JP2010149408A - Image processing apparatus, image processing method, image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of keeping sharpness of edges of high density characters even in the case of executing density correction processing to printing jobs. <P>SOLUTION: The image processing apparatus applying the density correction to individual objects included in the printing jobs, in which the individual objects included in the printing jobs are character object, determines whether or not the character density of the objects is the predetermined value or more (S303, S304), and excludes the character objects whose character densities are determined to be the predetermined value or more from the objects of the density correcting processing (S304, S305). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, an image processing method, and an image processing program for executing density correction processing on individual objects included in a print job.

  Conventionally, in black-and-white printing, the problem of “blackout” has been pointed out that the gradation of the shadow part cannot be sufficiently reproduced and the whole is painted black. As a remedy for this problem, a method of printing by reducing the density of the output image uniformly is widely adopted.

  As a method of reducing the density of the output image in this way, a method of printing with the developing potential lowered on the printer engine side, a method of performing a density correction process using a tone curve on the output image data on the printer controller side, etc. are considered. It is done.

  However, in the method of lowering the development potential on the engine side, the toner adhesion amount is not stable, so that there is a problem that density unevenness occurs in the image after printing and the image quality is remarkably deteriorated. In addition, when performing density correction processing using a tone curve, image quality deterioration due to density unevenness does not occur, but even high-density characters that should be emphasized are uniformly reduced in density by the density correction processing. As a result of binarization by processing, there arises a problem that the sharpness of the edge portion of the character is impaired.

In relation to this, the following Patent Document 1 proposes a technique of applying special screen processing in which the print density is shifted to the low density side only for character objects below a predetermined point. However, the technique is intended to eliminate bleeding at the time of printing a small character of about 2 or 3 points, and has a problem that the sharpness of the character is lowered due to the density correction processing uniformly applied to the image data. Is not a solution.
JP 2004-306555 A

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to maintain the sharpness of the edge of a high-density character even when density correction processing is performed on a print job. An image processing apparatus, an image processing method, and an image processing program are provided.

  The above object of the present invention is achieved by the following means.

  (1) An image processing apparatus that performs density correction on individual objects included in a print job, wherein each object included in the print job is a character object, and whether the character density of the object is a predetermined value or more. A determination unit configured to determine whether or not, and a density correction unit configured to perform the density correction on the object excluding the character object that has been determined that the character density is equal to or higher than the predetermined value. An image processing apparatus.

  (2) The image processing apparatus according to (1), wherein the determination unit determines that only a character object having a character density of 100% is a character object having a density greater than or equal to the predetermined density.

  (3) The determination unit includes a first determination unit that determines whether each object included in the print job is a character object, and the first determination unit that determines that the first determination unit is a character object. The image processing apparatus according to (1) or (2), further comprising: a second determination unit that further determines whether or not the character density is equal to or higher than a predetermined value.

  (4) The image processing apparatus according to any one of (1) to (3), wherein the density correction is density correction using a tone curve.

  (5) The print job is print data described in PostScript (registered trademark), and the first determination unit determines based on the presence or absence of a show operator included in the print data, and the second determination unit The image processing apparatus according to (3), wherein the determination is performed based on any one operand of a setgray operator, a setcmykcolor operator, and a setrgbcolor operator included in the print data.

  (6) An image processing method executed in an image processing apparatus that performs density correction on an individual object included in a print job, wherein each object included in the print job is a character object, and the character density of the object A determination step for determining whether or not is greater than or equal to a predetermined value, and a density correction step for performing the density correction on the object excluding the character object for which the character density is determined to be greater than or equal to the predetermined value in the determination step And an image processing method.

  (7) In the determination step, it is determined that only a character object having a character density of 100% is a character object having a character density equal to or higher than the predetermined value.

  (8) The determination step includes a first determination step of determining whether or not each object included in the print job is a character object, and the object determined to be a character object in the first determination step. The image processing method according to (6) or (7), further including a second determination step of further determining whether or not the character density of the character is greater than or equal to a predetermined value.

  (9) The image processing method according to any one of (6) to (8), wherein the density correction is density correction using a tone curve.

  (10) The print job is print data described in PostScript (registered trademark). In the first determination step, a determination is made based on the presence or absence of a show operator included in the print data, and the second determination The image processing method according to (8), wherein in the step, determination is performed based on any one operand of a setgray operator, a setcmykcolor operator, and a setrgbcolor operator included in the print data.

  (11) An image processing program for controlling an image processing apparatus that performs density correction on each object included in a print job, wherein each object included in the print job is a character object, and the character of the object A determination procedure for determining whether or not the density is equal to or higher than a predetermined value; and a density correction for performing the density correction on the object excluding the character object for which the character density is determined to be equal to or higher than the predetermined value in the determination procedure An image processing program that causes the image processing apparatus to execute a procedure.

  (12) The image processing program according to (11), wherein in the determination procedure, only a character object having a character density of 100% is determined to be a character object having a character density greater than or equal to the predetermined density.

  (13) The determination procedure includes a first determination procedure for determining whether or not each object included in the print job is a character object, and the object determined to be a character object in the first determination procedure. The image processing program according to (11) or (12), further including a second determination procedure for further determining whether or not the character density of the character is equal to or higher than a predetermined value.

  (14) The image processing program according to any one of (11) to (13), wherein the density correction is density correction using a tone curve.

  (15) The print job is print data described in PostScript (registered trademark). In the first determination procedure, a determination is made based on the presence or absence of a show operator included in the print data, and the second determination The image processing program according to (13), wherein in the procedure, the determination is performed based on any one operand of a setgray operator, a setcmykcolor operator, and a setrgbcolor operator included in the print data.

  (16) A computer-readable recording medium on which the program described in any one of (11) to (15) is recorded.

  According to the present invention, it is possible to maintain the sharpness of the edge of a high-density character by excluding character objects having a character density of a predetermined value or more from the target of density correction processing. As a result, it is possible to maintain the character quality of the original image while preventing shadows from being blacked out.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
-System configuration (Figs. 1-6)
FIG. 1 is a block diagram showing an overall configuration of an image forming system A to which an image processing apparatus according to an embodiment of the present invention is applied.

  The image forming system A according to the present embodiment includes a PC 1 as a client device that generates a print job according to a user instruction, and an MFP 2 as an image forming device that executes printing based on the print job received from the PC 1. These are connected by a network 3 so that they can communicate with each other. Note that the PC 1 and the MFP 2 may be directly connected (locally connected) between devices without going through the network 3.

  Here, the MFP 2 is based on a printer controller 21 as an image processing apparatus that executes various image processing including rasterization processing on a print job received from the PC 1, and image processed image data transferred from the printer controller 21. And a printer engine 22 as a printing apparatus for executing printing. However, the printer printer controller 21 as an image processing apparatus may not be an apparatus included in the MFP 2 as in this example, but may be a single apparatus independent of the MFP 2.

  FIG. 2 is a block diagram showing a configuration of the PC 1 shown in FIG. The PC 1 includes a control unit 11, a recording unit 12, a display unit 13, an input unit 14, and a network interface 15, which are connected to each other via a bus 16 for exchanging signals.

  The control unit 11 is a CPU, and controls the above units and performs various arithmetic processes according to a program.

  The storage unit 12 stores various programs and parameters for controlling basic operations of the PC 1, RAM for temporarily storing programs and data as work areas, and various operations of the OS (operating system, basic software) and the PC 1. It includes a hard disk for storing a program for controlling, parameters, and the like. In the present embodiment, the hard disk of the storage unit 12 converts a document creation application for creating a document file into a page description language (PDL: Page Description Language) that can be interpreted by the printer controller 21. A printer driver for generating a print job (hereinafter also referred to as “PDL data”), a density correction application for performing settings related to density correction processing executed on the PDL data by the printer controller 21 described later, and the like are stored. Has been.

  The display unit 13 is a display device such as a CRT display or a liquid crystal display, and displays various types of information to the user. The input unit 14 is a keyboard, a mouse, or the like, and is used by a user who performs various inputs to the PC 1. The network interface 15 is an interface for connecting to the network 3 and communicating with other devices on the network 3, and standards such as Ethernet (registered trademark), token ring, and FDDI are used.

  FIG. 3 is a block diagram showing a configuration of the printer controller 21 of the image forming system A shown in FIG. The printer controller 21 includes a control unit 211, a storage unit 212, a data analysis unit 213, an RIP unit 214, a network interface 215, and a printer engine interface 216, which are mutually connected via a bus 217 for exchanging signals. It is connected to the.

  The control unit 211 is a CPU, and controls the above units and performs various arithmetic processes according to a program.

  The storage unit 212 stores various programs and parameters for controlling basic operations of the printer controller 21, RAM that temporarily stores programs and data as work areas, and an OS (operating system, basic software) and the printer controller 21. Including a hard disk or the like for storing programs and parameters for controlling various operations. In particular, in the present embodiment, it is assumed that a tone curve to be applied to the density correction of PDL data received from the PC 1 is stored in the storage unit 212 in advance. This point will be further described later.

  The data analysis unit 213 analyzes the print job (PDL data) received from the PC 1. More specifically, the data analysis unit 213 analyzes the received PDL data to specify a tone curve to be applied to the PDL data in the density correction process, and each object included in the PDL data is a character object. Or whether the character density of the character object is equal to or higher than a predetermined value. This point will be further described later.

  The RIP processing unit 214 executes rasterization processing for expanding the PDL data received from the PC 1 into multi-value image data in the bitmap format. In addition, the RIP processing unit 214 sequentially executes density correction processing and screen processing on the multi-value image data generated by the rasterization processing.

  Here, the density correction process is a process for correcting the density of the image data by applying a tone curve stored in the storage unit 212 to the multi-value image data. The screen processing is processing for generating binary image data in which gradation is expressed by the size of halftone dots from multi-valued image data after density correction. The tone curve is a function used when adjusting the brightness, gradation, and color tone of an image with photo retouching software, and is represented by a straight line with the horizontal axis as input and the vertical axis as output. Generally, the tone curve before adjustment is a straight line with a 45 ° upward slope. The user can execute density correction by changing the inclination and position of the straight line by a mouse operation or the like and finely adjusting the brightness, gradation, and color tone of the image.

  FIG. 4 is a block diagram conceptually showing the operation of the RIP processing unit 214. As shown in FIG. 4, the RIP processing unit 214 sequentially executes rasterization processing, density correction processing, and screen processing on the PDL data received from the PC 1, and outputs the density-corrected binary image data generated as a result to the printer. Transmit to the engine 22. Then, an image based on the image data received by the printer engine 22 is printed on a recording sheet by the printing unit 225 as described later.

  Referring to FIG. 3 again, the network interface 215 is an interface for connecting to the network 3 and communicating with other devices on the network 3. The printer engine interface 216 is an interface for communicating with the printer engine 22 and is, for example, a parallel interface such as IEEE1394.

  FIG. 5 is a block diagram showing the configuration of the printer engine 22 of the image forming system A shown in FIG. The printer engine 22 includes a control unit 221, a storage unit 222, an image reading unit 223, an operation unit 224, a printing unit 225, and a printer controller interface 226, which are mutually connected via a bus 227 for exchanging signals. It is connected.

  The control unit 221 is a CPU, and controls the above units and performs various arithmetic processes according to a program. The storage unit 222 stores various programs and parameters for controlling basic operations of the printer engine 22, a RAM that temporarily stores programs and data as a work area, and an OS (operating system, basic software) and the printer engine 22. Including a hard disk or the like for storing programs and parameters for controlling various operations.

  The image reading unit 223 applies a light source such as a fluorescent lamp to a document set at a predetermined reading position on the document table or a document conveyed to a predetermined reading position by an ADF (Auto Document Feeder). Light is irradiated, and the reflected light is scanned by a light receiving element such as a CCD image sensor or a CMOS image sensor, thereby generating digital data of an original image.

  The operation unit 224 is an operation panel including a display device such as a liquid crystal display for displaying various types of information to the user, and an input device such as a touch panel and a keyboard for acquiring a reprint instruction from the user.

  The printing unit 225 prints an image based on the image data received from the printer controller 21 on a recording medium such as a recording sheet, using an electrophotographic image forming process. The printer controller interface 226 is an interface for communicating with the printer controller 21.

  FIG. 6 is a schematic diagram illustrating a specific configuration of the printing unit 225. As shown in FIG. 6, the printing unit 225 includes a photosensitive drum a that rotates in the direction of an arrow, a charging device b, an exposure device c, a developing device d, a transfer device e, a cleaning device f, a fixing device g, and a paper feeding device h. , A paper discharge device i is provided. The image forming process by the printing unit 225 is as follows.

  1) The surface of the photosensitive drum a rotating counterclockwise by the charging device b is uniformly charged. 2) An electrostatic latent image is formed on the surface of the photosensitive drum a by laser irradiation of the exposure device c. 3) To the electrostatic latent image on the surface of the photosensitive drum a, toner is provided from developing rollers of C (cyan), M (magenta), Y (yellow), and K (black) colors constituting the developing device d. The image is visualized. 4) The visualized toner images of CMYK colors are sequentially transferred to the intermediate transfer belt of the transfer device e. 5) The color image formed on the intermediate transfer belt is transferred onto the recording paper supplied from the paper feeding device by the transfer device e. 6) The color image transferred on the recording paper is fixed on the recording paper by the fixing device.

The recording paper on which the image based on the image data is printed in this manner is appropriately discharged to a discharge tray or the like by the discharge device i through post-processing steps such as stapling and punching.
-PC processing (Figs. 7 and 9)
(A) Tone curve storage processing (FIG. 7)
Next, an outline of the operation of the PC 1 according to the present embodiment will be described. FIG. 7 shows a process in which the PC 1 according to the present embodiment receives a tone curve adjustment instruction from the user and stores the adjusted tone curve in the printer controller 21 for the subsequent printing process (hereinafter simply referred to as “tone curve storage process”). It is an example of the flowchart which shows the procedure of (it is also called). The algorithm shown in the flowchart of FIG. 7 is stored as a control program in the ROM of the storage unit 12, and is read out and executed by the control unit 11 when the operation starts.

  First, when receiving an instruction to start tone curve saving processing from the user, the PC 1 activates a density correction application stored in the hard disk (S101). The instruction is accepted when the user performs a predetermined operation on the UI screen provided by the printer driver, for example.

  When the density correction application is activated in S101, a tone curve adjustment UI screen u1 for adjusting a tone curve to be applied by the user for density correction is displayed on the display unit 13. FIG. 8 is a schematic diagram illustrating an example of a tone curve adjustment UI screen u1 according to the present embodiment.

  As shown in FIG. 8, the tone curve adjustment UI screen u1 of the present embodiment includes a “test chart” pull-down menu M1 for obtaining a selection result of a test chart used for tone curve adjustment from the user, a tone currently being adjusted. A tone curve display window W1 for displaying a curve and obtaining a tone curve adjustment instruction from the user, a preview display window W2 for displaying a density correction result by the tone curve before and after the adjustment so that the user can compare and contrast, and after the adjustment And a “save” button B1 for obtaining an instruction from the user that the tone curve should be saved.

  A user who performs tone curve adjustment using such a UI screen first selects an appropriate test chart from the pull-down menu M1. Here, the test chart is sample image data displayed in the preview display window W2 during tone curve adjustment, and is stored in the hard disk of the storage unit 12 or the like. Usually, a plurality of types of test charts are prepared, and the user can reproduce a desired finished state more faithfully by selecting a test chart that is close to a document image to be printed later. Then, the user adjusts the tone curve in the following procedure while viewing the test chart preview displayed in the preview display window W2.

  At the time when the UI screen u1 is displayed, the tone curve in the initial state is displayed in the tone curve display window W1. The tone curve in the initial state is, for example, a straight line with an upward 45 ° angle. Then, the user adjusts the tone curve by dragging and deforming the tone curve currently displayed in the tone curve display window W1 with a mouse, for example. Here, in the preview display window W2, a preview to which the tone curve before adjustment (in the initial state) is applied and a preview to which the tone curve after adjustment is applied are displayed side by side. Are sequentially updated according to the tone curve adjustment by the user. Therefore, the user can easily create a tone curve that realizes a desired density correction by operating the mouse or the like while observing the change in the preview after adjustment.

  Finally, the user can name and save the adjusted tone curve by pressing the “Save” button B1. The tone curve stored in this way is appropriately selected in the subsequent printing process and applied to the density correction process of the PDL data. This point will be further described later.

  Referring to FIG. 7 again, the PC 1 connects to the printer controller 21 (S102) and starts communication with the printer controller 21. Then, the PC 1 specifies a test chart used for tone curve adjustment (S103), and reads out image data of the test chart from the storage unit 12. More specifically, the PC 1 acquires a selection result for the pull-down menu M1 of “test chart” from the user.

  Subsequently, the PC 1 receives a tone curve adjustment instruction from the user (S104). More specifically, the PC 1 acquires a tone curve adjustment instruction from the user through the tone curve display window W1.

  Subsequently, after adjusting the tone curve in accordance with the adjustment instruction received in S104, the PC 1 generates a preview image in which the adjusted tone curve is applied to the test chart specified in S103, and displays the preview image (on the right side thereof). (S105). At this time, the PC 1 may instruct the printer controller 21 to print a test chart to which the adjusted tone curve is applied so that the user can confirm the actual print result.

  Thereafter, the PC 1 repeatedly executes the processes of S104 to S105 until receiving an instruction to save the adjusted tone curve (NO in S106). The above instruction is accepted when the user presses the “save” button B1 on the UI screen u1. When the PC 1 acquires the above instruction (YES in S106), the tone curve is given a name and saved in the connected printer controller 21 (S107), and the series of processing ends (end). At this time, the PC 1 displays a text input screen (not shown) for the user to input a tone curve name, and information about the adjusted tone curve including the tone curve name acquired there is stored in the storage unit of the printer controller 21. save.

(B) Print setting process (FIG. 9)
The tone curve stored in the printer controller 21 in the procedure of FIG. 7 can be referred to as appropriate in the subsequent print setting process. FIG. 9 is an example of a flowchart illustrating a procedure of print setting processing by the PC 1. The algorithm shown in the flowchart of FIG. 9 is stored as a control program in the ROM of the storage unit 12, and is read out and executed by the control unit 11 when the operation starts.

  First, when receiving an instruction for starting print settings from the user, the PC 1 activates the printer driver described above (S201). The instruction is accepted when the user installs the PC 1 and performs a predetermined operation on the document creation application, for example.

  Subsequently, the PC 1 displays on the display unit 13 a print setting UI screen u2 for obtaining an instruction regarding print settings from the user. FIG. 10 is a schematic diagram illustrating an example of the print setting UI screen u2.

  As shown in FIG. 10, the print setting UI screen u2 is composed of a large number of setting screens of “detailed settings”, “basic settings”, “layout”, “finish”, “image quality”, “others”. The user switches the tab for each setting item, displays a desired setting screen, and performs print settings. What is displayed in FIG. 10 is a setting screen relating to an “image quality” tab for setting a tone curve and the like to be applied to density correction.

  Here, the UI screen u2 in FIG. 10 is provided with a “tone curve” pull-down menu M2 for selecting a tone curve to be applied to the density correction. From the pull-down menu M2, the above-described tone curve is provided. A tone curve saved in advance by the saving process (FIG. 7) can be selected.

  Referring to FIG. 9 again, the PC 1 receives instructions regarding various print settings through the print setting UI screen u2 (S202). Instructions received by the PC 1 at this time include not only basic settings such as the number of copies to be printed and output size, but also post-processing settings such as punching and stapling on the “finish” setting screen, and screen methods and tones on the “image quality” setting screen. Instructions regarding image processing settings such as curves are included.

Finally, the PC 1 generates PDL data in a predetermined format such as PostScript (registered trademark) or PCL (registered trademark) based on the print settings received in step S202, and transmits this to the printer controller 21 as a print job. (S203), a series of processing ends (end). The PDL data transmitted to the printer controller 21 in this way is converted into bitmap format image data by the RIP unit 214 in the order of arrival. This point will be further described later.
-Printer controller processing (Fig. 11)
Next, an outline of the operation of the printer controller 21 according to the present embodiment will be described. FIG. 11 shows a binary in bitmap format by the RIP unit 214 of the printer controller 21 that has received a print job (PDL data) from the PC 1 executing rasterization processing, density correction processing, and screen processing on the PDL data. 4 is an example of a flowchart showing a procedure of processing for generating image data and transmitting it to the printer engine 22 (hereinafter also simply referred to as “RIP processing”). The algorithm shown in the flowchart of FIG. 11 is stored as a control program in the ROM of the storage unit 212, and is read out and executed by the control unit 11 when the operation starts. The following processing is executed for each object included in the PDL data, and is repeatedly executed until the processing for all the objects included in the PDL data is completed.

  First, the PC 1 analyzes the PDL data (S301) and determines whether or not the object currently being processed is a character object. If the object is a character object, the character density of the character object is predetermined. It is further determined whether or not it is greater than or equal to the value (for example, 80% or more). A specific determination method at this time is as follows.

  FIG. 12 is a diagram showing the structure of print data described in PostScript (registered trademark) as an example of PDL data, and o1 to o3 in the figure correspond to individual objects. Here, the determination of “whether or not the object (currently being processed) is a character object” is made based on the presence or absence of the “show” operator in the print data. Here, the “show” operator is a command for instructing printing of a character string in PostScript (registered trademark). For example, “(This is 100%) show” is a character “This is 100%”. This is a command for instructing printing of a column. That is, if a “show” operator is included in a portion corresponding to an object having print data, the object is a character object.

  The determination of “whether or not the character density of the character object (currently being processed) is equal to or higher than a predetermined value” is made based on the operand value of the “setgray” operator in the print data. Here, the “setgray” operator is a command for defining the black density of the object by receiving the operand (x) between 0 and 1, and “x setgray” is the black density of the object (1−x ) × 100% command.

In the print data described in PostScript (registered trademark), when the density of the object is expressed in the CMYK color space, it is an operand of the “Setcmykcolor” operator representing the density of each color in the CMYK color space (Cyan, Magenta). , Yellow, Black) is substituted into a predetermined conversion formula to calculate the black density. Here, the predetermined conversion formula is
Black density (%) = {min (1.0, 0.3 × Cyan + 0.59 × Magenta + 0.11 × Yellow) −Black} × 100
It is. In the above conversion formula, “min (1.0,“ calculation formula ”)” is a function that means that the smaller one of 1.0 or “calculation formula” is adopted.

Further, when the density of an object is expressed in the RGB color space in the print data described in PostScript (registered trademark), it is an operand of a “Setrgb” operator representing the density of each color in the RGB color space (Red, Green) , Blue) is substituted into a predetermined conversion formula to calculate the black density. Here, the predetermined conversion formula is
Black density (%) = {1− (0.3 × Red + 0.59 × Green + 0.11 × Blue)} × 100
It is.

  As described above, in the example of FIG. 12, the object o1 is the character string “This is 100%” with the density of 100%, the object o2 is the character string “This is 90%” with the density of 90%, and the o3 Is a character string “This is 80%” with a concentration of 80%.

  Referring to FIG. 11 again, the PC 1 executes rasterization processing on the PDL data to generate multi-value image data in the bitmap format (S302). Then, the PC 1 branches the subsequent processing according to the analysis result of S301 (S303, S304).

  That is, if the object currently being processed is not a character object (NO in S303), the PC 1 executes density correction processing using a tone curve for the image data generated in S302 (S305), and further executes screen processing. (S306), the image data is transmitted to the printer engine 22 (S307), and a series of processing ends (end). Note that the tone curve applied in the density correction in S305 is the tone curve selected by the user in the above-described print setting process (FIG. 9).

  Similarly, when the object currently being processed is a character object and the character density is less than a predetermined value (YES in S303, NO in S304), the PC 1 similarly applies to the image data generated in S302. After executing the density correction processing (S305) and the screen processing (S306) (S306), the image data is transmitted to the printer engine 22 (S307), and the series of processing ends (end).

  On the other hand, when the object currently being processed is a character object and the character density is equal to or higher than a predetermined value (YES in S303, YES in S304), the PC 1 applies tone to the image data generated in S302. After executing only the screen processing without executing the density correction processing by the curve (S306), the image data is transmitted to the printer engine 22 (S307), and the series of processing ends (end).

  FIG. 13 is a diagram conceptually showing the operation of the printer controller 21 of the present embodiment. As shown in FIG. 13, the printer controller 21 excludes some objects from the density correction processing target according to the analysis result of the PDL data. In other words, the printer controller 21 unconditionally executes density correction processing for objects other than character objects, while it executes density correction processing for character objects only when the character density is less than 80%. If the character density is 80% or more, the character object is excluded from the density correction target.

  As described above, according to the MFP 2 of the present embodiment, a character object having a character density of a predetermined value (for example, 80%) or more is excluded from the density correction processing target by the printer controller 21, thereby It becomes possible to maintain the sharpness of the edge. As a result, it is possible to maintain the character quality of the original image while preventing shadows from being blacked out.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, in the above embodiment, an example has been described in which the printer controller 21 excludes a character object having a character density of 80% or more from the target of density correction processing. However, the present invention is not necessarily limited thereto, and the printer controller 21 has a character density of 100. It is also possible to assume an example in which only% character objects are excluded from the density correction processing targets.

  In the above embodiment, the print data described in PostScript (registered trademark) is determined whether it is a character object based on the presence or absence of the “show” operator included in the print data. In some cases, the character density was determined based on the operands of the “setgray” operator, the “setcmycolor” operator, and the “setrgbcolor” operator. However, these operators are only representative examples, and other operators are used for the determination. Also good.

  Furthermore, in the above-described embodiment, an example in which the MFP 2 executes print processing based on a print job received from the PC 1 has been described. However, the present invention is not necessarily limited to this, and image data read by the image reading unit 223 by the MFP 2 can be used. An example in which a printing process is executed based on this can also be assumed.

  The image processing apparatus according to the present invention can be realized by a dedicated hardware circuit for executing each procedure described above, or by executing a program describing each procedure described above by the CPU. When the present invention is realized by the latter, a program for operating the image processing apparatus may be provided by a computer-readable recording medium such as a floppy (registered trademark) disk or a CD-ROM, or via a network such as the Internet. May be provided online. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a ROM, hard disk or the like. The program may be provided as a single application software, or may be incorporated into the software of the apparatus as a function of the image processing apparatus.

1 is a block diagram illustrating a configuration of an image forming system according to an embodiment of the present invention. It is a block diagram which shows the structure of PC concerning one Embodiment of this invention. 1 is a block diagram illustrating a configuration of a printer controller according to an embodiment of the present invention. FIG. It is a figure which shows notionally operation | movement of the RIP part of the printer controller which concerns on one Embodiment of this invention. 1 is a block diagram illustrating a configuration of a printer engine according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a printing unit of a printer engine according to an embodiment of the present invention. It is a flowchart which shows the procedure of the tone curve preservation | save process based on one Embodiment of this invention. It is a figure which shows an example of UI screen for tone curve adjustment which concerns on one Embodiment of this invention. 6 is a flowchart illustrating a procedure of print setting processing according to an embodiment of the present invention. 5 is a diagram illustrating an example of a print setting UI screen according to an embodiment of the present invention. FIG. It is a flowchart which shows the procedure of the RIP process which concerns on one Embodiment of this invention. It is a figure which shows an example of the PDL file which concerns on one Embodiment of this invention. It is a figure which shows notionally the operation | movement of the printer controller which concerns on one Embodiment of this invention.

Explanation of symbols

1 PC,
2 MFP,
21 Printer controller,
212 storage unit,
213 Data analysis unit,
214 RIP section,
22 Printer engine,
225 printing section,
M1, M2 pull-down menu,
u1 UI screen for tone curve adjustment,
u2 UI screen for print settings,
W1, W2 windows.

Claims (16)

An image processing apparatus that performs density correction on individual objects included in a print job,
A determination unit that determines whether or not each object included in the print job is a character object, and the character density of the object is equal to or higher than a predetermined value;
An image processing apparatus comprising: a density correction unit that performs the density correction on the object excluding the character object for which the character density is determined to be equal to or greater than the predetermined value.   The image processing apparatus according to claim 1, wherein the determination unit determines that only a character object having a character density of 100% is a character object having a density equal to or higher than the predetermined density.   The determination unit includes: a first determination unit that determines whether each object included in the print job is a character object; and the character density of the object that the first determination unit has determined to be a character object. The image processing apparatus according to claim 1, further comprising: a second determination unit that further determines whether or not the value is equal to or greater than a predetermined value.   The image processing apparatus according to claim 1, wherein the density correction is density correction using a tone curve. The print job is print data described in PostScript (registered trademark).
The first determination unit makes a determination based on the presence or absence of a show operator included in the print data,
The image processing apparatus according to claim 3, wherein the second determination unit performs determination based on any one operand of a setgray operator, a setcmykcolor operator, and a setrgbcolor operator included in the print data. An image processing method executed in an image processing apparatus that performs density correction on individual objects included in a print job,
A determination step of determining whether or not each object included in the print job is a character object and the character density of the object is equal to or higher than a predetermined value;
An image processing method, comprising: a density correction step for performing the density correction on the object excluding the character object for which the character density is determined to be equal to or higher than the predetermined value in the determination step.   The image processing method according to claim 6, wherein in the determination step, it is determined that only a character object having a character density of 100% is a character object having a character density equal to or higher than the predetermined value.   The determination step includes a first determination step for determining whether or not each object included in the print job is a character object, and a character density of the object determined to be a character object in the first determination step. The image processing method according to claim 6, further comprising: a second determination step of further determining whether or not is equal to or greater than a predetermined value.   9. The image processing method according to claim 6, wherein the density correction is density correction using a tone curve. The print job is print data described in PostScript (registered trademark).
In the first determination step, a determination is made based on the presence or absence of a show operator included in the print data,
The image processing method according to claim 8, wherein in the second determination step, the determination is performed based on any one operand of a setgray operator, a setcmykcolor operator, and a setrgbcolor operator included in the print data. An image processing program for controlling an image processing apparatus that performs density correction on individual objects included in a print job,
A determination procedure for determining whether each object included in the print job is a character object, and whether the character density of the object is equal to or higher than a predetermined value;
An image processing apparatus that causes the image processing apparatus to execute a density correction procedure for performing the density correction on the object excluding the character object that has been determined that the character density is equal to or higher than the predetermined value in the determination procedure. Processing program.   12. The image processing program according to claim 11, wherein, in the determination procedure, it is determined that only a character object having a character density of 100% is a character object having a character density of the predetermined value or more.   The determination procedure includes a first determination procedure for determining whether each object included in the print job is a character object, and a character density of the object determined to be a character object in the first determination procedure. The image processing program according to claim 11, further comprising: a second determination procedure for further determining whether or not is equal to or greater than a predetermined value.   The image processing program according to claim 11, wherein the density correction is density correction using a tone curve. The print job is print data described in PostScript (registered trademark).
In the first determination procedure, a determination is made based on the presence or absence of a show operator included in the print data,
14. The image processing program according to claim 13, wherein in the second determination procedure, the determination is performed based on any one operand of a setgray operator, a setcmykcolor operator, and a setrgbcolor operator included in the print data.   The computer-readable recording medium which recorded the program as described in any one of Claims 11-15.