JP6750357B2 - Image processing apparatus, image processing method and program - Google Patents

Description

The present invention relates to an image processing device, an image processing method and a program.

In an electrophotographic image forming apparatus, registration deviation or skew deviation occurs, and in an image forming apparatus capable of printing on the front and back sides, front and back deviation occurs. Therefore, there is known a correction technique that measures the amount of deviation and performs image position correction and deformation correction in advance so as to cancel the deviation.

For example, in Patent Document 1, an image dividing unit that divides image information in a first direction, a random number storing unit that generates and stores a random number, or stores a pre-generated random number, and a first direction A reference position, which is a reference when determining a pixel to be a correction process for inserting or thinning out a pixel in each area of the divided image information, is a second direction orthogonal to the first direction. In each area of the image information divided in the first direction in accordance with the reference position determining means for determining different positions in, and the random number stored in the random number storage means and the reference position determined by the reference position determining means. Pixel determining means for determining pixels to be corrected, and image width changing means for performing correction processing on the pixels determined by the pixel determining means to change the image width of the image information in the first direction. There is disclosed an image processing device including:

In this image processing device, the pseudo gradation process is performed on the input image, and the binary image after the pseudo gradation process is subjected to the image width changing process accompanied by the fluctuation of the reference position.

However, according to such a conventional image processing apparatus, when the input image includes a binary pattern such as a halftone dot, neither the cycle of the binary pattern nor the screen cycle of the pseudo gradation process interferes with each other. As described above, it is difficult to determine the variation cycle of the reference position, and as a result, moire (interference fringes) may occur in the corrected image.

The present invention has been made in view of the above, and an object thereof is to prevent moire from occurring in a corrected image even when the input image includes a binary pattern such as halftone dot meshing.

In order to solve the above-mentioned problems and achieve the object, the present invention provides a deviation amount acquisition unit for acquiring a deviation amount of an input image generated at the time of printer output , and coordinate points of the input image with respect to the input image. or after adding a fluctuation with respect to the input image, a geometric correction I line in accordance with the shift amount, and geometric correction means for calculating a pixel value of the coordinate point after the geometric correction by interpolation, said geometric correction relative to said input image, and a pseudo gradation processing means for performing a pseudo gradation processing which represents the density gradation of the input image in the pseudo gradation, Bei El a, and wherein the.

According to the present invention, it is possible to prevent the occurrence of moire even when the input image includes a binary pattern such as a mesh.

FIG. 1 is a hardware block diagram showing a hardware configuration of an image forming apparatus including the image processing apparatus according to the first embodiment. FIG. 2 is a functional block diagram showing a functional configuration of the image processing apparatus according to the first embodiment. FIG. 3 is a diagram showing an example of geometric correction with respect to image distortion, and FIG. 3A is a diagram showing an example of an input image and an output image output from a printer without geometric correction without geometric correction. Is. FIG. 3B is a diagram showing an example of a geometrically corrected image obtained by geometrically correcting the input image and an output image obtained by outputting the geometrically corrected image to a printer. FIG. 4 is a functional block diagram showing a detailed configuration of the geometric correction unit. FIG. 5 is a diagram illustrating the function of the corresponding coordinate point calculation unit. FIG. 6 is a diagram illustrating the function of the interpolation calculation unit. FIG. 7 is a diagram illustrating the function of the fluctuation adding unit. FIG. 8 is a diagram showing an example of the fluctuation function. FIG. 9 is a diagram for explaining the effect of adding fluctuation, and FIG. 9A is a diagram showing an example of an input image. FIG. 9B is a diagram showing an example of a result of lateral magnification correction performed on the input image without adding fluctuation. FIG. 9C is a diagram showing an example of a result of pseudo gradation processing performed on the image of FIG. 9B. FIG. 9D is a diagram showing an example of a result obtained by adding fluctuation to the input image and performing lateral magnification correction. FIG. 9E is a diagram showing an example of a result of pseudo gradation processing performed on the image of FIG. 9D. FIG. 10 is a flowchart showing the flow of processing performed by the image processing apparatus according to the first embodiment. FIG. 11 is a flowchart showing the flow of geometric correction. FIG. 12 is a functional block diagram showing the detailed configuration of the geometric correction unit in the modification of the first embodiment. FIG. 13 is a diagram illustrating the function of the fluctuation adding unit. FIG. 14 is a functional block diagram showing a functional configuration of the image processing apparatus according to the second embodiment. FIG. 15 is a diagram for explaining the effect of adding fluctuation. FIG. 16 is a flowchart showing the flow of processing performed by the image processing apparatus according to the second embodiment.

(Description of First Embodiment)
Hereinafter, a first embodiment for carrying out the present invention will be described with reference to the drawings. First, a hardware configuration of an embodiment of an image forming apparatus including an image processing apparatus of the present invention will be described with reference to the hardware block diagram of FIG.

The image forming apparatus 100a illustrated in FIG. 1 includes a controller 101, an engine control unit 110, an image reading unit 111, an electrophotographic plotter unit 112, an image processing unit 113, and an operation unit 108. .. The image forming apparatus 100a is configured as, for example, a copying machine, a printer, a facsimile apparatus, a digital multi-function peripheral (MFP), or the like.

The controller 101 includes a CPU 102, a RAM 103, a ROM 104, an HDD (Hard Disk Drive) 105, a communication I/F (interface) 106, and an operation I/F 107, and the operation I/F 107 is connected to the operation unit 108. These components are connected to each other by the system bus 109. The controller 101 has a general microcomputer configuration.

The CPU 102 controls the entire image forming apparatus 100a by executing a program stored in the ROM 104 or the HDD 105 using the RAM 103 as a work area. The program is provided by being pre-installed in the ROM 104 or the HDD 105. The program is recorded in a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disc) in the form of an installable or executable file. It may be configured to be provided. Further, the program may be stored in a computer connected to a network such as the Internet and may be provided by being downloaded via the network. Further, the program may be provided or distributed via a network such as the Internet.

The ROM 104 and the HDD 105 are nonvolatile storage media (storage means), and store various programs executed by the CPU 102 and various fixed data.

The communication I/F 106 is an interface for connecting the image forming apparatus 100a to a network such as a LAN (not shown in FIG. 1).

The operation I/F 107 is an interface for connecting the operation unit 108 to the system bus 109 and enabling control from the CPU 102.

The operation unit 108 is a user interface including operation means such as keys, buttons, and touch sensors for receiving operations from the user, and display means such as a display for presenting information to the user.

The image reading unit 111 is an image reading unit having a function of reading an image on a document and acquiring the image data.

The plotter unit 112 has a function of forming an image on output paper (paper) and outputting to a printer based on image data read by the image reading unit 111 or image data input from the outside via the communication I/F 106. It is an electrophotographic image forming means provided.

The image processing unit 113 is an image processing unit that performs various types of image processing described later on the image data read by the image reading unit 111 or the image data input from the outside. The image processing unit 113, the CPU 102, the RAM 103, the ROM 104, the HDD 105, the engine control unit 110, and the plotter unit 112 constitute the image processing device 115a in the present invention.

The engine control unit 110 is a control unit that controls the image reading unit 111, the plotter unit 112, and the image processing unit 113 according to a command received from the CPU 102 via the system bus 109.

(Description of functional configuration of image processing apparatus)
Next, the functional configuration of the image processing apparatus 115a according to the first embodiment of this invention will be described with reference to FIG. FIG. 2 is a functional block diagram showing a functional configuration of the image processing apparatus 115a according to the first embodiment.

The image processing apparatus 115a includes a drawing instruction acquisition unit 1, a rendering unit 2, a deviation amount acquisition unit 3, a geometric correction parameter setting unit 4, a geometric correction unit 5a, a pseudo gradation processing unit 6, and a printer output unit 7a.

The printer output unit 7a of the image processing apparatus 115a corresponds to the plotter unit 112 shown in FIG. In addition, each unit of the image processing apparatus 115a except the printer output unit 7a is realized by the controller 101, the engine control unit 110, and the image processing unit 113 illustrated in FIG.

The drawing instruction acquisition unit 1 acquires the input image I1 (see FIG. 3) described in the page description language. In addition, instructions that reflect the results of various selections made by the user, such as instructions for single-sided printing or double-sided printing and instructions for drawing cutting marks for cutting in the corners of the output paper, are also acquired. The "dragonfly" is also called a register mark, and it is a mark that is printed on the left and right corners of the top and bottom of the block to cut the printed material into finished size or to register it in multicolor printing when creating the printed material. Is.

The rendering unit 2 interprets the page description language acquired by the drawing instruction acquisition unit 1 and converts the input image I1 into, for example, a bitmap image having a gradation value of 8 bits for each color. At that time, object information such as characters, lines, graphics, and images included in the input image I1 is also interpreted and given to each pixel of the bitmap image.

The deviation amount acquisition unit 3 is a deviation amount acquisition unit that measures and acquires how the coordinate points at the four corners change (how much they deviate) when printed by a printer without performing the geometric correction processing described later. Therefore, the registration marks for measuring the deviation amount are printed on the four corners of the front surface and the back surface of the output paper, and the respective coordinate points are measured. For the measurement, there are a method of automatically measuring with a sensor built in the device, and a method of manually measuring what is printed on a recording medium with a ruler and inputting the result.

The geometric correction parameter setting unit 4 is a geometric correction parameter setting unit that calculates a geometric correction parameter from the coordinate data acquired by the shift amount acquisition unit 3. The geometric correction parameter is a parameter for the geometric correction unit 5a to perform geometric correction on the input image I1 according to the amount of deviation. The shift amount is the shift amount of each of the four coordinate points on the front surface and the back surface of the output paper.

The geometric correction unit 5a is a geometric correction unit that performs geometric correction on an image (for example, a bitmap image) output by the rendering unit 2 according to the amount of deviation by image processing. That is, the geometrical correction unit 5a applies the geometrical correction parameter calculated by the geometrical correction parameter setting unit 4 to perform geometrical correction by projective transformation in anticipation of positional deviation and distortion occurring at the time of output. Details will be described later. Further, the geometric correction unit 5a performs fluctuation addition described later.

The pseudo gradation processing unit 6 performs screen processing on the geometrically corrected bitmap image and binarizes white pixels and black pixels. The pseudo gradation processing unit 6 switches the screen to be applied according to the object information. That is, when the object is a character or a line, for example, a screen with about 300 lines is applied. When the object is a graphic or an image, a screen with about 200 lines is applied, for example.

(Explanation of geometric correction for image distortion)
Next, geometric correction for image distortion in this embodiment will be described with reference to FIG. FIG. 3A shows an example of the input image I1 by a broken line. As an example of image distortion that occurs when the input image I1 is output to a printer without geometric correction, an example of the output image I2 without geometric correction is shown. It is shown by a solid line. That is, according to the present embodiment, when the input image I1 is printed out without geometric correction, the input image I1 is deformed wider toward the lower side and narrower toward the upper side.

Further, in FIG. 3B, in anticipation of image distortion, the geometrically corrected image I3 inversely corrected in advance is shown by a solid line, and the output image I4 when the geometrically corrected image I3 is geometrically corrected is shown. Is indicated by a broken line. That is, the geometrically corrected image I3 is an image to which distortion has been added in advance so that the output image I4 has the same shape as the input image I1.

For example, in the case of front and back misalignment, the input image I1 is the front side, the output image I2 without geometric correction is the back side output image when no geometric correction is performed, and the inversely corrected geometrically corrected image I3 is the geometrically corrected image for the back side and the output. The image I4 becomes an image obtained by outputting the inversely corrected geometrically corrected image I3 to a printer. Note that, here, it is assumed that no distortion occurs on the front surface even when output to a printer.

The shift amount acquisition unit 3 acquires the coordinate data of the four corners of the input image I1 and the coordinate data of the four corners of the output image I2 without geometric correction. Then, the geometric correction parameter setting unit 4 performs the inverse correction in anticipation of the distortion of the image generated at the time of printer output, and calculates and sets the geometric correction parameter for generating the post-geometric correction image I3.

(Detailed configuration of the geometric correction unit)
Next, the detailed configuration of the geometric correction unit 5a will be described. FIG. 4 is a functional block diagram showing a detailed configuration of the geometric correction unit 5a included in the image processing apparatus 115a.

As shown in FIG. 4, the geometric correction unit 5a includes a corresponding coordinate point calculation unit 51, a four-point extraction unit 52a, an interpolation calculation unit 53, and a fluctuation addition unit 54a.

The corresponding coordinate point calculating unit 51 is an example of corresponding coordinate point calculating means. The corresponding coordinate point calculation unit 51 calculates the coordinate point (X, Y) on the input image I1 corresponding to the coordinate point (x, y) on the post-geometric correction image I3 from the geometric correction parameters h1, h2,... Calculate using h8. The coordinate point (X, Y) is calculated as a real value having a value below the decimal point.

The four-point extraction unit 52a extracts four neighboring points surrounding the coordinate point (X, Y) based on the values of the integer parts of X and Y.

The interpolation calculator 53 is an example of an interpolation calculator. The interpolation calculation unit 53 performs the interpolation calculation on the pixel values of the four neighboring points surrounding the coordinate point (X, Y), and calculates the result of the interpolation calculation as the pixel value of the coordinate point (x, y).

The fluctuation adding unit 54a performs a process of adding fluctuation to, for example, an 8-bit image input to the geometric correction unit 5a before performing the interpolation calculation.

(Explanation of corresponding coordinate point calculation processing)
Next, the corresponding coordinate point calculation process performed by the corresponding coordinate point calculation unit 51 will be described with reference to FIG. The corresponding coordinate point calculation unit 51 uses the two-dimensional projective transformation formulas shown in Formula 1 and Formula 2 to correspond to the coordinate point (x, y) on the geometrically corrected image I3 on the input image I1 (X , Y) is calculated.

In Equation 1 and Equation 2, h1, h2,..., H8 described as coefficients respectively represent geometric correction parameters. The values of these geometric correction parameters h1, h2,..., H8 are determined by extracting at least four pairs of corresponding points between the image before geometric correction and the image after geometric correction. Specifically, for each of the extracted at least four pairs of corresponding points (the coordinate point (X, Y) on the input image I1 and the coordinate point (x, y) on the geometrically corrected image I3), Formulas 1) and 2 are generated. Then, the values of the geometric correction parameters h1, h2,..., H8 are determined by solving the simultaneous equations regarding the geometric correction parameters h1, h2,.

After that, the pixel value of the coordinate point (X, Y) and the object information in the input image I1 are obtained by interpolation calculation, and the pixel value and the object information of the coordinate point (x, y) of the post-geometric correction image I3 are obtained. The geometric correction of the input image I1 is performed.

(Explanation of the operation of the interpolation calculation unit)
Next, the operation of the interpolation calculation unit 53 will be described with reference to FIG. First, in the 4-point extraction unit 52a (FIG. 4), the coordinate point (X0, Y0) corresponding to the integer part of the coordinate point (X, Y) and the coordinate point (X0+1) adjacent to the coordinate point (X0, Y0). , Y0), (X0, Y0+1), (X0+1, Y0+1), respectively, for a total of four coordinate points.

The interpolation calculation unit 53 applies the weighting factors wx (0≦wx≦1) and wy (0≦wy≦1) to the pixel values of the four coordinate points described above, and performs linear interpolation represented by Expression 3. The pixel value of the coordinate point (x, y) is calculated. The pixel value of the coordinate point (α, β) is represented by I(α, β).
I(x,y)
=I(X,Y)
=I(X0,Y0)*(1-wx)*(1-wy)+
I(X0+1,Y0)*wx*(1-wy)+
I(X0,Y0+1)*(1-wx)*wy+
I(X0+1,Y0+1)*wx*wy (Formula 3)

(Explanation of adding fluctuation)
Next, the operation of the fluctuation adding section 54a will be described. The fluctuation adding unit 54a calculates a coordinate point (X′, Y′) in which fluctuation is added to the coordinate point (X, Y) by the following Expressions 4 and 5.
X'=X+F(Y%P) (Formula 4)
Y'=Y+F(X%P) (Formula 5)
Here, F() represents the fluctuation function of the period P pixel and the amplitude Q pixel. Further, Y% P represents the remainder when Y is divided by P, and X% P represents the remainder when X is divided by P. The fluctuation function F() will be described in detail later.

FIG. 7 is a diagram illustrating the function of the fluctuation adding unit 54a. As shown in FIG. 7, for example, the point R1(X,Y) is converted into a point R1′(X′,Y) in the printing direction of the plotter unit 112 (FIG. 1), that is, in the main scanning direction. As a result, vertical line fluctuation is added to the vertical line. This has the effect of swaying the vertical line. In addition, by converting the point R2(X,Y) into a point R2'(X,Y') in the paper transport direction, that is, the sub-scanning direction, horizontal line fluctuation is added to the horizontal line. It This has the effect of swaying the horizontal line.

The pixel value I(X', Y') of the coordinate point (X', Y') to which the fluctuation is added can be obtained by the interpolation calculation shown in Expression 3.

Next, a specific example of the fluctuation function F(n) will be described with reference to FIG. The fluctuation function F(n) can be generated by using, for example, a trigonometric function of sin or cos. FIG. 8 shows an example in which the fluctuation function F(n) is generated from the cos function. The fluctuation function F(n) generated at this time is expressed by Expression 6.
F(n)=Qcos(2πn/P) (n=1, 2, 3,...) (Equation 6)

In FIG. 8, the horizontal axis represents n and the vertical axis represents the fluctuation function F(n). The value of the fluctuation function F(n) may be calculated each time and added to the coordinate point (X, Y), or the value of the fluctuation function F(n) calculated in advance may be used as a table, for example, in the HDD 105 (FIG. 1). ), and the value read from the table may be added to the coordinate point (X, Y).

(Explanation of the effect of adding fluctuation)
Next, the effect of adding the fluctuation described above will be described with reference to FIG. FIG. 9 is a diagram illustrating the effect of adding fluctuation based on an actual example.

When the input image I1 includes a binary pattern, the addition of fluctuation has an effect of suppressing the occurrence of moire. The case where a halftone dot pattern is used as the binary pattern will be described below as an example.

When the magnification correction is performed on the halftone dot pattern of the input image I1, the pixel values of the white dots and the pixel values of the black dots are averaged by the interpolation calculation. A gray pixel area in which the pixel values of white dots are averaged is generated. Further, when no fluctuation is added to the input image I1 shown in FIG. 9A, as shown in FIG. 9B, an area with a large amount of gray pixels and an area with a small amount of gray pixels are generated. , Appear alternately. As shown in FIG. 9C, an area in which the amount of gray pixels generated is large and an area in which the amount of gray pixels is small are, as shown in FIG. , Are replaced. Due to the writing characteristics of the plotter unit 112 (FIG. 1), it is difficult to output the same density on the output paper surface for the area where the dot shape collapse is large and the area where the dot shape collapse is small. Therefore, moire occurs.

By adding the fluctuation, the gray pixels are scattered and generated in the whole halftone dot pattern, so that the bias of the gray pixel appearance frequency depending on the region is reduced as shown in FIG. 9D. Therefore, as shown in FIG. 9E, even after the pseudo gradation process, the regional deviation of dot shape collapse is reduced, and moire is less likely to occur.

As can be seen from FIG. 9, in order to suppress the occurrence of moire in the lateral direction (X direction, main scanning direction) magnification correction, it is effective to add vertical line fluctuation. On the other hand, in order to suppress moire in the magnification correction in the vertical direction (Y direction, sub-scanning direction), it is effective to add horizontal line fluctuation.

Even if fluctuation is added to the solid area (flat portion) included in the input image I1, the grayscale distribution inside the solid area does not change at all. That is, it is the same as the state where no fluctuation is added. Therefore, moiré does not occur due to the interference of the fluctuation cycle and the screen cycle of the pseudo gradation process in the solid area.

The fluctuation period P and the amplitude Q shown in FIG. 8 may be determined in consideration of the fact that the interference with the binary pattern included in the input image I1 is inconspicuous. However, it becomes a side effect if it can be visually recognized on the output image (especially, a character part other than the binary pattern part), and therefore it is necessary to make the level invisible so small.

(Explanation of the process flow of the first embodiment)
The flow of processing performed by the image processing apparatus 115a will be described below with reference to FIG. FIG. 10 is a flowchart showing the flow of processing performed by the image processing apparatus 115a.

The drawing instruction acquisition unit 1 acquires the input image I1 and the drawing instruction (step S10).

The rendering unit 2 converts the input image I1 into, for example, a bitmap image having a gradation value of 8 bits for each color (step S12).

The deviation amount acquisition unit 3 measures and acquires the deviation amount generated by the printer output (step S14).

The geometric correction parameter setting unit 4 calculates the values of the geometric correction parameters h1, h2,..., H8 (Equation 1, Equation 2) based on the coordinate data acquired by the deviation amount acquisition unit 3 (step S16).

The geometric correction unit 5a performs geometric correction on the image (bitmap image) output by the rendering unit 2 according to the amount of deviation by image processing (step S18). The detailed flow of the processing performed by the geometric correction unit 5a is shown in FIG. 11 described later.

The pseudo gradation processing unit 6 performs pseudo gradation processing on the geometrically corrected bitmap image, and binarizes white pixels and black pixels (step S20).

The printer output unit 7a forms an image on a sheet and outputs it to the printer (step S22).

(Explanation of the flow of processing performed by the geometric correction unit)
Next, the flow of geometric correction performed by the geometric correction unit 5a will be described with reference to FIG. FIG. 11 is a flowchart showing the flow of processing performed by the geometric correction unit 5a.

The fluctuation adding unit 54a adds fluctuation to the bitmap image (step S30).

The corresponding coordinate point calculation unit 51 calculates the coordinate point (X, Y) on the input image I1 corresponding to the coordinate point (x, y) on the geometrically corrected image I3 (step S32).

The four-point extraction unit 52a calculates four neighboring points surrounding the coordinate point (X, Y) (step S34).

The interpolation calculation unit 53 performs the interpolation calculation on the pixel values of the four neighboring points surrounding the coordinate point (X, Y), and the result of the interpolation calculation is the pixel value I(x, y) of the coordinate point (x, y). Is calculated as (step S36). Then, the process returns to the main routine (FIG. 10).

(Explanation of Modification of First Embodiment)
Next, an image forming apparatus 100b which is a modified example of the first embodiment of the image processing apparatus of the present invention will be described. The image forming apparatus 100b has substantially the same configuration as the image forming apparatus 100a described in the first embodiment, and includes an image processing apparatus 115b instead of the image processing apparatus 115a included in the first embodiment. .. The configuration of the image processing apparatus 115b is almost the same as the configuration of the image processing apparatus 115a (FIG. 2), but only the configuration of the geometric correction unit 5a is different.

FIG. 12 is a functional block diagram illustrating a detailed configuration of the geometric correction unit 5b included in the image processing apparatus 115b included in the image forming apparatus 100b according to the modified example of the first embodiment. The geometric correction unit 5b includes a corresponding coordinate point calculation unit 51, a four-point extraction unit 52b, an interpolation calculation unit 53, and a fluctuation addition unit 54b.

Unlike the first embodiment, the fluctuation adding unit 54b adds fluctuation not to the bitmap image but to the coordinate point data. Addition of fluctuations is performed using Equations 4 and 5 as in the first embodiment. Here, a method of adding fluctuations performed by the fluctuation adding unit 54b will be described with reference to FIG. As shown in FIG. 13, the fluctuation adding unit 54b calculates a coordinate point (X', Y') in which fluctuation is added to the coordinate point (X, Y). Then, the four-point extraction unit 52b extracts the coordinates of the four neighboring points P1, P2, P3, and P4 surrounding the coordinate point (X', Y') to which the fluctuation is added, from the input image I1. After that, the interpolation calculation unit 53 obtains the pixel value I(X', Y') of the coordinate point (X', Y') by the interpolation calculation of the pixel values of the four points P1, P2, P3, P4.

Since the geometric correction unit 5b adds fluctuation to the coordinate point data, not the coordinate points on the input image I1 but the coordinate position for obtaining the pixel value by interpolation calculation fluctuates. However, if viewed relatively, it can be considered that the coordinate point on the input image I1 is swaying with respect to the coordinate position where the pixel value is calculated by the interpolation calculation. Therefore, as the output value from the geometric correction unit 5b, Other than the quantization error described later, it is the same as in the first embodiment.

That is, since the geometric correction unit 5a in the first embodiment adds fluctuation to the bitmap image output by the rendering unit 2, both the fluctuation adding unit 54a and the interpolation calculation unit 53 perform interpolation calculation. Therefore, the quantization error is inevitably increased. On the other hand, since the geometric correction unit 5b in the modification of the first embodiment adds fluctuation to the coordinate point data, the interpolation calculation is performed only once in the interpolation calculation unit 53, and the quantization error does not increase. The difference is that it is configured.

(Explanation of the Second Embodiment)
Next, an image forming apparatus 100c according to a second embodiment of the image processing apparatus of the present invention will be described. The image forming apparatus 100c according to the second embodiment includes an image processing apparatus 115c instead of the image processing apparatus 115a with respect to the image forming apparatus 100a described in the first embodiment. FIG. 14 is a functional block diagram showing a functional configuration of the image processing apparatus 115c according to the second embodiment. The configuration of the image processing device 115c will be described below with reference to FIG.

As shown in FIG. 14, the image processing apparatus 115c includes a drawing instruction acquisition unit 1, a rendering unit 2, a deviation amount acquisition unit 3, a geometric correction parameter setting unit 4, a geometric correction unit 5a, and a pseudo gradation process. It has a unit 6 and a printer output unit 7b. The printer output unit 7b corresponds to the plotter unit 112 in FIG. 1 and includes a write timing control unit 8 which is a write timing control unit.

The image processing device 115c further includes a correction mode determination unit 9, a correction amount distribution unit 10, and a write control parameter setting unit 11. Each unit of the image processing apparatus 115c except the printer output unit 7b is realized by the controller 101, the engine control unit 110, and the image processing unit 113 shown in FIG.

The drawing instruction acquisition unit 1, in addition to acquiring the input image I1 described in the page description language, instructs whether single-sided printing or double-sided printing, an instruction to draw a registration mark for cutting in a corner of the output paper, and the like. An instruction that reflects the result of various selections by the user is also acquired. Note that the "register mark" is a mark that is attached to the left and right corners of the top and bottom of the block for registering the position to cut the printed matter into the finished size and the registration of multicolor printing when creating the printed matter. Also say.

The geometric correction parameter setting unit 4 is a geometric correction parameter setting unit that calculates a geometric correction parameter from the coordinate data acquired by the deviation amount acquisition unit 3 and distributed by the correction amount distribution unit 10.

The correction mode determination unit 9 is a correction mode determination unit that selects and determines a correction mode according to at least the deviation amount acquired by the deviation amount acquisition unit 3.

The correction mode determination unit 9 selects and determines one of the first correction mode and the second correction mode when the input image is output to the printer in accordance with the shift amount acquired by the shift amount acquisition unit 3. .. The first correction mode is a correction mode in which the geometric correction unit 5a performs geometric correction in the main scanning direction and the sub scanning direction. On the other hand, the second correction mode is a correction mode in which the geometric correction unit 5a performs geometric correction in the main scanning direction and the writing timing control unit 8 performs geometric correction in the sub scanning direction.

The correction mode determination unit 9 further sets the correction mode based on the instruction from the drawing instruction acquisition unit 1 whether single-sided printing or double-sided printing and instruction information such as whether to draw a cutting mark for cutting on a corner of the output paper. You may decide.

For example, when the correction function necessary for the deviation amount correction is a geometric correction other than the registration correction, the magnification correction, and the skew correction (for example, trapezoidal correction), the first correction mode is selected with emphasis on the function. Even when the user gives an instruction to draw a trimming mark on the corner of the paper, the first correction mode is selected with emphasis on the positional accuracy. Even when double-sided printing is selected by the user, it is desirable to select the first correction mode with an emphasis on positional accuracy.

On the other hand, when the correction function required for the deviation amount correction is any one of the registration correction, the magnification correction, the skew correction, or the geometrical correction by a combination thereof, and the registration mark drawing instruction for cutting is not given, and the one-sided printing is performed. Selects the second correction mode. In the case where the correction function can be applied even in the second correction mode and the positional accuracy is relatively unimportant, it is desirable to select the second correction mode in which there is no fear of moire.

The write control parameter setting unit 11 calculates a write control parameter for the write timing control unit 8 to perform geometric correction on the input image according to the shift amount, based on the shift amount acquired by the shift amount acquiring unit 3. Write control parameter setting means.

The correction amount distribution unit 10 is a correction amount distribution unit that transfers the coordinates of each of the four front and back points acquired by the displacement amount acquisition unit 3 to the geometric correction parameter setting unit 4 and the write control parameter setting unit 11.

When the first correction mode is selected by the correction mode determination unit 9, the geometric correction unit 5a performs geometric correction in both the main scanning direction (the horizontal direction of the input image) and the sub-scanning direction (the vertical direction of the input image). Perform processing. That is, the correction amount distribution unit 10 and the geometrical correction parameter setting unit 4 and the write control parameter setting unit 11 perform the correction processing on the coordinate data acquired by the displacement amount acquisition unit 3 by the geometrical correction unit 5a in any direction. To each of the.

On the other hand, when the second correction mode is selected by the correction mode determination unit 9, the write timing control unit 8 performs the geometric correction processing in the main scanning direction and the geometric correction unit 5a in the sub scanning direction. Performs geometric correction processing by. That is, the correction amount distribution unit 10 applies the coordinate data acquired by the displacement amount acquisition unit 3 to each of the geometric correction parameter setting unit 4 and the write control parameter setting unit 11 so that the above-described geometric correction processing is performed. Hand over.

The writing timing control unit 8 of the printer output unit 7b sets the writing start position and the writing start position in the main scanning direction for the coordinate data distributed from the correction amount distribution unit 10 according to the parameters calculated by the writing control parameter setting unit 11. Adjust the write clock period. This corresponds to geometric correction by electric control. The registration correction and the magnification correction by adjusting the write start position in the main scanning direction and the write clock cycle are existing image correction techniques.

When the first correction mode is selected by the correction mode determination unit 9, both the vertical line fluctuation and the horizontal line fluctuation shown in FIG. 7 are added, as in the first embodiment.

On the other hand, when the second correction mode is selected by the correction mode determination unit 9, only vertical line fluctuations are added as shown in FIG. It is the geometric correction by the geometric correction unit 5a that is involved in the moire, not the geometric correction by the write timing control unit 8. In the second correction mode, the geometric correction by the geometric correction unit 5a is performed only in the main scanning direction. Therefore, if only vertical line fluctuations that have a moire suppressing effect on the magnification correction in the main scanning direction are given by Equation 4, Good.

In the second correction mode, contrary to the above, geometric correction may be performed in the main scanning direction and geometric correction by writing timing control may be performed in the sub scanning direction. In that case, when the second correction mode is selected by the correction mode determination unit 9, only the horizontal line fluctuation may be given by Expression 5.

(Explanation of the process flow of the second embodiment)
Hereinafter, with reference to FIG. 16, regarding the flow of processing performed by the image processing apparatus 115c, when the correction mode determination unit 9 selects the second correction mode, the geometry of the writing timing control unit 8 with respect to the main scanning direction. A case where the correction processing is performed and the geometric correction processing is performed by the geometric correction unit 5a in the sub-scanning direction will be described as an example. FIG. 16 is a flowchart showing the flow of processing performed by the image processing apparatus 115c.

The drawing instruction acquisition unit 1 acquires the input image I1 and the drawing instruction (step S40).

The rendering unit 2 converts the input image I1 into, for example, a bitmap image having a gradation value of 8 bits for each color (step S42).

The deviation amount acquisition unit 3 measures and acquires the deviation amount generated by the printer output (step S44).

The geometric correction parameter setting unit 4 calculates the geometric correction parameter based on the coordinate data acquired by the shift amount acquisition unit 3 (step S46).

The correction mode determination unit 9 selects the correction mode (step S48).

The controller 101 (FIG. 1) determines whether the selected correction mode is the first correction mode (step S50). When the first correction mode is selected (step S50; Yes), the process proceeds to step S52, and when it is not (step S50; No), the process proceeds to step S56.

The geometric correction unit 5a performs geometric correction on the image (bitmap image) output by the rendering unit 2 according to the amount of deviation by image processing in both the main scanning direction and the sub scanning direction (step S52). The detailed flow of the processing performed by the geometric correction unit 5a is as described in the first embodiment (FIG. 11).

The pseudo gradation processing unit 6 performs pseudo gradation processing on the geometrically corrected bitmap image, and binarizes white pixels and black pixels (step S53).

The printer output unit 7b forms an image on a sheet and outputs it to the printer (step S54). Then, the process of FIG. 16 is completed.

In step S50, when the second correction mode is selected (step S50; No), the geometric correction unit 5a sets the image (bitmap image) output by the rendering unit 2 only in the sub-scanning direction. The process corrects the geometry according to the amount of deviation (step S56). Note that the flow of processing performed by the geometric correction unit 5a is as described in the first embodiment (FIG. 11).

The pseudo gradation processing unit 6 performs pseudo gradation processing on the geometrically corrected bitmap image, and binarizes white pixels and black pixels (step S57).

The printer output unit 7b forms an image on a sheet and outputs it to the printer, while the writing timing control unit 8 performs geometric correction by writing timing control in the main scanning direction (step S58). Then, the process of FIG. 16 is completed.

As described above, according to the image processing apparatus 115a (115b) according to the first embodiment, the deviation amount acquisition unit 3 (deviation amount acquisition means) causes the deviation of the coordinate points when the input image I1 is output to the printer. After acquiring the amount, either the geometric correction unit 5a or the geometric correction unit 5b (geometric correction unit) performs the geometric correction on the input image I1 according to the shift amount. At this time, the geometric correction unit 5a performs geometric correction after the fluctuation adding unit 54a adds fluctuation to the coordinate points of the input image I1. Further, the geometric correction unit 5b geometrically corrects the coordinate points of the input image I1, and then adds fluctuation to the geometrically corrected coordinate points by the fluctuation adding unit 54b. Then, the interpolation calculation unit 53 calculates the pixel value of the geometrically corrected coordinate point by the correction calculation, and the pseudo gradation processing unit 6 (pseudo gradation processing unit) processes the geometrically corrected input image I1. Then, the pseudo gradation process for expressing the density gradation by the pseudo gradation is performed. Therefore, since the pseudo gradation process is performed on the deformed image after the image is deformed with the addition of the fluctuation, even if the input image I1 includes a binary pattern such as a mesh, the printer It is possible to prevent the occurrence of moire in the output.

Particularly, according to the image processing apparatus 115a according to the first embodiment, the deviation amount acquisition unit 3 (deviation amount acquisition means) acquires the deviation amount of the coordinate point when the input image I1 is output to the printer, The geometric correction unit 5a (geometric correction means) performs geometric correction on the input image I1 according to the amount of deviation. At that time, the geometric correction unit 5a adds the fluctuation of the pixel value of the coordinate point after the geometric correction to the coordinate point of the input image I1 by the fluctuation adding unit 54a (fluctuation adding means), and then the interpolation calculation unit 53. The (interpolation calculation means) calculates the pixel value of the coordinate point after geometric correction by performing an interpolation calculation. Therefore, even if the input image I1 includes a binary pattern such as halftone dot meshing, a simple process of adding fluctuation can prevent the occurrence of moire in the printer output.

Further, according to the image processing apparatus 115a according to the first embodiment, the fluctuation adding unit 54a (fluctuation adding means) uses the trigonometric function to generate the fluctuation function F(n) representing the magnitude of the fluctuation to be added. To generate. Alternatively, the magnitude of the fluctuation to be added is calculated by using the stored value of the table that stores the generated fluctuation function F(n) data. Therefore, the magnitude of the fluctuation can be easily calculated with the existing function.

Further, in particular, according to the image processing apparatus 115b according to the modification of the first embodiment, the deviation amount acquisition unit 3 (deviation amount acquisition means) causes the deviation amount of the coordinate point when the input image I1 is output to the printer. Then, the geometric correction unit 5b (geometric correction means) performs geometric correction on the input image I1 according to the amount of deviation. At this time, the geometric correction unit 5b adds the fluctuation to the coordinate point after the geometric correction by the fluctuation adding unit 54b (fluctuation adding means), and then calculates the pixel value of the coordinate point after the geometric correction to which the fluctuation is added. The interpolation calculation unit 53 (interpolation calculation means) calculates the pixel value of the corresponding coordinate point of the input image I1 by performing interpolation calculation. Therefore, since the interpolation calculation needs to be performed only once in the interpolation calculation unit 53, the quantization error generated by the calculation is greater than the case where fluctuation is added to, for example, a bitmap image generated from the input image I1. Can be kept small. That is, the geometric correction can be performed with higher accuracy.

Then, according to the image processing apparatus 115c according to the second embodiment, when the second correction mode is selected by the correction mode determination unit 9 (correction mode determination unit), the fluctuation addition unit 54a (fluctuation addition unit). ), the vertical line fluctuation which is the fluctuation in the main scanning direction is added, and the horizontal line fluctuation which is the fluctuation in the sub scanning direction is not added. Therefore, it has a moire suppressing effect on the magnification correction in the main scanning direction. Furthermore, by suppressing the addition of fluctuations to the necessary minimum, it is possible to suppress the occurrence of unnecessary side effects such as an increase in fluctuations in the character portion.

Further, according to the image processing apparatus 115c according to the second embodiment, when the second correction mode is selected by the correction mode determination unit 9 (correction mode determination unit), the fluctuation addition unit 54a (fluctuation addition unit). ), the horizontal line fluctuation which is the fluctuation in the sub-scanning direction is added, and the vertical line fluctuation which is the fluctuation in the main scanning direction is not added. Therefore, it has a moire suppressing effect in the sub-scanning direction. Furthermore, by suppressing the addition of fluctuations to the necessary minimum, it is possible to suppress the occurrence of unnecessary side effects such as an increase in fluctuations in the character portion.

Although the embodiment has been described above, the specific configuration of each part, the content of processing, and the like are not limited to those described in each embodiment.

For example, the image processing apparatuses 115a, 115b, and 115c, instead of operating the CPU 102 according to a program, by mounting a dedicated ASIC (Application Specific Integrated Circuit) having the same arithmetic function and control function as the program executes, You may operate by hardware.

3 Deviation amount acquisition unit (deviation amount acquisition means)
5a, 5b Geometric correction unit (geometric correction means)
6 Pseudo gradation processing unit (pseudo gradation processing means)
8 Write Timing Control Unit (Write Timing Control Unit)
9 Correction mode determination unit (correction mode determination means)
51 Corresponding coordinate point calculating unit (corresponding coordinate point calculating means)
53 Interpolation calculation unit (interpolation calculation means)
54a, 54b Fluctuation adding unit (fluctuation adding means)
Image forming apparatus 100a, 100b, 100c Image processing apparatus 115a, 115b, 115c

Japanese Patent No. 4003803

Claims (8)

Deviation amount acquisition means for acquiring the deviation amount of the input image generated at the time of printer output,
With respect to the input image, after appending the fluctuation relative coordinate point or the input image of the input image, I row geometric correction according to the deviation amount, the pixel value of the coordinate point after the geometric correction Geometric correction means for calculating by interpolation calculation ,
The relative geometry corrected the input image, and a pseudo gradation processing means for performing a pseudo gradation processing which represents the density gradation of the input image in the pseudo gradation, Ru provided with,
The image processing apparatus according to claim and this. The geometric correction means,
Corresponding coordinate point calculating means for calculating corresponding coordinate points of the input image corresponding to the coordinate points after geometric correction according to the displacement amount in the input image,
Fluctuation adding means for adding fluctuation to the coordinate points of the input image,
Interpolation calculation means for calculating the pixel value of the coordinate point after the geometric correction by performing interpolation calculation of the pixel value of the corresponding coordinate point of the input image to which the fluctuation is added. 1. The image processing device according to 1. The geometric correction means,
Corresponding coordinate point calculating means for calculating corresponding coordinate points of the input image corresponding to the coordinate points after geometric correction according to the displacement amount in the input image,
Fluctuation adding means for adding fluctuation to the coordinate points after the geometric correction;
Interpolation calculation means for calculating the pixel value of the coordinate point after the geometric correction to which the fluctuation is added by interpolating the pixel value of the corresponding coordinate point of the input image. 1. The image processing device according to 1. The fluctuation adding means generates the fluctuation using a trigonometric function,
Alternatively, the fluctuation is generated by using a stored value of a table that stores data representing the magnitude of the generated fluctuation,
The image processing apparatus according to claim 2 or claim 3, characterized in that. Writing timing control means for performing geometric correction according to the amount of deviation by controlling writing timing with respect to the input image;
A geometric correction is performed by the geometric correction means in the main scanning direction of the input image and the sub-scanning direction of the input image according to the shift amount acquired by the shift amount acquiring means when the input image is output to a printer; 1 correction mode and a second correction mode in which geometric correction is performed by the geometric correction means in the main scanning direction and geometric correction is performed by the write timing control means in the sub-scanning direction. Correction mode determining means for selecting one of them,
When the second correction mode is selected, the fluctuation adding means adds vertical line fluctuation that is fluctuation in the main scanning direction, and does not add horizontal line fluctuation that is fluctuation in the sub-scanning direction.
The image processing apparatus according to any one of claims 2 to 4, wherein Writing timing control means for performing geometric correction according to the amount of deviation by controlling writing timing with respect to the input image;
A geometric correction is performed by the geometric correction means in the main scanning direction of the input image and the sub-scanning direction of the input image according to the shift amount acquired by the shift amount acquiring means when the input image is output to a printer; 1 correction mode and a second correction mode in which geometric correction is performed by the geometric correction means in the sub-scanning direction and geometric correction is performed by the write timing control means in the main scanning direction. Correction mode determining means for selecting one of them,
When the second correction mode is selected, the fluctuation adding means adds horizontal line fluctuation that is fluctuation in the sub-scanning direction and does not add vertical line fluctuation that is fluctuation in the main scanning direction.
The image processing apparatus according to any one of claims 2 to 4, wherein A deviation amount acquisition step of acquiring the deviation amount of the input image generated at the time of printer output,
With respect to the input image, after appending the fluctuation relative coordinate point or the input image of the input image, I row geometric correction according to the deviation amount, the pixel value of the coordinate point after the geometric correction Geometric correction step calculated by interpolation calculation ,
The relative geometry corrected the input image, and a pseudo gradation processing step of performing pseudo gradation processing for representing the gray scale of the input image in the pseudo gradation, Ru provided with,
An image processing method characterized by and this. Computer,
Deviation amount acquisition means for acquiring the deviation amount of the input image generated at the time of printer output,
With respect to the input image, after appending the fluctuation relative coordinate point or the input image of the input image, I row geometric correction according to the deviation amount, the pixel value of the coordinate point after the geometric correction Geometric correction means for calculating by interpolation calculation ,
The relative geometry corrected the input image, and a pseudo gradation processing means for performing a pseudo gradation processing which represents the density gradation of the input image in the pseudo gradation, Ru is to function,
Program which is characterized a call.

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