the target pixel is set to the first output density value equal to or lower than the density value. The image processing apparatus according to claim 9, wherein the image processing apparatus is characterized.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel When the density value of the arbitrary color component is equal to or higher than a predetermined density upper limit value, the density value of the arbitrary color component of the target pixel is set to the first output density value equal to or lower than the density value, The magnitude of the change in the density value of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or higher than the density sum threshold, and the density of the arbitrary color component of the target pixel 13. The density value of the arbitrary color component of the target pixel is set to the first output density value equal to or higher than the density value when the value is equal to or lower than a predetermined density lower limit value. The image processing apparatus described.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel When the threshold value of the arbitrary color component is within the density value range, the first output density value is set based on the magnitude of change in the density value of the arbitrary color component of the target pixel. The image processing apparatus according to any one of claims 12 to 14.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel When the density value of the arbitrary color component is equal to or higher than the density upper limit value, the first output density value is set so as to decrease as the magnitude of the density value change of the target pixel increases, The magnitude of the change in the density value of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or higher than the density sum threshold, and the density of the arbitrary color component of the target pixel 15. The first output density value is set such that when the value is equal to or less than the density lower limit value, the density value changes as the magnitude of a change in density value of the target pixel increases. The image processing apparatus described.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel 17. The first output density value is set based on the density sum when a threshold value of the arbitrary color component is within the density value range. 17. The image processing apparatus described.   The density determination unit is configured such that the magnitude of the density value change of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold, the density sum is equal to or greater than the density sum threshold, and the target pixel When the density value of the arbitrary color component is equal to or higher than the upper limit density value, the first output density value is set so as to decrease as the density sum increases, and the arbitrary color component of the target pixel is set. The magnitude of the change in the density value is greater than or equal to the density change amount threshold, the density sum is greater than or equal to the density sum threshold, and the density value of the arbitrary color component of the target pixel is the density lower limit value. The image processing apparatus according to claim 12, wherein the first output density value is set so as to increase as the density sum increases. An image data receiving step for receiving predetermined image data composed of a plurality of pixels;
A density value obtaining step for obtaining density values of the plurality of pixels;
A target pixel selection step of selecting at least one of the plurality of pixels as a target pixel;
A density change amount detecting step for detecting a magnitude of a change in density value of the target pixel in the image data;
When the magnitude of the change in the density value of the target pixel is equal to or greater than a predetermined density change amount threshold, the density value of the target pixel suppresses toner scattering that occurs when the target pixel is printed on recording paper. A density determination step for setting the first output density value;
When the magnitude of change in the density value of the target pixel is equal to or greater than the density change amount threshold, the first output density value set in the density determination step is output, and the density value change of the target pixel is output. A density output step of outputting the density value of the pixel of interest acquired in the density value acquisition step when the magnitude of is less than the density change amount threshold;
An image processing method comprising: An image data receiving step for receiving predetermined color image data composed of a plurality of pixels;
A density value acquisition step of acquiring the density value of each of the plurality of pixels for each color component;
A target pixel selection step of selecting at least one of the plurality of pixels as a target pixel;
A density change amount detecting step for detecting a magnitude of a change in density value of an arbitrary color component of the target pixel in the color image data;
When the magnitude of change in the density value of the arbitrary color component of the target pixel is equal to or greater than a predetermined density change amount threshold and the density sum is equal to or greater than the predetermined density sum threshold, the arbitrary of the target pixel A density determination step of setting the density value of the color component to a first output density value that suppresses toner scattering that occurs when the target pixel is printed on recording paper;
When the magnitude of the change in the density value of the arbitrary color component of the target pixel is equal to or greater than the density change amount threshold value and the density sum is equal to or greater than the density sum threshold value, it is set in the density determination step. The first output density value is output, the magnitude of change in the density value of the arbitrary color component of the target pixel is greater than or equal to the density change amount threshold value, and the density sum is less than the density sum threshold value. A density output step for outputting the density value of the arbitrary color component of the target pixel acquired in the density value acquisition step;
An image processing method comprising:

Images