JP2007221226A - Trapping method, printer controller, printer and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform trapping to acquire a better-quality print image than a conventional image. <P>SOLUTION: For preparation of trapping, quantity of print misregistration to be generated when an image forming apparatus 2 prints an image on each of segmented regions obtained by segmenting a sheet into a plurality of segments is acquired (#11, #12) in advance for each segmented region. Trapping characteristic data 73 indicating a trap width to be applied in execution of trapping are acquired for each segmented region on the basis of the print misregistration quantity (#13-#15). When an object image to be printed by the image forming apparatus 2 is designated, a color boundary is searched in the object image. A trap width to be indicated in the trap characteristic data 73 of a segmented region to which the color boundary belongs is applied as the trap width of the searched color boundary, and the image forming apparatus 2 is caused to execute trapping. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a trapping method in a printer that performs printing using a plurality of colorants.

  If misregistration (registration misregistration, misregistration) occurs during multicolor printing, there will be a gap at the transition of the color, for example, at the boundary between one color object and another color object. May appear. That is, white spots may occur. The following methods have been proposed as a method for preventing white spots from occurring.

  One of them is a method of directly correcting misregistration. That is, the characteristics of misregistration are predicted, and on the basis of the prediction result, for each color (for example, four colors of CMYK), writing timing or writing period modulation by a laser or LED (Light Emitting Diode), mirror inclination Correct such as.

  Trapping is widely known as another method. As described in Patent Documents 1 and 2, trapping is a method of preventing a gap from occurring by making one color thicker and overlapping with the other color at the boundary between two colors, that is, the color boundary.

  Patent Documents 1 and 2 disclose a method for improving the trapping accuracy. According to the method disclosed in Japanese Patent Laid-Open No. 2004-228561, after specifying the intensity of the basic color and the trap processing range by the input operation unit, the processing target image is read from the external storage unit. Next, the trap target pixel determining means defines the color intensity based on the intensity of the basic color and the density of the basic color, and a certain pixel within the trap processing range on the read processing target image is set as the target pixel. Compare the color intensity of the pixel of interest with the color intensity of surrounding pixels within a specified range from this pixel of interest, and whether the pixel of interest is a pixel to be trapped (trap target pixel) according to the comparison result Decide if. Subsequently, trap processing is performed by adding color components of peripheral pixels having different color configurations to the trap target pixel by the image changing means.

According to the method disclosed in Patent Document 2, the misregistration input unit generates a predicted misregistration value predicted by the color image output unit and inputs the predicted misregistration value to the misregistration suppression processing unit. The misregistration suppression processing means changes the size of the area to be trapped according to the misregistration predicted value, and processes the color image data input from the image input means. The halftone processing means reduces the value of the image data necessary for outputting the image data from the misregistration suppression processing means by the color image output means, and the color image output means outputs the color represented by the color material color signal. The image signal data is output in color on paper or the like.
JP 2000-307844 A JP 2004-122692 A

  By the way, in the case of an electrophotographic printer, for example, the writing accuracy or position accuracy of a laser or LED, the position accuracy of a photoconductor, the rotation accuracy or position accuracy of a drive system, and other various conditions should be matched with ideal conditions. Is difficult. That is, errors such as uneven writing of a laser or the like, uneven rotation of the drive system, or misalignment of each component inevitably occur. Misregistration occurs due to these errors.

  Also, white spots do not always occur uniformly in the entire image printed on paper. That is, the size of the white spots that occur may differ depending on where on the sheet two adjacent objects having different colors are printed. This is considered to be due to the fact that the various errors described above affect each other in a complex manner, and the state of plate misregistration varies depending on the position on the paper.

  In order to cope with the characteristic that the size of the white spot varies depending on the printing position on the paper using the conventional methods described in Patent Documents 1 and 2, the largest white spot size that can occur is predicted. However, it is conceivable to determine the entire trap width in accordance with this.

  However, in this case, the trap width becomes thick even at a position where white spots hardly occur, and the printed matter looks worse. In order to increase the output quality level of printed matter, it is important to prevent the occurrence of white spots, but it is also required to make the trap width as narrow as possible.

  The present invention has been made in view of such problems, and an object of the present invention is to perform trapping for obtaining a printed image with higher quality than before.

  A trapping method according to the present invention is a trapping method in a printer having a function of printing using a plurality of colorants of a predetermined color, in which a sheet is divided into a plurality of areas in advance in preparation for trapping. For each area, the amount of misregistration that occurs when the printer prints an image in the divided area is acquired, and trap width characteristic information indicating the trap width to be applied when trapping is performed for each divided area. Obtained based on the amount of misregistration in the divided area, and when a target image that is an image to be printed by the printer is designated, a color boundary is searched from the target image, and the searched As the trap width of the color boundary, the trap width indicated in the trap width characteristic information of the divided region to which the color boundary belongs is applied to trap the color boundary. Causing the serial printer, trapping method characterized by.

  Preferably, the amount of misregistration of the divided areas is determined by printing the predetermined marks of the predetermined colors on the paper at predetermined positions separated from each other in the divided areas on a sheet. This is obtained by scanning the divided area on which the predetermined mark is printed, and obtaining the difference between the position of the predetermined mark in the scanned divided area and the original position of the predetermined mark.

  According to the present invention, it is possible to perform trapping for obtaining a print image with higher quality than before.

  FIG. 1 is a diagram showing an example of the overall configuration of a system constituted by the personal computer 1 and the image forming apparatus 2, FIG. 2 is a diagram showing an example of the hardware configuration of the personal computer 1, and FIG. 4 is a diagram illustrating an example of a functional configuration, FIG. 4 is a diagram illustrating an example of a hardware configuration of the image forming apparatus 2, and FIG. 5 is a diagram illustrating an example of a functional configuration of the image forming apparatus 2.

  As shown in FIG. 1, the personal computer 1 and the image forming apparatus 2 are connected to each other via an interface such as USB, RS-232C, or Ethernet.

  As shown in FIG. 2, the personal computer 1 includes a CPU 10a, a RAM 10b, a ROM 10c, a hard disk 10d, a control circuit 10e, a communication interface 10f, an input / output interface 10g, an input device 10h, a display 10j, and the like.

  The control circuit 10e is a circuit for controlling the hard disk 10d, the communication interface 10f, the input / output interface 10g, the input device 10h, the display 10j, and the like.

  The communication interface 10f is a NIC (Network Interface Card) or a modem. The input / output interface 10g is an interface such as USB or RS-232C. The input device 10h is a device such as a keyboard or a mouse for a user to perform operations for inputting data, commands, and the like to the personal computer 1. The display 10j is a device for displaying the processing result by the CPU 10a to the user.

  The hard disk 10d includes a measurement chart print command unit 101, a print chart data receiving unit 102, a misregistration characteristic calculation unit 103, a trap characteristic data generation unit 104, a target document data acquisition unit 105, a target document data acquisition unit 105, as shown in FIG. Programs and data for realizing functions such as the trap width calculation unit 106, the target document print command unit 107, and the trap characteristic data storage unit 1DB are installed. These programs and data are read into the RAM 10b as necessary, and the programs are executed by the CPU 10a.

  The image forming apparatus 2 is a processing apparatus that integrates various functions such as copy, scanner, fax, network printing, and document server. In general, it may be called a multi-function peripheral or MFP (Multi Function Peripherals). As shown in FIG. 4, the image forming apparatus 2 includes a CPU 20a, a RAM 20b, a ROM 20c, a hard disk 20d, a control circuit 20e, a communication interface 20f, an input / output interface 20g, an operation panel 20h, a printing unit 20j, a scanner unit 20k, and the like. Consists of.

  The control circuit 20e is a circuit for controlling the hard disk 20d, the communication interface 20f, the input / output interface 20g, the operation panel 20h, the printing unit 20j, the scanner unit 20k, and the like.

  The communication interface 20f is a NIC (Network Interface Card) or a modem. The input / output interface 20g is an interface such as USB or RS-232C.

  The operation panel 20h is configured by a touch panel and a numeric keypad. The user operates the numeric keypad to give an instruction to the image forming apparatus 2 such as start or stop of processing, designate processing conditions such as data destination, printing conditions, or scanning conditions, and various others. Can be specified. On the touch panel, a screen for giving a message or an instruction to the user, a screen for inputting the type of processing and processing conditions desired by the user, a screen showing the result of the processing executed by the CPU 20a, and the like are displayed. The Further, the user can give a command or make a designation by touching a predetermined position on the touch panel. As described above, the operation panel 20 h serves as a user interface for a user who operates the image forming apparatus 2.

  The scanner unit 20k optically reads an image of a document such as a sentence, a mathematical formula, a symbol, a photograph, a chart, or an illustration drawn on a sheet and generates image data.

  The printing unit 20j converts an image into cyan (C), magenta (M), yellow (Y), and black (Y) based on image data obtained by the scanner unit 20k or image data transmitted from the personal computer 1 or the like. Printing on paper by electrophotography using four color toners of K).

  The hard disk 20d is installed with programs and data for realizing functions such as a print command reception unit 201, a normal print control unit 202, a trapping print control unit 203, and a print chart data transmission unit 204 as shown in FIG. Has been. These programs and data are read into the RAM 20b as necessary, and the programs are executed by the CPU 20a. Alternatively, some or all of the functions shown in FIG. 5 may be realized by the control circuit 20e.

  FIG. 6 is a diagram showing an example of a measurement chart SYC, FIG. 7 is a diagram showing an example of the positional relationship of each color mark in the divided area RY, and FIG. 8 is a diagram showing an example of a measurement print chart SYC ′. .

  Next, processing contents of each part of the personal computer 1 shown in FIG. 3 and each part of the image forming apparatus 2 shown in FIG. 5 will be described.

  In FIG. 5, a print command receiving unit 201 of the image forming apparatus 2 performs processing for receiving various processing execution commands and data necessary for the processing from the personal computer 1. Alternatively, a process execution command may be acquired from the operation panel 20h.

  The normal printing control unit 202 and the trapping printing control unit 203 start printing processing according to the command and data obtained by the printing command etc. receiving unit 201. This will be sequentially described later.

  In FIG. 3, when a predetermined command is input to the measurement chart print command unit 101 of the personal computer 1, a measurement chart SYC as shown in FIG. 6 is transferred to a predetermined size sheet (for example, A4 size sheet). The image forming apparatus 2 is instructed to perform printing. At this time, the printing data 71 of the measurement chart SYC and the printing condition information 72 indicating the printing conditions such as the printing mode are transmitted to the image forming apparatus 2. Hereinafter, for the sake of simplicity of explanation, in the present embodiment, it is assumed that a sheet of the predetermined size is used, and the entire sheet is within the printing range.

  Data corresponding to the page description language of the image forming apparatus 2 is transmitted as the print data 71. When the image forming apparatus 2 supports PDF (Portable Document Format) or TIFF (Tagged Image File Format), the image data (image file) of the measurement chart SYC in these formats may be transmitted.

  The image forming apparatus 2 is provided with a trapping print mode in which printing is performed by applying a trapping process (trap process) and a normal printing mode in which printing is performed without applying trapping. The measurement chart print command unit 101 transmits print condition information 72 indicating that the print mode is the normal print mode to the image forming apparatus 2.

  Incidentally, the measurement chart SYC in FIG. 6 is used to obtain data when correcting the misregistration (registration misregistration, misregistration) generated in the image forming apparatus 2 by the trapping process. The measurement chart SYC is divided into a plurality of rectangular areas. Hereinafter, these areas are referred to as “divided areas RY”. In addition, these divided regions RY may be described separately from “divided regions RY01”, “divided regions RY02”,..., “Divided regions RY12”, respectively.

  In each of the divided areas RY (RY01 to RY12), at least one predetermined mark (mark) is arranged for each toner color of the image forming apparatus 2. The positions of these predetermined marks are determined in advance.

  In the present embodiment, as shown in FIG. 7, three black cross-shaped marks (hereinafter referred to as “black mark Mk1”, “black mark Mk2”, and “black mark Mk3”), 1 One cyan cross mark (hereinafter referred to as “cyan mark Mc”), one magenta cross mark (hereinafter referred to as “magenta mark Mm”), and one yellow cross mark This mark (hereinafter referred to as “yellow mark My”) is arranged for each divided region RY.

  The horizontal bar of the black mark Mk1 and the horizontal bar of the cyan mark Mc are on the same straight line, the horizontal bar of the black mark Mk2 and the horizontal bar of the magenta mark Mm are on the same straight line, and the horizontal bar of the black mark Mk3. And the horizontal bar of the yellow mark My are on the same straight line. The horizontal bars of these marks are all parallel to each other. The vertical bar of the black mark Mk1, the vertical bar of the magenta mark Mm, and the vertical bar of the black mark Mk3 are on the same straight line. The vertical bar of the cyan mark Mc, the vertical bar of the black mark Mk2, and the vertical bar of the yellow mark My It is on the same straight line. The vertical bars of these marks are all parallel to each other. The vertical bar of the black mark Mk1 and the vertical bar of the cyan mark Mc are separated by a predetermined distance DY1, and the horizontal bar of the black mark Mk1 and the horizontal bar of the magenta mark Mm are separated by a predetermined distance DT1, and the horizontal bar of the magenta mark Mm. And the horizontal bar of the black mark Mk3 are separated by a predetermined distance DT2. The positions of the black marks Mk1 to Mk3, the cyan mark Mc, the magenta mark Mm, and the cyan mark Mc are determined by the respective centers, that is, the positions of the intersections of the crosses.

  Returning to FIG. 3 and FIG. 5, the normal print control unit 202 of the image forming apparatus 2 receives the print command, the print data 71, and the print condition information 72 by the print command etc. receiving unit 201. When the normal printing mode is indicated, the printing unit 20j is controlled to execute the printing process in the normal printing mode using the printing data 71. For example, when image data of the measurement chart SYC is received as the print data 71, the measurement chart SYC as shown in FIG. 6 is printed on a sheet.

  When the image forming apparatus 2 prints the measurement chart SYC on the paper in the normal printing mode, as shown in FIG. 8, the black marks Mk1 to Mk3, the cyan mark Mc, the magenta mark Mm, and the yellow mark My are caused by the misregistration. May slightly deviate from the original printing position.

  Hereinafter, the measurement chart printed on the paper may be referred to as “measurement print chart SYC ′” in order to distinguish it from the original measurement chart SYC. Further, the areas corresponding to the divided areas RY01, RY02,..., RY12 of the original measurement chart SYC printed on the paper are respectively divided into "divided areas RY01 '", "divided areas RY02'", ..., "divided areas RY12 '. ". The divided areas RY01 ', RY02', ..., RY12 'may be collectively referred to as "divided areas RY'".

  In the present embodiment, as shown in FIG. 8, the direction in which the shorter side of the paper is parallel to the axis of the photosensitive drum of the printing unit 20j, that is, the line direction (main scanning direction) for dividing the image during printing. It is assumed that the orientation of the paper during printing is determined so that the longer side is parallel to the paper feed direction, that is, the sub-scanning direction during printing. Hereinafter, in order to distinguish the main scanning direction and the sub-scanning direction during printing from the main scanning direction and the sub-scanning direction during image reading in the scanner unit 20k, they are referred to as “main direction” and “sub-direction”, respectively. With this printing process, three rows of divided areas RY 'are arranged in the main direction of the paper, and four rows of divided areas RY' are arranged in the sub direction.

  9 is a diagram illustrating an example of the amount of misregistration between toner colors in a certain divided region RY ′, FIG. 10 is a diagram illustrating an example of the amount of misregistration in each divided region RY ′, and FIG. 11 is a diagram illustrating each divided region RY. FIG. 12 is a diagram illustrating an example in which the misregistration of the image is expressed by the number of pixels, FIG. 12 is a diagram illustrating the center position of each divided region RY ′ of the measurement print chart SYC ′, and FIG. 13 is a diagram illustrating the target pixel and each divided region RY ′. FIG. 14 is a diagram for explaining the positional relationship with the center, and FIG. 14 is a diagram showing an example of the distribution of trap widths in the main direction and the sub direction shown in the trap characteristic data 73.

  5 performs a process of causing the scanner unit 20k to read the image of the measurement print chart SYC 'printed on the paper and transmitting the image data 81 of the image to the personal computer 1. Note that the reading resolution is preferably the same as the printing resolution of the measurement chart SYC. Alternatively, it may be read at a higher resolution and reduced to the printing resolution.

  The print chart data receiving unit 102 of the personal computer 1 performs processing for receiving the image data 81 from the image forming apparatus 2.

  The misregistration characteristic calculation unit 103 is based on the image data 81 received from the image forming apparatus 2 and the amount (magnitude) of misregistration generated in each divided region RY ′ on the sheet when the image forming apparatus 2 performs printing. ) Is calculated. That is, the positional deviation of each toner color is measured for each divided region RY ′ in the measurement print chart SYC ′ indicated in the image data 81. In this embodiment, each color, that is, a combination of black and cyan, a combination of black and magenta, a combination of black and yellow, a combination of cyan and magenta, a combination of cyan and yellow, and a combination of magenta and yellow Measure the amount of deviation for each.

  For example, the amount of deviation between black and cyan in the divided area RY01 ′ is the vector from the position of the black mark Mk1 to the position of the cyan mark Mc in the divided area RY01 ′ in the measurement print chart SYC ′ and the original measurement. The calculation is performed by obtaining the difference from the vector from the position of the black mark Mk1 to the position of the cyan mark Mc in the divided area RY01 of the chart SYC. As described above with reference to FIG. 7, the black mark Mk1 and the cyan mark Mc in each divided region RY of the measurement chart SYC are separated by the distance DY1 in the main direction, but the sub-direction components of both marks are the same. It is. Therefore, for example, in the divided area RY01 ′ of the measurement print chart SYC ′, the component in the main direction of the vector from the black mark Mk1 to the cyan mark Mc is increased by 0.10 mm (millimeters) from the distance DY1, and the cyan mark Mc is the black mark. When the deviation is 0.05 mm in the sub direction from Mk1, it is calculated as “deviation of 0.10 mm in the main direction and 0.05 mm in the sub direction”. Or, when the component in the main direction is reduced by 0.10 mm from the distance DY1 and the cyan mark Mc is shifted by 0.05 mm in the reverse direction of the sub direction from the black mark Mk1, “the shift by −0.10 mm in the main direction, It is calculated that “−0.05 mm has shifted in the direction”.

  Similarly, the amount of deviation between black and magenta is calculated based on the vector from the black mark Mk2 to the magenta mark Mm, and the amount of deviation between black and yellow is based on the vector from the black mark Mk3 to the yellow mark My. calculate. The amount of deviation between cyan and magenta is calculated based on the vector from the cyan mark Mc to the magenta mark Mm, and the amount of deviation between cyan and yellow is calculated based on the vector from the cyan mark Mc to yellow mark My. The amount of deviation between magenta and yellow is calculated based on the vector from the magenta mark Mm to the yellow mark My.

  In this way, it is possible to measure the amount of shift in the main direction and the sub direction between the colors in the divided region RY01 '. As a result, six sets of deviation amounts are obtained. The misregistration characteristic calculation unit 103 selects, from these misregistration amounts, the one having the maximum absolute value in each of the main direction and the sub direction. These absolute values are determined as the amount of misregistration in the divided area RY01 '. For example, when a measurement result as shown in FIG. 9 is obtained, the amounts of deviation in the main direction and the sub direction are set to “0.15 mm” and “0, 10 mm”, respectively. Similarly, the amount of misregistration is obtained for the other divided regions RY02 'to RY12'. Thereby, a result as shown in FIG. 10 is obtained.

  The trap characteristic data generation unit 104 calculates a trap width to be applied to each pixel when the image forming apparatus 2 performs printing in the trapping print mode. Then, trap characteristic data 73 indicating it is generated. The trap characteristic data 73 is generated as follows based on the calculation result by the misregistration characteristic calculation unit 103.

  The trap characteristic data generation unit 104 first determines the trap width in the main direction for each divided region RY ′ according to the output resolution (print resolution) when the image forming apparatus 2 prints the measurement print chart SYC ′. The width of misregistration is calculated by converting it into the number of pixels (pixels, dots).

  On the other hand, the trap width in the sub-direction is calculated as follows which is common to all the divided regions RY ′. The maximum value is selected from the widths of misregistration in the sub-direction of all the divided areas RY ′. Then, the maximum value is converted into the number of pixels according to the output resolution. Round up or down after the decimal point.

  For example, the image forming apparatus 2 prints the measurement chart SYC at an output resolution of 1200 × 1200 dpi, and scans the printed material, that is, the measurement of the measurement print chart SYC ′ is performed by the misregistration characteristic calculation unit 103. It is assumed that information on misregistration characteristics as shown in FIG. 10 is obtained as a result of the execution. In this case, the trap widths in the main direction and the sub direction as shown in FIG. 11 are calculated for each divided region RY ′.

  By the way, if the trap width of each divided region RY ′ as shown in FIG. 11 is used for the trapping process as it is, the trap width in the main direction may suddenly change at the boundary of the divided region RY ′. In this case, the boundary between the two objects (color boundary) may be unnatural. Therefore, the trap characteristic data generation unit 104 further interpolates the trap width in the main direction of FIG. 11 as follows.

  Attention is paid to one pixel on the measurement print chart SYC '. The trap width in the main direction at the target pixel is interpolated (calculated) according to the position of the target pixel (hereinafter referred to as “target pixel”).

In the case where the pixel of interest is located in the rectangular range KHA indicated by the thick line frame in FIG. 12, that is, as shown by the point Pf (xf, yf) shown in FIG. If the pixel of interest is located in a rectangular area formed by the respective centers Pa (x1, y1), Pb (x2, y1), Pc (x1, y2), Pd (x2, y2), the following ( 1) The trap width in the main direction at the target pixel is calculated using equation (1).
Z = [[((D4-D2)-(D3-D1)] * m + C-D1] * n + (D2-D1) * m + D1
(1)
Here, Z is the number of pixels representing the trap width in the main direction at the target pixel.
D1, D2, D3, and D4 are trap widths shown in FIG. 11 of each divided region RY ′ having centers Pa, Pb, Pc, and Pd, respectively. For example, when the target pixel is located in a rectangular region formed by the centers of the divided regions RY01 ′, RY02 ′, RY04 ′, and RY05 ′, D1 = 7, D2 = 2, D3 = 7, D4 = 2, It becomes.
m = (xf−x1) / (x2−x1).
n = (yf−y1) / (y2−y1).

When the pixel of interest is located in the rectangular range KHB or KHC indicated by the thick line frame in FIG. 12, that is, among the three directions of the lower right, lower left, and lower right like the point Pg (xg, yg) shown in FIG. Where the center of the divided region RY ′ exists in at least two directions, but where the center of the divided region RY ′ does not exist in the upper right, upper left, and directly above directions or of the three directions in the upper right, upper left, and directly above When the pixel of interest is located at a position where the center of the divided region RY ′ exists in at least two directions but the center of the divided region RY ′ does not exist in the lower right, lower left, and right lower direction, the following (2) The trap width in the main direction at the target pixel is calculated using the equation.
Z = D2 * k + D1 * (1-k) (2)
However, k = (xg−x1) / (x2−x1).

When the pixel of interest is located in the rectangular range KHD or KHE indicated by the thick frame in FIG. 12, that is, in the three directions of the upper right, lower right, and right horizontal directions like the point Ph (xh, yh) shown in FIG. Where the center of the divided region RY ′ exists in at least two directions, but where the center of the divided region RY ′ does not exist in the upper left, lower left, and left horizontal directions or in the upper left, lower left, and left horizontal directions If the pixel of interest is located in a location where the center of the divided region RY ′ exists in at least two directions but the center of the divided region RY ′ does not exist in the upper right, lower right, and right horizontal directions, 3) The trap width in the main direction at the target pixel is calculated using equation (3).
Z = D3 * q + D1 * (1-q) (2)
However, q = (yh−y1) / (y3−y1).

  When the pixel of interest is located in the rectangular range KHF, KHG, KHH, or KHI indicated by the thick line frame in FIG. 12, that is, the upper right, lower right, upper left, and lower left like the point Pj (xj, yj) shown in FIG. When the pixel of interest is located in a place where the center of the divided region RY ′ exists only in any one of the four directions, the divided region RY ′ to which the pixel of interest belongs without performing the interpolation process. Is determined as the trap width in the main direction of the target pixel.

  As described above, the trap width in the main direction of each pixel in the measurement print chart SYC ′ is the main direction shown in FIG. 11 for each of the divided regions RY ′ to which the pixel belongs and the divided regions RY ′ adjacent to the pixel. The trap width is calculated by interpolating according to the distance between the pixel and the center of each of the divided regions RY ′. Interpolation formulas other than formulas (1) to (3) may be used. A known calculation formula may be used.

  By performing the above calculation for each pixel of the measurement print chart SYC ', the trap width in the main direction of each pixel to be applied at the time of printing is interpolated (calculated). The distribution of the trap width in the main direction interpolated for each pixel is, for example, as shown in FIG. As described above, since the trap width in the sub-direction is used in common, the distribution thereof has the same value for all the pixels as shown in FIG.

  Then, the trap characteristic data generation unit 104 generates trap characteristic data 73 indicating the calculation results of the trap widths in the main direction and the sub direction as shown in FIG. The generated trap characteristic data 73 is associated with identification information (for example, an IP address) of the image forming apparatus 2 and stored in the trap characteristic data storage unit 1DB.

  Note that the reason why the trap width in the sub direction is made common regardless of the position of the pixel is as follows. In general, the plate misalignment in the sub direction, that is, the paper feeding direction, is largely caused by uneven rotation of the drive system. Therefore, there are many cases where white spots are generated differently every time printing is performed. On the other hand, since white spots in the main direction often occur regularly, the trap width corresponding to the pixel position is obtained.

  15 is a flowchart for explaining an example of the flow of boundary trap width calculation processing, FIG. 16 is a diagram showing an example of a target document MSR, and FIG. 17 is a diagram for explaining processing for searching for a boundary between two objects OJ1 and OJ2. 18 shows an example of the boundary pixel group KPG. FIG. 19 shows the boundary pixel group KPG in the trap width distribution in the main direction of the trap characteristic data 73 based on the position of the boundary pixel group KPG on the paper at the time of printing. It is a figure which shows the example which overlaps.

  The target document data acquisition unit 105 in FIG. 3 performs processing for acquiring print data 71 of a document that is intended to be printed by the user (hereinafter referred to as “target document MSR”). For example, it is assumed that the user starts drawing software on the personal computer 1, creates an illustration using the drawing software, and instructs the image forming apparatus 2 to print the illustration. Then, the target document data acquisition unit 105 acquires the image data of the illustration as print data 71. At this time, the image data of the illustration is converted into a format corresponding to the image forming apparatus 2 as necessary.

  When the target document MSR is printed in the trapping print mode, the trap width calculation unit 106 in the target document performs a process of calculating a trap width applied to the target document MSR. Such processing is performed in the procedure as shown in FIG. A pair of adjacent objects is extracted (searched) from the image of the target document MSR (# 101 in FIG. 15). In this embodiment, “object” means a group of pixels having the same attribute such as color. Therefore, there is an object boundary at the color change. Usually, white spots occur due to misregistration at this boundary.

  For example, when a target document MSR as shown in FIG. 16 is a processing target, a pair of objects OJ1 and OJ2, a pair of objects OJ2 and OJ3, and three pairs of objects OJ4 and OJ5 are extracted.

  For each of these extracted pairs of objects, processing is performed to extract the boundary between the two objects, that is, the portion to be trapped (# 103). Here, the processing procedure will be described by taking as an example the case of extracting the boundary of the pair of objects OJ1 and OJ2.

  As shown by the dotted frame in FIG. 17A, a rectangle is circumscribed on each of the objects OJ1 and OJ2. Then, as shown by a thick line frame in FIG. 17B, a portion where two rectangles overlap each other is generated. Since there is a boundary between the objects OJ1 and OJ2 in the overlapping portion, the trap width calculation unit 106 in the target document pays attention to the pixels in the thick line frame, and searches for a place where the pixel value changes, thereby determining the boundary. Extract. By such processing, the boundary can be quickly found. For example, when the pixel value of each pixel of the object OJ1 is “A” and the pixel value of the object OJ2 is “B”, the pixel value is “A” as shown by a thick frame in FIG. Find an adjacent pixel with a pixel value of “B”. Then, these found pixel groups are extracted as boundaries. Hereinafter, the pixel group extracted as the boundary is referred to as “boundary pixel group KPG”. It is also possible to find a pixel having a pixel value “A” adjacent to a pixel having a pixel value “B”, and extract these pixel groups as the boundary pixel group KPG.

  Returning to the flowchart, the trap widths in the main direction and the sub direction of the extracted boundary pixel group KPG are obtained based on the trap characteristic data 73, for example, as follows (# 104).

  Regarding the trap width in the main direction, first, it is determined at which position on the paper each pixel of the extracted boundary pixel group KPG should be printed (that is, the print position). Then, the trap width in the main direction corresponding to the position is obtained from the trap characteristic data 73. That is, for example, as shown in FIG. 19, the boundary pixel group KPG is superimposed on the distribution of trap widths in the main direction indicated by the trap characteristic data 73 so as to be arranged at the printing position. By obtaining the trap width value at the overlapping position, the trap width in the main direction of each pixel of the boundary pixel group KPG is obtained.

  In the example of FIG. 19, the trap width in the main direction near both ends of the boundary pixel group KPG is 3 pixels, and the trap width in the main direction near the center is 2 pixels. When a plurality of types of values are obtained as the trap width in the main direction, the maximum value may be unified as the trap width in the main direction of the entire boundary pixel group KPG. Alternatively, the most frequently obtained value may be unified as the trap width in the main direction of the entire boundary pixel group KPG.

  On the other hand, the trap width in the sub-direction is commonly used in all areas of the paper as described above. Therefore, when the trap characteristic data 73 indicates the trap width as shown in FIG. .

  Steps # 103 and # 104 are executed for all object pairs. In this way, the trap width calculation unit 106 in the target document calculates the trap width at the boundary between adjacent objects in the target document MSR.

  The target document print command unit 107 instructs the image forming apparatus 2 to print the target document MSR. At this time, the boundary data 74 indicating the trap width and position of the boundary pixel group KPG calculated by the trap width calculation unit 106 in the target document, the print data 71 of the target document MSR, and the current print mode are the trapping print mode. Print condition information 72 indicating the presence or the like is transmitted to the image forming apparatus 2.

  In the image forming apparatus 2, when the print data 71, the print condition information 72, and the boundary data 74 are received by the print command etc. receiving unit 201, the trapping print control unit 203 reads the target document related to the print data 71. The printing unit 20j is controlled so that the MSR is subjected to the trapping process and printed on the paper. That is, the portion of the outer periphery of the object included in the target document MSR that matches the boundary pixel group KPG indicated by the boundary data 74 is thickened by the trap widths in the main direction and the sub direction indicated by the boundary data 74. (Expanded outward) to control printing.

  In this way, the target document MSR to which the trapping printing mode is applied, that is, the target document MSR subjected to the trapping process is printed on the paper.

  20 is a flowchart for explaining an example of the overall processing flow when acquiring the trap characteristic data 73, and FIG. 21 is a flowchart for explaining an example of the overall processing flow when printing the target document MSR. .

  Next, the overall processing flow of the personal computer 1 and the image forming apparatus 2 will be described with reference to flowcharts.

  In FIG. 20, when acquiring data indicating the trap width characteristic at the time of printing in the image forming apparatus 2, that is, the trap characteristic data 73, the personal computer 1 sends the measurement chart SYC (see FIG. 6) to the image forming apparatus 2. Print processing is executed (# 11). The printing mode at this time is set to the normal printing mode so that the misregistration characteristics can be confirmed.

  The image forming apparatus 2 acquires the image data 81 of the measurement print chart SYC ′ by scanning the paper on which the measurement chart SYC is printed, and transmits it to the personal computer 1 (# 12). That is, data indicating misregistration characteristics is acquired.

  Based on the image data 81, the personal computer 1 calculates trap widths in the main direction and the sub direction to be applied to each pixel when the image forming apparatus 2 performs printing in the trapping print mode (# 13, # 14). ). Then, the calculation result is stored in the trap characteristic data storage unit 1DB as trap characteristic data 73 (# 15).

  In FIG. 21, when the personal computer 1 obtains the print data 71 of the document that the user desires to print, that is, the target document MSR (# 21), trap characteristic data 73 relating to the trap width to be applied to the target document MSR. Is generated (# 22). The method for generating the trap characteristic data 73 is as described above with reference to FIG. Then, the printing data 71, printing condition information 72 indicating that printing is performed in the trapping printing mode, and trap characteristic data 73 are transmitted to the image forming apparatus 2, and the print processing of the target document MSR is transmitted to the image forming apparatus 2. Execute (# 23).

  According to the present embodiment, when trapping an image to be printed, the trap width corresponding to the position of each pixel of the image is applied, so that the amount of extending the color boundary can be reduced as compared with the conventional case. . Therefore, it is possible to obtain a printed matter with higher quality than before.

  In this embodiment, the trap width in the sub-direction, that is, the paper feed direction is made common regardless of the pixel position. However, if white spots occur regularly, the trap width in the main direction is the same as in the case of the trap width in the main direction. The trap width may be obtained for each pixel position.

  In this embodiment, the image forming apparatus 2 prints the measurement chart SYC on a sheet based on a command from the personal computer 1, but prints it based on a command given by the user operating the operation panel 20h. May be.

  In this embodiment, data indicating misregistration is obtained by analyzing image data obtained by scanning a sheet on which the measurement chart SYC is printed. The distance between the marks on the sheet is determined using a loupe or the like. The measurement result may be obtained by causing the user to perform an operation of inputting the result using the operation panel 20h or the input device 10h.

  FIG. 22 is a diagram illustrating an example of the network NW. As shown in FIG. 22, when a personal computer 1 and a plurality of image forming apparatuses 2 form a network NW such as a LAN, the personal computer 1 uses the trap characteristic data 73 for each of these image forming apparatuses 2 and You may make it manage with a database (trap characteristic data storage part 1DB of FIG. 3). When any one of the image forming apparatuses 2 executes the printing process, the trap width (boundary data 74) to be applied to the target document MSR is obtained using the trap characteristic data 73 corresponding to the image forming apparatus 2. What should I do?

  Some of the functions of the personal computer 1 shown in FIG. 3 may be provided in the image forming apparatus 2. For example, the image forming apparatus 2 may be provided with a function of generating the boundary data 74 based on the trap characteristic data 73, that is, the function of the target document trap width calculation unit 106. In this case, the target document print command unit 107 of the personal computer 1 may issue a print command by transmitting the print data 71 and the print condition information 72 of the target document MSR to the image forming apparatus 2. Alternatively, the misregistration characteristic calculation unit 103, the trap characteristic data generation unit 104, the target document data acquisition unit 105, the target document trap width calculation unit 106, and the trap characteristic data storage unit 1DB are provided in the image forming apparatus 2, and the image forming apparatus You may enable it to implement | achieve this invention by 2 single-piece | units. In other words, the image forming apparatus 2 itself extracts (searches) the color boundary and performs the trap characteristic data 73 corresponding to the color boundary during so-called PC printing (processing as a personal computer printer) or copying. The trapping processing is performed by obtaining the trap width to be applied to the color boundary based on the call.

  The present invention can also be applied to a printing apparatus (printer) that does not have a scanner function. In this case, the image data of the measurement print chart SYC ′ may be obtained by reading the paper printed by the printing apparatus with a scanner connected to the personal computer 1. The present invention can also be applied to printing apparatuses other than the electrophotographic system, such as an ink jet printer or an offset printing machine.

  Since the characteristics of each part of the image forming apparatus 2 change day by day, the trap characteristic data 73 may be regenerated regularly (for example, every month). Further, the trap characteristic data 73 may be regenerated after the maintenance of the image forming apparatus 2 or after the installation location of the image forming apparatus 2 is changed.

  In the present embodiment, the shift amount between the CMYK colors is measured only once for one divided region RY ′ in the measurement print chart SYC ′. However, the number of marks of each color is increased and the same combination is obtained. Alternatively, the amount of deviation at a plurality of locations may be measured. Then, an average value of the measured values may be adopted as the deviation amount. Further, the arrangement of the marks of the respective colors may be other than those shown in FIG.

  The present invention can also be applied to a printing apparatus that employs a combination of colors other than CMYK colors. For example, the present invention can be applied to a two-color printing apparatus.

  In this embodiment, the case where a certain predetermined size of paper is used has been described as an example. However, for each size of paper (for example, for each of B5 size, B4 size, A4 size, and A3 size paper) ) Trap characteristic data 73 may be obtained. Then, when performing printing in the trapping printing mode, the boundary data 74 may be obtained using the trap characteristic data 73 relating to the sheet of the size specified by the user, and the trapping process may be performed.

  In the present embodiment, the trap width of each pixel is calculated by interpolating the trap width of each divided region RY ′ as shown in FIG. 11, but the trap width data shown in FIG. The data 73 may be used. In this case, the trap width of the divided region RY ′ to which the boundary pixel group KPG belongs in the data shown in FIG. 11 may be applied during the trapping process. This increases the processing speed of the trapping process. However, since the trapping quality is lowered, it is desirable to reduce the size of the divided region RY 'as much as possible.

  In addition, the configuration of the entire personal computer 1 and the image forming apparatus 2 or each unit, the processing content, the processing order, and the like can be appropriately changed in accordance with the spirit of the present invention.

1 is a diagram illustrating an example of an overall configuration of a system configured by a personal computer and an image forming apparatus. It is a figure which shows the example of the hardware constitutions of a personal computer. It is a figure which shows the example of a functional structure of a personal computer. 2 is a diagram illustrating an example of a hardware configuration of an image forming apparatus. FIG. 2 is a diagram illustrating an example of a functional configuration of an image forming apparatus. FIG. It is a figure which shows the example of the chart for a measurement. It is a figure which shows the example of the positional relationship of the mark of each color in a division area. It is a figure which shows the example of the printing chart for a measurement. 6 is a diagram illustrating an example of the amount of misregistration between toner colors in a certain divided area. It is a figure which shows the example of the amount of misregistration of each division area. It is a figure which shows the example which represented the plate shift of each division area with the number of pixels. It is a figure which shows the center position etc. of each division area of the printing chart for a measurement. It is a figure for demonstrating the positional relationship of an attention pixel and the center of each division area. It is a figure which shows the example of distribution of the trap width of each of the main direction shown by trap characteristic data, and a sub direction. It is a flowchart explaining the example of the flow of a boundary trap width | variety calculation process. It is a figure which shows the example of a target document. It is a figure for demonstrating the process which searches the boundary of two objects. It is a figure which shows the example of a boundary pixel group. It is a figure which shows the example which superimposes a boundary pixel group on the distribution of the trap width | variety of the main direction of trap characteristic data based on the position on the paper of the boundary pixel group at the time of printing. It is a flowchart explaining the example of the flow of the whole process at the time of acquiring trap characteristic data. It is a flowchart explaining the example of the flow of the whole process at the time of printing a target document. It is a figure which shows the example of a network.

Explanation of symbols

2 Image forming device (printer)
1 Personal computer (printer controller)
RY 'Divided area 102 Print chart data receiving unit (print displacement amount acquisition means)
103 Misregistration characteristic calculation unit (registration amount acquisition unit)
104 Trap characteristic data generation unit (trap width characteristic information acquisition means)
106 Target document trap width calculator (color boundary search means)
107 Target document print command section (trapping control means)
73 Trap characteristic data (trap width characteristic information)
KPG boundary pixel group (color boundary)
MSR Objective Document (Object Image)

Claims (10)

A trapping method in a printer having a function of printing using a plurality of colorants of a predetermined color,
In preparation for trapping,
For each divided area obtained by dividing the paper into a plurality of areas, the amount of misregistration that occurs when the printer prints an image in the divided area is acquired.
For each of the divided areas, trap width characteristic information indicating a trap width to be applied when trapping is acquired based on the amount of misregistration of the divided area,
When a target image that is an image to be printed by the printer is designated,
Search for a color boundary from the target image,
Applying the trap width indicated in the trap width characteristic information of the divided region to which the color boundary belongs as the trap width of the searched color boundary, causing the printer to perform trapping of the color boundary.
A trapping method characterized by the above. The amount of misregistration in the divided areas is determined by printing the predetermined marks of the predetermined colors on the paper at predetermined positions separated from each other in the divided areas on the paper. Is obtained by scanning the divided area printed with, and obtaining the deviation between the position of each predetermined mark and the original position of each predetermined mark in the scanned divided area,
The trapping method according to claim 1. The amount of misregistration in the divided areas is determined by printing the predetermined marks of the predetermined colors on the paper at predetermined positions separated from each other in the divided areas on the paper. The positional relationship between the predetermined marks is calculated for each combination of the predetermined marks of two colors of the predetermined colors, and the positional relationship between the predetermined marks related to the calculated combination is calculated for each combination. By calculating the amount of deviation from the original positional relationship between the predetermined marks, and obtaining the largest amount of the calculated amount of deviation, to obtain,
The trapping method according to claim 1. The trap width characteristic information of the divided area is obtained by calculating the number of pixels corresponding to the amount of misregistration of the divided area based on the print resolution when the printer prints the predetermined mark. ,
The trapping method according to claim 2 or claim 3. As the amount of misregistration, the printer acquires the amount of misregistration in each of the line direction and the paper feed direction of the paper for dividing the image during printing,
As the trap width characteristic information, obtain information indicating the trap width in each of the line direction and the paper feed direction,
Applying the trap width in the line direction and the paper feed direction indicated in the trap width characteristic information of the divided area to which the color boundary belongs to cause the printer to perform trapping of the color boundary,
The trapping method according to any one of claims 1 to 4. A trapping method in a printer having a function of printing using a plurality of colorants of a predetermined color,
In preparation for trapping,
For each divided area obtained by dividing the paper into a plurality of areas, the amount of misregistration that occurs when the printer prints an image in the divided area is acquired.
For each divided area, calculate the number of misregistration pixels, which is the number of pixels corresponding to the amount of misregistration in the divided area,
For each pixel in the divided area, a trap width to be applied when trapping is performed based on the number of misregistration pixels in the division area to which the pixel belongs and the number of misregistration pixels in the division area adjacent to the pixel. The trap width characteristic information indicating
When a target image that is an image to be printed by the printer is designated,
Search for a color boundary from the target image,
The trap width indicated in the trap width characteristic information of the pixel in the divided region corresponding to the pixel is applied as the trap width of each pixel of the searched color boundary, and the printer performs trapping of the color boundary. ,
A trapping method characterized by the above. A printer control device for controlling a printer having a function of printing using a plurality of colorants of a predetermined color,
A misregistration amount acquisition unit that acquires an amount of misregistration that occurs when the printer prints an image in the division area for each of the divided areas obtained by dividing the paper into a plurality of areas;
Trap width characteristic information acquisition means for acquiring trap width characteristic information indicating a trap width to be applied when performing trapping for each divided area based on the amount of misregistration of the divided area;
Color boundary search means for searching for a color boundary from a target image that is an image to be printed by the printer;
Trapping control means for applying the trap width indicated by the trap width characteristic information of the divided region to which the color boundary belongs as the trap width of the searched color boundary, and causing the printer to perform trapping of the color boundary; ,
A printer control device comprising: A printer having a function of printing using a plurality of colorants of a predetermined color,
For each divided area obtained by dividing the paper into a plurality of areas, the amount of misregistration that occurs when the printer prints an image on the divided area is obtained, and further, the trap width to be applied when performing trapping is divided. Trap width characteristic information storage means for storing trap width characteristic information acquired by obtaining based on the amount of misregistration of a region;
Color boundary search means for searching for a color boundary from a target image that is an image to be printed;
Trapping means for trapping the color boundary by applying the trap width indicated in the trap width characteristic information of the divided region to which the color boundary belongs as the trap width of the searched color boundary;
A printer comprising: A computer program used in a computer for controlling a printer having a function of printing using a plurality of colorants of a predetermined color,
For each divided area obtained by dividing the paper into a plurality of areas, a process of acquiring the amount of misregistration that occurs when the printer prints an image in the divided area;
For each of the divided areas, a process of acquiring trap width characteristic information indicating a trap width to be applied when performing trapping based on the amount of misregistration of the divided areas;
A process of searching for a color boundary from a target image that is an image to be printed by the printer;
Applying the trap width indicated in the trap width characteristic information of the divided area to which the color boundary belongs as the trap width of the searched color boundary, and causing the printer to perform trapping of the color boundary;
A computer program for causing a computer to execute. A computer program for controlling a printer having a function of printing using a plurality of colorants of a predetermined color,
Color boundary search means for searching for a color boundary from a target image that is an image to be printed;
For each divided area obtained by dividing the paper into a plurality of areas, the amount of misregistration that occurs when the printer prints an image on the divided area is obtained, and further, the trap width to be applied when performing trapping is divided. The trap width characteristic information of the divided area to which the searched color boundary belongs is stored from the trap width characteristic information storage means for storing the trap width characteristic information obtained by obtaining based on the amount of misregistration of the area. Process to call,
The trapping process of the color boundary applying the trap width indicated by the called trap width characteristic information as the trap width of the searched color boundary,
A computer program that causes a printer to execute.