JP2012218346A - Ink droplet size replacing device, ink droplet size replacing method, program, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress jaggies of a character part and a texture in a picture part.SOLUTION: The ink droplet size replacing device replaces a predetermined ink droplet size depending on a type of image information printed on a paper. The ink droplet size replacing device includes: a means for calculating a used amount of ink by a head which prints the image information; a means for calculating a tentative used amount of the ink by a reference head when assumed that the image information is printed; a means for comparing the used amount of the ink and the tentative used amount of the ink; a means for determining whether the image information is printed by a plurality of kinds of heads or not; a means for replacing the predetermined ink droplet size with a different ink droplet size when the used amount of the ink and the tentative used amount of the ink do not correspond and it is determined that the image information is printed by the plurality of kinds of heads as a result of comparison between the used amount of the ink and the tentative used amount of the ink.

Description

  The present invention relates to an ink droplet size replacement device, an ink droplet size replacement method, a program, and an image processing device.

  In recent years, in an inkjet image forming apparatus, a plurality of inkjet heads, called a line head method, are arranged in the main scanning direction, and the main scanning size is secured, thereby fixing the inkjet head and removing a sheet as a printing medium. There is already known a technique for forming an image at high speed by conveying and operating it to form an image.

  As an ink jet image forming apparatus employing such a line head method, Patent Document 1 discloses the size of ink droplets based on a plurality of image data for the purpose of appropriately expressing gradation expression. Techniques for changing are disclosed. The purpose of this is to appropriately express the gradation (the density of the image) by changing the ink droplet size depending on the image density.

  However, when the image brightness difference correction is performed using the conventional ink droplet size replacement method, the replacement method is not fixed, so that the texture (texture roughness) is conspicuous in the photo portion of the image, or the character portion is aliased. There was a problem that (rattle) would occur.

  Further, even if gradation expression is appropriately expressed by changing the ink droplet size based on a plurality of image data described in Patent Document 1, lightness difference correction is performed by the ink droplet size replacement method. In such a case, the problem that the texture (roughness) is conspicuous in the photo portion and the alias (rattle) occurs in the character portion has not been solved.

  Therefore, the present invention has been made in view of the above-described problems, and is a texture (rough texture) image in a photographic part that occurs when lightness difference correction is performed by an ink droplet size replacement method. An object of the present invention is to provide an ink droplet size replacement device, an ink droplet size replacement method, a program, and an image forming apparatus capable of suppressing aliasing (rattle) in a character portion.

  In order to solve the above-described problem, an ink droplet size replacement device according to the first aspect of the present invention is an ink droplet size replacement device that replaces a predetermined ink droplet size in accordance with the type of image information to be printed on paper. An ink usage amount calculating means for calculating an ink usage amount of a head for printing the image information, and a temporary ink usage amount of a reference head which is a predetermined head when the image information is assumed to be printed. A temporary ink usage amount calculating means for calculating, an ink usage amount comparing means for comparing the ink usage amount and the temporary ink usage amount, and a head for determining whether or not the image information is printed by a plurality of types of heads; As a result of the comparison by the type determining means and the ink use amount comparing means, the ink use amount and the temporary ink use amount are inconsistent, and the head type Ink that replaces the predetermined ink droplet size with an ink droplet size different from the predetermined ink droplet size when the determination means determines that the image information is printed by the plurality of types of heads And a drop size replacing means.

  An ink droplet size replacement device according to the present invention is the ink droplet size replacement device according to claim 1, wherein the image information includes a photographic image and a character image.

  Furthermore, the ink droplet size replacement device according to the present invention is the ink droplet size replacement device according to claim 1 or 2, further comprising image information identification means for identifying whether the image information is a photographic image or a character image. Further, according to the result identified by the image information identification means, the ink droplet size is replaced with an ink droplet size corresponding to the image information.

  The ink droplet size replacement device according to the present invention is the ink droplet size replacement device according to any one of claims 1 to 3, wherein the ink droplet size replacement unit includes the ink usage amount and the ink temporary usage amount. The predetermined ink droplet size is not replaced depending on the type of the image information even if they do not match.

  The ink droplet size replacement device according to any one of claims 1 to 4 is the ink droplet size replacement device according to any one of claims 1 to 4, wherein the image information is identified by the image information identification unit. When the image is identified as a photographic image, the ink droplet size is replaced so that the replacement rate of the ink droplet size per unit area in the region printed on the paper is uniform.

  In addition, the ink droplet size replacement device according to the present invention is the ink droplet size replacement device according to claim 5, wherein the ink droplet size replacement unit has identified the image information as a photographic image by the image information identification unit. In this case, a new ink droplet size is not replaced in an area where no printing is performed on the paper before the ink droplet size is replaced in the area.

  Furthermore, the ink droplet size replacement device according to the present invention is the ink droplet size replacement device according to claim 5, wherein the ink droplet replacement unit is identified by the image information identification unit as the image information is a character image. In this case, the ink droplet size is preferentially replaced in the region from the vicinity of the region where the ink droplet size larger than the ink droplet size before the ink droplet size is replaced is applied. .

  An image forming apparatus according to the present invention includes the ink droplet size replacing device according to any one of claims 1 to 7.

  In order to solve the above problem, the ink droplet size replacement method according to the present invention described in claim 9 is an ink droplet size that replaces a predetermined ink droplet size according to the type of image information to be printed on paper. In the replacement method, the ink use amount calculating unit calculates the ink use amount of the head for printing the image information, and the ink use amount calculating unit is predetermined when the ink temporary use amount calculating unit is assumed to print the image information. A step of calculating a temporary ink usage amount of a reference head, which is a selected head, a step in which an ink usage amount comparison unit compares the ink usage amount with the temporary ink usage amount, and a head type determination unit includes the image As a result of comparing the step of determining whether or not information is printed by a plurality of types of heads with the step of comparing the ink droplet size replacement unit, the ink use And the temporary ink use amount and the image information is determined to be printed by the plurality of types of heads in the determining step, the predetermined ink droplet size is And a step of substituting an ink droplet size different from the determined ink droplet size.

  In order to solve the above problem, the program according to the present invention described in claim 10 controls an ink droplet size replacement device that replaces a predetermined ink droplet size in accordance with the type of image information to be printed on paper. It is a program, which is determined in advance when it is assumed that the ink usage amount calculating means calculates the ink usage amount of the head that prints the image information, and the ink temporary usage amount calculation means prints the image information. A process of calculating a temporary ink use amount of a reference head that is a head, a process of comparing an ink use amount with the ink temporary use amount, and a head type determination unit including the image information As a result of comparison between the process of determining whether or not the ink is printed by a plurality of types of heads and the ink droplet size replacing means by the process of comparing. When the dose and the temporary ink use amount are inconsistent and the image information is determined to be printed by the plurality of types of heads by the determination process, the predetermined ink droplet size is And a process of substituting with an ink droplet size different from a predetermined ink droplet size.

  According to the present invention, when an ink droplet size is changed in an ink jet type image forming apparatus that performs ink droplet size replacement, the ink image size is appropriately determined according to image information (photograph portion / character portion region) of the input image. Since the ink drop size replacement method is specified, the brightness difference between different inkjet heads can be reduced without causing texture (texture roughness) in the photo portion and aliasing (rattle) in the character portion. Ink droplet size replacement device, ink droplet size replacement method, program, and image forming apparatus can be obtained.

It is a figure showing arrangement of an ink jet head of a line head type image forming device in an embodiment of the present invention. It is a flowchart which shows operation | movement of the image processing of the image processing apparatus in embodiment of this invention. It is a flowchart which shows operation | movement of the discharge droplet information conversion means of the ink droplet size replacement apparatus in embodiment of this invention. It is a flowchart which shows operation | movement of the discharge droplet information conversion means of the ink droplet size replacement apparatus in embodiment of this invention. It is a figure explaining the magnitude | size of the ink droplet of the ink droplet size replacement apparatus in embodiment of this invention. It is a figure explaining the replacement method of the ink droplet size in (a) photograph part and (b) character part of the image processing apparatus provided with the ink droplet size replacement apparatus in the embodiment of the present invention. It is a figure explaining the replacement method of the ink droplet size of the character part of the image processing apparatus provided with the ink droplet size replacement device value in the embodiment of the present invention. It is a figure explaining the replacement method of the ink droplet size of the shaded part of the image processing apparatus provided with the ink droplet size replacement device value in the embodiment of the present invention. It is a figure explaining mixing of the ink droplet size of the image processing apparatus provided with the ink droplet size replacement apparatus value in the embodiment of the present invention. It is a figure explaining the method to detect the density difference by the difference in the ink droplet size of the image processing apparatus provided with the ink droplet size replacement apparatus value in the embodiment of the present invention. It is a figure explaining the determination method of the ink droplet size replacement of the image processing apparatus provided with the ink droplet size replacement device value in the embodiment of the present invention. FIG. 10 is a diagram illustrating a countermeasure when the density of the reference head and the ejection head A of the image processing apparatus having the ink droplet size replacement device value according to the embodiment of the present invention does not match.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. The present invention relates to an ink-jet type image forming apparatus that performs ink droplet size replacement, and changes the ink droplet size in accordance with image information (photograph portion / character portion region) of the input image. Therefore, the ink droplet size is replaced with an appropriate ink droplet size for each region such as a photo part and a character part, and the density generated between the inkjet heads is corrected. It is characterized by being done.

  An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an arrangement of an inkjet head of a line head type image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, a plurality of inkjet heads are arranged in a direction perpendicular to the main scanning direction of the printing paper (the arrow direction in FIG. 1). The position of the inkjet head is fixed, and when the printing paper is transported, ink is ejected from the inkjet head and an image is formed on the printing paper.

  In FIG. 1, cyan (Cyan: C1 to C5), magenta (Magenta: M1 to M5), yellow (Yellow: Y1 to Y5), black (Black: Black: K1 to K5), the ink droplet amount and density of each inkjet head. Are stored in advance, a reference head (hereinafter also referred to as a “reference head”) is determined, and brightness difference correction is performed based on difference data from the reference head and each data of the inkjet head. Like that.

  For example, when C1, M1, Y1, and K1 are used as reference heads, C1 and C2 to C5, M1 and M2 to M5, Y1 and Y2 to Y5, and ink discharge amounts (density) between K1 and K2 to K5, respectively. Ink droplets that can correct the brightness difference from the difference data and appropriate amounts of the respective heads of C1 to C5, M1 to M5, Y1 to Y5, and K1 to K5. Try to change the size.

  In FIG. 1, C1, M1, Y1, and K1 are used as reference heads for convenience, but the reference head may be any of C1 to C5, M1 to M5, Y1 to Y5, and K1 to K5. In addition, the target value of the inkjet head is determined in advance without determining the reference head, and the difference between the target value of the head and each of C1 to C5, M1 to M5, Y1 to Y5, and K1 to K5 is obtained. It doesn't matter.

  Next, the image processing operation of the inkjet image forming apparatus according to the embodiment of the present invention will be described. FIG. 2 is a flowchart showing the image processing operation of the image processing apparatus according to the embodiment of the present invention. In FIG. 2, when image information such as photographs and characters is captured by the scanner (step (hereinafter referred to as “S”) 20), image processing such as separation processing, filter processing, color correction, and γ conversion is performed. After that (S21), in the separation process performed in this image processing, the image data of the photograph part and the character part are separated as separation data, and the process proceeds to S24. The process of S24 will be described with reference to FIGS.

  After the image processing in S21, gradation processing is performed (S22), and then rendering (image generation) processing is performed (S23). In S24, the rendered image data and the image processing in S21 are separated. Discharge droplet information conversion processing is performed on the separated data. That is, as a feature of the present invention, the ejection droplet information conversion process (S24) is performed after rendering (image generation). In this process of S24, separation data is input from the process of S21, and the photograph In each region of the part and the character part, replacement with an appropriate ink droplet size based on different regulations is performed, and the density generated between the inkjet heads is corrected. A specific operation of the ejection droplet information conversion process (S24) will be described with reference to FIGS.

  Next, the ejection droplet information conversion process (S24) of FIG. 2 will be described in detail with reference to FIGS. 3 and 4 are flowcharts showing the operation of the ejection droplet information converting means of the ink droplet size replacing device in the embodiment of the present invention. In FIG. 3, first, it is confirmed whether or not there is a difference in ink amount between the reference head and a print head other than the reference head. That is, the ink amount A at the print head is calculated at S30, the virtual ink amount B at the reference head is calculated at S31, and the ink amount A at the print head and the virtual ink amount B at the reference head are calculated at S32. To determine whether or not there is a difference between them (S33). If there is no difference between the two (S33: NO), the process proceeds to S39, and this flow is terminated without replacing the ink droplet size.

  When the ink amount A at the print head is compared with the virtual ink amount B at the reference head and there is a difference between the two (S33: YES), the image data having a connection to be printed is one inkjet. It is determined whether or not printing is possible with only the head, that is, whether or not the image data is data across a plurality of heads (S34). If the image data can be printed by only one inkjet head, that is, if the image data is not data that spans multiple heads (S34: NO), the process proceeds to S39, and this flow is performed without replacing the ink droplet size. Exit.

  When the image data is data across a plurality of heads (S34: YES), data replacement is performed (S35). Before the replacement, it is determined whether the target image data is a photographic part. (S36). When the target image data is a photographic part (S36: YES), an ink droplet replacement process for the photographic part is performed (S37), and when the target image data is a character part (S36: NO), an ink drop replacement process for the character portion is performed (S38), and the process is terminated. Note that the method of replacing the ink droplet size in the photographic part and the character part in S37 and S38 will be specifically described in FIG.

  FIG. 4 is also basically the same as the flow of FIG. 3, and the processing from S40 to S46 is the same as the processing from S30 to S36 in FIG. In FIG. 4, in determining whether the target image data is a photographic part before replacement (S46), when the target image data is a photographic part (S46: YES), The ink drop replacement process is the same (S47), but if the target image data is a character part (S46: NO), the ink drop replacement process for the character part is not executed (S48). ), The process is terminated. This is a flow in which the ink droplet size replacement is not performed when the ink droplet size replacement portion matches the character portion because the difference in density due to the brightness difference is not noticeable for the character portion.

  As an embodiment of the present invention, there are three types of ink droplets, large droplets, medium droplets, and small droplets. These ink droplets are replaced as ink droplets after replacement. The following description will be given on the assumption that three types of large droplets, substituted medium droplets, and substituted small droplets are mixed. FIG. 5 is a diagram for explaining the size of ink droplets in the ink droplet size replacement device according to the embodiment of the present invention. Black circles are ink droplets before replacement, and hatched circles are replaced ink droplets.

  Next, a method for replacing the ink droplet size will be specifically described with reference to FIGS. 6A and 6B are diagrams for explaining a method of replacing the ink droplet size in the (a) photographic part and (b) character part of the image processing apparatus provided with the ink droplet size replacing apparatus in the embodiment of the present invention. FIG. 5 is a diagram for explaining a method of replacing the ink droplet size of the character portion of the image processing apparatus having the ink droplet size replacement device according to the embodiment of the present invention.

  FIG. 6A shows the relationship between image data before changing the ink droplet size in the photograph (upper figure) and image data after changing the ink droplet size (lower figure) as image data hit by the inkjet head. . The replacement method for the photographic part will be described with reference to FIG. 6A. When replacement is performed in which the ink droplet size per unit area is fixed at a specific position in the image data of the photographic part, the entire printed image is viewed. In addition, the high density portion and the low density portion are easily visually recognized, and as a result, texture (texture roughness) is generated. In order to prevent this, as shown in the lower diagram of FIG. 6A, the ink droplet size is replaced so that the replacement locations are evenly spaced within the unit area. That is, the replacement rate within the unit area is made uniform. Further, in the present embodiment, in order to match the ink droplet size conversion of the photographic portion with the density of the reference head, additional ink is added to a portion where no ink droplets are ejected in the image data before the ink droplet size change. It is assumed that no droplets are ejected.

  FIG. 6B shows the relationship between the image data before changing the ink droplet size (upper figure) and the image data after changing the ink droplet size (lower figure) as image data hit by the inkjet head. . The character part replacement method will be described with reference to FIG. 6B. In the character part, as in the case of the photograph part, when ink droplet size replacement is performed uniformly per unit area, the character part is surrounded by characters and lines. When ink drops are conspicuously present with a gap between them, protrusions such as corners occur around the characters and lines, resulting in aliases (rattles) in the characters and lines. Will occur. In order to avoid such a state, the character portion is preferentially replaced from the periphery of the large ink droplet. The replacement of the ink droplet size with respect to the character portion will be described in a little more detail with reference to FIG.

  As shown in FIG. 7A, when the ink droplet size is replaced at equal intervals, as in the photograph portion, the portion where the ink droplet size is replaced at the upper and lower portions of the horizontal line becomes protrusions such as corners. As a result, aliases (rattle) appear in the lines and characters. Therefore, as shown in FIG. 7B, regarding the character portion, the ink droplet size is replaced by continuously replacing the ink droplet size around the large ink droplet size. Avoid aliasing characters and lines.

  FIG. 8 is a diagram illustrating a method for replacing the ink droplet size in the shaded portion of the image processing apparatus having the ink droplet size replacement device according to the embodiment of the present invention. As shown in FIG. 8A, when the ink droplet size is replaced so as to increase the size of the hatched ink dot (dot), the ink droplets are not smoothly connected, resulting in an alias ( Rattling). For this reason, as shown in FIG. 8B, only when the density of the oblique line is increased, a new ink droplet point (dot) between the point (dot) and the point (dot) existing in the original data (hatched line) is used. By adding dots), the diagonal lines can be reproduced smoothly.

  FIG. 9 is a diagram for explaining mixing of ink droplet sizes in an image processing apparatus having an ink droplet size replacement device according to an embodiment of the present invention. When replacing the ink droplet size, as shown in FIG. 9A, when ink droplets having non-continuous sizes such as large droplets and small droplets are mixed, the ink droplet sizes are replaced uniformly. However, when printed on paper, the density difference due to the size of the ink droplet size is large, resulting in a texture (texture roughness). In order to avoid this, as shown in FIG. 9 (b), the number of ink droplet size replacement locations increases, but mixing of non-consecutive droplets (or droplets in which the amount of ink droplets are separated) is avoided. Control as follows.

  Next, a method for detecting a density difference due to a difference in ink droplet size will be described. FIG. 10 is a diagram illustrating a method for detecting a density difference due to a difference in ink droplet size in an image processing apparatus having an ink droplet size replacement device according to an embodiment of the present invention. First, an image having a halftone dot area ratio of 50% is printed using only each ink droplet size (small droplet / medium droplet / large droplet) for each color and each head. Next, the printed image is read by a scanner, and each droplet size (small droplet / medium droplet / large droplet) is obtained by using the calculation formula shown in FIG. Drop) Read data per drop.

  Next, an ink droplet size replacement determination method will be described using a specific example with reference to FIG. FIG. 11 is a diagram illustrating a method for determining ink droplet size replacement in an image processing apparatus having an ink droplet size replacement device according to an embodiment of the present invention. A drop information holding unit (not shown) holds in advance data on each drop size of the reference head and data on each drop size of the ejection head other than the reference head. Based on these pieces of information, for data to be actually printed, the density obtained when printing is actually performed by the head A that ejects ink is calculated. Subsequently, the density obtained when the same image data is printed by the reference head is calculated. Comparing these two data, the difference between the density obtained by the reference head and the density obtained by the ejection head A that actually prints an image, which ink droplet is changed for any size and how much is changed. It is determined whether the density matches the density of the reference head. Then, the ink head data is replaced by the determined replacement number, and printing is performed on the paper. In this way, the difference in density between each ejection head and the reference head is corrected.

  Taking FIG. 11 as an example, in the drop information holding unit (not shown), as the reference head data, the density data for one small drop is 0.02, the density data for one medium drop is 0.05, The density data for one large drop is 0.10, and as the data for the ejection head A, the density data for one small drop is 0.01, the density data for one medium drop is 0.04, and the density for one large drop is Each data is held at 0.08. As the data to be actually printed, when there are 12 small droplets, 9 medium droplets, and 0 large droplets, the density when printing with the discharge head A is 0.01 × 12 + 0. 04 × 9 + 0.08 × 0 = 0.48 On the other hand, the density when printing with the reference head is 0.02 × 12 + 0.05 × 9 + 0.10 × 0 = 0.69. 0.21. Here, in order to match the density when printing is performed with the ejection head A to the density when printing is performed with the reference head, the density is changed to 0.03 by changing the ink droplet size of the ejection head A from small droplets to medium droplets. As the ink droplet size is replaced, by replacing 7 small droplets with medium droplets, the density becomes 0.03 × 7 = 0.21. The density in this case matches.

  Next, a countermeasure when the density when printing with the reference head does not match the density when printing with the ejection head A will be described with reference to FIG. FIG. 12 is a diagram illustrating a countermeasure when the densities of the reference head and the ejection head A of the image processing apparatus having the ink droplet size replacement device value according to the embodiment of the present invention do not match. In FIG. 12, in the printing areas (A) to (K), an image is formed by each of the following heads. That is, the area (a) is the reference head only, the area (b) is the reference head and the ejection head A, the area (c) is the ejection head A only, the area (d) is the ejection head A and the ejection head B, and the area (e). Is the discharge head B only, the region (f) is the discharge head B and the discharge head C, the region (g) is only the discharge head C, the region (c) is the discharge head C and the discharge head D, and the region (g) is the discharge head D. Only.

  Here, a case where the section α is printed is considered. The print data in the section α is printed by using the ejection head B and the ejection head C for the photographic part. Here, regarding the reference head and the ejection head B and the reference head and the ejection head C, it is determined whether or not the ink droplet size needs to be replaced. Now, based on the comparison result between the density of the reference head and the density of the ejection head B, it is assumed that the adjusted predicted density does not match and the density of the ejection head B is slightly higher than the density of the reference head. It is also assumed that the density of the discharge head C is slightly lower than the reference head density because the adjusted predicted density does not match even in the comparison result between the density of the reference head and the density of the discharge head C.

  Under such an assumption, when the photographic part in FIG. 12 is printed, the density difference between the ejection head B and the ejection head C becomes conspicuous as a result. In order to avoid such a situation, in the same continuous image (in the region of the photographic part in FIG. 12), adjustment is performed so that the density relationship between the ejection head used for printing and the reference head is the same. In the case of this assumption, that is, in the comparison result between the reference head and the ejection head B, the adjusted predicted density does not match and becomes slightly darker than the reference head, and the adjustment is made in the comparison result between the reference head and the ejection head C. If the predicted densities do not match and become slightly lighter than the reference head, the ink droplets that intentionally make the discharge head C darker than the reference head in the relationship between the predicted densities of the reference head and the discharge head C. By performing the size replacement, it is possible to prevent the occurrence of a density difference by matching the predicted density relationship between the reference head and the ejection head B.

  In order to execute each operation described in the above embodiment, a control unit (not shown) that controls the operation of each unit constituting the ink droplet size replacement device includes a ROM (Read Only Memory) and a RAM (Random Access Memory). It goes without saying that the program is executed on the basis of a computer-readable program stored in a memory (not shown) composed of, for example.

  As described above, according to the present invention, in the ink jet image forming apparatus that performs ink droplet size replacement, when changing the ink droplet size, the image information of the input image (such as the photographic part / character part) Since an appropriate ink drop size replacement method according to the area is specified, different ink jet heads can be used without causing texture (roughness) in the photo portion and aliasing (rattle) in the character portion. Thus, it is possible to obtain an ink droplet size replacement device, an ink droplet size replacement method, a program, and an image forming apparatus that can reduce the brightness difference between them.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

JP 2007-021729 A

Claims (10)

An ink droplet size replacement device that replaces a predetermined ink droplet size according to the type of image information to be printed on paper,
An ink use amount calculating means for calculating an ink use amount of a head for printing the image information;
A temporary ink use amount calculating means for calculating a temporary ink use amount of a reference head which is a predetermined head when it is assumed that the image information is printed;
An ink use amount comparing means for comparing the ink use amount and the temporary ink use amount;
Head type determination means for determining whether or not the image information is printed by a plurality of types of heads;
As a result of the comparison by the ink use amount comparison means, the ink use amount and the temporary ink use amount are inconsistent, and the image information is printed by the plurality of types of heads by the head type determination means. An ink droplet size replacing means for replacing the predetermined ink droplet size with an ink droplet size different from the predetermined ink droplet size when determined;
An ink droplet size replacement device.   2. The ink droplet size replacement device according to claim 1, wherein the image information includes a photographic image and a character image.   Further comprising image information identifying means for identifying whether the image information is a photographic image or a character image, and depending on the result identified by the image information identifying means, an ink droplet size corresponding to the image information is obtained. The ink droplet size replacement device according to claim 1 or 2, wherein the replacement is performed.   The ink droplet size replacing unit does not replace the predetermined ink droplet size depending on the type of the image information even if the ink usage amount and the ink temporary usage amount do not match. The ink droplet size replacement device according to any one of claims 1 to 3.   The ink droplet size replacement means has a uniform replacement ratio of the ink droplet size per unit area in the area printed on the paper when the image information identification means identifies the image information as a photographic image. The ink droplet size replacing device according to any one of claims 1 to 4, wherein the ink droplet size is replaced so as to satisfy the following condition.   The ink droplet size replacement unit is configured to change an area in which no printing is performed on the paper before the ink droplet size is replaced in the region when the image information identification unit identifies the image information as a photographic image. 6. The ink droplet size replacing device according to claim 5, wherein the ink droplet size does not replace a new ink droplet size.   The ink droplet replacement means is an ink drop having a larger ink droplet size before the ink droplet size is replaced in the region when the image information identifying means identifies the image information as a character image. 6. The ink droplet size replacement device according to claim 5, wherein the ink droplet size is replaced preferentially from the vicinity of a region to which the size is applied.   An image forming apparatus comprising the ink droplet size replacement device according to claim 1. An ink droplet size replacement method that replaces a predetermined ink droplet size according to the type of image information to be printed on paper,
A step of calculating an ink usage amount of a head for printing the image information;
A step of calculating a temporary ink use amount of a reference head, which is a predetermined head when the temporary ink use amount calculating unit assumes that the image information is printed;
A step of comparing the ink use amount with the ink temporary use amount by an ink use amount comparing means;
A step of determining whether or not the image information is printed by a plurality of types of heads;
As a result of comparing the ink droplet size replacement means in the comparing step, the ink usage amount and the temporary ink usage amount are inconsistent, and the image information is determined by the plurality of types of heads in the determining step. Replacing the predetermined ink droplet size with an ink droplet size different from the predetermined ink droplet size when it is determined to be printed;
An ink droplet size replacement method comprising: A control program for an ink droplet size replacement device that replaces a predetermined ink droplet size according to the type of image information to be printed on paper,
A process of calculating an ink usage amount of a head that prints the image information;
A process of calculating a temporary ink use amount of a reference head, which is a predetermined head when the temporary ink use amount calculating unit is assumed to print the image information;
A process in which an ink use amount comparing means compares the ink use amount with the temporary ink use amount;
A process for determining whether or not the image information is printed by a plurality of types of heads;
As a result of the comparison by the comparing process, the ink droplet size replacing means does not match the ink usage amount and the temporary ink usage amount, and the image information is determined by the plurality of types of heads by the determining process. A process of replacing the predetermined ink droplet size with an ink droplet size different from the predetermined ink droplet size when it is determined to be printed;
The program characterized by including.

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