JP6613732B2 - Image processing apparatus and image processing program - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing program.

  Patent Document 1 discloses an unnecessary area extracting unit that extracts an unnecessary area that is not necessary as an image from an original image, and an unnecessary area removing unit that removes the unnecessary area extracted by the unnecessary area extracting unit from the original image. And an image processing apparatus that compresses the original image from which the unnecessary area has been removed.

  In Patent Document 2, in an image encoding method for encoding a plurality of regions extracted from an image, an area detection step for obtaining the area of each of the extracted regions, and the top N regions having the largest areas A determination step of determining the extraction region as an encoding target region and determining a remaining region other than the encoding target region as a non-extraction region, and using the shape and the representative value of the signal in the region as the encoding target region A region image encoding stage that encodes by applying the first encoding method, and an out-of-extraction region in which the non-extraction region is encoded using a second encoding method different from the first encoding method. An image coding method characterized by comprising a region coding step is disclosed.

  Patent Document 3 discloses rasterizing means for rasterizing image data to be printed to a certain resolution, compression means for compressing image data rasterized by the means, and a compression code as a compression result by the means. An image forming apparatus having a storage means for storing in a compression memory, comprising: a plurality of types of compression means as the compression means; and a compression selection means for selecting a compression means according to a certain condition. Is disclosed.

JP 2004-229096 A JP 2000-197046 A JP-A-9-102879

  When transferring image data that exceeds the bandwidth of the communication line, the image data is generally compressed and converted into image data that is equal to or less than the bandwidth of the communication line. Image data compressed at a high compression rate is efficient for transferring image data over a communication line, but if it takes too much time to decompress the image data at the transfer destination, the newly compressed image data is It cannot be accepted at the forwarding destination. As a result, the transfer start of the newly compressed image data is awaited, and as a result, the effective transfer rate of the communication line is lowered.

  In an image forming apparatus that forms an image on a recording medium such as paper based on image data after expansion processing, once the image forming process is started, the image forming speed (recording medium conveyance speed) in the image forming unit is increased. The drawing process must continue to be executed in time, but if the effective transfer rate of image data decreases, the drawing process may not be able to keep up with the image forming speed.

  The present invention provides an image processing apparatus and an image processing program capable of suppressing a reduction in the effective transfer rate of image formation data as compared with a case where all image formation data is compressed unconditionally. With the goal.

According to the first aspect of the present invention, there is a dividing means for dividing the image represented by the image forming data into a plurality of division units, and the compression priority is high until the compression degree of the divided data of the plurality of division units achieves the required compression degree. Compression means for sequentially compressing the divided data , wherein the dividing means divides a plurality of page images included in the image into divided data of a plurality of division units, and the compression means includes the page image. Each time, the degree of compression of the divided data of the plurality of division units is the first transfer speed of the communication line for transferring the compressed data compressed by the compression means, and the image represented by the image forming data is recorded on the recording medium. The page calculated from the second requested transfer rate calculated from the image forming conditions at the time of forming, the reference required compression level calculated from the page rate, and the compression level of the page image compressed in the past Until achieving the required degree of compression of the image, the compression priority compressing the divided data in the descending order.

  The invention according to claim 2 sets the compression priority for each of the divided data of the plurality of division units from a compression cost calculated from a feature amount representing a feature of an image element included in an image represented by the divided data. Setting means is provided.

  According to a third aspect of the present invention, the feature amount is an area of a region where the image element included in the image represented by the divided data is drawn or a data amount of the image element.

  According to a fourth aspect of the present invention, the setting means calculates the compression cost from a coefficient determined for each feature amount and each type of the image element.

  According to a fifth aspect of the present invention, the setting unit updates the coefficient based on a degree of compression when the divided data including the image element is compressed in the past.

  According to a sixth aspect of the present invention, the divided data is represented by data obtained by dividing the image represented by the image formation data for each color component, data obtained by dividing the image represented by the image formation data for each region, and the image formation data. One of the data obtained by dividing the image for each image element.

According to a seventh aspect of the present invention, the compressed data obtained by compressing the divided data and the non-compressed non-compressed data of the divided data are processed in the order of processing when the image represented by the image forming data is formed on a recording medium. And control means for controlling the uncompressed data to be output to a communication line.

In the invention according to claim 8, the compression means compresses the divided data by lossless compression.

The invention of claim 9 is an image processing program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 8 .

According to the first and ninth aspects of the present invention, the effective transfer rate of the image forming data is suppressed from being reduced as compared with the case where all of the image forming data is compressed unconditionally. Compared to the case of compressing in units, it is possible to suppress compressing more than necessary.

  According to the second aspect of the present invention, it is possible to set the compression priority with higher accuracy than in the case where the compression priority is set from the feature amount representing the feature other than the image element included in the image represented by the divided data.

  According to the invention of claim 3, compared with the case where the compression priority is set from the feature amount other than the area of the image element drawn in the image represented by the divided data and the data amount of the image element, Compression priority can be set with high accuracy.

  According to the fourth aspect of the present invention, it is possible to set the compression priority with high accuracy as compared with the case where the compression cost is calculated regardless of the type of the image element.

  According to the fifth aspect of the present invention, it is possible to set the compression priority with higher accuracy than when the coefficient is fixed.

  According to the sixth aspect of the present invention, it is possible to easily divide the image forming data as compared with the case where the image forming data is divided in units other than each color component, each region, and each image element.

According to the invention of claim 7 , compared with the case where the compressed data and the uncompressed data are output to the communication line without being rearranged in the processing order when the image represented by the image forming data is formed on the recording medium There is no need to rearrange the compressed data and the uncompressed data in the processing order.

According to the invention described in claim 8 , the image quality can be maintained as compared with the case where the divided data is compressed by irreversible compression.

1 is a schematic configuration diagram illustrating a configuration of an image processing apparatus according to a first embodiment. It is a flowchart which shows an example of the flow of a process of the image processing program which concerns on 1st Embodiment. It is a figure for demonstrating the compression priority based on 1st Embodiment. It is a schematic block diagram which shows the structure of the image processing apparatus which concerns on 2nd Embodiment. It is a flowchart which shows an example of the flow of a process of the image processing program which concerns on 2nd Embodiment. It is a figure for demonstrating the compression priority based on 2nd Embodiment. It is a flowchart which shows an example of the flow of a process of the image processing program which concerns on 3rd Embodiment. It is a figure for demonstrating the compression priority based on 3rd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  (First embodiment)

  First, the configuration of the image processing apparatus 10 according to the present embodiment will be described with reference to FIG. The image processing apparatus 10 includes a data input unit 12, a raster generation unit 14 as an example of a dividing unit, a requested compression rate calculation unit 16, a data compression unit 18 as an example of a compression unit, and a DRP control unit 20. The image processing apparatus 10 is connected to the DRP 22 via a bus 23 as an example of a communication line. In FIG. 1, solid arrows indicate the flow of various data, and broken arrows indicate the flow of various parameters.

  The data input unit 12 inputs print data as an example of image formation data instructed to print and print conditions as an example of image formation conditions, outputs the print data 24 to the raster generation unit 14, and sets the print conditions. The requested compression rate calculation unit 16 outputs the result.

  The print data 24 is PDL data described in a page description language (PDL) as an example in the present embodiment. Hereinafter, the print data 24 is referred to as PDL data 24.

  The printing conditions are conditions relating to the page size and printing performance of a recording medium such as paper on which an image represented by the PDL data 24 is printed. Here, the page size is represented by, for example, the number of pixels in the width direction and the length direction of the recording medium. The printing performance is the performance of an image forming apparatus (not shown) that is an output destination of data processed by the image processing apparatus 10. The image forming apparatus is an apparatus that forms an image on a recording medium by, for example, a so-called electrophotographic method. Specifically, the image forming apparatus includes a charging device for charging the photosensitive drum, and an electrostatic charge corresponding to the image on the photosensitive drum by exposing the charged photosensitive drum with light corresponding to the image. An exposure device that forms a latent image, a developing device that develops toner on an electrostatic latent image formed on a photosensitive drum, a transfer device that transfers a toner image formed on a photosensitive drum to a recording medium, and a transfer to a recording medium And a fixing device for fixing the toner image. Note that an ink jet recording apparatus may be used as the image forming apparatus. In this case, the image forming apparatus includes an inkjet recording head that discharges ink onto a recording medium according to an image.

  Therefore, in the case of the image forming apparatus as described above, the performance of the image forming apparatus includes the number of colors of toner or ink used for forming an image on a recording medium, resolution, printing speed, and the like. For example, if the color of the toner or ink used is C (cyan), M (magenta), Y (yellow), or K (black), the number of colors is four. In the present embodiment, a description will be given of a case where the output destination of the data processed by the image processing apparatus 10 is an image forming apparatus that forms an image on a recording medium based on CMYK four color component data. Further, the resolution is represented by, for example, dpi (dot per inch). The printing speed is represented by, for example, PPM (Page Per Minute) indicating the number of printable sheets per minute.

  The raster generation unit 14 interprets the PDL data 24 input from the data input unit 12 and generates raster data 26 that is bitmap data for each color component. Note that when generating raster data from the PDL data 24, compression priority is given to the raster data 26 for each color component based on object information regarding an object as an example of an image element included in the image represented by the PDL data 24. Set. Then, the raster generation unit 14 outputs the set compression priority order to the data compression unit 18. The object information includes information such as the type of object and the area of the object. Examples of object types include, but are not limited to, images and graphics.

  Although the details will be described later, the required compression rate calculation unit 16 performs compression based on the printing conditions input from the data input unit 12, that is, the page size and printing performance, and the compression rate of the pages compressed by the data compression unit 18 in the past. The requested compression rate of the target page is calculated and output to the data compression unit 18.

  The data compression unit 18 compresses the raster data 26 of each color according to the compression priority set by the raster generation unit 14 until the requested compression rate calculated by the requested compression rate calculation unit 16 is satisfied for the page to be compressed. Processes are executed sequentially. The raster data 26 of each color is compressed from the raster data 26 of a color that can be expected to have a high compression rate, and the raster data 26 of the remaining colors is not compressed when the required compression rate is satisfied. Thus, it is possible to suppress spending more time than necessary for the decompression process. As a result, it is possible to prevent the DRP 22 from being in a state where the decompression process is in a standby state and being unable to transfer data, and the effective transfer rate of the bus 23 is prevented from decreasing. In the present embodiment, the compression processing is performed by reversible compression as an example. This embodiment is a method for compressing an image without degrading it, and a method in which the compression rate cannot be known without actually performing compression processing, that is, the amount of data after compression depends on the content of data to be compressed. A reversible compression of an indefinite length code compression system which is a different system is used. Examples of lossless compression include, but are not limited to, LZH, ZIP, CAB, PNG, GIF, and the like. Not only the lossless compression but also the irreversible compression, the irreversible compression may be used as long as it is not a fixed length code compression method but an indefinite length code compression method.

  For the compressed color component, the data compression unit 18 outputs compressed data 28 obtained by compressing the raster data 26 of the color component to the DRP control unit 20, and for the uncompressed color component, the uncompressed raster component. Data 26 is output to the DRP control unit 20. Further, the data compression unit 18 calculates a compression rate from the result of the compression process, and outputs the calculated compression rate to the requested compression rate calculation unit 16.

  The DRP control unit 20 outputs the compressed data 28 and the raster data 26 input from the data compression unit 18 to the DRP 22 to request image processing (color conversion processing, brightness adjustment processing, screen processing, etc.), and the compressed data For 28, in addition to a request for image processing, a request for decompression processing is output to the DRP 22.

  The DRP 22 is a dynamically reconfigurable processor, and in accordance with an instruction from the DRP control unit 20, the above-described image processing (color conversion processing, brightness adjustment processing, screen processing, etc.) and decompression of the compressed data 28 are performed. Execute processing etc.

  The image processing apparatus 10 may be configured by a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a nonvolatile memory. In this case, the CPU reads and executes the image processing program stored in the ROM. The image processing program may be provided by being recorded on a storage medium such as a CD-ROM, or may be provided by a network.

  Next, image processing executed by the image processing apparatus 10 will be described as an operation of the present embodiment. The processing shown in FIG. 2 is a flowchart showing the flow of image processing executed by the image processing apparatus 10. This image processing is executed when printing is instructed by the user, for example, and print data and printing conditions are input to the image processing apparatus 10.

  In step S <b> 100, the data input unit 12 outputs the print data out of the input print data and print conditions to the raster generation unit 14, and outputs the print conditions to the requested compression rate calculation unit 16.

  In step S <b> 102, the required compression rate calculation unit 16 calculates the reference required compression rate of the PDL data 24. The reference required compression rate is calculated from the printing condition input from the data input unit 12, the transfer rate A as the first transfer rate predetermined by the standard of the bus 23 connecting the DRP control unit 20 and the DRP 22. It is calculated by dividing by the transfer rate B as the second transfer rate. The transfer speed B is a transfer speed required when data is transferred from the DRP control unit 20 to the DRP 22 without compression when printing is performed under the printing conditions input from the data input unit 12.

  For example, when the page size of the image represented by the PDL data 24 is 20 × 12 inches, the number of colors used for printing is four colors of CMYK, the resolution is 1200 dpi, and the printing speed is 300 ppm, the DRP control unit 20 The transfer rate B required when data is transferred from the DRP 22 to the DRP 22 without compression is 6.4 GB / sec. On the other hand, if the transfer rate A of the bus 23 connecting the DRP control unit 20 and the DRP 22 is 4.0 GB / sec, the reference required compression rate is 4.0 / 6.4 = 0.625 ( 62.5%).

  In step S104, the raster generation unit 14 initializes a counter n for counting the number of pages of the image represented by the PDL data 24 to 1.

  In step S106, the raster generation unit 14 interprets the PDL data 24 and generates raster data 26 of the nth page for each color of CMYK. Further, when interpreting the PDL data 24, the compression priority is set based on the type of object included in the nth page image represented by the PDL data 24, the feature amount, and the coefficient determined for each type of object. In this embodiment, a predetermined value is used as the coefficient.

  For example, a case will be described in which the CMYK color images on the nth page are images 30C, 30M, 30Y, and 30K as shown in FIG.

  Note that the types of objects include, for example, graphics images and image images. The graphics image is an image such as a text character, for example, and the image image is an image such as a photograph. Note that the types of objects are not limited to these.

  In the present embodiment, the area of the object is used as the feature amount of the object. For example, the cyan image 30C includes an object 32C whose object type is an image. In this case, the area of the rectangular area 34C surrounding the object 32C is defined as an area S1c of the object 32C. For example, in FIG. 3, if the range of the rectangular area 34C in the X direction is x = (xc1, xc2), the range of the rectangular area 34C in the Y direction is y = (yc1, yc2), and the upper left corner of the image is the origin, The area of the rectangular region 34C is calculated by (xc2-xc1) × (yc2-yc1). The area of the rectangular region 34C is defined as an area S1c of the object 32C. The area S1m of the object 32M included in the magenta image 30M and the area S1k of the object 32K included in the black image 30K are also calculated in the same manner as the area S1c of the object 32C included in the cyan image 30C. The black image 30K includes an object 36K whose type of object is graphics. For this object 36K as well, the area of a rectangular region surrounding the object 36K is calculated, and this is taken as the area S2k of the object 36K. That's fine.

  Then, the area S1x of the image object included in the image, the coefficient of the image object K1 is set, the area S2x of the graphic object included in the image is set to K2, and the coefficient of the graphics object is K2, and the compression cost Fx is calculated by calculate. When an image includes a plurality of image objects, the area S1x is a value obtained by adding the areas of the plurality of image objects. Similarly, when the image includes a plurality of graphics objects, the area S2x is a value obtained by adding the areas of the plurality of graphics objects.

Fx = S1x × K1 + S2x × K2 (1)

  However, x is a code | symbol showing each color, and is either c, m, y, or k in the example of FIG.

  Here, the compression cost Fx corresponds to the time required for the compression process. The higher the compression cost Fx, the larger the data size after compression, and the longer the time required for the compression process. As a result, the time required for the decompression processing of the compressed data also becomes longer. In addition, for example, an object of an image such as a natural image is generally lower in compression rate than a graphic object such as a character or a figure, and it is expected that the compression rate becomes lower as the area of such an object increases. . That is, as shown in the above equation (1), the larger the area of the image or graphics object included in the image, the longer the time required for the compression process, the lower the compression rate, and the higher the compression cost Fx.

  Therefore, the compression priority is set higher as the compression cost Fx is lower, and the compression priority is set lower as the compression cost Fx is higher.

  For example, in the case of FIG. 3, when the coefficient K1 of the image object is set to 0.05 and the coefficient K2 of the graphics object is set to 0.01, the area S1c of the object 32C and the image 30M included in the image 30C. If the area S1m of the object 32M included in each is 1 million pixels, the compression cost Fc of the image 30C and the compression cost Fm of the image 30M are 50,000 from the above equation (1).

  Further, since no object is included in the image 30Y, the compression cost Fy is 0 from the above equation (1).

  If the area S1k of the image object 32K included in the image 30K is 1 million pixels and the area S2k of the graphics object 36K is 800,000 pixels, the compression cost Fk of the image 30K is 5 from the above equation (1). 80,000.

  Accordingly, since the compression relationship between the images is Fy <Fc = Fm <Fk, the compression priority is in the order of decreasing compression cost, that is, image 30Y> image 30C = image 30M> image 30K.

  In step S <b> 108, the required compression rate calculation unit 16 calculates the required compression rate of the nth page raster data and outputs it to the data compression unit 18. The required compression rate is calculated from the reference required compression rate calculated in step S102 and the compression rate of the previously compressed page. Specifically, the reference required compression rate is C1, the average compression rate from the first page compressed in the past to the (n−1) th page is C2, and the required compression rate C3 of the nth page is calculated by the following equation. calculate.

C3 = (C1 × n) − {C2 × (n−1)} (2)

  For example, when n = 11 and the reference required compression rate C1 is 62.5% and the average value C2 of the compression rates from the first page to the tenth page is 60.0%, the required compression of the nth page The rate C3 is 87.5% from the above equation (2).

  In step S110, the data compression unit 18 selects and compresses the raster data 26 of the color component having the highest compression priority set in step S106 from the raster data 26 of the unprocessed color component of the nth page. .

  In step S112, the data compression unit 18 calculates the compression rate of the nth page based on the result of the compression process of step S110, and outputs the calculated compression rate of the nth page to the requested compression rate calculation unit 16. The compression rate of the n-th page is the total value of the data size of the compressed data 28 after compression of the color compressed at this time, the total value of the data size of the raster data 26 of the uncompressed color at this time, Is divided by the total value of the data sizes of the raster data 26 of each color before compression. Specifically, for example, when the image of page n is subjected to compression processing in the order of image 30Y, image 30C, image 30M, and image 30K according to the compression priority order, before image 30Y, image 30C, image 30M, and image 30K are compressed. Are respectively D1y, D1c, D1m, and D1k. If the compressed data amounts of the images 30Y and 30C at the time when the compression processing of the images 30Y and 30C is finished are D2y and D2c, respectively, the images 30M and 30K are uncompressed at this time, so the nth page is compressed. The rate is calculated by (D2y + D2c + D1m + D1k) / (D1y + D1c + D1m + D1k).

  In step S114, the data compression unit 18 determines whether or not the compression ratio calculated in step S112 has achieved the requested compression ratio calculated in step S108, that is, the compression ratio calculated in step S112 is the request calculated in step S108. It is determined whether or not the compression rate is below. If the determination in step S114 is affirmative, the process proceeds to step S118. If the determination in step S114 is a negative determination, the process proceeds to step S116. As described above, if the raster data 26 of all the color components is not compressed unconditionally, but the compression rate calculated in step S112 is less than or equal to the required compression rate calculated in step S108, the remaining uncompressed remaining data The compression process of the color raster data 26 is skipped.

  In step S116, the data compression unit 18 determines whether or not the compression process has been completed for raster data of all colors. If the determination is affirmative, the process proceeds to step S118. On the other hand, if the determination in step S116 is negative, the process returns to step S110, and the same processing as described above is executed for the raster data 26 of the color having the next highest compression priority.

  In step S118, the data compression unit 18 determines whether or not the above-described compression processing has been completed for all pages. If the determination is affirmative, the process proceeds to step S122. If the determination is negative, the process proceeds to step S120. .

  In step S120, the data compression unit 18 increments n by one and proceeds to step S106, and executes the same processing as described above for the next page.

  In step S122, the data compression unit 18 outputs the compressed data 28 for the color obtained by compressing the raster data 26, and the raster data 26 for the color obtained by compressing the raster data 26 to the DRP control unit 20, respectively. In addition, the data compression unit 18 outputs compressed / uncompressed information regarding the color obtained by compressing the raster data 26 and the color obtained by compressing the raster data 26 to the DRP control unit 20.

  In step S 124, the DRP control unit 20 outputs data including at least one of the compressed data 28 and the raster data 26 input from the data compression unit 18 to the DRP 22. At this time, control is performed so that the compressed data 28 and the raster data 26 are output to the bus 23 in the processing order when the image represented by the PDL data 24 is formed on the recording medium. In addition, the DRP control unit 20 instructs the DRP 22 to execute decompression processing and image processing on the compressed data 28 and to execute only image processing on the uncompressed raster data 26.

  As a result, the DRP 22 executes the image processing after performing the decompression process on the compressed data 28, executes only the image process on the uncompressed raster data 26, and prints the image-processed data (not shown). Output to the device. Thereby, an image is printed on a recording medium such as paper.

  As described above, in the present embodiment, the raster data 26 of all colors is not compressed unconditionally, but when the compression rate of the compressed page is equal to or lower than the required compression rate of the page, the remaining The compression process of the color raster data 26 is skipped. For this reason, the raster data 26 is compressed more than necessary, and it is suppressed that the effective transfer rate when the data is transferred from the DRP control unit 20 to the DRP 22 due to the time required for the decompression process in the DRP 22 is reduced. The

  In the present embodiment, the case where compression processing is performed for each of the CMYK four color components has been described. However, if there is a spot color component other than CMYK in the image represented by the PDL data 24, the raster data of the spot color component is subject to compression. May be included. If tag data having attribute information of each pixel exists, the tag data may be included in the compression target.

  (Second Embodiment)

  Next, a second embodiment of the present invention will be described. FIG. 4 shows a block diagram of the image processing apparatus 40 according to the second embodiment. The same parts as those of the image processing apparatus 10 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, the image processing apparatus 40 has the same device configuration as the image processing apparatus 10 of FIG. 1, but the processes of the raster generation unit 14 and the data compression unit 18 are different.

  The raster generation unit 14 interprets the PDL data 24 input from the data input unit 12 and generates band raster data 27 that is bitmap data obtained by dividing the image represented by the PDL data 24 for each band (for each region). Note that, when generating the band raster data 27 from the PDL data 24, a compression priority order is set for each band raster data 27 based on the object information regarding the object included in the image represented by the PDL data 24. Then, the raster generation unit 14 outputs the set compression priority order to the data compression unit 18.

  The data compression unit 18 performs band raster data 27 of each band according to the compression priority set by the raster generation unit 14 until the requested compression rate calculated by the requested compression rate calculation unit 16 is satisfied for the page to be compressed. The band compression data 29 is generated and output to the DRP control unit 20.

  Next, image processing executed by the image processing apparatus 40 will be described as an operation of the present embodiment. The processing shown in FIG. 5 is a flowchart showing the flow of processing of an image processing program executed by the image processing device 40. Note that steps for executing the same processing as the image processing in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Steps S100 to S104 are the same as those in FIG.

  In step S106A, the raster generation unit 14 interprets the PDL data 24 and generates band raster data 27 for each band image obtained by dividing the n-th page image. Further, when interpreting the PDL data 24, the compression priority is set based on the type of object included in the nth page image represented by the PDL data 24, the feature amount, and the coefficient determined for each type of object.

  For example, a case where the image on page n is an image 50 as shown in FIG. 6 will be described. In the present embodiment, for example, the image 50 is divided into three in the Y direction, which is the vertical direction of the image 50, to be band images 50-1 to 50-3. The dividing method is not limited to the method shown in FIG. For example, the number of divisions is not limited to three and may be an arbitrary number of divisions of two or more. Moreover, you may divide | segment into the X direction orthogonal to a Y direction. Moreover, you may divide | segment into both the X direction and the Y direction so that a division area may become tile shape. Furthermore, in the example of FIG. 6, the band images 50-1 to 50-3 are divided so that the sizes are uniform, but may be divided so that the sizes of the bands are not uniform.

  As shown in FIG. 6, an image 50 includes objects 52A and 52B whose object type is an image, and an object 54 whose object type is graphics. The object 52A is disposed across the band images 50-1 to 50-2. The object 52B is arranged in the band image 50-3. The object 54 is disposed across the band images 50-2 to 50-3.

  In this case, as in the first embodiment, the area of the rectangular area surrounding each object is the area of each object. The compression cost is calculated by the following equation, where the area S1y of the image object included in each band image, the coefficient of the image object K1 is the area S2y of the graphic object included in the image, and the coefficient of the graphic object is K2. Fy is calculated. When a plurality of image objects are included in the band, the area S1y is a value obtained by adding the areas of the plurality of image objects. Similarly, in the case where the area S2y includes a plurality of graphics objects, the area S2y is a value obtained by adding the areas of the plurality of graphics objects.

Fy = S1y × K1 + S2y × K2 (2)

  However, y is a code | symbol showing each band image, and is either 1-3 in the example of FIG.

  Similar to the first embodiment, the compression cost Fy corresponds to the time required for the compression process. The higher the compression cost Fx, the longer the time required for the compression process and the longer the time required for the decompression process. That is, as shown in the above equation (2), the larger the area of the image or graphics object included in the band image, the longer the time required for the compression process, the lower the compression rate, and the higher the compression cost Fy.

  Therefore, the compression priority is set higher as the compression cost Fy is lower, and the compression priority is set lower as the compression cost Fy is higher.

  For example, in the case of FIG. 6, when the coefficient K1 of the image object is set to 0.05 and the coefficient K2 of the graphics object is set to 0.01, the area S11 of the object 52A included in the band image 50-1. Is 700,000 pixels, the compression cost F1 of the band image 50-1 is 35,000 from the above equation (2).

  If the area S12 of the object 52A included in the band image 50-2 is 300,000 pixels and the area S22 of the object 54 included in the band image 50-2 is 600,000 pixels, the compression cost F2 of the band image 50-2 Is 21,000 from the above equation (2).

  If the area S13 of the object 52B included in the band image 50-3 is 1 million pixels and the area S23 of the object 54 included in the band image 50-3 is 1 million pixels, the compression cost F3 of the band image 50-3 is as follows. Is 60,000 from the above equation (2).

  Therefore, since the magnitude relationship of the compression cost of each band image is F2 <F1 <F3, the compression priority is in the order of low compression cost, that is, band image 50-2> band image 50-1> band image 50-. 3

  Step S108 is the same as that shown in FIG.

  In step S110A, the data compression unit 18 selects and compresses the band raster data 27 of the band image having the highest priority set in step S106A among the unprocessed band images of the nth page.

  Steps S112 to S114 are the same as those in FIG. In this way, if the band raster data 27 of all band images is not compressed unconditionally, but the compression rate calculated in step S112 is less than or equal to the required compression rate calculated in step S108, the uncompressed remaining The compression processing of the band raster data 27 of the band image is skipped.

  In step S116A, the data compression unit 18 determines whether or not the compression process has been completed for the band raster data 27 of all band images. If the determination is affirmative, the process proceeds to step S118. On the other hand, if the determination in step S116A is negative, the process returns to step S110A, and the same processing as described above is performed on the band raster data 27 of the band image having the next highest compression priority.

  Steps S118 to S124 execute processing in which “color” is replaced with “band image”, and the processing is the same as in FIG.

  As described above, in this embodiment, the band raster data 27 of all band images is not compressed unconditionally, but the compression rate of the page compressed for each band image is equal to or lower than the required compression rate of the page. If this is the case, the compression processing of the band raster data 27 of the remaining uncompressed band image is skipped. For this reason, it is suppressed that the band raster data 27 is compressed more than necessary, and the effective transfer rate at the time of data transfer from the DRP control unit 20 to the DRP 22 is reduced due to excessive time required for the decompression process in the DRP 22. Is done.

  In the present embodiment, the case where the image 50 illustrated in FIG. 6 is equally divided in the Y direction has been described. However, the image 50 may be divided for each object. In this case, as shown in FIG. 6, the object 52A, the object 52B, the object, and other areas are divided.

  (Third embodiment)

  Next, a third embodiment of the present invention will be described. In the third embodiment, a mode in which a coefficient determined for each type of object is updated will be described. Note that the image processing apparatus according to the present embodiment is the same as the image processing apparatus 40 described in the second embodiment, and thus detailed description thereof is omitted.

  Next, image processing executed by the image processing apparatus 40 will be described as an operation of the present embodiment. The processing shown in FIG. 7 is a flowchart showing the flow of processing of an image processing program executed by the image processing device 40. Note that the image processing shown in FIG. 7 differs from the image processing shown in FIG. 5 in that step S105 is added, and the other steps are the same as those in FIG. To do.

  In step S105, the coefficient determined for each object type is updated based on the compression ratio of the page compressed in the past.

  For example, in the case of variable printing in which a form is the same but is printed with different contents, it may be divided into a form object that is standard data and a variable object that is non-standard data. Since the form object is likely to be an object that is repeatedly used, the coefficient set for the type of the form object is updated based on the compression ratio when the page including the form object is compressed in the past. Thereby, the compression priority is set with high accuracy.

  In the present embodiment, for example, as shown in FIG. 8, a case where the image of the (n-1) th page is an image 60 as shown in FIG. In the present embodiment, the image 60 is equally divided in the Y direction in FIG. 8 to be band images 60-1 to 60-3, respectively.

  As shown in FIG. 8, an image 60 includes variable objects 62A and 62B in which the object type is an image and atypical data, a variable object 64 in which the object type is graphics and atypical data, It includes a form object 66 whose type is graphics and fixed data. The form object 66 is disposed across the band images 60-1 to 60-2. The variable object 62A is arranged in the band image 60-1, the variable object 62B is arranged in the band image 60-3, and the variable object 64 is arranged in the band image 60-2. .

  Then, similarly to the second embodiment, the compression cost Fy of each band image is calculated by the above equation (2).

  For example, in the case of FIG. 8, when the coefficient K1 of the image object is set to 0.05 and the coefficient K2 of the graphics object is set to 0.01, the area of the variable object 62A included in the band image 60-1 Is 640,000 pixels, and the area of the form object 64 included in the band image 60-1 is 2.25 million pixels, the compression cost F1 of the band image 60-1 is 54.50,000 according to the above equation (2).

  Also, assuming that the area of the variable object 64 included in the band image 60-2 is 1.6 million pixels and the area of the form object 66 included in the band image 60-2 is 3.75 million pixels, the compression cost F2 of the band image 60-2. Is 5350,000 from the above equation (2).

  If the area of the object 62B included in the band image 60-3 is 1 million pixels, the compression cost F3 of the band image 60-3 is 50,000 according to the above equation (2).

  Therefore, since the compression relationship of the compression cost of each band image of the (n−1) page is F3 <F2 <F1, the compression priority of the (n−1) page is in order of decreasing compression cost, that is, Band image 60-3> band image 60-2> band image 60-1.

  The (n-1) -th page image is compressed in the order of the band image 60-3 and the band image 60-2, and the band image 60-3 is not compressed. It is also assumed that the image on the nth page is the same as the image 60 on the (n−1) th page. In this case, a correction value for updating the coefficient of the form object 66 among the graphics objects is calculated as follows.

  First, the ratio x of the area of the form object 66 to the entire area of the band image 60-2 including the form object 66 is calculated.

  Next, a ratio y (= F2 / F3) of the compression cost F2 of the band image 60-2 to the compression cost F3 of the band image 60-3 of the (n-1) th page calculated in step S106A of FIG. 7 is calculated. . The ratio y uses the compression cost of the band image with the higher compression priority as the denominator.

  Next, the ratio z (= A2 / A3) of the compression rate A2 of the band image 60-2 to the compression rate A3 of the band image 60-3 when the (n-1) th page is compressed in step S110A of FIG. ) Is calculated. The ratio z uses the compression rate of the band image with the higher compression priority as the denominator. Then, the correction value M is calculated by the following equation.

M = 1− (z−y) × x (3)

  When calculating the compression costs F2 and F3 of the band images 60-2 and 60-3 including the n-th form object 66 in step S106A of FIG. 7, the coefficient K2 to be multiplied by the area of the form object 66 is calculated. By multiplying the correction value M, the coefficient K2 for the form object 66 is updated.

  For example, the ratio x of the area of the form object 66 to the entire area of the band image 60-2 including the form object 66 is 0.7, and the compression cost F3 of the band image 60-3 of the (n-1) th page. The ratio y of the compression cost F2 of the band image 60-2 is 1.07 (= 5350,000 / 50,000), and the compression rate A3 of the band image 60-3 when the compression processing is performed for the (n-1) th page. When the compression rate A2 of the band image 60-2 is 0.33 (ratio z = F2 / F3 = 0.85), M = 0.84 from the above equation (3). As a result, the coefficient K2 after being corrected by the correction value M becomes 0.084 and is corrected downward.

  As a result, the compression cost F1 of the band image 60-1 including the form object 66 is also corrected downward to “51006”, and the compression cost F2 of the band image 60-2 is “47677”. Further, since the band image 60-3 does not include the form object 66, the compression cost F3 remains 50,000. Therefore, the compression priority order is band image 60-2, band image 60-3, and band image 60-1. That is, the compression priority order of the band image 60-2 and the band image 60-3 is reversed as compared with the compression priority order of the (n-1) th page. This is because the compression cost of the band image 60-2 is the compression cost of the band image 60-3 based on the result of the actual compression processing of the band image 60-2 and the band image 60-3 on page (n-1). It is because it is lower than.

  In this way, since the coefficient determined for each type of object is updated from the compression result of the past band image, the compression priority is set with high accuracy.

  When all of the band images 60-1 to 60-3 are compressed, for example, correction values M are calculated for all combinations of two band images selected from the three band images, and the average value thereof is calculated. The correction value M may be used.

  The correction value M may be calculated and overwritten every time a band image including a form object is compressed.

  Although the embodiment has been described above, the technical scope of the present invention is not limited to the scope described in the embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which the changes or improvements are added are also included in the technical scope of the present invention.

  For example, in the above embodiment, the case where the raster data 26 is divided for each color component or each band image has been described. However, intermediate data is generated from the raster data 26, and the generated intermediate data is generated for each color component and each band image. You may make it divide | segment. Here, the intermediate data is data in a format in which bitmap data is generated in a shorter processing time compared to the case where bitmap data is directly generated from print data described in PDL.

  In the above-described embodiment, the case where the compression priority is set using the area of the object as the feature amount of the object has been described. However, the present invention is not limited to this, and compression priority is given using the data amount of the intermediate data as the feature amount of the object. A ranking may be set.

  Moreover, although the said embodiment demonstrated the case where a compression rate was used as an example of a compression degree, it is not restricted to this, Other compression degrees, such as a compression ratio and the difference of the data before compression, and the data after compression, are shown. You may use what you represent.

  Moreover, although the said embodiment demonstrated the case where there was one DRP22, you may provide multiple DRP22.

  In the above embodiment, the case where the image processing program is preinstalled in the ROM has been described. However, the present invention is not limited to this. For example, the image processing program may be provided by being stored in a storage medium such as a CD-ROM (Compact Disk Read Only Memory) or provided via a network.

  In addition, the configuration of the image processing apparatuses 10 and 40 described in the above embodiment (see FIGS. 1 and 4) is merely an example, and unnecessary portions may be deleted or newly added without departing from the gist of the present invention. Needless to say, you can add parts.

  The processing flow of the image processing program described in the above embodiment (see FIGS. 2, 5, and 7) is also an example, and unnecessary steps can be deleted or new ones can be used without departing from the gist of the present invention. It goes without saying that steps may be added or the processing order may be changed.

DESCRIPTION OF SYMBOLS 10, 40 Image processing apparatus 12 Data input part 14 Raster generation part 16 Request compression ratio calculation part 18 Data compression part 20 DRP control part 23 Bus 24 PDL data 26 Raster data 27 Band raster data 28 Compression data 29 Band compression data 30C, 30K , 30M, 30Y, 50 Images 32C, 32K, 32M, 32C, 36K, 52A, 52B, 54 Object 34C Rectangular area 50-1 to 50-3 Band image

Claims (9)

Dividing means for dividing the image represented by the image formation data into a plurality of division units;
Compression means for compressing the divided data in descending order of compression priority until the compression degree of the divided data of the plurality of division units achieves the required compression degree;
Equipped with a,
The dividing unit divides the data into a plurality of divided data for each of a plurality of page images included in the image,
For each page image, the compression unit includes a first transfer rate of a communication line for transferring the compressed data compressed by the compression unit, and a compression rate of the divided data of the plurality of division units. Calculated from the second transfer speed calculated from the image forming conditions when forming the image represented on the recording medium, the reference required compression degree calculated from the above, and the compression degree of the page image compressed in the past An image processing apparatus that compresses the divided data in descending order of compression priority until the required compression level of a page image is achieved . The setting means for setting the compression priority for each of the divided data of the plurality of division units, based on a compression cost calculated from a feature amount representing a feature of an image element included in an image represented by the divided data. The image processing apparatus according to 1. The image processing apparatus according to claim 2, wherein the feature amount is an area of a region where the image element included in the image represented by the divided data is drawn or a data amount of the image element. The image processing apparatus according to claim 2, wherein the setting unit calculates the compression cost from a coefficient determined for each type of the feature amount and the image element. The image processing apparatus according to claim 4, wherein the setting unit updates the coefficient based on a degree of compression when the divided data including the image element is compressed in the past. The divided data includes data obtained by dividing the image represented by the image formation data for each color component, data obtained by dividing the image represented by the image formation data for each area, and the image represented by the image formation data for each image element. The image processing apparatus according to any one of claims 1 to 5, wherein the image processing apparatus is any one of the processed data. Compressed data obtained by compressing the divided data and non-compressed non-compressed data of the divided data are communicated between the compressed data and the non-compressed data in the order of processing when the image represented by the image formation data is formed on a recording medium The image processing apparatus according to any one of claims 1 to 6 , further comprising a control unit that performs control so that the signal is output to a line. It said compression means, the image processing apparatus according to any one of claim 1 to 7, compressing the divided data by the lossless compression. The image processing program for a computer to function as each means of the image processing apparatus according to any one of claims 1-8.