JP3119124U - Image processing device - Google Patents

Abstract

An image processing apparatus that performs RIP processing on original image data to acquire raster data, and performs smoothing processing on the acquired raster data to generate output image data so as to perform RIP processing at a lower resolution. To do.
Relative output pixels P00, P10 are used by overlapping the same pixels I10, I11, I12 of raster data by associating the filters so as to overlap each other in the main scanning direction and / or the sub-scanning direction. Are respectively calculated, and RIP processing is performed on the original image data at a resolution corresponding to the overlap of the filters.
[Selection] Figure 4

Description

  The present invention relates to an image processing apparatus that performs RIP processing on original image data to acquire raster data, and performs smoothing processing on the acquired raster data to generate output image data.

  Conventionally, original image data including graphics such as characters and illustrations is created by a computer, the original image data is output from a computer in PDL format (page description language), and RIP processing is performed on the original image data in PDL format. An image forming method is proposed in which raster data of C (cyan) component, M (magenta) component, Y (yellow) component, and K (black) component is created and a color image is formed by an inkjet recording apparatus based on the raster data. Has been.

  Here, for example, when the character “A” is formed based on the raster data created as described above, the edge of the character depends on the size (resolution) of the dot as shown in FIG. Shaking occurs in the part.

  Therefore, in the case of an ink jet recording apparatus capable of expressing multiple gradations, for example, by performing smoothing processing on raster data using an oversampling method or the like to generate intermediate density data, the above-described rattling can be achieved. A method has been proposed for making the image inconspicuous. The oversampling method is a method of generating output image data by dividing high-resolution raster data into n × n pixel sets and using the average density value of each pixel set as the density value of one pixel.

  Specifically, for example, in the case of an ink jet recording apparatus that can express 8 gradations (8 values) per pixel by switching the number of ink ejections within a range of 0 to 7 drops for each pixel, The above density value is calculated using a sampling method, pixel values of eight gradations are generated based on the density values, and dots are formed by changing the number of ink drops by eight steps based on the pixel values of the eight gradations. By doing so, the shakiness can be made inconspicuous by arranging dots of intermediate density at the edge portion of the character (see FIG. 9B).

Here, for example, when output image data input to an inkjet recording apparatus in which an output resolution is set to 300 × 600 dpi and an output gradation is set to 6 gradations is generated by performing oversampling as described above, conventionally, For example, RIP processing is performed on the original image data so that two-tone raster data with a resolution of 900 × 1200 dpi is obtained, and the 900 × 1200 dpi raster data is converted into a 3 × 2 pixel set as shown in FIG. In other words, oversampling is performed by calculating the mathematical formula shown in FIG. 10 to calculate each output pixel value P00, and output image data is generated. As described above, the RIP processing at the resolution of 900 × 1200 dpi is performed when the output resolution is 300 × 600 dpi and the output gradation is 6 gradations, and the data amount is 300 × 600 × 5 (the maximum number of ink drops). ) = 900,000, and if the RIP processing is performed at 900 × 1200 dpi, the data amount is 900 × 1200 dpi = 1080000, which is sufficient. The data amount means the number of gradations per unit area. Here, as an example, the case of the number of gradations per square inch is described.
JP 11-69163 A JP-A-10-336454 Japanese Patent Laid-Open No. 5-233792 JP-A-9-149242 JP 2001-105663 A

  However, in reality, there is a problem that ripping cannot be performed at a resolution of 900 × 1200 dpi in which the main scanning direction and the sub-scanning direction are different, or if the input resolution exceeds a certain level, processing cannot be performed due to insufficient resources. . Moreover, there is a problem that the processing speed decreases in proportion to the input resolution.

  As described above, the present invention provides an image processing apparatus that performs RIP processing on original image data to acquire raster data, and performs smoothing processing on the acquired raster data to generate output image data at a lower input resolution. An object of the present invention is to provide an image processing apparatus that can perform ripping and perform appropriate smoothing processing.

  An image processing apparatus according to the present invention includes a RIP processing unit that performs RIP processing on original image data at a predetermined resolution to obtain raster data, a filter associated with the raster data acquired by the RIP processing unit, and a raster in the filter An image processing apparatus comprising: an output image data generation unit configured to perform smoothing processing by calculating an output pixel value based on a pixel value of data and generate output image data having a resolution smaller than a predetermined resolution; The output image data generation unit calculates the values of adjacent output pixels by using the same pixel of the raster data redundantly by associating the filters so as to overlap in the main scanning direction and / or the sub-scanning direction. The RIP processing unit performs RIP processing on the original image data with a resolution corresponding to the overlap of the filters. Characterized in that it is intended to acquire the raster data.

  In the image processing apparatus according to the present invention, the filter can be configured from values calculated by weighting according to the overlap of the filters.

  In addition, the filter can be configured from values calculated based on the positional relationship between the pixel position of the raster data and the position of the output pixel.

  According to the image processing apparatus of the present invention, the values of adjacent output pixels are used by overlapping the same pixels of raster data by associating the filters so as to overlap in the main scanning direction and / or the sub-scanning direction. Since the raster data is obtained by performing RIP processing on the original image data at a resolution corresponding to the overlap of the filters, the RIP processing is performed at a lower resolution than the conventional image processing apparatus. Can do.

  Further, when the filter is composed of values calculated by weighting according to the overlap of the filters, a more appropriate smoothing process can be performed.

  Hereinafter, an inkjet recording system using an embodiment of an image processing apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the ink jet recording system.

  As shown in FIG. 1, the present inkjet recording system is installed with an application capable of creating original image data including characters, photographs, illustrations, and the like, and a computer 10 that outputs the original image data in a PDL format (page description language). The RIP processing unit 20 that receives the original image data output from the computer 10 and generates R component, G component, and B component raster data by applying RIP processing to the original image data. RIP resolution acquisition unit 21 that acquires RIP resolution at the time of processing, and R component, G component, and B component raster data generated by RIP processing unit 20 are rasterized as C component, M component, Y component, and K component In the RGB-CMYK conversion unit 30 and the RGB-CMYK conversion unit 30 for converting data A smoothing processing unit 40 that performs smoothing processing on the converted C component, M component, Y component, and K component raster data to generate respective output image data, and is used when the smoothing processing unit 40 performs the smoothing processing. A filter value acquisition unit 41 for calculating a filter value, a filter size acquisition unit 42 for acquiring a filter size used when performing the smoothing process, an output resolution acquired in advance, and a maximum ink drop number to be described later An input resolution acquisition unit 43 that acquires an input resolution based on the above, a screening processing unit 50 that performs screening processing on each output image data generated in the smoothing processing unit 40 to generate output image data that has undergone screening processing, and a screening processing unit Generated in 50 And a ink jet recording apparatus 60 for recording an image based on screening processed output image data.

  Next, the operation of the ink jet recording system will be described.

  First, in the computer 10, original image data including characters, photos, illustrations, and the like is created by an application. Then, a print instruction is issued in the application of the computer 10. The computer 10 outputs the original image data to the RIP processing unit 20 in the PDL format according to the print instruction.

  Then, RIP processing is performed on the original image data in the PDL format in the RIP processing unit 20, and a method for determining the RIP resolution at that time will be described.

  First, the output resolution of the inkjet recording apparatus 60 is acquired in advance, and the maximum number of ink drops is selected in advance. The output resolution and the maximum number of ink drops may be set in advance in the inkjet recording apparatus 60 or may be set in advance in the computer 10.

  The maximum number of ink drops is the number of ink drops with the maximum density of each dot recorded on the printing paper, and is information corresponding to the number of output gradations. The maximum number of ink drops may be selected directly, or for example, the maximum ink drop may be selected by associating the type of printing paper with the maximum number of ink drops and selecting the type of printing paper. The number may be selected.

  Note that the type of printing paper and the maximum number of ink drops may be associated with the type of printing paper and the number of ink drops having the maximum dot density that can be expressed on the printing paper. This is because the degree of ink bleeding and back-through varies depending on the type of printing paper, and the maximum dot density that can be expressed differs.

  The output resolution and the maximum ink drop number acquired as described above are input to the input resolution acquisition unit 43. Then, the input resolution acquisition unit 43 acquires the input resolution based on the output resolution and the maximum number of ink drops.

  Specifically, for example, when the output resolution is 300 × 600 dpi and the maximum number of ink drops is 5, the data amount is output resolution × maximum number of ink drops = 300 × 600 × 5 = 900,000. Since 900 × 1200 dpi = 1080000, it is sufficient to achieve smoothing if two-tone raster data is obtained with a resolution of 900 × 1200 dpi, and this input resolution is acquired.

  The input resolution 900 × 1200 dpi acquired as described above is output to the filter size acquisition unit 42 together with the output resolution 300 × 600 dpi. The filter size acquisition unit 42 calculates the greatest common divisor 300 of the input resolution 900 and the output resolution 300 in the main scanning direction, and obtains the greatest common divisor 600 of the input resolution 1200 and the output resolution 600 in the sub scanning direction. Calculated. The input resolution 900 in the main scanning direction is divided by the greatest common divisor 300 in the main scanning direction to obtain the filter size 3 in the main scanning direction. Further, the input resolution 1200 in the sub-scanning direction is divided by the greatest common divisor 600 in the sub-scanning direction to obtain the filter size 2 in the sub-scanning direction. Then, a 3 × 2 filter as shown in FIG. 2 is set. The filter size acquired as described above is output to the RIP resolution acquisition unit 21.

  Here, for example, raster data subjected to smoothing processing using the filter set as described above has pixel values I00, I01, I02, I10, I11, I12, I20, In the case of I21, I22, I30, I31, and I32, conventionally, the pixel values I00, I01, I02, I10, I11, and I12 are referred to by the input reference matrix r1, and the pixel values and the filters are Corresponding oversampling is performed to calculate the output pixel value P00, and then the range of the pixel values I20, I21, I22, I30, I31, and I32 is referred to by the input reference matrix r2, and the pixel values and the filters are associated with each other. In addition, the output pixel value P10 is calculated by oversampling.

  On the other hand, in this embodiment, as shown in FIG. 4, the range of pixel values I00, I01, I02, I10, I11, I12, I20, I21, and I22 is defined as an input reference matrix R, and the input reference matrix R The output pixel value is calculated by referring to the partial pixel values I10, I11, and I12 in the range. Specifically, first, the output pixel value P00 is calculated by associating the pixel values I00, I01, I02, I10, I11, and I12 with the filter and calculating the following equation, and then the pixel values I10, I11. , I12, I20, I21, I22 and the filter are associated with each other and the following expression is calculated to calculate the output pixel value P10. The values of W00, W01, W02, W10, W11, and W12 will be described in detail later.

P00 = (I00 × W00 + I01 × W01 + I02 × W02 + I10 × W10 + I11
× W11 + I12 × W12) / (W00 + W01 + W02 + W10 + W11 +
W12)
P10 = (I10 × W00 + I11 × W01 + I12 × W02 + I20 × W10 + I11
× W11 + I22 × W12) / (W00 + W01 + W02 + W10 + W11 +
W12)
As described above, the same pixel value is referred to redundantly in the sub-scanning direction, so that the RIP resolution in the sub-scanning direction can be calculated as follows.

RIP resolution in the sub scanning direction = size of the input reference matrix R in the sub scanning direction / size of the filter in the sub scanning direction × output resolution in the sub scanning direction = 3/2 × 600 = 900
As described above, the RIP resolution is acquired by the RIP resolution acquisition unit 21, and a resolution of 900 × 900 dpi is output to the RIP processing unit 20. Note that the size of the input reference matrix R in the sub-scanning direction is set in the RIP resolution acquisition unit 21 in advance.

  The RIP processing unit 20 generates R component, G component, and B component raster data by performing RIP processing on the original image data based on the RIP resolution acquired as described above. Note that each pixel data of R data, G component, and B component raster data is, for example, data represented by 8 bits.

  The R component, G component, and B component raster data generated by the RIP processing unit 20 is output to the RGB-CMYK conversion unit 30, and the RGB-CMYK conversion unit 30 outputs the C component, M component, Y component, and K. Converted to component raster data. The pixel data of raster data of C component, M component, Y component, and K component is also data represented by 8 bits, for example.

  The raster data of the C component, M component, Y component, and K component generated by the RGM-CMYK conversion unit 30 is output to the smoothing processing unit 40, and the smoothing processing unit 40 performs the raster processing as described with reference to FIG. Each output pixel value is calculated by associating the data with the filter, and output image data of 300 × 600 dpi is generated.

  Here, how to obtain the filter value used when the smoothing processing unit 40 calculates the output pixel value will be described.

  As described above, in this embodiment, since the RIP resolution is 900 × 900 dpi, the positional relationship between the input reference pixel values I00, I01, I02, I10, I11, I12, I20, I21, and I22 is shown in FIG. The relationship is as shown. In FIG. 5, the position of the input reference pixel is indicated by a black circle.

  Then, the positional relationship between the input reference pixels as shown in FIG. 5 and the position of the output pixel value are associated as shown in FIG. In FIG. 6, the positions of the output pixels P00 and P10 are indicated by crosses.

  Then, the distance in the sub-scanning direction from the input reference pixel to the output pixel is calculated. Specifically, the distances from the input reference pixels I00, I01, I02, I10, I11, and I12 to the output pixel P00 are obtained. The distance from the input reference pixels I00, I01, I02 to the output pixel P00 is 1/3600 = (1/900 + 1/1800) − (1/1200 + 1/1800), and the input reference pixels I10, I11, I12 to the output pixel P00. The distance to is 3/3600.

  Then, as shown in FIG. 7A, the filter value for the output pixel P00 is obtained by normalizing the reciprocal of the distance.

  Similarly to the above, the distances from the input reference pixels I10, I11, I12, I20, I21, and I22 to the output pixel P10 are obtained. The distance from the input reference pixels I10, I11, I12 to the output pixel P10 is 3/3600, and the distance from the input reference pixels I20, I21, I22 to the output pixel P10 is 1/3600.

  Then, the reciprocal of the distance is normalized to obtain a filter value for the output pixel P10 as shown in FIG.

  In the present embodiment, the filter value is obtained by normalizing the reciprocal of the distance between the input reference pixel and the output pixel as described above. However, the present invention is not limited to this. The filter value may be obtained by normalizing the reciprocal of the distance in the sub-scanning direction and / or main scanning direction.

  Then, the filter value calculated as described above is acquired by the filter value acquisition unit 41, the filter value is applied to the filter acquired by the filter size acquisition unit 42, and the filter is output to the smoothing processing unit 40. The

  In the smoothing processing unit 40, the input reference pixel values I00, I01, I02, I10, I11, I12, I20, I21, and I22 are associated with the filters, and the output pixel values P00 and P10 are calculated by calculating the following equations. Is calculated.

P00 = (I00 × 3 + I01 × 3 + I02 × 3 + I10 × 1 + I11 × 1 + I12 ×
2) / (3 + 3 + 3 + 1 + 1 + 1)
P10 = (I10 × 1 + I11 × 1 + I12 × 1 + I20 × 3 + I21 × 3 + I22 ×
3) / (1 + 1 + 1 + 3 + 3 + 3)
Then, by calculating each output pixel value for the raster data of each component as described above, output image data of 300 × 600 dpi is generated for each component.

  The output image data generated for each component as described above is output to the screening processing unit 50. Then, the screening processing unit 50 performs screening processing on the output image data of each component in consideration of the number of gradations selected in advance. As the screening processing, for example, halftone processing or error diffusion processing is performed. Note that the previously selected number of gradations is the number of gradations corresponding to the maximum number of ink drops.

  The screening process is performed so that each dot is expressed by the density of the number of gradations. For example, when the determined number of gradations is 8 gradations, each pixel data of each screened output image data is converted into 3-bit data.

  Then, the screened output image data of each component generated as described above is output to the ink jet recording apparatus 60, and ink is ejected from the recording head of each component based on the screened image output data of each component. The image is recorded on the printing paper. For example, when the screened output image data is data representing 6 gradations, an image is recorded by being ejected from a recording head onto a printing paper with a dot density of 6 gradations from 0 to 5 drops. The operation of image recording in the ink jet recording apparatus will be described in detail later.

  Next, the ink jet recording apparatus 60 in the ink jet recording system will be briefly described.

  As shown in FIG. 8, the inkjet recording apparatus 60 includes a control unit 70 that generates a control signal based on each screened output image data output from the screening processing unit 50, and a control signal from the control unit 70. Ink jet head unit 61 that ejects ink onto printing paper and records an image, paper feeding unit 62 on which the printing paper is placed, and printing paper fed from paper feeding unit 62 are conveyed to ink jet head unit 61. A belt conveying unit 63; a double-sided belt conveying unit 64 for conveying printing paper during double-sided printing; a double-sided stack tray 65 for temporarily discharging printing paper subjected to single-sided printing during double-sided printing; A print sheet on which an image is recorded is discharged by the inkjet head unit 61 while being transported by the transport unit 63. Paper portion 66, and an input touch panel capable 67 a predetermined printing conditions.

  The ink head jet unit 61 includes recording heads 61 </ b> A to 61 </ b> D corresponding to output image data that has undergone screening processing of Y component, M component, C component, and K component.

  The belt conveyance unit 63 is formed of an endless belt having a number of holes in the belt, and adsorbs the printing paper to the belt with negative pressure generated by sucking air from the holes by a suction fan (not shown), It is conveyed in the direction of arrow A.

  The double-sided belt conveyance unit 64 is formed of an endless belt having a plurality of holes formed in the belt, similarly to the belt conveyance unit 63, and conveys printing paper subjected to single-sided printing to the double-sided stack tray 65, The paper is discharged to the double-sided stack tray 65.

  In the double-sided stack tray 65, the single-sided printed printing paper conveyed by the double-sided belt conveyance unit 64 is temporarily placed, and the placed single-sided printed printing paper is placed in the order in which it is placed. By feeding out, the single-side printed printing paper is discharged to the belt conveyance unit 63 so that printing is performed on the back side of the printing paper.

  Next, the operation of the ink jet recording apparatus 60 will be described.

  The printing paper placed on the paper feed unit 62 is sent out to the belt conveyance unit 63, and the belt conveyance unit 63 conveys the printing paper in the direction of arrow A at a predetermined constant conveyance speed to the vicinity of the inkjet head unit 61. Transport. Then, ink is ejected onto the printing paper conveyed by the belt conveyance unit 63 based on the control signal output from the control unit 70 from the recording heads 61A to 61D, and an image is recorded. When performing single-sided printing, the printing paper on which the image is recorded as described above is discharged to the paper discharge unit 66. When performing duplex printing, the single-sided printed paper on which an image has been recorded as described above is held between the roller pair 68 and sent to the conveyance path 69. The single-sided printed printing sheet sent to the conveyance path 69 is further held between the roller pair 70 and conveyed to the double-sided belt conveyance unit 64. The double-sided belt conveyance unit 64 conveys the single-sided printed paper in the direction of arrow B. At this time, the single-sided printed paper is conveyed with the surface on which the image is recorded facing downward. Then, the single-sided printed paper is discharged to the double-sided stack tray 65 with the side on which the image is recorded facing down. Then, the single-sided printed printing sheet discharged to the double-sided stack tray 65 is again fed out from the bottom surface side of the double-sided stack tray 65 to the double-sided belt transport unit 64 by a pickup roller (not shown), and again during the above single-sided printing. An image is recorded on the back side of the printing paper by a similar process. However, when printing on the back side, the image recorded on the front side needs to have the same orientation as that of the image. Therefore, the image is recorded on the basis of the output image data that has been subjected to the rotation process by 180 °. Done.

The block diagram which shows schematic structure of the inkjet recording system using one Embodiment of the image processing apparatus of this invention. Diagram showing filter Diagram for explaining conventional oversampling The figure for demonstrating the smoothing process of the image processing apparatus of this invention The figure which shows the position of the pixel of the raster data of 900x900 dpi The figure which matched the position of the pixel of raster data of 900x900 dpi, and the position of the output pixel of output image data of 300x600 dpi Diagram for explaining how to calculate the filter value Schematic configuration diagram of inkjet recording apparatus The figure which shows the edge part of a character when smoothing processing is not performed (A), The figure which shows the edge part of a character when smoothing processing is performed (B) The figure for demonstrating the conventional smoothing process

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Computer 20 RIP process part 21 RIP resolution acquisition part 30 RGB-CMYK conversion part 40 Smoothing process part 41 Filter value acquisition part 42 Filter size acquisition part 43 Input resolution acquisition part 50 Screening process part 60 Inkjet recording device 61 Inkjet head unit 62 Supply Paper part 63 Belt conveying part 64 Double-sided belt conveying part 65 Double-sided stack tray 66 Paper discharging part 67 Touch panel 68 Roller pair 69 Conveying path 70 Control part

Claims (3)

RIP processing unit that performs RIP processing on original image data at a predetermined resolution to obtain raster data, a filter associated with the raster data acquired by the RIP processing unit, and a pixel value of the raster data in the filter An output image data generation unit that performs a smoothing process by calculating a value of an output pixel based on the output image data and generates output image data having a resolution smaller than the predetermined resolution,
The output image data generation unit associates the filters so that a part of the filter overlaps in the main scanning direction and / or the sub-scanning direction, so that the same pixel of the raster data is used in an overlapping manner. Each value is calculated,
The image processing apparatus, wherein the RIP processing unit performs raster processing on the original image data at a resolution corresponding to the overlap of the filters to obtain raster data.   The image processing apparatus according to claim 1, wherein the filter includes a value calculated by weighting according to the overlap of the filters.   The image processing apparatus according to claim 2, wherein the filter includes a value calculated based on a positional relationship between a pixel position of the raster data and a position of the output pixel.