CN102642381B - Image data generating device and image data generating method - Google Patents

Abstract

An image data generating device and an image data generating method which eliminate blurring of a character portion with a simple structure without reducing the density when generating image data, and improve character reproducibility. The image data generation device is used to generate image data representing an image recorded on a recording medium in a printing device, and includes: a binarization processing part (111b, 112a) for binarizing input image data; a pixel density calculation part (114 ), select the pixels in the binarized image data in turn as attention pixels, calculate the number of pixels of black pixels in the plurality of pixels contained in the reference area (A1) including the attention pixel (E1) to calculate the pixel density; thinning rate calculation part (115), according to the pixel density, refer to the table data (D1) representing the corresponding relationship between the pixel density and the thinning rate to calculate the thinning rate of each pixel; the thinning processing part (116), according to the pattern corresponding to the thinning rate, perform thinning processing to reduce the concentration of each pixel .

Description

Image data generating device and image data generating method

technical field

The present invention relates to an image data generating device for generating image data representing an image recorded on a recording medium in master plate making used in stencil printing, or in printing devices other than inkjet printers and laser printers, and image data generate method.

Background technique

Conventionally, a stencil printing device has been used as one of the printing devices. In this stencil printing device, binarized data is obtained by performing predetermined image processing and pixel value conversion processing on image data, followed by binarization. The thermal head generates heat locally based on the acquired binarized data, and makes contact with the thermal stencil base paper to perforate the base paper, thereby producing the base paper. Then, the ink is transferred to the printing medium through the perforated portion of the prepared base paper to obtain a printed matter.

In such a stencil printing machine, when there is a β portion (a portion where the local printing ratio is 100%) in the image data, the amount of ink transferred from the base paper to the printing medium increases. When a subsequent recording medium is discharged and overlapped on the printing medium, there is a possibility that the ink on the previous printing medium is transferred to the back side of the latter recording medium. When ink is transferred from other printing media to the back side, the ink can be seen through the front side of the printing media, so-called "back printing" occurs, and there is a problem of poor printing quality.

To solve such problems, there are techniques disclosed in Patent Documents 1 and 2, for example. In the techniques disclosed in these Patent Documents 1 and 2, the β portion of image data is recognized, and the ink amount of the β portion is thinned out. This can reduce the occurrence of "back printing".

However, in the techniques disclosed in Patent Documents 1 and 2, it is the β portion of the image data that is subjected to thinning processing, and therefore cannot suppress the "scratch" that occurs when fine characters are printed using a printing medium with a large dot gain (dot gain). "Blurred characters", that is, a phenomenon in which thin lines of characters are blurred due to smudging of thin lines of characters.

In particular, in the case of low-pulp content printing paper and kenaf paper, which are easily affected by dot gain, uneven fiber arrangement and size, and ink penetration rate fluctuations, compared with high-grade paper, it is more likely to occur. "Text blurry". In addition, especially in the case of a character size of 10 or less and Chinese characters with a large number of strokes, the characters in small characters often blur, and there is a problem that the reproducibility of the characters is low.

Conventionally, a method of reducing the reading density when creating image data without thinning the amount of ink in the β portion of the image, and a method of reducing the printing pressure during printing have also been proposed. Moreover, in the technical fields such as inkjet printers, techniques for extracting outlines in image data, replacing ink droplets in this portion with small droplets, or making the number of droplets thinner have also been proposed (for example, Patent Document 3).

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 5-22582

Patent Document 2: Japanese Patent Application Laid-Open No. 5-22583

Patent Document 3: Japanese Patent Laid-Open No. 2002-292848

However, in the above-described method of reducing the read density, when the density is uniformly reduced using a single threshold, blanks are generated in thin characters. In addition, even if the density is reduced by error diffusion processing or the like, problems such as blurring of thin characters cannot be avoided. Therefore, in the method of reducing the reading density, there is a problem that the reproducibility of fine characters cannot be improved.

Also, in the case of reducing the printing density by reducing the printing pressure of the base paper on the printing medium, although the reproducibility of fine characters is improved, the β part is not filled and voids are generated.

In addition, in the technology disclosed in the above-mentioned Patent Document 3, contour lines extending in a specific direction on the document are extracted as feature quantities, etc., feature parts in an image are extracted to detect contour parts, and thinning processing is performed. However, in the case of image data read from a document by, for example, a scanner, the contour line in the image data itself rarely extends along a straight line. This is because, when printing a document whose image data has been read by a scanner, the outline of the document is less likely to be a clear straight line unless image data that has been properly thinned out is used. Therefore, even if the technique of Patent Document 3 is used for thin-line thinning processing, it is difficult to obtain an effective result.

Contents of the invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image data generating device and an image data generating method so that when image data representing an image recorded on a recording medium can be generated in a printing device such as stencil printing, even For printing media prone to smudging, thinning of thin line parts of characters can be reliably performed without reducing the concentration of β parts, and blurring of characters can be eliminated, thereby improving the reproducibility of characters.

In order to achieve the above objects, the present invention provides an image data generating device for generating image data representing an image recorded on a recording medium in a printing device, including: a binarization processing unit that performs processing on the input image data binarization; a pixel density calculation unit that sequentially selects pixels in the binarized image data as pixels of interest, and calculates a pixel of a black pixel among a plurality of pixels included in a reference area of a predetermined range including the pixel of interest. number, calculating the pixel density of the reference region corresponding to the pixel of interest based on the number of pixels of the black pixels; The definition data of the correspondence relationship between the pixel density and the thinning rate of the reference area is used to calculate the thinning rate for each pixel; Thinning processing, defining the relationship between the pixel density and the thinning rate in the definition data, so that within the range of pixel density higher than the predetermined threshold, the more the pixel density increases, the lower the thinning rate, and the pixel density below the predetermined threshold Low thinning rates in the pixel density range.

In the above invention, the thinning rate of each pixel (each pixel of interest) is calculated from the pixel density of the reference region corresponding to the pixel of interest. Therefore, based on the relationship between the pixel density of interest and its surrounding pixels, it can be determined, for example, whether the pixel of interest is a β portion or a thin character portion, thereby determining the degree of thinning. Specifically, at a position such as a β portion where the pixel density is higher than a predetermined threshold value, the thinning rate decreases as the pixel density increases, and thinning out becomes more difficult as the density increases. In addition, the thinning rate is lowered at a position such as a β portion where the pixel density is higher than a predetermined threshold value, compared with a position such as a thin character portion where the pixel density is lower than a predetermined threshold value. In this way, it is possible to ensure thinning of thin characters without reducing the density of the β part, thereby eliminating blurring of characters and improving the reproducibility of characters and the like.

In particular, the reference area includes pixels in a predetermined range including the pixel of interest, and the pixel density of the reference area is calculated based on the number of black pixels included in the reference area. Therefore, by determining the thinning rate based on the pixel density of the reference region, the thinning rate can be changed in accordance with changes in the distribution of the pixel of interest and its surrounding pixels.

For example, at a position where the pixel density is low, such as a position where the reference area transitions from a blank portion to a β portion, thinning is performed at a thinning rate corresponding to the pixel density, and the reference area moves from the outline of the β portion to the inside of the β portion. When , the thinning rate decreases step by step as the pixel density increases, and the thinning rate changes in this way. As a result, even in the contour of the β portion, etc., no sharp density change occurs, and smooth thinning can be performed.

Furthermore, in the above-mentioned invention, the analysis of the thinning rate is performed after the image data is binarized, thereby reducing the amount of data to be processed in printing, reducing the burden and speeding up of printing processing, and realizing calculation Miniaturization and low cost of processing devices and storage devices.

Also, in the above invention, when the pixel density calculation unit calculates the pixel density of the reference region corresponding to the pixel of interest, the pixel density calculation unit has a function of changing the area or shape of the reference region according to the content of the image data. Function.

In the above invention, the area or shape of the reference region is changed according to the contents of the image data. The content of the image data includes, for example, the font size and style of the characters contained in the image data, the type of character decoration, and the like. By changing the area or shape of the reference region in accordance with these, the relationship between the pixel of interest and its surrounding pixel density can be more accurately determined, and the accuracy of the thinning out process can be improved.

As this reference area, the number and shape of pixels of 5×5 are generally sufficient, but, for example, in the case of 10-point bold bold font, the white pixels are reduced and easily blurred. The pixel density of the region can be evaluated by reducing the ratio of the white pixel part to the reference region, and the pixel density of this part is increased, and countermeasures such as reducing the thinning rate can be taken similarly to the β part.

In the above invention, in the definition data, the thinning ratio of the pixel density below a predetermined threshold is defined as a specific upper limit value less than 100%.

In the above-mentioned invention, by setting the thinning ratio to an upper limit of less than 100% at the position where the pixel density is low, such as a thin character portion, it is possible to properly thin out text without blanking, and eliminate the blurring of the text portion, thereby further improving Reproducibility of characters, etc.

In the above invention, the specific upper limit is 50%, and the thinning out processing unit forms a pattern corresponding to the thinning rate of the specific upper limit in a checkered pattern every other pixel.

In the above invention, even when the reference area is located at the position where the thinning rate is at the maximum pixel density, by setting the specific upper limit value to 50% and performing thinning in a checkered pattern every other pixel, it is possible to It is not possible to appropriately thin out the spaces of fine characters to such an extent that it cannot be seen visually.

In the above invention, further comprising: a binarized data storage unit that stores image data binarized by the binarization processing unit; and an image selection unit that obtains the type of the recording medium and the When the acquired type is a preset specific type, the image data stored in the binarized data storage unit is read out, and the thinning out rate of the read out image data is calculated in the thinning out rate calculation unit. calculate.

In the above invention, the above thinning process can be performed only when generating image data to be printed on a recording medium such as low-pulp content printing paper or kenaf paper that is prone to ink bleeding, and the image data can be generated in accordance with the characteristics of the recording medium. . In particular, when image data to be printed on plain paper is generated, for example, binarized image data is stored in the binarized data storage unit, and the binarized image data is stored in the The type of medium to read for sparse processing operations. Since the amount of binarized data is smaller than that of normal multivalued data, the storage area can be reduced, and the size and cost of the storage device can be reduced.

In other words, since the binarized image data is image data printed on general plain paper, when the recording medium is a type that does not require thinning processing, such as plain paper, the binarized image data is used for general printing. The printing process and base paper plate making process, and then save in the binarized data storage unit. When the recording medium is low-pulp content printing paper or kenaf paper, etc. that need to be thinned out, the pre-saved data can be read. Image data, altered to perform sparse processing. As a result, not only the miniaturization and cost reduction of the storage device can be realized, but also the reuse of binarized image data can be realized. Therefore, when binarized image data is required in general printing processing and original paper plate making processing, there is no need to It is necessary to perform arithmetic processing for binarizing multi-valued data with a large data capacity every time, and it is possible to reduce the load and speed up the printing process.

In order to achieve the above object, the present invention also provides an image data generation method for generating image data representing an image recorded on a recording medium in a printing device, including: a binarization processing step, which processes the input image data performing binarization; a pixel density calculation step, which sequentially selects pixels in the binarized image data as attention pixels, and calculates the number of black pixels included in a plurality of pixels included in a reference area of a predetermined range including the attention pixels. The number of pixels, calculating the pixel density of the reference area corresponding to the attention pixel according to the number of pixels of the black pixels; the thinning rate calculation step, which refers to the corresponding relationship between the pixel density and the thinning rate that defines the reference area According to the pixel density calculated in the pixel density calculation step, the thinning rate for each pixel is calculated, wherein the defined data is the following data. In the range of pixel density higher than the predetermined threshold, the pixel density increases Then the thinning rate is lower and lower than the thinning rate in the range of pixel density below the predetermined threshold; and a thinning processing step, which reduces each Thinning of pixel density.

According to the present invention, when image data representing an image recorded on a recording medium is generated in a printing device such as stencil printing, even a printing medium that is prone to smudging does not reduce the density of the β part, and it is reliable for thin line parts of characters and the like. Thinning processing can be performed accurately to eliminate the blurring of the text and improve the reproducibility of the text. In addition, ink bleeding on recording media such as low-pulp-content printing paper and kenaf paper can be reduced, and opportunities to use paper with low adverse effects on the environment can be increased.

Description of drawings

FIG. 1 is a schematic sectional view showing an internal structure of a stencil printing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing modules related to image data generation processing in the arithmetic processing unit of FIG. 1 .

FIG. 3 is an explanatory diagram showing an outline of pixel density calculation performed by a pixel density calculation unit in FIG. 2 .

(a) in FIG. 4 is a diagram showing the correspondence relationship between the pixel density and the thinning rate used in the thinning rate calculation performed by the thinning rate calculation unit in FIG. An explanatory diagram of a configuration example of a threshold matrix used for thinning processing.

(a)-(d) in FIG. 5 are explanatory diagrams showing the structure of the threshold value matrix corresponding to the thinning ratio of FIG. 4 .

FIG. 6 is a flowchart showing an overview of an image data generation method according to an embodiment of the present invention.

(a) in FIG. 7 is an explanatory diagram showing digital data after thinning processing by the thinning processing unit in FIG. 2 , and (b) is a plan view showing an image screen printed based on the digital data in (a).

(a) in FIG. 8 is an explanatory diagram showing conventional digital data without thinning out, and (b) is a plan view showing an image screen printed based on the digital data in (a).

Detailed ways

The overall structure of the stencil printing device

Embodiments in which the image data generating apparatus according to the present invention is used to generate image data for plate making in a stencil printing apparatus will be described in detail below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the internal structure of a stencil printing apparatus 1 according to the present embodiment.

As shown in FIG. 1 , the stencil printing device 1 of the present embodiment includes: an image reading unit 10 that reads an original document image and outputs image data; Plate-making processing is performed to make the first and second plate-making sections 30 and 35 of the base paper; the first and second plate-making sections 33 for printing the printing paper P1 are carried out using the heat-sensitive stencil base paper 33 made in the first and second plate-making sections 30 and 35. 1 and the second printing unit 40, 50; the paper feeding unit 20 that supplies the printing paper P1 to the first printing unit 40; P2 , the intermediate storage unit 46 that supplies to the second printing unit 50 at a predetermined timing;

The image reading unit 10 is a scanning device that has a line image sensor that photoelectrically reads image information of a document, scans the document with the line image sensor to read the document, and outputs image data.

The first plate making section 30 has a thermal head unit 31 in which a plurality of heating elements are arranged in a row, and uses the thermal head unit 31 to perform a plate making process on a thermal stencil base paper 33 sent out from a stencil base paper roll. It should be noted that the first plate making unit 30 performs the plate making process based on the processed image data output from the arithmetic processing unit 100 described later.

Like the first plate making section 30 , the second plate making section 35 also has a thermal head unit 36 , and uses the thermal head unit 36 to perform a plate making process on the thermal stencil paper 33 sent out from the stencil paper roll. It should be noted that the second plate making unit 35 also performs plate making processing based on the processed image data output from the arithmetic processing unit 100 described later.

The first printing unit 40 has: a cylindrical first printing drum 41 through which ink can pass through a porous metal plate, a mesh structure, etc.; 42 ; and the first peeling claw 43 for peeling off the printing paper P2 printed on one side from the first printing drum 41 . On the outer periphery of the first printing drum 41 , the base paper perforated on the heat-sensitive stencil base paper 33 in the first plate making section 30 is wound and attached. In addition, the first pressure roller 42 is extended along the direction in which the central axis of the cylinder of the first printing drum 41 extends (the depth direction of the paper in FIG. 1 ).

Like the first printing unit 40, the second printing unit 50 has: a cylindrical second printing drum 51; Pressure roller 52; And the second peeling claw 53 that peels off the printing paper P3 after duplex printing from the second printing drum 51. On the outer periphery of the second printing drum 51 , the base paper perforated in the second plate making unit 35 is wound and attached. In addition, the second pressure roller 52 is extended along the direction in which the central axis of the cylinder of the second printing drum 51 extends (the depth direction of the paper in FIG. 1 ).

The paper feed unit 20 has: a paper feed table 21 on which the printing paper P1 is loaded; a primary paper feed roller 22 for taking out the printing paper P1 one by one from the paper feed table 21 and sending it to the secondary paper feed roller 23; On the downstream side of the conveyance direction of the primary paper feed roller 22, the head end of the printing paper P1 conveyed by the primary paper feed roller 22 is temporarily stopped, and the printing paper P1 is fed to the first printing drum 41 and the first pressure roller 42 at a predetermined timing. The secondary paper feed roller 23 sent out between.

The discharge section 70 has: a discharge conveyor section 72 that conveys the double-sided printed printing paper P3 to the discharge table 71; and stacks the double-sided printed printing paper P3 conveyed by the paper discharge conveyor section 72 The discharge table 71 of.

Furthermore, between the first printing unit 40 and the intermediate storage unit 46 , a curved transport unit 44 is provided. As shown in FIG. 1 , the curved conveying section 44 has a guide plate having a curved surface along the conveying path. On the curved surface of the guide plate, a conveyor belt provided with a suction port for sucking the printing paper P1 sent out from the first printing unit 40 is provided. Moreover, the pulley 45 which circulates this conveyor belt is provided. The curved conveying part 44 sucks the printing paper P2 printed on one side through the suction port of the conveying belt, and by rotating the pulley 45, the printing paper P2 printed on one side is conveyed along the curved surface of the guide plate by the conveying belt. .

Between the intermediate storage unit 46 and the second printing unit 50 are provided: a pick-up roller 47 for picking up the single-sided printed printing paper P2 sent out from the intermediate storage unit 46; The printing paper P2 is sequentially fed out to the timing roller 48 between the second printing drum 51 and the second pressure roller 52 at predetermined timings.

image data generation device

The stencil printing apparatus 1 according to the present embodiment has an arithmetic processing unit 100 that generally performs plate making processing, image processing, printing control, and control of each driving means. In the present embodiment, the arithmetic processing unit 100 has the function of an image data generating device that performs predetermined density conversion processing on the image data output from the image reading unit 10 and outputs them to the first and second plate making units 30 respectively. , 35. FIG. 2 is a block diagram showing modules related to image data generation processing in the arithmetic processing unit 100 according to the present embodiment. It should be noted that the "module" used in the description refers to a functional unit configured by hardware such as a device or device, or software having the function, or a combination thereof, for realizing a predetermined operation.

As shown in FIG. 2 , the arithmetic processing unit 100 includes a job data receiving unit 101 , an operation signal acquiring unit 102 , a storage unit 103 , and an image forming control unit 110 as modules related to image data generation processing.

The job data receiving unit 101 is an interface for receiving job data as a series of print processing units through the image reading unit 10 and/or the external communication interface 104, and transfers data contained in the received job data to the image forming unit. module of the control unit 110 . Communication via the external communication interface 104 includes, for example, an intranet (network within an enterprise) formed by 10BASE-T or 100BASE-TX, or a local area network (LAN) such as a home network, as well as infrared communication. short-range communication.

The operation signal acquisition part 102 is an external interface, which is connected to the operation panel 100a and the external communication interface 104 for the network, and acquires user operations performed by the operation panel 100a and the external equipment (for example, information terminals such as personal computers) of the network and compares them. After analysis, it is input to each module in the arithmetic processing unit 100 . It should be noted that the user operation here includes the image mode set by the user, etc., and the image mode includes the following setting information: an image mode switching signal for selecting photo processing or word processing in image generation processing; The type of recording medium (plain paper, low-pulp content printing paper, etc.) to be subjected to the printing process using the base paper after plate making.

The storage unit 103 (an example of the binarized data storage unit) is a storage device that stores and holds various data and programs. In particular, in this embodiment, it records and saves the following data: binarized image data; Table data D1 (refer to FIG. 4( a )) of definition data representing a correspondence relationship between pixel density and thinning rate; pixel density threshold value data; and threshold value matrix data M1 (refer to FIG. 4( b )). These stored data are read and referred to in each process of the image formation control unit 110 described later.

The image formation control unit 110 is an arithmetic processing unit that performs specialized image processing, that is, digital signal processing, and is a module that performs image formation processing such as conversion of image data required for printing. In particular, in this embodiment, in the image forming control unit 110, as a plate making control mechanism that controls the driving of the thermal head units 31 and 36 and controls the overall plate making process, it includes a photo processing unit 111, a word processing unit 112, an image selection section 113 , pixel density calculation section 114 , thinning ratio calculation section 115 , thinning processing section 116 , and image output section 117 .

The photo processing unit 111 is a module for performing photo processing on a photo image included in the image data, and includes a gamma conversion processing unit 111 a and a binarization processing unit 111 b.

The gamma conversion processing unit 111 a is a module that converts the density of each pixel in the image data into a density suitable for midtones by gamma conversion.

The binarization processing unit 111b is a module that binarizes the pixel values of the photo image included in the gamma-converted image data, and converts the value of each pixel that is multi-valued data, that is, the density or reflectance of the document, through binarization. The error diffusion processing unit 111c of the processing unit 111b compares it with a predetermined threshold value, and performs halftone binarization with respect to the magnitude of the threshold value. The energization of the thermal head is turned on/off based on this binarized data for turning energization of the thermal head on/off (ON/OFF) to form perforations on the base paper (that is, to form an image on the base paper).

The word processing unit 112 is a module that performs word processing on a character image in image data, and includes a binarization processing unit 112 a.

The binarization processing unit 112a is a module that binarizes the pixel value of the character portion included in the image data to turn on/off the energization of each heating element of the thermal head using a single threshold. The binarization processing unit 112a performs binarization by comparing each pixel that is multivalued data with a single threshold, turning on the energization when the threshold is greater than the threshold, and turning the energization off when the threshold is less than the threshold. The binarized data is input to the image selection unit 113 . According to the binarized data input to the image selection part 113, the power on/off of the thermal head is made to form perforations on the base paper (that is, the density of the image is changed to the power on/off of the thermal head irrespective of the length of time, In this way, the heating of the thermal head is turned on/off, so that the base paper has no perforation, and an image is formed on the base paper in this way).

The image selection unit 113 is a module that selects image data subjected to word processing or photo processing according to the image mode set by the user on the operation panel 100 a, and inputs the image data to the pixel density calculation unit 114 . In addition, the image selection unit 113 has a function of reading out the recording medium stored in the memory when the type of the recording medium to be printed using the plate-making base paper is acquired and the acquired type is a specific type set in advance. The image data stored in the part 103 is calculated by the thinning rate calculation part 115 on the image data read out. It should be noted that the type of recording medium is acquired from the image mode set by the user using the operation panel 100a. In addition, in the present embodiment, after the photo processing and word processing are performed in parallel, the image selection unit 113 selects an image, but, for example, an image selection unit may be arranged upstream of the photo processing unit 111 and the word processing unit 112. The unit 113 selects a photograph and a character before the binarization process, and appropriately switches the input destination of the image data.

As shown in FIG. 3 , the pixel density calculation unit 114 is a module that counts the number of pixels included in a predetermined range (reference area A1) including the pixel E1 of interest, and calculates the number of pixels in the predetermined range as the number of pixels corresponding to the pixel E1 of interest. Corresponding to the pixel density of the reference area A1. Specifically, each pixel in the binarized image data is sequentially selected as the pixel of interest E1. The number of black pixels in 25 pixels in the reference area A1 formed by merging each pixel of interest E1 and 24 (5×5−1=24) pixels around it as the center is calculated. The pixel density ( In the example of Figure 3, 20/25 equals 0.80). The pixel density calculated by the pixel density calculation unit 114 is input to the thinning rate calculation unit 115 .

It should be noted that the pixel density calculation unit 114 has a function of changing the area or shape of the reference area A1 according to the font size and typeface of the characters contained in the image data, the type of character modification, and the like. Specifically, the default area and shape of the reference area A1 is a square area with 5×5 pixels. However, the pixel density calculation unit 114 can extract the font size and font of the characters, the type of character decoration, etc. in the job data. Information related to the image data contained in and change the area or shape of the reference area A1. In addition, the information related to the image data here can be obtained from the processing character font size selection signal included in the job data.

With this function of changing the area or shape of the reference area A1, for example, in the case where the white pixel portion has a 10-point bold font that is slightly blurred, the reference area A1 is changed to 7×7, and the pixel density is obtained. . In this way, the ratio of the white pixel portion to the reference area A1 is evaluated to be small so that the pixel density of this portion is high, and the thinning rate is reduced similarly to the β portion.

The thinning rate calculation unit 115 refers to the table data D1 of the storage unit 103 based on the pixel density calculated by the pixel density calculation unit 114 to calculate the thinning rate for the corresponding pixel E1 of interest. In this embodiment, the table data D1 is data showing the correspondence relationship between pixel density and thinning rate using the curve shown in FIG.

In this embodiment, the relationship between the pixel density and the thinning rate of the table data D1 is set such that the thinning rate of the pixel density above a predetermined threshold (pixel density threshold T1) is less than a specific upper limit of 100% (FIG. 4 In the example of (a), it is 50%), and in the range of pixel density higher than the pixel density threshold T1 (in the example of FIG. An increase in density proportionally reduces the thinning rate. Specifically, in the table data D1 here, when the pixel density is 0 to 36%, the thinning rate is generally set to 50%, and for the area higher than the pixel density of 36%, as the pixel density approaches 100%, the thinning rate is reduced to close to 0%. In this way, the thinning rate can be reduced for the β portion with high pixel density, etc., and the thinning rate can be increased for the blank portion with low pixel density.

The thinning rate calculation unit 115 inputs the thinning rate of each pixel calculated for each pixel to the thinning processing unit 116 as arrangement data related to coordinate information. The thinning processing unit 116 is a module that performs thinning processing for reducing the density of each pixel according to a pattern corresponding to the thinning rate. The thinning processing unit 116 uses the threshold value matrix data M1 stored in the storage unit 103 in the thinning processing.

The threshold value matrix data M1 is a filter for defining a thinning rate threshold value for all pixels by using 4×4 16 pixels shown in FIG. 4( b ) as a unit pattern and repeating this operation. In the threshold value matrix data M1, a high threshold value and a low threshold value are arranged in a Bayer arrangement so that pixels to be sparse are not biased.

The thinning out processing unit 116 sequentially selects 4×4 16 pixels from the image data included in the job data without duplication. Furthermore, thinning-out processing is performed for each of 4×4 16 pixels using the threshold value matrix data M1. Specifically, each of the thinning rates calculated by the thinning rate calculation section 115 of the selected 16 pixels is compared with the thresholds respectively defined for the corresponding pixel positions in the threshold matrix data M1. As a result of the comparison, as shown in FIG. 5 , when the thinning rate of each pixel is higher than the threshold, the pixel is replaced with a white pixel and thinned out, and when the thinning rate is lower than the threshold, the pixel is not thinned out. Note that in FIG. 5 , pixels that are thinned out are represented by white, and pixels that are not thinned out are represented by shades.

In particular, in the present embodiment, the threshold value matrix data M1 is configured such that the sparse pattern at a specific upper limit (50%) of the table data D1 becomes an alternate grid pattern of every other pixel as shown in FIG. 5( a ). . That is, among the respective thresholds in the threshold matrix data M1, 50% or more of the thresholds are arranged such that one pixel is separated from each other in the x-axis direction and the y-axis direction. In this way, even when the thinning rate is maximized, pixels can be thinned without bias and without omission.

Also, as described above, the thinning rate is set so that the relationship between the pixel density and the thinning rate of the table data D1 is such that the thinning rate decreases in proportion to the increase in the pixel density within the range of pixel density higher than the pixel density threshold T1 . Therefore, as the pixel density exceeds the pixel density threshold T1 (36%), the thinning rate drops sharply to 20% (at a pixel density of 50%), and then gradually decreases as the pixel density becomes higher than 50%. , from 20% to 0%. Along with this, the sparse pattern formed by the threshold value matrix data M1 changes. For example, when the thinning rate is 35%, the thinning pattern changes to the pattern shown in FIG. 5( b ), and when the thinning rate is 25%, the thinning pattern changes to the pattern shown in FIG. 5( c ). Furthermore, when the thinning rate decreased to 10%, the thinning pattern changed to the pattern shown in Fig. 5(d). Furthermore, the thinning rate is made close to 0% as the pixel density approaches 100%, and the thinning rate is 0% near the pixel density of 100%, so thinning is not performed.

The image output unit 117 is a module that controls the thermal head units 31 and 36 and each drive mechanism based on image data, and controls the entire plate making mechanism. The image output unit 117 of the present embodiment has a mode of directly making a plate from the image data included in the job data received by the job data receiving unit 101 and a mode of making a plate using the image data thinned out by the thinning out processing unit 116. These modes are determined by the user. or automatically selected according to the type of recording medium to be printed on the base paper after plate making, and plate making is performed based on image data in each mode.

Image data generation method

The image data generating method of the present invention can be realized by operating the image data generating device having the above configuration. FIG. 6 is a flowchart showing the outline of an image data generation method according to this embodiment.

First, when a plate making process is performed, the job data receiving unit 101 receives job data, and inputs image data included in the received job data to the image forming control unit 110 (steps S101, S102). In the image formation control unit 110 , photo processing for photo images in the image data and character processing for character images are performed in parallel. Specifically, in photo processing, the gamma conversion in the gamma conversion processing unit 111a is used to convert to a density suitable for midtones (step S103), and after the binarization processing performed by the binarization processing unit 111b, Halftone processing of error diffusion is performed by the error diffusion processing unit 111c (step S104). On the other hand, in word processing, binarization by a single threshold is performed (step S105).

Next, in the image selection unit 113, image data subjected to word processing or photo processing is selected according to the image mode set by the user on the operation panel 100a, and input to the pixel density calculation unit 114 (step S106). In addition, in this step S106, the image selection unit 113 acquires the type of the recording medium to be printed on the plate-made base paper, and when the acquired type is a preset specific type, reads the type of the recording medium stored in the storage unit 103. The stored image data and the read image data are input to the thinning rate calculation unit 115 . It should be noted that the type of recording medium here is obtained from the image mode set by the user using the operation panel 100a.

The pixel density calculation unit 114 calculates the number of black pixels in a plurality of pixels included in the reference area A1 in a predetermined range including the pixel E1 of interest from the input image data, and calculates the pixel density of the pixel E1 of interest. Specifically, the pixel density calculation unit 114 sequentially selects pixels in the image data binarized by each binarization processing unit 111b or 112a as the pixel of interest E1, and calculates the pixel density in the reference area A1 centered on the pixel of interest E1. The number of black pixels in which the power to the heating element of the thermal head is ON among the pixels. By dividing this calculated number of pixels by the total number of pixels in the reference area A1 (5×5=25), the number of pixels per unit area is calculated as the pixel density.

It should be noted that in step S107 , the pixel density calculation unit 114 changes the area or shape of the reference area A1 according to the font size and font of the characters included in the image data, the type of character modification, and the like. Specifically, the default area and shape of the reference area A1 is a square area with 5×5 pixels. However, the pixel density calculation unit 114 can extract the font size and font of the characters, the type of character decoration, etc. in the job data. Information related to the image data contained in and change the area or shape of the reference area A1.

The pixel density calculated by the pixel density calculation unit 114 as described above is input to the thinning rate calculation unit 115 in the form of arrangement data related to the coordinate information of each pixel. It should be noted that, in this embodiment, the above-mentioned step S107 is performed on each pixel through loop processing, and the calculation of the pixel density is completed for all pixels, and then the next step S108 is entered.

In step S108 , based on the pixel density of each pixel, the thinning rate for each pixel is calculated by referring to the table data D1 stored in the storage unit 103 . In the present embodiment, the table data D1 reduces the thinning rate to approximately zero for the β portion with high pixel density, etc., and increases the thinning rate as the pixel density decreases. However, for a blank portion with a low pixel density, etc., the thinning rate is uniformly set to 50% in the portion where the pixel density is 0 to 36%.

The thinning rate calculation unit 115 inputs the calculated thinning rate to the thinning processing unit 116 as array data related to the coordinate information of each pixel. In the thinning processing unit 116, pixel thinning processing is performed based on a pattern corresponding to the thinning rate calculated by the thinning rate calculation unit 115 (step S109). Specifically, in the thinning processing unit 116, using the threshold value matrix data M1, the thinning rate of each pixel calculated by the thinning rate calculation unit 115 is compared with the threshold value in the matrix corresponding to the coordinates of each pixel, and the Pixels below a predetermined thinning rate are replaced with white pixels.

Then, the image output unit 117 controls the driving of the thermal head units 31 and 36 based on the thinned out image data, generates a base paper corresponding to the thinned out image data by the thinned out processing unit 116, and forms an image (step S110) .

Beneficial effect

According to the present embodiment described above, the thinning rate of each pixel (each pixel of interest) is calculated based on the pixel density of the reference area A1 corresponding to the pixel of interest E1. Whether the pixel E1 of interest is a β portion or a thin character portion can determine the degree of thinning. In this way, thin characters can be reliably thinned without reducing the density of the β part, and blurring of characters can be eliminated to improve the reproducibility of characters and the like.

In particular, in this embodiment, thinning processing is performed according to the type of recording medium to be printed, so printing can be performed only on recording media that are prone to ink bleed, such as low-pulp content printing paper or kenaf paper. The aforementioned thinning process can be performed on the image data, and image data matching the characteristics of the recording medium can be generated. Specifically, in the past, the image data (digital data) shown in FIG. In the case of printing, as shown in FIG. 8( b ), the small characters of characters with a large number of strokes are stained, blurred characters occur, and the reproducibility of fine characters decreases. On the other hand, according to this embodiment, the image data generated by the thinning out process shown in FIG. In the case of , as shown in FIG. 7( b ), the blurring of characters is improved, and the reproducibility of fine characters is improved.

In addition, since the reference area A1 includes a predetermined number of pixels, the thinning rate can be determined according to the pixel density of the reference area A1. Thinning can be performed at a thinning rate corresponding to the pixel density. When the reference area A1 moves from the outline of the β part to the inside of the β part, the thinning rate gradually decreases as the pixel density increases, and it is possible to correspond to the pixel density of interest. The thinning rate is changed by changing the distribution of E1 and its surrounding pixels.

Furthermore, in the above-mentioned invention, the analysis of the thinning rate is performed after the image data is binarized, thereby reducing the amount of data to be processed by printing, reducing the burden and speeding up the printing process, and also Miniaturization and low cost of arithmetic processing devices and storage devices are realized.

In addition, in the above-mentioned embodiment, the pixel density calculation unit 114 has the function of changing the area or shape of the reference area A1, so the reference area A1 can be changed according to the font size and font of the characters contained in the image data, the type of character modification, etc. area and shape. In this way, according to the present embodiment, the relationship between the pixel density of interest and its surroundings can be more accurately determined, and the accuracy of the thinning out process can be improved.

In addition, in this embodiment, the relationship between the pixel density and the thinning rate of the table data D1 is set such that the thinning rate is set in a range of pixel densities higher than a predetermined threshold so that it is approximately inversely proportional to the pixel density, and The thinning ratio of the above-mentioned predetermined threshold value is less than a specific upper limit value of 100%. Therefore, for example, at a position where the pixel density is high such as a β portion, set the thinning rate so that it is roughly inversely proportional to the pixel density, so that the higher the density, the harder it is to thin out. When the upper limit is set to be less than 100%, it is possible to moderately thin the characters without causing blanks in the characters, and it is possible to eliminate the blurring of the characters to further improve the reproducibility of the characters and the like.

In the present embodiment, the specific upper limit value is set to 50% in the table data D1, and the thinning out processing unit 116 makes the thinning pattern of the specific upper limit value into an alternate grid pattern of every other pixel. In this way, even when the reference area A1 is located at the position where the thinning rate is at the maximum pixel density, it is possible to appropriately thin out the margins of fine characters to such an extent that they cannot be seen visually.

In addition, in this embodiment, for example, when outputting image data to be printed on plain paper, the binarized image data is stored in the storage unit 103, and the binarized image data is based on the The type of the recording medium is read out from the storage unit 103 and used for the calculation of the thinning process. Since the amount of binarized data is smaller than that of normal multivalued data, the storage area can be reduced, and the size and cost of the storage device can be reduced.

In other words, the binarized image data is image data printed on ordinary plain paper, so when the recording medium is a type that does not require thinning processing, such as plain paper, the binarized image data is used for ordinary paper. The printing process and base paper platemaking process are stored in the storage unit 103 without thinning processing. When the recording medium is a type that requires thinning processing such as low pulp content printing paper or kenaf paper, the image data stored in advance is read out. Make changes for sparse processing. As a result, not only the size and cost of the storage device can be reduced, but also by reusing the binarized image data, it is not necessary to perform the calculation processing for binarization again, and the burden of calculation processing can be realized. Lighten and speed up.

As a result, according to the present embodiment, when image data for plate making of a stencil printing apparatus is generated, a position for performing thinning processing of the image is appropriately selected, thereby reliably thinning out the thin line parts of the characters and eliminating the blurring of the characters. In addition, the thinning out process is not performed on the low-density area of the image, so that the reproducibility of characters can be improved. In addition, ink bleeding to recording media such as low-pulp-content printing paper and kenaf paper can be reduced, and opportunities to use paper with low adverse environmental effects can be increased.

In addition, in this embodiment, the case where the present invention is applied to generation of image data for plate making in a stencil printing apparatus is described, but the present invention is not limited thereto, and the present invention is also applicable to For example, all devices that print on recording media based on image data, such as inkjet printers, laser printers, thermal recording devices, and thermal transfer recording devices.

Explanation of reference signs:

1 stencil printing device

10Image reading unit

20 paper supply department

21 paper table

22 primary feed roller

23 secondary feed roller

30 The first plate-making department

31 thermal head unit

33 thermal stencil base paper

35 Second plate making department

36 thermal head unit

40 First Printing Department

42 first pressure roller

43 first stripping claw

44 curved conveying part

45 pulley

46 Intermediate storage department

47 pick up roller

48 timing rollers

50 Second Printing Department

51 second printing drum

52 second pressure roller

53 second stripping claw

70 Finishing department

71 paper table

72 bands

100 operation processing department

100a operation panel

101 Job Data Receiving Department

102 Operation Signal Acquisition Department

103 storage department

104 external communication interface

110 Image Formation Control Unit

111 Photo Processing Department

111a Gamma conversion processing unit

111b binarization processing unit

111c error diffusion processing unit

112 Word Processing Department

112a Binarization processing unit

113 Image Selection Department

114 pixel density calculation department

115 Sparse Rate Calculation Department

116 Sparse Processing Department

117 Image output department

A1 reference area

D1 table data

E1 attention pixel

M1 Threshold Matrix Data

P1 printing paper

P2 printing paper after single-sided printing

P3 printing paper after duplex printing

T1 pixel density threshold

Claims (6)

1. An image data generating device for generating image data representing an image recorded on a recording medium in a printing device, comprising: a binarization processing section that binarizes the input image data; and a pixel density calculation unit that sequentially selects pixels in the binarized image data as pixels of interest, and calculates the number of black pixels among a plurality of pixels included in a reference area of a predetermined range including the pixel of interest, based on the calculating the pixel density of the reference region corresponding to the attention pixel by using the pixel quantity of the black pixel, It is characterized in that the image data generation device also includes: a thinning rate calculation unit that calculates a thinning rate for each pixel with reference to definition data indicating a correspondence relationship between a pixel density and a thinning rate in the reference region based on the pixel density calculated by the pixel density calculation unit; and a thinning processing unit that performs thinning processing for reducing the density of each pixel based on the pattern corresponding to the thinning rate, The relationship between the pixel density and thinning rate is defined in the definition data, so that in the range of pixel density higher than the predetermined threshold, the more the pixel density increases, the lower the thinning rate, and the range of pixel density below the predetermined threshold The sparsity rate inside is low. 2. The image data generation device according to claim 1, wherein The pixel density calculation unit has a function of changing the area or shape of the reference region according to the content of the image data. 3. The image data generation device according to claim 1, wherein: In the definition data, the thinning rate of the pixel density below the predetermined threshold is defined as a certain upper limit value less than 100%. 4. The image data generating device according to claim 3, wherein: The specific upper limit is 50%, and the thinning processing unit makes the pattern corresponding to the thinning rate of the specific upper limit a checkered pattern with every other pixel. 5. The image data generating device according to any one of claims 1 to 4, further comprising: a binarized data storage unit storing image data binarized by the binarization processing unit; and The image selection unit reads out the image data stored in the binarized data storage unit when the type of the recording medium is acquired and the acquired type is a predetermined specific type, and in the The thinning rate calculation unit calculates the thinning rate of the read image data. 6. An image data generating method for generating image data representing an image recorded on a recording medium in a printing device, comprising: a binarization processing step of binarizing the input image data; and a pixel density calculation step of sequentially selecting pixels in the binarized image data as pixels of interest, calculating the number of black pixels among a plurality of pixels included in a reference region of a predetermined range including the pixel of interest, based on the pixels of interest calculating the pixel density of the reference region corresponding to the attention pixel by using the pixel quantity of the black pixel, It is characterized in that, the image data generation method also includes: a thinning rate calculation step of calculating a thinning rate for each pixel based on the pixel density calculated in the pixel density calculation step with reference to definition data defining a correspondence relationship between the pixel density and the thinning rate of the reference area, wherein the The definition data is the following data. In the range of pixel density higher than the predetermined threshold, the thinning rate decreases as the pixel density increases, and is lower than the thinning rate in the range of pixel density below the predetermined threshold; and a thinning processing step of performing thinning processing for reducing the density of each pixel based on a pattern corresponding to the thinning rate calculated in the thinning rate calculation step.