JP2009296590A - Image processing device and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device and an image processing method reducing data size and allowing to output a high quality image. <P>SOLUTION: The image processing device 1 generates a display list based on an input PDL, calculates a data size when the display list is reversibly compressed and compares the calculated data size with a threshold stored in advance in a storage section 16. The device selects a plane for depicting the display list generated based on a comparison result from first and second image data planes. A reversibly compressing section 14 reversibly compresses an image depicted on the first image data plane. An irreversibly compressing section 14 irreversibly compresses an image depicted on the second image data plane. The device generates and outputs a printed image based on the reversibly and irreversibly compressed images. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus such as a digital multifunction peripheral and an image processing method.

  Conventionally, an image processing apparatus performs rasterization (RIP processing) based on a page description language (PDL) that is print data. The image processing apparatus forms a print image by performing RIP processing. The print image formed by the image processing apparatus by the RIP process has high resolution and a large amount of data. For example, when using a large amount of data in sort printing or the like, the image processing apparatus has a problem that processing takes time. Therefore, conventionally, a method of compressing a print image and storing it in an auxiliary storage device such as a hard disk drive (HDD) is used.

  The print data included in the PDL includes a drawing operator for instructing printing of elements such as characters and figures having a large image quality deterioration when compressed, and sampling elements such as image data having a small image quality deterioration when compressed. A drawing operator for instructing the printing of the image.

  For example, the image forming system described in Patent Document 1 includes a plurality of compression processing units using different methods in advance. The image forming system determines the type of the PDL drawing operator. The image forming system performs high-resolution and low-gradation compression processing on an image generated based on a character / graphic element drawing operator. In addition, the image forming system performs low resolution / high gradation compression processing on an image generated based on a sampling element drawing operator. As a result, the image forming system can suppress the data size of the print image and output smooth characters and graphics at the edge portion.

  However, the above-described image forming system fixes the compression method according to the PDL drawing operator type. For this reason, depending on the print data, there is a possibility that the compression rate is lowered or the image quality is deteriorated. For example, when characters or graphics are included in the image data, there is a problem that the image forming system outputs degraded characters or graphics.

  SUMMARY An advantage of some aspects of the invention is that it provides an image processing apparatus and an image processing method capable of suppressing a data size and outputting a high-quality image.

  An image processing apparatus according to an embodiment of the present invention includes an input unit to which a PDL is input, a display list generation unit that generates a display list based on the PDL input to the input unit, and the display list generation unit. A first image data plane for drawing the generated display list, a second image data plane for drawing the display list generated by the display list generation unit, and the display list generation unit A data size calculation unit for calculating a data size when the display list is subjected to lossless compression, a storage unit for storing a threshold value in advance, a data size calculated by the data size calculation unit, and a threshold value stored in the storage unit And a comparison unit for comparing the comparison unit and the comparison unit based on the comparison result A selection unit for selecting whether to display the display list generated by the display list generation unit on the first image data plane or the second image data plane; and a display list generated on the first image data plane A reversible compression unit that performs reversible compression on the image to be imaged, an irreversible compression unit that performs irreversible compression on an image drawn on the second image data plane, the image compressed by the reversible compression unit, and the A print image generation unit that generates a print image based on the image compressed by the lossy compression unit; and an output unit that outputs the print image generated by the print image generation unit.

  The image processing method according to an embodiment of the present invention generates a display list based on input PDL, calculates a data size when the generated display list is subjected to lossless compression, and calculates the calculation Comparing the data size and the threshold value stored in advance, and selecting a plane for drawing the generated display list based on the comparison result between the first image data plane and the second image data plane, An image rendered on the first image data plane is subjected to lossless compression, an image rendered on the second image data plane is subjected to irreversible compression, and the image compressed by the lossless compression is irreversibly compressed. A print image is generated on the basis of the compressed image and the generated print image is output.

  According to one embodiment of the present invention, it is possible to provide an image processing apparatus and an image processing method capable of suppressing the data size and outputting a high-quality image.

FIG. 1 is a block diagram for explaining a configuration of a printer controller according to an embodiment of the present invention. FIG. 2 is a block diagram for explaining the configuration of the RAM shown in FIG. FIG. 3 is an explanatory diagram for explaining an example of the configuration of the PDL. FIG. 4 is a conceptual diagram for explaining the operation of the printer controller. FIG. 5 is a flowchart for explaining the operation of the printer controller.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram for explaining a configuration example of a printer controller 1 according to an embodiment of the present invention.
The printer controller 1 functions as an image processing apparatus. The printer controller generates a print image based on the PDL received from the host computer 3 and outputs it to the printer engine 2.

  The printer engine 2 includes an image forming unit for printing an image. The image forming unit prints an image on a sheet based on the print image received from the printer controller 1.

  The host computer 3 generates a PDL using, for example, Postscript (registered trademark). The PDL generated by Postscript includes character / graphic element drawing operators such as “show” (for character drawing), “fill” (for area filling), “stroke” (for line drawing drawing), and “imagemask” (for binary mask drawing). And a sampling element drawing operator (for drawing sampling image elements represented by a rectangular array).

  The printer controller 1 includes a CPU 11, a network I / F 12, a RIP processing unit 13, a compression / decompression processing unit 14, a printer I / F 15, a ROM 16, a RAM 17, and an HDD.

  The CPU 11 functions as a control unit that controls the entire printer controller 1. The CPU 11 performs various processes based on the control program and control data stored in the ROM 16 or the HDD 18.

  The network I / F 12 is an interface for connecting to a LAN or a public line. The network I / F 12 functions as an input unit to which PDL is input from the host computer 3.

  The RIP processing unit 13 is an arithmetic processing unit that performs Raster Image Processing (RIP). That is, the RIP processing unit 13 generates an image (raster image) with a predetermined resolution based on each PDL drawing operator.

  The compression / decompression processing unit 14 compresses and decompresses images. The compression / decompression processing unit 14 can perform compression and decompression using a plurality of different compression methods. For example, the compression / decompression processing unit 14 compresses and decompresses data by the LZW method, which is a lossless compression method, or the JPEG method, which is a lossy compression method.

  The printer I / F 15 is an interface for communicating with the printer engine 2. The printer controller 1 functions as an output unit that outputs a print image to the printer engine 2 by the printer I / F.

  The ROM 16 stores a boot program necessary for starting up the system of the printer controller 1, a program executed by the CPU 11, and the like. The ROM 16 stores data used for a program executed by the CPU 11. The ROM 16 stores programs and data at the manufacturing stage. That is, the ROM 16 stores a program and data according to the specifications of the printer controller 1 in advance.

  The RAM 17 is a volatile memory that functions as a working memory. The RAM 17 functions as a work area for the CPU 11. That is, the RAM 17 temporarily stores programs and data processed by the CPU 11.

  The HDD 18 stores various programs and data. The HDD 18 temporarily stores PDL received from the host computer 3. Furthermore, the HDD 18 temporarily stores the print image compressed by the compression / decompression processing unit 14.

  The CPU 11 causes the RIP processing unit 13 to perform RIP processing for each received PDL drawing operator to generate a raster image. In this case, the RIP processing unit 13 generates a raster image (first raster image) for performing lossless compression and a raster image (second raster image) for performing lossy compression separately. Further, when the generated raster images are combined, the RIP processing unit 13 generates layer information for determining which raster image is to be visualized.

  The first and second raster images generated by the RIP processing unit 13 have a resolution of 1200 dpi and are 8-bit data.

  The layer information is information indicating the vertical relationship between the two types of raster images generated by the RIP processing unit 13 for each pixel. The layer information is, for example, data having a resolution of 1200 dpi and 2 bits of data for each pixel.

FIG. 2 is a block diagram for explaining the configuration of the RAM 17 shown in FIG.
The RAM 17 includes a first image data plane 171, a second image data plane 172, and a layer information plane 173.

  The first image data plane 171 is a storage area for storing a first raster image generated by the RIP processing unit 13. The second image data plane 172 is a storage area for storing the second raster image generated by the RIP processing unit 13. The layer information plane 173 is a storage area for storing layer information generated by the RIP processing unit 13.

  The compression / decompression processing unit 14 performs compression processing on the raster image stored in the first image data plane 171 by a lossless compression method. In addition, the compression / decompression processing unit 14 performs compression processing on the raster image stored in the second image data plane 172 by an irreversible compression method. Further, the compression / decompression processing unit 14 performs compression processing on the data stored in the layer information plane 173 by a lossless compression method.

FIG. 3 is an explanatory diagram for explaining an example of the configuration of the PDL.
The PDL includes “print setting / definition of entire job”, “print setting / definition of each page”, “image drawing command group of each page”, “image data of each page”, and the like.

  When receiving PDL from the host computer 3, the CPU 11 performs spooling for temporarily storing the PDL in the HDD 18. The CPU 11 reads the PDL stored in the HDD 18 and inputs it to the RIP processing unit 13. The RIP processing unit 13 performs RIP processing based on the PDL received from the CPU 11.

FIG. 4 is a conceptual diagram for explaining the operation of the printer controller.
The RIP processing unit 13 functions as a display list generation unit. When RIP processing is performed, the RIP processing unit 13 performs drawing based on each drawing operator of the PDL to generate a display list. Based on the control of the CPU 11, the RIP processing unit 13 stores the generated display list in each image data plane, that is, the first image data plane 171 and the second image data plane 172. Further, the RIP processing unit 13 stores the layer information 513 in the layer information plane 173.

  The display list is a format preceding the raster image and is an image drawn based on the PDL. The RIP processing unit 13 draws one or a plurality of display lists in an overlapping manner, converts them into band data of Y (yellow), M (magenta), C (cyan), and Bk (black), and converts the raster image to Generate.

  In this case, the CPU 11 calculates the data size when the display list for each drawing operator generated by the RIP processing unit 13 is compressed by the lossless compression method by calculation. The CPU 11 functions as a data size calculation unit. The ROM 16 functions as a storage unit that stores a data size value as a preset threshold value. The CPU 11 compares the threshold value stored in the ROM 16 with the compressed data size calculated from the display list. The CPU 11 generates plane designation information for designating a plane for drawing the display list based on the comparison result.

  That is, the CPU 11 functions as a selection unit that selects a plane for drawing a display list based on the comparison result between the first image data plane 171 and the second image data plane 172.

  For example, when the compressed data size is less than the threshold, the CPU 11 generates plane designation information for designating the first image data plane 171 and outputs the plane designation information to the RIP processing unit 13.

  When receiving the plane designation information for designating the first image data plane, the RIP processing unit 13 stores the display list 511 in the first image data plane 171.

  For example, when the data size after compression is equal to or greater than the threshold, the CPU 11 generates plane designation information for designating the second image data plane 172 and outputs the plane designation information to the RIP processing unit 13.

  When receiving the plane designation information for designating the second image data plane, the RIP processing unit 13 stores the display list 512 in the second image data plane 172.

  The RIP processing unit 13 converts the display lists drawn on the first image data plane 171 and the second image data plane 172 into YMCK signals, respectively, and acquires a raster image.

  That is, the RIP processing unit 13 converts the display list 511 into the raster image 521. Further, the RIP processing unit 13 converts the display list 512 into a raster image 522. Further, the RIP processing unit 13 converts the layer information 513 into a raster image 523.

  The compression / decompression processing unit 14 performs compression processing on the raster image 521 stored in the first image data plane 171 by a lossless compression method, and generates lossless compression information 531. In addition, the compression / decompression processing unit 14 performs compression processing on the raster image 522 stored in the second image data plane 172 by the lossy compression method, and generates lossy compression information 532. Further, the compression / decompression processing unit 14 performs compression processing on the raster image 523 stored in the layer information plane 173 using a lossless compression method, and generates lossless compression information 533. The CPU 11 stores each data compressed by the compression / decompression processing unit 14 in the HDD 18.

  That is, the compression / decompression processing unit 14 functions as a lossless compression unit that performs lossless compression on the data stored in the first image data plane 171. The compression / decompression processing unit 14 functions as an irreversible compression unit that performs irreversible compression on data stored in the second image data plane 172.

  The CPU 11 reads data stored in the HDD 18 in accordance with the printing order. That is, the CPU 11 reads the lossless compression information 531, the lossy compression information 532, and the lossless compression information 533.

  The CPU 11 decompresses each read data by the compression / decompression processing unit 14. That is, the compression / decompression processing unit 14 decompresses the lossless compression information 531 and acquires the lossless decompression information 541. Further, the compression / decompression processing unit 14 decompresses the lossy compression information 532 and acquires the lossy decompression information 542. Further, the compression / decompression processing unit 14 decompresses the lossless compression information 533 and acquires the lossless decompression information 543.

  The CPU 11 combines the reversible decompression information 541, the irreversible decompression information 542, and the reversible decompression information 543 to generate a print image 555 that can be printed by the printer engine 2. In this case, the CPU 11 functions as a print image generation unit. The CPU 11 outputs the generated print image 555 to the printer engine 2 through the printer I / F 15.

  For example, when lossless compression is performed on a display list that includes a large number of characters and graphics, the data size is reduced. Thus, blurring of the edge portion can be prevented by reversibly compressing the display list having a small size after the reversible compression.

  Further, for example, when a display list having a large size after reversible compression is reversibly compressed, there is a problem that the printing speed is slow. For this reason, in this embodiment, lossy compression processing is performed on a display list having a large size after lossless compression. Thereby, it is possible to prevent the printing speed from being lowered.

  Note that although the CPU 11 has been described as selecting whether to perform lossless compression or lossy compression based on the data size and threshold when the display list is losslessly compressed, the present invention is not limited to this configuration. For example, the structure determined based on the compression rate in lossless compression may be sufficient.

  For example, when the PDL is based on Postscript, the CPU 11 determines the size of the data compressed by the compression filter (for example, DCTDDecode, CCITFaxDecode, RunLengthDecode, etc.) and the width and height of the image when the compression filter is expanded. Calculate the compression ratio based on it.

Further, for example, when the PDL is compressed by ASCII Hex Decode, ASCII 85 Decode, or the like, the CPU 11 calculates the compression ratio by performing lossless compression on the display list actually generated based on the PDL. The CPU 11 functions as a compression rate calculation unit.
In this case, the ROM 16 functions as a storage unit that stores a compression rate value as a preset threshold value. The CPU 11 compares the threshold value stored in the ROM 16 with the compression ratio after compression calculated from the display list. In this case, the CPU 11 functions as a comparison unit. The CPU 11 generates plane designation information for designating a plane for drawing the display list based on the comparison result.

  That is, when the calculated compression rate is less than the threshold value, the CPU 11 generates plane designation information for designating the first image data plane 172 and outputs it to the RIP processing unit 13. If the calculated compression rate is equal to or greater than the threshold, the CPU 11 generates plane designation information for designating the second image data plane 172 and outputs the plane designation information to the RIP processing unit 13.

  Further, the CPU 11 may be configured to select whether to perform lossless compression or lossy compression based on a compression method applied to image data described in PDL. For example, when irreversible compression is performed on the PDL image data, the CPU 11 does not calculate the data size or the compression rate, but compresses the data by irreversible compression, that is, the second image data. The RIP processing unit 13 is controlled to draw the display list on the plane 172.

FIG. 5 is a flowchart for explaining the operation of the printer controller.
When the PDL is received by the network I / F 12 (step S11), the CPU 11 starts processing.

  The CPU 11 performs spooling for temporarily storing the received PDL in the HDD 18 (step S12). The CPU 11 reads the PDL stored in the HDD 18 (step S13) and inputs it to the RIP processing unit 13.

  The RIP processing unit 13 generates a display list for each PDL drawing operator (step S14).

  The CPU 11 calculates the data size when each display list generated by the RIP processing unit 13 is compressed by the lossless compression method (step S15).

  The CPU 11 compares the threshold value stored in advance in the ROM 16 with the compressed data size calculated from the display list (step S16).

  If the data size after compression is less than the threshold, the CPU 11 selects the first image data plane 171, generates plane designation information that designates the first image data plane 171, and outputs the plane designation information to the RIP processing unit 13. (Step S17).

  When receiving the plane designation information for designating the first image data plane 171, the RIP processing unit 13 stores the display list 511 in the first image data plane 171. The RIP processing unit 13 converts the display list 511 stored in the first image data plane 171 to generate a raster image 521 (step S18).

  The compression / decompression processing unit 14 performs compression processing on the raster image 521 stored in the first image data plane 171 by the lossless compression method, and generates lossless compression information 531 (step S19).

  If the compressed data size is equal to or larger than the threshold value in step S16, the CPU 11 selects the second image data plane 172, generates plane designation information for designating the second image data plane 172, and RIP The data is output to the processing unit 13 (step S20).

  When receiving the plane designation information for designating the second image data plane 172, the RIP processing unit 13 stores the display list 512 in the second image data plane 172. The RIP processing unit 13 converts the display list 512 stored in the second image data plane 172 to generate a raster image 522 (step S21).

  The compression / decompression processing unit 14 performs compression processing on the raster image 522 stored in the second image data plane 172 by the lossy compression method, and generates lossy compression information 532 (step S22).

  The CPU 11 stores each data compressed by the compression / decompression processing unit 14 in the HDD 18 (step S23).

  Further, the CPU 11 reads out data stored in the HDD 18 in accordance with the printing order, performs decompression processing, and combines the decompressed data to generate a print image 555. The CPU 11 outputs the generated print image 555 to the printer engine 2 through the printer I / F 15 and ends the process.

  As described above, the printer controller 1 according to the present embodiment selects a raster image compressed by the lossless compression method and a raster image compressed by the lossy compression method based on the data size after the lossless compression processing or the compression rate. To do. Thereby, the printer controller 1 can perform the compression process by a compression method suitable for an image to be actually drawn regardless of the operator type of the PDL.

  As a result, it is possible to provide an image processing apparatus and an image processing method capable of reducing the data size and outputting a high-quality image.

  In addition, this invention is not limited to the said embodiment as it is, It can implement by changing a component in the range which does not deviate from the summary in an implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

  For example, the printer controller 1 may further include hardware for calculating a data size or a compression rate. In this case, the data size or the compression rate can be calculated in parallel with the processing of the CPU 11 and the RIP processing unit 13. Thereby, a reduction in processing speed can be prevented.

  Further, according to the above-described embodiment, the data drawn on the second image data plane 172 is less likely to include characters or graphics. For example, the data size of the print image 555 can be suppressed by setting the resolution of the first image data plane 171 to 1200 dpi and the resolution of the second image data plane 172 to 600 dpi.

  That is, by setting the resolution of the display list 512 to be drawn on the second image data plane 172 smaller than the resolution of the display list 511 to be drawn on the first image data plane 171, the data of the final print image 555 is set. The size can be reduced.

  Thereby, even if the resolution of the printer increases in the future, a print image that can be processed efficiently can be generated by appropriately selecting the resolution.

  In the above-described embodiment, the PDL is described as being described by Postscript. However, the present invention is not limited to this. For example, the same processing can be performed even in a PDF format, an XPS format, or another PDL language.

  In the above-described embodiment, the ROM 16 is described as storing the threshold value in advance, but the present invention is not limited to this. For example, a configuration may be adopted in which a storage area for storing a threshold value is provided in the HDD 18 and the threshold value is appropriately set based on data input by the network I / F 12 or the like. For example, by setting the threshold value high, it is possible to increase the number of raster images to be processed by the lossless compression method. However, in this case, the data size of the final print image 555 also increases. For this reason, the user can adjust the balance between processing time and fineness by setting a threshold value.

  DESCRIPTION OF SYMBOLS 1 ... Printer controller, 2 ... Printer engine, 3 ... Host computer, 11 ... CPU, 12 ... Network I / F, 13 ... RIP processing part, 14 ... Compression / decompression processing part, 15 ... Printer I / F, 16 ... ROM, 17 ... RAM, 18 ... HDD, 171 ... first image data plane, 172 ... second image data plane, 173 ... layer information plane.

JP 2000-184205 A

Claims (10)

An input unit for inputting PDL;
A display list generation unit that generates a display list based on the PDL input to the input unit;
A first image data plane for drawing a display list generated by the display list generation unit;
A second image data plane for rendering the display list generated by the display list generation unit;
A data size calculation unit that calculates a data size when reversible compression is performed on the display list generated by the display list generation unit;
A storage unit for storing a threshold value in advance;
A comparison unit that compares the data size calculated by the data size calculation unit with a threshold value stored in the storage unit;
A selection unit that selects whether to display the display list generated by the display list generation unit on the first image data plane or the second image data plane based on the comparison result of the comparison unit;
A reversible compression unit that performs reversible compression on an image drawn on the first image data plane;
An irreversible compression unit that performs irreversible compression on an image drawn on the second image data plane;
A print image generation unit that generates a print image based on the image compressed by the lossless compression unit and the image compressed by the lossy compression unit;
An output unit that outputs the print image generated by the print image generation unit;
An image processing apparatus comprising:   The selection unit draws the display list generated by the display list generation unit when the data size calculated by the data size calculation unit is less than a threshold stored in the storage unit in the comparison result of the comparison unit. The image processing apparatus according to claim 1, wherein the first image data plane is selected as a plane.   The selection unit draws the display list generated by the display list generation unit when the data size calculated by the data size calculation unit in the comparison result of the comparison unit is equal to or larger than a threshold stored in the storage unit. The image processing apparatus according to claim 1, wherein the second image data plane is selected as a plane.   When the display list generated by the display list generation unit includes irreversibly compressed image data, the selection unit generates the second image as a plane for drawing the display list generated by the display list generation unit. The image processing apparatus according to claim 1, wherein a data plane is selected. An input unit for inputting PDL;
A display list generation unit that generates a display list based on the PDL input to the input unit;
A first image data plane for drawing a display list generated by the display list generation unit;
A second image data plane for rendering the display list generated by the display list generation unit;
A compression rate calculation unit that calculates a compression rate when reversible compression is performed on the display list generated by the display list generation unit;
A storage unit for storing a threshold value in advance;
A comparison unit that compares the compression rate calculated by the compression rate calculation unit with a threshold value stored in the storage unit;
A selection unit that selects whether to display the display list generated by the display list generation unit on the first image data plane or the second image data plane based on the comparison result of the comparison unit;
A reversible compression unit that performs reversible compression on an image drawn on the first image data plane;
An irreversible compression unit that performs irreversible compression on an image drawn on the second image data plane;
A print image generation unit that generates a print image based on the image compressed by the lossless compression unit and the image compressed by the lossy compression unit;
An output unit that outputs the print image generated by the print image generation unit;
An image processing apparatus comprising:   The selection unit draws the display list generated by the display list generation unit when the compression rate calculated by the compression rate calculation unit in the comparison result of the comparison unit is less than a threshold stored in the storage unit. The image processing apparatus according to claim 5, wherein the first image data plane is selected as a plane.   The selection unit draws the display list generated by the display list generation unit when the compression rate calculated by the compression rate calculation unit in the comparison result of the comparison unit is equal to or greater than a threshold stored in the storage unit. The image processing apparatus according to claim 5, wherein the second image data plane is selected as a plane.   When the display list generated by the display list generation unit includes irreversibly compressed image data, the selection unit generates the second image as a plane for drawing the display list generated by the display list generation unit. 6. The image processing apparatus according to claim 5, wherein a data plane is selected. Generate a display list based on the input PDL,
Calculate the data size when lossless compression is applied to the generated display list,
Comparing the calculated data size with a threshold stored in advance,
A plane for drawing the generated display list based on the comparison result is selected between the first image data plane and the second image data plane,
Performing lossless compression on the image rendered on the first image data plane;
Irreversible compression is performed on the image drawn on the second image data plane;
Generate a print image based on an image compressed by lossless compression and an image compressed by lossy compression,
Outputting the generated print image;
An image processing method. Generate a display list based on the input PDL,
Calculating the compression ratio when the generated display list is subjected to lossless compression;
Comparing the calculated compression rate with a threshold stored in advance,
A plane for drawing the generated display list based on the comparison result is selected between the first image data plane and the second image data plane,
Performing lossless compression on the image rendered on the first image data plane;
Irreversible compression is performed on the image drawn on the second image data plane;
Generate a print image based on an image compressed by lossless compression and an image compressed by lossy compression,
Outputting the generated print image;
An image processing method.

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