JP5825149B2 - Image processing apparatus and program - Google Patents

Description

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

  Japanese Patent Application Laid-Open No. H10-228561 describes a technique for giving a uniform gloss to an image of a printing result using a transparent color material. In this apparatus, the color material amount prediction circuit receives the Y signal, the M signal, the C signal, and the K signal from which the undercolor has been removed, and calculates the total toner amount for each unit area of the area where the color image is formed. Find the total coverage shown. The transparent color material amount calculation circuit calculates the transparent color material for each unit area according to the total coverage from the color material amount prediction circuit and the characteristic for calculating a preset amount of the transparent color material. Calculate the amount of superimposition. Information indicating the overlay amount of the transparent color material is subjected to area modulation in the halftone circuit and supplied to the transparent color material image forming unit, and the image of the transparent color material is superimposed on the image holding material.

  In Patent Document 2, in the image processing apparatus that regulates the total amount of toner, when the total amount of toner when the transparent toner is applied exceeds the total amount regulation value, the amount of each toner including the transparent toner is corrected to decrease, and In this correction, there is disclosed control for suppressing excessive reduction in gloss due to excessive reduction of the transparent toner.

  The transparent toner needs to be superimposed on a process color (for example, Y, M, C, K) toner image on the paper. For this reason, in electrophotographic printing using an intermediate transfer member, the transparent toner layer must be the lowest layer on the intermediate transfer member, and the photosensitive member for transparent toner is a tandemly arranged photosensitive member in the printing apparatus. It will be located at the most upstream.

  Now, in an intermediate transfer body type printing apparatus having a tandem photoconductor, a part of the toner transferred from the upstream photoconductor to the intermediate transfer body is reversely transferred to the downstream photoconductor. The thicker the toner in the lower layer, the greater the amount of reverse transfer of the toner on it. Therefore, in the printing using the transparent toner, the amount of reverse transfer of the process color is larger than in the case where the transparent toner is not used, and the saturation is lower than in the case where the transparent toner is not used.

Japanese Patent Laid-Open No. 10-055089 JP 2011-150026 JP

  SUMMARY OF THE INVENTION An object of the present invention is to allow an amount of color toner equivalent to the case of not using a transparent toner to remain on the intermediate transfer body after reverse transfer even when using a transparent toner in printing of the intermediate transfer body type. .

  According to a first aspect of the present invention, for each unit area of the input color image, based on the amount of toner of each color in the unit area, the transparent toner amount calculation means for calculating the amount of transparent toner applied to the unit area; An intermediate transfer type electrophotography based on a reverse transfer rate according to the calculated amount of transparent toner and a reverse transfer rate when no transparent toner is applied for at least one color toner for each unit region In the case of applying the calculated amount of transparent toner as the amount of toner of the color remaining after the reverse transfer of the toner of the color to the photoreceptor group downstream of the photoreceptor in the printing apparatus, the transparent toner is not applied. The amount of toner of the corresponding color is corrected so as to be equivalent to the case, and a signal indicating the corrected amount of toner is supplied to the electrophotographic printing apparatus together with the signal indicating the calculated amount of transparent toner. A positive means is an image processing apparatus comprising a.

  In the invention according to claim 2, the correction unit is configured to calculate, for each unit region, a total sum of the corrected total amount of toner of each color and the amount of transparent toner calculated by the transparent toner amount calculation unit. The image processing apparatus according to claim 1, further comprising a correction for reducing the amount of the transparent toner when the total toner amount regulation value specified in advance is exceeded.

  The invention according to claim 3 is a transparent toner amount calculation means for calculating, for each unit region of the input color image, the amount of transparent toner applied to the unit region based on the amount of toner of each color in the unit region. For each of the unit areas, for the toner of at least one color, based on the calculated reverse transfer rate according to the amount of transparent toner and the reverse transfer rate when no transparent toner is applied, In the electrophotographic printing apparatus, the amount of the toner of the color remaining after the reverse transfer of the toner of the color to the photoreceptor group downstream of the photoreceptor is the transparent toner when the calculated amount of the transparent toner is applied. The amount of toner of the corresponding color is corrected so as to be equivalent to the case where it is not applied, and the signal representing the amount of toner after correction is combined with the signal representing the amount of calculated transparent toner in the electrophotographic printing Is a program for functioning as a correction means, and supplies the location.

  According to the first or third aspect of the invention, in the case of the intermediate transfer body type printing, even when the transparent toner is used, the same amount of color toner remains on the intermediate transfer body after the reverse transfer as when the transparent toner is not used. Can be.

  According to the invention which concerns on Claim 2, the correction result which satisfy | fills total amount regulation can be obtained.

FIG. 2 is a diagram schematically illustrating an intermediate transfer body type tandem print engine using transparent toner and five color toners. FIG. 6 is a diagram for explaining a difference in reverse transfer rate according to the presence or absence of transparent toner. FIG. 6 is a diagram for explaining a difference in the remaining amount of toner after reverse transfer based on a difference in reverse transfer rate according to the presence or absence of transparent toner. It is a functional block diagram which shows an example of a structure of the image processing apparatus of embodiment. It is a functional block diagram which shows an example of an internal structure of a color correction part. It is a figure for demonstrating the specific example of the correction calculation of embodiment. It is a figure which shows an example of the process sequence of the correction value calculation part in a modification.

  Hereinafter, an embodiment of an image processing apparatus according to the present invention will be described with reference to the drawings.

  The image processing apparatus according to the embodiment is for performing image processing for an electrophotographic full-color print engine of an intermediate transfer body type that uses a transparent toner to improve gloss of a printed result.

  Because of the requirement that the transparent toner layer be the uppermost layer in the printing result, in the case of the intermediate transfer body method, first, the transparent toner is transferred to the intermediate transfer body, and then Y (yellow), M in order on the transparent toner layer. (Magenta), C (cyan), K (black), etc. (not necessarily in the order of YMCK), toner of each color is transferred (toner for color reproduction such as YMCK etc. is used as a transparent toner. In order to distinguish it from “color toner”). Therefore, for example, in the case of the print engine illustrated in FIG. 1 in which the photoreceptors for the respective toners are arranged in tandem (elements that are not related to the features of the embodiment are omitted), the most upstream in the traveling direction of the intermediate transfer belt 4. Further, a photosensitive member 2 for forming an image of the transparent toner T is disposed. Further, the photoreceptors 2 for the respective color toners X, Y, M, C, and K are disposed downstream of the photoreceptor 2 of the transparent toner T (however, the order of XYMCK shown in the drawing is merely an example). . In this example, an additional color X is used in addition to the general four primary colors Y, M, C, and K as color toners for color reproduction. X is, for example, orange, green, violet and the like. In the example of FIG. 1, the toner images formed on each photoconductor 2 are transferred (primary transfer) on the intermediate transfer belt 4 in registration in the order of T, X, Y, M, C, and K. As a result, a full-color toner image including the layer of the transparent toner T as the lowermost layer is formed on the intermediate transfer belt 4. This full-color toner image is transferred (secondary transfer) to the medium 5 (for example, sheet-like paper) conveyed by the medium conveyance system 6 in the secondary transfer unit 8. As a result, a full color toner image having the transparent toner T layer as the uppermost layer is formed on the surface of the medium 5, and this full color toner image is fixed to the medium 5 by the fixing unit 9.

  The configuration provided with the additional color X is illustrated in FIG. 1 because the number of photoconductors increases by the amount of the additional color X, and as a result, the toner on the intermediate transfer body is transferred back to the downstream photoconductor group. This is because the amount of the reverse transfer is larger than that in the case where there is no additional color, and the problem of reverse transfer is easily revealed. Hereinafter, a configuration including the print engine illustrated in FIG. 1 will be described as an example of a device configuration of the present embodiment. However, as will be understood from the following description, the processing method of the present embodiment can be applied to a print engine using only YMCK that does not use the additional color X, and also applied to a print engine that uses two or more additional colors. Is possible. Further, FIG. 1 shows a tandem type print engine using an intermediate transfer body belt, but the processing system of the present embodiment is applicable to a print engine using an intermediate transfer body in general. In other words, the processing method of this embodiment can be applied to the case where an intermediate transfer member that is not a belt is used. Also, for example, a rotary method other than the tandem method (different toners are sequentially applied to one photoconductor in time order). As a result, the present invention can also be applied to an apparatus of a system in which toner images formed in order are superimposed on an intermediate transfer member. Since the rotary system uses only one photoconductor, there is no arrangement of the photoconductors from upstream to downstream in a spatial sense as in the tandem system. However, even in the rotary system, one photoconductor functions as a photoconductor for different toners in order of time, so when viewed on the time axis, each toner is applied from upstream to downstream in the order of application of each toner. Can be considered to be present (for each period during which each toner is applied).

  Examples of experimental results relating to the reverse transfer characteristics of toner in such a print engine are shown in FIGS. In this example, in the print engine illustrated in FIG. 1, numbers # 1 to # 6 are assigned in order from the upstream to the photoreceptors 2 of the respective colors, and among them, the color components of # 2 (that is, X color = this example). This is an example in which there is an image only in orange), and no image is present in the color components # 3 to # 6 downstream thereof (that is, the toner amount is 0). FIG. 2 shows the reverse transfer amount of the # 2 toner transferred onto the intermediate transfer belt on the downstream # 3 to # 6 photoconductors (the amount per unit area. (Good) is shown for the case where the # 1 transparent toner is present (that is, when a predetermined amount of transparent toner is transferred to the intermediate transfer belt) and when it is not present (when the transparent toner is not used). As can be seen from FIG. 2, the reverse transfer occurs at a substantially constant rate on each photoconductor with and without the transparent toner, and the amount of reverse transfer is greater when the transparent toner # 1 is present. high. FIG. 3 shows the amount of toner remaining on the intermediate transfer belt after the reverse transfer on the respective downstream # 3 to # 6 of the # 2 toner transferred onto the intermediate transfer belt. The case where the transparent toner of # 1 is present and the case where it is not present are respectively shown. As can be seen from FIG. 3, the remaining amount of orange toner transferred by the photoconductor # 2 decreases at a substantially constant rate in each of the downstream photoconductors # 3 to # 6. The reduction rate is larger.

  Due to such a decrease in color toner due to the influence of the transparent toner, there is a concern that the quality of color reproduction may be deteriorated such as a decrease in saturation and a change in hue. In the present embodiment, a mechanism for compensating for the decrease in color toner due to the influence of the transparent toner and printing the same amount of color toner as in the case without the transparent toner even when the transparent toner is present is proposed.

  FIG. 4 shows an example of a main part configuration of the image processing apparatus according to the present embodiment.

  In FIG. 4, an image data input unit 10 prints an image such as RGB generated by interpreting print data expressed in a page description language or read by a scanner or the like. YMCK four-color bitmap image data generated by converting the image data is input. The color conversion unit 12 uses the color values of each pixel of the image data, that is, the pixel values (Y, M, C, and K), that is, five colors that are used by the print engine 18 (exemplified in FIG. 1), that is, XYMCK colors The color values in space (X, Y ′, M ′, C ′, K ′) are converted. In this conversion, since the values expressed in four colors are re-expressed in five colors, the values of the respective color components Y, M, C, and K are changed from the values in the original YMCK color space. , C, K components are distinguished from values before conversion by adding dashes. Each component of the converted color values (X, Y ′, M ′, C ′, K ′) corresponds to the toner amount per pixel of each color toner of X, Y, M, C, K. The color values (X, Y ′, M ′, C ′, K ′) of these pixels are input to the transparent toner amount calculation unit 14 and the color correction unit 16.

  The transparent toner amount calculation unit 14 calculates, for each pixel, the amount T of transparent toner to be applied to the pixel from the input color values (X, Y ′, M ′, C ′, K ′) of the pixel. . That is, the transparent toner amount calculation unit 14 is based on the amount X, Y ′, M ′, C ′, K ′ of each color toner applied to the pixel, and the amount of transparent toner for giving appropriate gloss to the pixel. Is calculated. As a method for calculating the amount of the transparent toner, any of conventional methods such as those exemplified in Patent Documents 1 and 2 may be used. For example, in the electrophotographic system, there are many apparatuses that regulate the total amount of toner for the purpose of avoiding fixing failure and saving toner. In such an apparatus, an allowable upper limit value of the total amount of toner per pixel (referred to as a total amount regulation value). An example is a method of obtaining the transparent toner amount T from a value obtained by subtracting the total amount of color toners from). In FIG. 4, the total amount regulation value Max is input to the transparent toner amount calculation unit 14 from the control unit 20 that controls the overall operation of the image processing apparatus. Of course, the transparent toner amount may be calculated without using the total amount regulation value Max. For example, in the method of Patent Document 1, the total (total amount) of color toner amounts X, Y ′, M ′, C ′, and K ′ applied to the pixel is calculated, and the total color toner amount prepared in advance is calculated. From the relationship with the transparent toner amount, an appropriate transparent toner amount T corresponding to the total amount is obtained. In any case, the unit of the transparent toner amount T may be the same as the units of the color components X, Y ′, M ′, C ′, and K ′. For example, when the color component is expressed by 8 bits = 256 levels, the transparent toner amount T may also be expressed by 8 bits. The obtained transparent toner amount T is input to the color correction unit 16.

  For each pixel, the color correction unit 16 receives the color value (X, Y ′, M ′, C ′, K ′) of the pixel input from the color conversion unit 12 and the transparent toner amount calculation unit 14. Based on the transparent toner amount T of the pixel, a process for correcting a decrease in color toner on the intermediate transfer member due to the presence of the transparent toner is performed. In this correction processing, the value of the color component corresponding to the color toner that is input to the print engine 18 so that the amount of color toner remaining on the intermediate transfer body after reverse transfer is equivalent to that when no transparent toner is used. Correct.

  An example of the internal configuration of the color correction unit 16 is shown in FIG. In this example, the color correction unit 16 includes a reverse transfer rate determination unit 160, a reverse transfer rate information holding unit 162, a reverse transfer number determination unit 164, and a correction value calculation unit 166.

  The reverse transfer rate determination unit 160 determines a reverse transfer rate corresponding to the input transparent toner amount T. This determination is made based on the information held in the reverse transfer rate information holding unit 162.

  The information held in the reverse transfer rate information holding unit 162 is, for example, information indicating the reverse transfer rate corresponding to the stage for each preset stage for the transparent toner amount. Here, the reverse transfer rate is a value indicating the ratio of the amount of toner transferred from a certain photosensitive member to the intermediate transfer member and reversely transferred to one downstream photosensitive member. As described with reference to FIG. 2 and the like, since this ratio is substantially constant for all the downstream photoconductors, the same value is used for all the photoconductors in this embodiment. It may be better to change the reverse transfer rate depending on the material of the toner and the number of the photoconductor from which the toner is transferred. A uniform reverse transfer rate is used for the toner transferred from the toner. However, a more precise investigation is performed, and for each photoconductor, the reverse transfer rate of the toner transferred from the photoconductor to the intermediate transfer member on the downstream photoconductor is obtained and registered in the reverse transfer rate information holding unit 162 for use. You may make it do.

  Further, the number of steps of the transparent toner amount in the reverse transfer rate information may be determined in consideration of correction accuracy, device restrictions (for example, limitation of storage capacity that can be prepared for the reverse transfer rate information holding unit 162), and the like. . In an extreme example, the number of steps of the transparent toner amount T may be two steps, i.e., greater than or less than a certain threshold, and conversely, the number of resolution limit steps in the data width representing the transparent toner amount T (if the data width is 8 bits). 256 stages) or an intermediate number of stages. Further, the width of each stage (the range of the transparent toner amount belonging to the stage) may not be constant, and may be different for each stage, for example. In any case, the lowest stage among the plurality of stages is handled as a state where there is no transparent toner. For example, in the case of two stages that are greater than or less than the threshold, the reverse transfer rate corresponding to the stage that is less than the threshold is the reverse transfer rate when the transparent toner is completely “absent”. For each stage other than the lowest stage, a reverse transfer rate corresponding to a representative value (for example, a lower limit, an upper limit, or a median value) of the transparent toner amount belonging to that stage is used. The reverse transfer rate at each of these stages (including the stage corresponding to the absence of transparent toner) may be obtained by experiments or the like.

  The reverse transfer rate information holding unit 162 may be mounted by any method. For example, it may be configured as a look-up table, or may be configured as a function representing a mathematical expression for obtaining the reverse transfer rate from the transparent toner amount T.

  The reverse transfer rate determination unit 160 obtains, for each pixel, a reverse transfer rate corresponding to the transparent toner amount T of the pixel input from the transparent toner amount calculation unit 14 from the reverse transfer rate information holding unit 162, and a correction value calculation unit. Input to 166. The reverse transfer rate determination unit 160 also inputs the reverse transfer rate when there is no transparent toner to the correction value calculation unit 166.

  The reverse transfer count determination unit 164 performs, for each pixel, at least one color component based on the color signal (X, Y ′, M ′, C ′, K ′) input from the color conversion unit 12. The number of times of reverse transfer to which the toner is subjected is obtained.

  In one example, the number of photoconductors downstream of the toner of a toner of a certain color component may be obtained as the number of reverse transfers that the toner of that color component suffers.

  Further, when another toner is superimposed on the toner transferred on the upstream first photosensitive member on the downstream second photosensitive member, the upstream toner is covered with the downstream toner, so that the reverse rotation is further performed. No copying takes place. In this case, the reverse transfer of the toner on the first photoconductor does not transfer the toner for the pixel between the first photoconductor and the second photoconductor (that is, the toner amount or color component value for the pixel). Will occur as many times as there are photoreceptors. As described above, the number of times of reverse transfer of the toner transferred from a certain photoconductor may be the number of photoconductors that do not transfer the toner for the relevant pixel immediately after the photoconductor. Even if the toner amount of the pixel on the downstream second photosensitive member is not zero, if the value is small, the ratio of covering the toner transferred from the upstream photosensitive member is small. The degree of prevention may be reduced. Therefore, the toner amount of the pixel in the downstream photoconductor is compared with a predetermined threshold value greater than 0, and if the toner amount is smaller than the threshold value, it is considered that there is no toner transfer on the downstream photoconductor. Is equal to or greater than the threshold value, it may be determined that there is toner transfer on the downstream photoconductor, and the number of times of reverse transfer for the toner on the upstream photoconductor may be obtained.

  In one example, the reverse transfer number determination unit 164 performs reverse transfer for each of the color components X, Y ′, M ′, and C ′ except the most downstream color component K ′ that does not cause reverse transfer by the above-described method. Find the number of times.

  In another example, the reverse transfer frequency determination unit 164 may calculate the reverse transfer frequency only for a predetermined number of upstream color components instead of all of X, Y ′, M ′, and C ′. Good. That is, in the case of the most upstream photoconductor, the transparent toner is added where there was no toner transfer upstream, so the change in the reverse transfer amount due to the presence of the transparent toner is Biggest of all. Since the downstream photoconductor originally has a larger number of upstream photoconductors (that is, even when no transparent toner is used), the relative weight of the transparent toner is small, and the correction considering the transparent toner is not performed. A good case is also possible. For this reason, only a predetermined number of color components from the most upstream side are subjected to toner amount correction considering the transparent toner, and the reverse transfer number determination unit 164 also performs the reverse transfer number only for those color components accordingly. May be requested.

  The correction value calculation unit 166 has, for each pixel, the color signal (X, Y ′, M ′, C ′, K ′) input from the color conversion unit 12 and the transparent toner amount input from the transparent toner amount calculation unit 14. T, the reverse transfer rate corresponding to the transparent toner amount T input from the reverse transfer rate determination unit 160, the reverse transfer rate when no transparent toner is used, and the reverse of each color component input from the reverse transfer number determination unit 164 Based on the copy rate, for each color component to be corrected, the amount of toner of the color component remaining on the intermediate transfer body after reverse transfer is input to the print engine 18 so as to be equivalent to the case where no transparent toner is used. The value of the color component corresponding to the color toner is corrected.

  This correction calculation will be described using a specific example. FIG. 6 shows a color A (X, Y ′, M ′, C ′, K ′) = (80, 0, 0, 0, 0) of one pixel and a color B (70, 0, 0) of another pixel. , 50, 0) is shown as an example of correction. In this example, the value of the color component is shown as a percentage when the maximum possible value is 100%. In this example, the reverse transfer rate information holding unit 162 holds two stages of reverse transfer rates: a reverse transfer rate of 7% when the transparent toner is present and a reverse transfer rate of 4% when the transparent toner is not present. For example, T = 60% is set as the threshold for distinguishing the presence or absence of transparent toner. In this example, the toner amount correction considering the transparent toner is performed only for the most upstream color component X. Further, in this example, the threshold value is set to, for example, 30% for the toner amount for determining that the color toner is present.

For the color A, it is assumed that the transparent toner amount calculation unit 14 calculates the transparent toner amount T as 100. In this case, the reverse transfer rate determination unit 160 determines that the reverse transfer rate corresponding to the transparent toner amount T = 100 is 7% (because 100 exceeds the threshold value 60), and corresponds to the determined transparent toner amount T. The reverse transfer rate 7% and the reverse transfer rate 4% when there is no transparent toner are supplied to the correction value calculation unit 166. Further, the reverse transfer number determination unit 164 recognizes that the toner amounts of the four color components downstream of the most upstream color component X from the value of each component of the color A (80, 0, 0, 0, 0) are all zero. Then, it is determined that the number of times of reverse transfer for the color component X is 4. The correction value calculation unit 166 determines the amount of the 80% density X toner transferred from the X photoconductor onto the intermediate transfer member after the four reverse transfers, without any transparent toner (reverse transfer rate = 4). %) And the case of the current transparent toner amount T (that is, the reverse transfer rate with transparent toner = 7%). When there is no transparent toner (reverse transfer rate = 4%), the amount of toner remaining after four reverse transfers is 80 × 0.96 ⁴ ≈68%. On the other hand, the remaining amount of toner after the four reverse transfers corresponding to the current transparent toner amount T is 80 × 0.93 ⁴ ≈60%. Therefore, in order to make the remaining amount of toner when the transparent toner is applied equal to the remaining amount when there is no transparent toner, the remaining amount of 60% may be increased to 68%. % May be corrected to 80 × 68 / 60≈91%. In this way, the correction value calculation unit 166 calculates 91% as the correction result value for the X component.

For color B, it is assumed that the transparent toner amount calculation unit 14 calculates the transparent toner amount T as 80. Since T = 80 also exceeds the threshold value 60, the corresponding reverse transfer rate is determined to be 7%. Also, it is the C component that is determined to have toner (that is, the toner amount is 30% or more) for the first time downstream of the X component, and for the X component, the Y and M component photoconductors between the X and C components. In total, reverse transcription occurs twice. In order to make the remaining amount after the reverse transfer rate of 7% when the transparent toner amount is applied and the amount of X component toner undergoes two reverse transfers equal to the remaining amount when the transparent toner is not used, The toner amount 70 of the component may be corrected to 70 × (0.96 / 0.93) ² ≈75. Since the C component is not a correction target in this example, the C component is maintained as it is (= 50).

  As described above, the correction value calculation unit 166 uses D as the input value of the color component to be corrected (X in the above specific example) for the pixel of interest, m as the number of times of reverse transfer for the color component, and transparent toner. If the reverse transfer rate is R (0) and the reverse transfer rate corresponding to the transparent toner amount T is R (T), the correction result toner amount D ′ is calculated by the following relational expression.

D ′ = D × {R (0) / R (T)} ^m

  In the above, a specific example in which only the X component is targeted for correction has been shown, but other components such as the Y component may be corrected by the same method.

  The toner amount signals (T ′, X ″, Y ″, M ″, C ″, K ″) obtained as a result of the correction calculation by the correction value calculation unit 166 are supplied to the print engine 18. In this example, since the amounts of the transparent toner and the most downstream K toner are not corrected, T ′ = T and K ′ = K ″. As for the X, Y, M, and C components between T and K, the predetermined number of components set in advance in the image processing apparatus as correction targets in advance are described above. The value of the correction result is calculated by the method, and the input value for the component is replaced with the correction result. For components that are not correction targets, input values are output to the print engine 18 as they are. The print engine 18 responds to the value of each component of the input toner amount signal (T ′, X ″, Y ″, M ″, C ″, K ″) with respect to the photoreceptor corresponding to each component. By controlling the exposure amount of the pixel, a toner amount that compensates for an increase in the reverse transfer amount due to the presence of the transparent toner adheres to the surface of the photosensitive member and is transferred to the intermediate transfer member. An amount of toner equivalent to that when the transparent toner is not applied remains on the intermediate transfer member.

  Next, a modified example will be described. In the above example, the toner total amount restriction is not applied to the correction result for compensating for the influence of the transparent toner, but in this modification, the total amount restriction is applied. As the amount of toner of any color component increases due to correction, the total amount of toner including transparent toner may exceed the total amount regulation value Max. In such a case, the total amount regulation value is maintained. is there.

  In one example, when the total toner amount after correction exceeds the total amount regulation value Max, the correction value calculation unit 166 reduces the transparent toner amount T by the excess amount (= total toner amount−Max). A transparent toner amount T ′ is obtained. By this correction, the total amount of toner becomes Max or less (assuming that the input values (T, X, Y ′, M ′, C ′, K ′) to the correction value calculation unit 166 are equal to or less than the total amount regulation value Max). .

  Here, if the correction for reducing the transparent toner amount T is performed as described above, the amount of reverse transfer of the color toner may be reduced accordingly. If the amount of this reduction is large, using the correction result of the color component obtained by the correction value calculation unit 166 as it is, the amount of toner to be realized for the color component (that is, a value assuming that there is no transparent toner). However, there may be a case where the actual toner amount becomes remarkably large (that is, beyond the level that can be visually recognized). Therefore, as another example, after the correction for reducing the transparent toner amount T, the same correction calculation as described above may be re-executed for each color component to be corrected using the transparent toner amount after the reduction correction. An example of this method is shown in FIG.

  In the procedure of FIG. 7, the correction value calculation unit 166 first performs a correction operation similar to that in the above-described embodiment (S12). It is determined whether the total amount of each toner obtained by the correction calculation is equal to or less than the total amount regulation value (S14). Here, if the sum exceeds the total amount regulation value, the correction value calculation unit 166 reduces and corrects the transparent toner amount by a predetermined reduction amount, for example, and instead of the previous transparent toner amount, the correction value is calculated. Using the transparent toner amount, the input color signals (X, Y ′, M ′, C ′, K ′) are corrected by the above correction calculation (S16). By repeating S <b> 14 and S <b> 16, the correction results for the transparent toner and the color toners whose total toner amount is equal to or less than the total amount regulation value are obtained.

  In the above embodiments and modifications, correction is performed in units of pixels, but the unit of correction calculation is not limited to pixels. For example, the same correction calculation as described above may be performed in units of blocks each including a predetermined number of pixels.

  The information processing function part (functional module group other than the print engine 18) of the image processing apparatus exemplified above is realized, for example, by causing a general-purpose computer to execute a program representing the processing of each functional module of the apparatus. Here, the computer includes, as hardware, a microprocessor such as a CPU, a memory (primary storage) such as a random access memory (RAM) and a read only memory (ROM), an HDD controller that controls an HDD (hard disk drive), Various I / O (input / output) interfaces, network interfaces that perform control for connection to a network such as a local area network, and the like have a circuit configuration connected via a bus, for example. Also, portable non-volatile recording of various standards such as a disk drive and a flash memory for reading and / or writing to a portable disk recording medium such as a CD or a DVD via the I / O interface, for example. A memory reader / writer for reading from and / or writing to a medium may be connected. A program in which the processing contents of each functional module exemplified above are described is stored in a fixed storage device such as a hard disk drive via a recording medium such as a CD or DVD, or via a communication means such as a network, and stored in a computer. Installed. The program stored in the fixed storage device is read into the RAM and executed by a microprocessor such as a CPU, thereby realizing the functional module group exemplified above.

10 image data input unit, 12 color conversion unit, 14 transparent toner amount calculation unit, 16 color correction unit, 18 print engine, 20 control unit, 160 reverse transfer rate determination unit, 162 reverse transfer rate information holding unit, 164 number of reverse transfer Determination unit, 166 correction value calculation unit.

Claims (3)

For each unit area of the input color image, based on the amount of toner of each color in the unit area, transparent toner amount calculation means for calculating the amount of transparent toner applied to the unit area;
For each unit region, an intermediate transfer type electronic device is used for at least one color toner based on the calculated reverse transfer rate according to the amount of transparent toner and the reverse transfer rate when no transparent toner is applied. In the photographic printing apparatus, the transparent toner is applied when the calculated amount of the transparent toner is applied after the reverse transfer of the toner of the color to the photoreceptor group downstream of the photoreceptor. Correction for correcting the amount of toner of the corresponding color so as to be equivalent to the case of not, and supplying a signal indicating the corrected toner amount to the electrophotographic printing apparatus together with a signal indicating the calculated amount of transparent toner Means,
An image processing apparatus comprising:   For each unit area, the correction unit is configured to determine a sum total of the corrected total amount of each color toner and the amount of the transparent toner calculated by the transparent toner amount calculation unit. The image processing apparatus according to claim 1, further comprising: a correction for reducing the amount of the transparent toner when the amount exceeds the upper limit. Computer
For each unit area of the input color image, based on the amount of toner of each color in the unit area, a transparent toner amount calculation means for calculating the amount of transparent toner applied to the unit area;
For each unit region, an intermediate transfer type electronic device is used for at least one color toner based on the calculated reverse transfer rate according to the amount of transparent toner and the reverse transfer rate when no transparent toner is applied. In the photographic printing apparatus, the transparent toner is applied when the calculated amount of the transparent toner is applied after the reverse transfer of the toner of the color to the photoreceptor group downstream of the photoreceptor. Correction for correcting the amount of toner of the corresponding color so as to be equivalent to the case of not, and supplying a signal indicating the corrected toner amount to the electrophotographic printing apparatus together with a signal indicating the calculated amount of transparent toner means,
Program to function as.

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