JP2818528B2 - Gravure plate making image data creation apparatus and creation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for producing image data for gravure prepress used in an electronic engraving system.
In particular, the present invention relates to an apparatus and a method for creating gravure platemaking image data having a different pixel arrangement from reference image data used in, for example, an offset platemaking device and having pixels arranged in a lattice.

[0002]

2. Description of the Related Art Various types of printing methods such as offset printing and gravure printing are used as printing types, but the density and arrangement of data for image formation may differ depending on each printing method. For example, the offset plate making image data has a high density of 300 to 2000 dpi (dot / inch), and the gravure plate making image data used in the electronic engraving method usually has a density of about 150 to 200 L / I (line / inch). . The pixel arrangement of the offset plate making image data has a square lattice shape, whereas the pixel arrangement of the gravure plate making image data has a rectangular shape.
Basically, a zigzag pattern in which pixels are arranged at two vertices and face-center points.

Since the offset plate making image data and the gravure plate making image data have different densities and pixel arrangements, the offset plate making image data cannot be directly used as the gravure plate making image data.
Therefore, conventionally, the offset plate making image data is first output to the film once by the offset plate making image output machine,
This film is mounted on the input side cylinder of a gravure plate making machine of the electronic engraving system, and the image of this film is read by a scanner dedicated to the gravure plate making machine to create gravure plate making image data. Using the image data, an image is output (engraved) to a gravure cylinder on the output side of the gravure plate-making machine.

[0004]

As described above, when gravure engraving is performed using the offset plate making image data, the offset plate making image data is once output to a film, and the film is again output from this film by the scanner of the gravure plate making machine. It is necessary to read the image data and create gravure prepress image data. For this reason, there is a problem that a complicated operation is required and it takes time.

An object of the present invention is to create gravure plate-making image data using reference image data in which pixels are arranged in a grid pattern without performing complicated operations.

[0006]

According to a first aspect of the present invention, there is provided a gravure engraving data generating apparatus for converting gravure plate-making image data in which pixels are arranged in a zigzag pattern using reference image data in which pixels are arranged in a lattice. The apparatus includes a data reading unit that reads reference image data, a data creation unit, and a data output unit that sequentially outputs gravure platemaking image data created by the data creation unit. The data creating means performs an interpolation operation using a specific number of data around the virtual pixels arranged in a staggered manner in the reference image data obtained by the data reading means, and performs gravure plate-making image data corresponding to the virtual pixels. Is a means for creating

A gravure engraving data creating method according to a second aspect of the present invention is a method for creating gravure plate-making image data in which pixels are arranged in a zigzag pattern using reference image data in which pixels are arranged in a lattice. is there. This method reads the reference image data, performs an interpolation operation using a specific number of data around the virtual pixels arranged in a staggered manner in the read reference image data, and obtains gravure plate-making image data corresponding to the virtual pixels. The gravure plate making image data is sequentially output.

[0008]

In the gravure plate making image data creating apparatus and method according to the present invention, reference image data, for example, offset plate making image data is read, and gravure plate making image data is created using the reference image data. The gravure platemaking image data is created by performing an interpolation operation using a specific number of reference image data arranged around the virtual pixels arranged in a staggered manner. The gravure plate making image data created in this way is output to, for example, a storage medium or a gravure plate making machine.

As described above, gravure plate making image data can be easily created using the reference image data without performing complicated work as in the prior art.

[0010]

FIG. 1 shows the positional relationship between pixels of offset plate making image data (hereinafter referred to as offset pixels) and pixels of gravure plate making image data (hereinafter referred to as gravure pixels). Note that the gravure pixels are indicated by diamond-shaped symbols with hatching inside. In this example, the density of the offset plate making image data is 400 dpi, and the density of the gravure plate making image data is 175 L / I. In this example, an example is shown in which each gravure pixel data is created by using 36 pieces of reference pixel data among the offset plate making image data.

Here, as is apparent from FIG. 1, there is no simple multiple relationship between the pitch of the offset pixel and the pitch between the centers of the gravure pixels. Exists. For this reason, as an interpolation calculation method, for example,
As shown in Japanese Patent Application Laid-Open No. 571/571, it is not possible to use an interpolation calculation in a case where a target pixel is located at the center of a spatial filter composed of 36 reference pixels.

FIG. 2 is a schematic block diagram of an image data creating apparatus for gravure plate making according to one embodiment of the present invention. The apparatus includes an input unit 1 for inputting offset plate making image data (hereinafter, simply referred to as image data), and created gravure plate making image data (hereinafter, simply referred to as engraving data).
And an output unit 2 that outputs The input unit 1 reads data from, for example, a magneto-optical disk storing image data. The output unit 2 outputs engraving data to an external storage medium 3 or a gravure engraving machine 4 that performs engraving on a gravure cylinder. The apparatus also has a buffer memory 5 for image data, a control unit 6, and a line memory 7 for storing the generated engraving data for one line in the main scanning direction. In this example, the buffer memory 5 includes six line memories LM1 to LM6, each of which can store one line of image data in the main scanning direction. Control unit 6
Includes a microcomputer including a CPU, a RAM, a ROM, etc., and performs an interpolation operation using a specific number of reference pixel data to create engraving data. The control unit 6 is connected with an operation panel 8 on which keys and the like for inputting conditions for data conversion are arranged, and a display unit 9 including a CRT.

Next, the processing in the control unit 6 will be described with reference to FIGS.
This will be described with reference to the flowchart of FIG. When the apparatus is started, first, initial settings are made in step S1. In this initial setting, various modes are set to a preset initial mode, or variables used for calculation are set to a preset initial value. In addition, a processing menu is displayed on the CRT of the display unit 9 by the initial setting. This menu includes a menu as to whether or not to create sculpture data using image data (hereinafter referred to as data conversion).

In step S2, it is determined whether or not a data conversion process has been selected. In step S3, it is determined whether or not another process has been selected. If another process is selected, the process moves from step S3 to step S4 to execute the selected process. If the data conversion process is selected in step S2, the program proceeds from step S2 to step S5. In step S5, each file name in the magneto-optical disk storing the image data is read and displayed on the CRT. In step S6, the process waits for the operator to select a file, and stores the selected file name. In step S7,
Perform condition input processing. In this condition input processing, selection is made as to whether the created engraving data is output to the external storage medium 3 or directly to the gravure engraving machine 4, and settings such as the density (number of lines) of the engraving data to be created are made. Do. Upon completion of the condition input process, the process proceeds to a step S8.

Next, in step S8, it is determined whether or not the initial values of the position information of the image data and the engraving data for performing the interpolation operation have been manually input. In step S9, the data conversion processing is performed. Determine whether the key has been pressed. If the initial value has been manually input, the process proceeds from step S8 to step S10. In step S10, the initial value input by the operator is set as the position information of the image data and the engraving data instead of the initial value set in step S1. When the data conversion processing execution key is pressed, the process shifts to step S11 to execute the data conversion processing.

In the data conversion process shown in FIG. 4, first, in step S15, an initial value of a variable Pds is set. The variable Pds is connected in the sub-scanning direction (horizontal direction in FIG. 1) and specifies image data of a plurality of lines (six lines) to be processed. Here, in this example, the variable Pd
s indicates the third line of the six lines to be processed,
When the initial value is automatically set, “2.0” is set. When an initial value is manually input in steps S8 and S10, the input value is set. Next, in step S16, an initial value of a variable Pes that virtually represents the position of the engraving data to be created in the sub-scanning direction is set. Here, “2.5” is set for automatic, and the input value in step S10 is set for manual setting. The gravure pixels corresponding to the created engraving data are referred to as virtual pixels. Next, step S1
In step 7, a variable Ln indicating the total number of lines of image data in the sub-scanning direction is set. The data Ln is written together with the image data on the disk storing the image data. The line numbers are assigned 0 to Ln-1. In step S17, an initial value (1) is set to a variable CT. This variable CT indicates a line number in the sub-scanning direction of engraving data created thereafter.

Next, in step S18, the image data of five lines is read from an external disk, and the data of each line is stored in the corresponding line memories LM1 to LM5. The line numbers of the image data stored in the line memories LM1 to LM5 are five lines of (Pds-2) to (Pds + 2). Next, in step S19, (Pds +
It is determined whether 3) is less than the total number Ln of lines of image data in the sub-scanning direction. That is, it is determined whether or not there are three or more lines of image data above the line indicated by the variable Pds in FIG. If there are no more than three lines of image data, it is recognized that the data is at the end of the image, and the interpolation operation is terminated.

On the other hand, if YES is determined in the step S19, the process shifts to a step S20. Step S2
At 0, image data (line number = Pds + 3) for one line in the sub-scanning direction is newly read and stored in the line memory LM6. Next, in step S21, the variable P
It is determined whether or not the position of the virtual pixel indicated by es in the sub-scanning direction is located between the line indicated by the variable Pds of the image data and the next line. If the virtual pixel is located between adjacent lines of the image data, the process proceeds to step S22. In step S22, an interpolation calculation process is performed to create engraving data for one line.
When the creation of the engraving data for one line is completed, the process proceeds to step S23, where the center pitch (inter-line pitch) Eps of the gravure pixel in the sub-scanning direction is added to the variable Pes, and the variable CT is incremented (+1). Move to step S24. If NO is determined in step S21, that is, if no virtual pixel is located between adjacent lines of the image data, the process skips steps S22 and S23 from step S21 and proceeds to step S24. In step S24, the contents of the buffer memory 5 are updated for one line. That is, the image data of each line of the line memories LM2 to LM6 is stored again in the line memories LM1 to LM5 for storing the previous line. Then, the process shifts to step S25, where the variable Pds is incremented (+1), and the process returns to step S19.

In this way, the gravure engraving data is created while sequentially updating the data for each line of the image data. Next, based on the flowchart of FIG.
The interpolation calculation processing of the engraving data for one line in step S22 will be described. First, in step S28,
An initial value of a variable Pem indicating the position of the virtual pixel in the main scanning direction is set. In this example, the initial value of this variable Pem is set to “2.5” in the case of automatic, and the initial value input in step S10 in the case of manual setting. In step S29, it is determined whether or not the variable CT is an odd number. If it is determined that the variable CT is an odd number, the process directly proceeds to step S31. If it is determined that the variable CT is not an odd number, the process proceeds to step S31 via step S30. I do. In step S30, half the center-to-center pitch Epm of the gravure pixels in the main scanning direction is added to the variable Pem. This processing is for arranging the engraving data in a staggered manner. Specifically, the engraving data arrangement of the even-numbered lines in the sub-scanning direction is shifted in the main scanning direction by half the center-to-center pitch Epm.

Next, at step S31, a variable Pn indicating the address of the line memory of the buffer memory 5 is set. The variable Pn is connected in the main scanning direction and specifies image data of a plurality of lines (six lines) to be processed. Pn = (int) Pem, and the integer part of the variable Pem is taken. This variable Pn is
The third line of the six lines to be processed is shown. Next, in step S32, the number of image data for one line,
That is, a variable Dn representing the number of data in the main scanning direction is set. The value of this variable Dn has been written to the external disk.

Next, in step S33, it is determined whether (Pn + 3) is smaller than the number Dn of data of one line of image data. That is, in the main scanning direction, the variable Pn
It is determined whether there are three or more lines of image data above the line indicated by. If there are three or more lines of image data, the process proceeds to step S34. Step S
34, each of the line memories LM1 to LM1 of the buffer memory 5
Addresses (Pn−2) to 6 for LM6
A total of 36 image data stored in (Pn + 3) are read. In step S35, interpolation processing is performed using these 36 pieces of image data to create one piece of engraving data. In step S36, the engraving data obtained in step S35 is once written in the line memory 7. In step S37, the center pitch Epm of the gravure pixels in the main scanning direction is added to the variable Pem, and step S33 is performed.
Return to Note that the center-to-center pitch Epm indicates a pixel pitch on each line in the main scanning direction, and is not a pitch for pixels on an adjacent line.

The above steps S33 to S37
Is repeatedly executed to create engraving data for one line. If one line of engraving data has been created, NO is determined in the step S33, and the process shifts to a step S38. In step S33, engraving data is output from the line memory 7 to the external storage medium 3 or the gravure engraving machine 4 via the output unit 2.

Next, based on the flowchart of FIG.
An interpolation calculation process for creating one piece of engraving data using 36 pieces of data will be described. In this interpolation calculation process,
First, in step S40, the barycentric positions G1 to G4 of each area when the 36 pieces of image data to be referred to are divided into the first to fourth areas are calculated. Here, the center of gravity position G1
G4 is the position of the center of gravity of weight values WD, Wa, and Wb, which will be described later, and the first to fourth regions are divided as shown in FIG. Each region includes a virtual pixel ES1 indicated by a symbol D.
, The three image data indicated by the symbol a located on the outer peripheral side thereof, and the virtual pixel ES1
And the five image data indicated by the symbol b farthest from the image data. Next, in step S41, the representative values Tn1 to Tn4 of each area are calculated according to the following equations.

Tn1 = WD × D1 + Wa × (a11 + a
12 + a13) + Wb × (b11 + b12 + b13 + b
14 + b15) Tn2 = WD × D2 + Wa × (a21 + a22 + a2)
3) + Wb × (b21 + b22 + b23 + b24 + b2
5) Tn3 = WD × D3 + Wa × (a31 + a32 + a3
3) + Wb × (b31 + b32 + b33 + b34 + b3
5) Tn4 = WD × D4 + Wa × (a41 + a42 + a4
3) + Wb × (b41 + b42 + b43 + b44 + b4
5) Here, WD, Wa, and Wb are weight values for weighting the respective image data, and in this example, each weight value is set so as to satisfy the following relationship.

WD.times.1 + Wa.times.3 + Wb.times.5 = 1 Next, in step S42, the centroid positions G1 to G4 of the respective regions.
And the area of a rectangle formed from the center of the virtual pixel ES1 (see FIG. 7) is obtained as S1, S2, S3 and S4. Next, in step S43, the ratio of each area is calculated by the following equation. r1 = S1 / (S1 + S2 + S3 + S4) r2 = S2 / (S1 + S2 + S3 + S4) r3 = S3 / (S1 + S2 + S3 + S4) r4 = S4 / (S1 + S2 + S3 + S4) And based on these data, in step S44,
The value EN of the final engraving data is calculated as in the following equation.

EN = Tn1 × r3 + Tn2 × r4 + Tn
3 × r1 + Tn4 × r2 The integer part of the value EN thus obtained is set as the engraving data value of the virtual pixel ES1. FIG. 8 and FIG. 9 show a conventional structure disclosed in Japanese Patent Publication No. 55-33060.
A comparison between an example in which image data is converted to engraving data for the character "3" by the point interpolation method and a comparison in the case where the same data conversion is performed using the 36-point interpolation method according to the present invention and printing is performed are shown. .

In the conventional method shown in FIG. 8, the horizontal line of "three" is represented by a large and small number of cells. In this case, the edge of the line is jagged in the printed matter, making the character difficult to see. Further, since the level difference between the high density cell and the low density cell is large, in an extreme case, the top line of “three” seems to be interrupted in the middle. On the other hand, in the example shown in FIG.
The horizontal line of "three" is represented by cells slightly smaller than the conventional method and very small cells. Also, the number of cells is large. Therefore, the edge portion of the line is appropriately blurred and has a good appearance. Further, since the density difference between the cells is smaller than that in the related art, the horizontal line does not appear broken.

As described above, in the present embodiment, when performing the interpolation calculation, all the image data are subjected to the calculation, so that the reproducibility of the data for offset printing is improved. Alternatively, adverse effects such as displacement of the line can be eliminated. Further, since the interpolation calculation is performed by changing the weight between the image data near the virtual pixel and the data far from the virtual pixel according to the distance, the degree of blurring of the obtained engraving data can be controlled.

In this embodiment, 36 data are stored in the first
To the fourth area, the position of the center of gravity and the representative value of each area are once obtained, and the engraving data is created based on these. For this reason, engraving data can be created in a short time with the same accuracy as compared to a case where interpolation is performed at once by using 36 image data without dividing the area and considering the weight and distance of each data. It can be performed. When the position of the offset pixel and the position of the virtual pixel overlap, 36
In the method of performing the interpolation operation on the pieces of data at a time, the distance between the overlapping data becomes “0”, so that it is necessary to perform another process for this case. However, in the present embodiment, since the interpolation calculation is performed by dividing the area to obtain the center of gravity, the position does not overlap with the position of the virtual pixel and the center of gravity does not become “0”, and the processing is simplified.

[Other Embodiments] (a) In the above embodiment, one image is obtained by using 36 pieces of image data.
Although individual engraving data was created, the number of image data to be referred to is not limited to the above embodiment,
Although it varies depending on the density ratio between the image data and the engraving data, in the case of the density ratio in the above embodiment, the image quality after data conversion can be prevented from deteriorating, particularly by using 12 or more pixel data. Table 1 below shows an example of the number of data used for the interpolation calculation. The rhombic spatial filter will be described later.

[0031]

[Table 1]

(B) In the above embodiment, the shape of the spatial filter is square, but the shape of the cell engraved in the gravure plate making is rhombic. Can be tightened. Here, when the shape of the spatial filter is rhombic, out of the 36 data in FIG.
1 to D4, a11 to a13, a21 to a23, a31 to
a33, a41 to a43, b11, b15, b21, b
What is necessary is just to select a total of 24, 25, b31, b35, b41, and b45, and perform the arithmetic processing in the same manner as in the above embodiment. In this case, the weight value of each data preferably satisfies WD × 1 + Wa × 3 + Wb × 2 = 1.

(C) The number of image data used for the spatial filter may be automatically determined in association with the density of the image data as shown in Table 2 below. Table 2 shows that the density of engraving data created after interpolation is 1
50 to 200 L / I.

[0034]

[Table 2]

(D) When the area of the spatial filter is expanded, the weight value and the representative value of each area are calculated as follows. The weight of the i-th data from the center of the virtual pixel is Wi
Then, each weight value is

[0036]

(Equation 1)

And the representative value is

[0038]

(Equation 2)

It is assumed that Here, d _ij indicates the j-th data in the i-th round from the center of the virtual pixel. Thus, the position of the center of gravity is obtained according to the weight of the data of each circumference, and the area counts r1 to r4 are calculated. In this case, even when the density of the image data used for the interpolation calculation changes, the optimum data conversion processing can be performed by changing the range or shape of the spatial filter.

(E) The present invention can be applied to either binary data or multi-valued data having gradations. (F) In the above embodiment, only the basic pixel arrangement, that is, only the engraving data arranged in a zigzag pattern is created. However, if the engraving data is created only in the main scanning direction at twice the density, it is arranged in a zigzag pattern. Including the engraving data to be created. Therefore, a configuration may be used in which engraving data is created at twice the density only in the main scanning direction and only the engraving data arranged in a zigzag pattern is sent to the gravure plate making machine when performing gravure engraving.

(G) In the above embodiment, engraving data is created from image data in which pixels are arranged in a grid in advance.
As the original data, any data can be used as long as it can be converted into pixels arranged in a grid pattern. For example, the present invention can be implemented by performing raster conversion even on vector data or run-length data. (H) In the above embodiment, step S41 of the interpolation calculation process
In, the representative values Tn1 to Tn4 are calculated using three weight values WD, Wa, and Wb that satisfy a specific relationship with respect to the image data in each region. For example, W1 to W9 may be provided.
However, the sum of the weight values W1 to W9 is 1, and accordingly, the formula for calculating the representative values Tn1 to Tn4 is also changed. For example, the representative value Tn1 is as follows.

Tn1 = W1 × D1 + W2 × a11 + W3
× a12 + W4 × a13 + W5 × b11 + W6 × b12
+ W7 × b13 + W8 × b14 + W9 × b15

[0043]

As described above, according to the present invention, the reference image data of the grid-like pixels such as the offset plate making image data can be converted into the gravure plate making image data by the calculation. Therefore, gravure engraving can be performed in a short time without performing a complicated operation such as temporarily outputting the reference image data to a film.

[Brief description of the drawings]

FIG. 1 is a diagram showing a positional relationship between pixels of offset plate making image data and pixels of gravure plate making image data.

FIG. 2 is a schematic block diagram of an image data creating apparatus for gravure plate making according to one embodiment of the present invention.

FIG. 3 is a control flowchart of the device.

FIG. 4 is a flowchart of a data conversion process.

FIG. 5 is a flowchart of a data conversion process.

FIG. 6 is a flowchart of an interpolation calculation process.

FIG. 7 is a pixel arrangement diagram for explaining an interpolation calculation process.

FIG. 8 is an enlarged view of a gravure print obtained by a conventional four-point interpolation process.

FIG. 9 is an enlarged view of a gravure print obtained by one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input part 2 Output part 5 Buffer memory 6 Control part 7 Line memory

Continuation of front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) B41C 1/00-1/18 G06T 1/00 H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (3)

(57) [Claims] 1. An apparatus for creating gravure plate-making image data in which pixels are arranged in a staggered pattern using reference image data in which pixels are arranged in a grid pattern, wherein the data reading means reads the reference image data. Means, among the reference image data obtained by the data reading means, perform an interpolation operation using a specific number of data around the virtual pixels arranged in a staggered manner, and gravure platemaking image data corresponding to the virtual pixels A gravure prepress image data generating apparatus, comprising: a data generating unit to be generated; and a data output unit that sequentially outputs the gravure prepress image data generated by the data generating unit. 2. A virtual pixel position output means for outputting a position of the virtual pixel based on a preset pixel pitch of gravure plate-making image data; Based on the virtual pixel position, among the reference image data, a data selection unit that selects a specific number of data located around the virtual pixel position, using the reference pixel data selected by the data selection unit, 2. The gravure plate-making image data generating apparatus according to claim 1, further comprising: an operation unit that performs an interpolation operation at a virtual pixel position. 3. A method for creating gravure plate-making image data in which pixels are arranged in a staggered pattern using reference image data in which pixels are arranged in a grid pattern, comprising: reading the reference image data; Among the read reference image data, an interpolation operation is performed using a specific number of data around the virtual pixels arranged in a staggered manner to create gravure plate-making image data corresponding to the virtual pixels, and the created gravure A gravure platemaking image data creation method for sequentially outputting platemaking image data.