JP2010211559A - Image processor, image processing method, and computer program for image processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate reduction in data quantity of raster data. <P>SOLUTION: An image processor creates raster data showing a result of drawing an object according to input data including the drawing instruction of the object. The image processor creates a color table for encoding the color of each pixel in the raster data by using codes corresponding to the number of colors to be used for drawing the object on the basis of the drawing instruction in creating the raster data, and creates the raster data in which the color of each pixel is encoded by referring to the color table. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rasterization technique for creating raster data from input data including an object drawing command.

  When printing a document created with a computer document creation application with a printer, the printer driver specifies data representing various objects such as characters, graphics, and photographs by specifying gradation values (colors) in pixel units. Rasterization is performed to convert the data into raster data representing. This rasterization is usually performed by expanding a rendering command included in page description language (PDL) data representing the contents of the object and the arrangement of the object on the page into raster data. In a printer that accepts PDL data, rasterization is performed in the printer.

  In such rasterization, band processing for performing rasterization by dividing raster data into a plurality of bands is performed in order to reduce the memory capacity for holding the developed raster data (for example, patent literature). 1).

JP-A-8-230249 JP 11-232468 A

  When rasterizing is performed by band processing, an object drawing command (command data) necessary for each band is developed. Therefore, if the amount of raster data increases and the raster data is divided into more bands, the number of objects that span multiple bands increases, and the overhead of expansion that expands the same drawing command multiple times increases. To do. Even when a sufficient memory capacity can be secured as in a computer, when the amount of raster data increases, the amount of data transmitted from the computer to the printer increases, and the time required for printing increases.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a technique for more easily reducing the amount of raster data.

  In order to solve at least a part of the above problems, the present invention can be realized as the following forms or application examples.

[Application Example 1]
An image processing apparatus for generating raster data representing a drawing result of an object based on input data including an object drawing command, and for drawing the object based on the drawing command A color table creating unit that creates a color table for encoding the color of each pixel in the raster data using a code corresponding to the number of colors, and the instruction expansion unit refers to the color table to each pixel Image processing apparatus for creating raster data in which the color of each is encoded.

  By encoding the color of each pixel in the raster data using a code corresponding to the number of colors used for drawing the object, the data amount of the raster data can be more easily reduced.

[Application Example 2]
The image processing apparatus according to Application Example 1, wherein the input data includes a first type of rendering command corresponding to the first type of object and a second type of image representation format different from that of the first type of object. A second type of rendering command corresponding to the object, and the command expansion unit has a high resolution in which the color of each pixel is encoded when the rendering command is the first type of rendering command. An image processing apparatus that creates raster data and creates low-resolution raster data in which the color of each pixel is not encoded in the case of the second type of rendering command.

  According to this application example, the data amount of the high resolution raster data can be reduced by encoding the color of each pixel with respect to the high resolution raster data. In addition, for low resolution raster data that originally has a small amount of data, the overhead required for encoding can be reduced by not encoding the color of each pixel.

[Application Example 3]
An image processing apparatus according to Application Example 2,
The instruction development unit is an image processing apparatus that creates the high resolution raster data by dividing it into a plurality of drawing bands, and creates the entire low resolution raster data at a time.

  According to this application example, by creating the high resolution raster data by dividing it into a plurality of drawing bands, the memory capacity for holding the created raster data can be reduced. For low-resolution raster data that originally has a small amount of data, by creating the entire raster data at once, the development overhead associated with the creation of low-resolution raster data can be eliminated.

[Application Example 4]
4. The image processing apparatus according to Application Example 2 or 3, wherein the first type object is a vector object, and the second type object is a raster object.

  In general, a vector object has a small number of colors, and the amount of data can be more efficiently reduced by encoding the color of each pixel.

[Application Example 5]
The image processing apparatus according to any one of Application Examples 2 to 4, further comprising: a transmission unit that transmits the raster data, wherein the transmission unit receives the low-resolution raster data before transmitting the high-resolution raster data. An image processing device for transmission.

  According to this application example, since the low-resolution raster data is transmitted before the high-resolution raster data is transmitted, the low-resolution raster data and the high-resolution raster data are received from the reception side that receives the high-resolution and low-resolution raster data. Processing such as color conversion and halftone processing can be performed sequentially. Therefore, the processing on the receiving side can be speeded up as compared with the case where high resolution raster data is transmitted prior to transmission of low resolution raster data.

[Application Example 6]
The image processing apparatus according to application example 1, wherein the instruction expansion unit generates the raster data by dividing the raster data into a plurality of drawing bands.

  By creating raster data by dividing it into a plurality of drawing bands, the memory capacity for holding the created raster data can be reduced.

[Application Example 7]
The image processing apparatus according to application example 1, wherein the instruction expansion unit creates the entire raster data at a time.

  By encoding the color of each pixel of the raster data, the data amount of the created raster data can be reduced. Therefore, even if the entire raster data is created at once, an increase in memory capacity for holding the created raster data can be suppressed. Further, by creating the entire raster data at a time, it is possible to eliminate the development overhead.

  The present invention can be realized in various modes. For example, an image processing apparatus and a control method and an image processing method thereof, and an image printing apparatus to which the image processing apparatus and the control method and image processing method are applied. And image printing method, or printing system including the image processing apparatus, computer program for realizing the apparatus, system and method, computer-readable medium storing the computer program, and including the computer program in a carrier wave It can be realized in the form of an embodied data signal or the like.

1 is a schematic configuration diagram illustrating a configuration of an image printing system according to a first embodiment. Explanatory drawing which shows a mode that raster data are produced from PDL data. Explanatory drawing which shows the relationship between the object drawn and a bandwidth. Explanatory drawing which shows an example of the PDL data used as the object of a rasterize process. Explanatory drawing which shows the correspondence of a unit band and a drawing command. Explanatory drawing which shows the color table produced with respect to the bit depth determined for every unit band, and a unit band. Explanatory drawing which shows the drawing band set. FIG. 4 is an explanatory diagram showing a state where a drawing command is developed for the drawing band 2. FIG. 5 is a schematic configuration diagram illustrating a configuration of an image printing system according to a second embodiment. Explanatory drawing which shows a mode that raster data is produced from PDL data in 2nd Example. Explanatory drawing which shows a mode that the drawing command of PDL data is matched with the unit band of high resolution raster data, and low resolution raster data. It is a schematic block diagram which shows the structure of the image printing system 10b in the modification of the high resolution raster data creation method.

Hereinafter, modes for carrying out the present invention will be described based on examples.
A. First embodiment:
A1. Image printing system:
FIG. 1 is a schematic configuration diagram illustrating a configuration of an image printing system 10 according to the first embodiment. The image printing system 10 is configured by connecting a computer 100 and a printing apparatus 200 via a transmission line TL. The computer 100 creates raster data from page description language (PDL) data created by the computer 100 itself or PDL data input from the outside to the computer 100. Here, “raster data” refers to data representing an image by designating a gradation value (color) in units of pixels. The created raster data is transmitted from the computer 100 to the printing apparatus 200 via the transmission path TL. The printing apparatus 200 prints an image on a print medium in accordance with raster data transmitted from the computer 100. As the transmission line TL, various data communication paths such as a USB cable and a wired or wireless network can be employed.

  The computer 100 includes a CPU 110, a RAM 120, a hard disk drive (HDD) 130, and a transmission interface 140. CPU 110 transfers the program code stored in HDD 130 or ROM (not shown) to RAM 120 and executes the program code transferred to RAM 120. Thus, the CPU 110 realizes functions as the instruction analysis unit 510, the drawing band setting unit 520, the instruction expansion unit 530, and the data transmission unit 540. The drawing band setting unit 520 has functions of a color table creation unit 522 and a bandwidth determination unit 524. In the RAM 120, a command memory 610, a band memory 620, a color table memory 630, and a development memory 640 used as a temporary memory of the instruction development unit 530 are secured as data storage areas. The transmission interface 140 is a connection interface with the transmission line TL. The configuration and function of each processing unit realized by the CPU 110 and the contents of data stored in each data storage area secured in the RAM 120 will be described later.

  The printing apparatus 200 includes a data reception unit 210, a print data creation unit 220, a printer control unit 230, and a printing unit 240. The data receiving unit 210 is a connection interface with the transmission line TL. The print data creation unit 220 performs processing such as color conversion and halftone processing on the raster data transmitted via the data reception unit 210 to create print data to be supplied to the print unit 240. The printer control unit 230 controls the printing unit 240. The printing unit 240 is a printing mechanism that executes printing according to print data. As the printing mechanism, various printing mechanisms such as a printing mechanism that forms an image by ejecting ink droplets onto a printing medium and a printing mechanism that forms an image by transferring and fixing toner onto the printing medium may be employed. it can. Thus, since the printing apparatus 200 performs printing based on the raster data generated in the computer 100, the printing apparatus 200 can also be referred to as “a printing unit that performs printing based on the raster data”.

  The configuration of the image printing system is not limited to the configuration shown in FIG. 1, and various configurations can be employed. For example, some of the elements of the computer 100 may be provided in the printing apparatus 200, and some of the elements of the printing apparatus 200 may be provided in the computer 100. Specifically, the computer 100 can be provided with a print data creation unit 220 that creates print data. In this case, the printing unit 240 of the printing apparatus 200 executes printing according to the print data supplied from the computer 100. Thus, since the printing unit 240 performs printing according to the print data created based on the raster data, the printing unit 240 can also be referred to as “a printing unit that performs printing based on the raster data”.

  In the first embodiment, an example of the image printing system 10 having the computer 100 and the printing apparatus 200 as separate apparatuses is shown, but the computer 100 and the printing apparatus 200 are not necessarily separate apparatuses. It can also be integrated into one device.

A2. Process overview:
FIG. 2 is an explanatory diagram showing how raster data is created from PDL data. The PDL data is created by a document creation application running on the computer 100, for example. The PDL data may be input to the computer 100 from the outside. As PDL data, various PDL-compliant data such as PostScript (trademark of Adobe Systems) can be used. The PDL data is expanded (rasterized) by the functions of the instruction analysis unit 510, the drawing band setting unit 520, and the instruction expansion unit 530 realized by the CPU 110, and raster data for one page is created. In addition, raster data is created from PDL data by the function of each of the processing units 510, 520, and 530. For this reason, the processing units 510 to 530 can be collectively referred to as an image processing apparatus that outputs raster data in accordance with input PDL data.

  As shown in FIG. 2, the PDL data is a list including N (N is an integer of 1 or more) drawing commands and a termination command indicating the end of the PDL data. Each drawing command represents one object to be drawn. The drawing command can represent various objects having different image representation formats. Objects can be classified into, for example, vector objects that represent characters and figures by designating the shape of lines and contours on the page, and raster objects that represent photographs and the like by designating colors for each pixel.

  In the example of FIG. 2, the PDL data includes N drawing commands, and the raster data includes N objects corresponding to the N drawing commands by executing expansion in accordance with the drawing commands. Be expanded. In FIG. 2, for convenience of illustration, illustration of objects corresponding to the drawing command 4 to the drawing command N-1 is omitted.

  In the first embodiment, raster data is created for each partial region (band) extending in the horizontal direction on the page. Specifically, the drawing command is expanded to the band memory 620 (FIG. 1). The raster data created for each band is transmitted to the printing apparatus by the data transmission unit 540 together with a color table described later.

  In the first embodiment, raster data is created for each band. When this band width is reduced, the size of raster data created at one time is reduced, and the memory capacity allocated to the band memory 620 can be reduced. On the other hand, the number of divisions of raster data increases. Since drawing commands for objects that span multiple bands are developed separately for each band, if the number of raster data divisions increases, the overhead of development for repeatedly developing the same drawing command increases. On the other hand, when the bandwidth is increased, the number of divisions is reduced and the development overhead is reduced, but the size of raster data created at one time is increased, and the memory capacity allocated to the band memory 620 is increased.

  Therefore, in the first embodiment, the number of colors after development is obtained based on the drawing command, and the bandwidth is determined according to the number of colors. Thus, for an area where the number of colors is small and the number of bits per pixel (bit depth) can be reduced, by reducing the bit depth, an increase in the memory capacity allocated to the band memory 620 is suppressed, The bandwidth can be increased.

  FIG. 3 is an explanatory diagram showing the relationship between the drawn object and the bandwidth. In the example of FIG. 3, three objects of a photograph, a multicolor character, and a black character are drawn. In the band A where the photograph is developed, since a large number of colors are required, the band width is set small. On the other hand, the band width is set larger than that of the band A in the band B in which multicolor characters having fewer colors than the photograph are developed. The band C in which black characters having a smaller number of colors are drawn is set to have a larger bandwidth than the band B. In this way, by determining the bandwidth according to the number of colors, it is possible to suppress an increase in development overhead accompanying an increase in the number of divisions of raster data while suppressing an increase in memory capacity allocated to the band memory 620. it can.

A3. Rasterize processing:
FIG. 4 is an explanatory diagram showing an example of PDL data to be subjected to rasterization processing. The PDL data shown in FIG. 4 includes N drawing commands. In FIG. 4, illustration of the termination instruction included in the PDL data is omitted. By rasterizing the PDL data, an object corresponding to each drawing command is developed in one page of raster data. In the example of FIG. 4, seven objects OB1 to OB7 corresponding to the drawing commands 1 to 7 are expanded on the raster data.

  In the first embodiment, an area obtained by dividing the entire page with a certain width is handled as a basic unit of band (unit band). In the example of FIG. 4, raster data for one page is divided into M unit bands. In the following description, each of these M unit bands is identified with reference numerals # 1 to #M.

  In the unit bands # 1 and # 2, objects OB1 and OB2 corresponding to the rendering commands 1 and 2 are expanded. A gradation is applied to the colors of these objects OB1 and OB2. Therefore, the number of colors of the unit bands # 1 and # 2 is 200 colors including the two objects OB1 and OB2 and the background. In the unit bands # 3 and # 4, objects OB3 and OB4 corresponding to the drawing commands 3 and 4 are expanded. In the objects OB3 and OB4, different colors are assigned to individual characters. Therefore, the number of colors of the unit bands # 3 and # 4 is 10 colors including the two objects OB3 and OB4 and the background. Similarly, the numbers of colors of the unit bands # 5, # 6, and # 7 are 10,000 colors, 256 colors, and 100,000 colors, respectively.

  The PDL data is first processed in the instruction analysis unit 510 (FIG. 1). The command analysis unit 510 analyzes the drawing command included in the PDL data, associates the drawing command with each unit band, and stores information about the correspondence between the unit band and the drawing command in the command memory 610.

  The drawing command included in the PDL data includes information related to the drawing position and size of the object. The drawing command includes, for example, the drawing start position of the object as information on the drawing position. As information on the size of an object, for example, a raster object drawing command such as a photograph includes a size after rasterization, and a character drawing command includes a font size.

  The instruction analysis unit 510 acquires the arrangement in the page of the object drawn by each drawing command based on the information regarding the drawing position and size of the object included in the drawing command in this way. Then, a drawing command used to create raster data of each unit band is specified from the acquired object arrangement, and information about the correspondence between the unit band and the drawing command is stored in the command memory 610.

  FIG. 5 is an explanatory diagram showing the correspondence between unit bands and drawing commands for the PDL data shown in FIG. As described above, the objects OB1 and OB2 corresponding to the rendering commands 1 and 2 are arranged across the unit bands # 1 and # 2. Therefore, the unit bands # 1 and # 2 are associated with two drawing commands (drawing commands 1 and 2), respectively. The objects OB3 and OB4 corresponding to the drawing commands 3 and 4 are arranged across the unit bands # 3 and # 4. Therefore, the unit bands # 3 and # 4 are associated with two drawing commands (drawing commands 3 and 4), respectively. Similarly, unit band # 5 is associated with drawing commands 5 and 6, unit band # 6 is associated with drawing command 6, and unit band # 7 is associated with drawing command 7.

  After association of the unit band and the drawing command by the command analysis unit 510, the drawing band setting unit 520 sets a drawing band for developing the drawing command at a time. In the first embodiment, the basic unit of the drawing band is a unit band. Therefore, the drawing band is set as a bundle of continuous unit bands.

  The color table creation unit 522 of the drawing band setting unit 520 calculates the number of colors used for each unit band from a drawing command associated with each unit band with reference to the command memory. For the calculation of the number of colors, information on the color of the object included in the drawing command is used. As information about colors, for example, a character drawing command includes character color designation information, and a graphic drawing command includes graphic color designation information. The color table creation unit 522 calculates the number of colors used for the vector object based on the color designation information. In addition, for a rendering command for a raster object such as a photograph, the color table creation unit 522 calculates the number of colors by analyzing an image embedded in the rendering command.

  When the raster object specifies the color of each pixel with the index color as in the GIF format image, the number of colors specified with the index color can be used as the number of colors of the raster object. It is. Further, when the raster object can express the number of colors equal to or greater than a predetermined threshold, such as an image in JPEG or TIFF format, the number of colors equal to or greater than a predetermined value (for example, 65537 colors) is analyzed without analyzing the image. It is also possible to handle it as having it. In these cases, it is preferable to calculate the number of colors by analyzing an image in that processing required for image analysis can be omitted.

The color table creation unit 522 determines the bit depth necessary for each unit band after calculating the number of colors for each unit band. In the first embodiment, the bit depth is determined according to the following table.

  Next, the color table creation unit 522 creates a color table for each unit band and stores it in the color table memory 630. FIG. 6 is an explanatory diagram showing the bit depth determined for each unit band and the color table created for the unit bands # 5 and # 6 for the PDL data shown in FIG.

  The number of colors used for the unit bands # 1 and # 2 is 200 colors as shown in FIG. Therefore, the bit depth of unit bands # 1 and # 2 is set to 8 bits. Similarly, the bit depth of unit bands # 3 and # 4 is 4 bits, the bit depth of unit band # 5 is 16 bits, the bit depth of unit band # 6 is 8 bits, and the bit depth of unit band # 7 is Set to 24 bits. As shown in FIG. 6, the color table of unit band # 5 has a hexadecimal 4-digit code and the color associated with each code, that is, red (R), green (G), and blue (B). It is expressed as a gradation value. The color table of unit band # 6 is represented as a hexadecimal two-digit code and RGB gradation values associated with each code. The color table memory 630 stores the bit depth of each unit band in addition to the color table shown in FIG.

  After the color table creation by the color table creation unit 522 (FIG. 1), the bandwidth determination unit 524 determines the width of the drawing band, that is, the number of unit bands included in the drawing band. As will be described later, the rasterized pixel color of each unit band is encoded using the code of the color table stored in the color table memory 630. Therefore, the amount of data when rasterizing a unit band is calculated using the bit depth. Therefore, the bandwidth determination unit 524 refers to the bit depth of each unit band in order from the top, so that the unit in which the sum of the data amounts of the unit bands included in the drawing band does not exceed the capacity of the band memory 620 is collected. Determine the maximum number of bands (ie, bandwidth). The drawing band setting unit 520 collects the unit bands in order from the top based on the bandwidth (number of unit bands) determined in this way, and sets the drawing band.

  FIG. 7 is an explanatory diagram showing a drawing band set for the PDL data shown in FIG. In the first embodiment, the band memory 620 is secured so that a unit band having a bit depth of 24 bits can be stored. Therefore, unit bands are grouped so that the sum of bit depths is 24 bits or less, and a drawing band is set. In the example of FIG. 7, the drawing band 1 includes four unit bands # 1 to # 4, and the drawing band 2 includes two unit bands # 5 and # 6.

  After the drawing band is set by the drawing band setting unit 520, the command expanding unit 530 expands the drawing command for each drawing band. FIG. 8 is an explanatory diagram showing how a drawing command is developed for the drawing band 2. First, as shown in FIG. 8, the instruction expansion unit 530, based on the correspondence between the drawing band and the unit band set by the drawing band setting unit 520, two unit bands # 5 and # 5 corresponding to the drawing band 2. Specify # 6. Next, drawing commands 5 and 6 used for rasterizing unit bands # 5 and # 6 are specified based on the correspondence between the unit bands stored in the command memory 610 and the drawing commands. Then, the rendering commands 5 and 6 are developed for the unit bands # 5 and # 6, and the raster data of the unit band # 5 and the raster data of the unit band # 6 are stored in the band memory 620. At this time, the instruction expansion unit 530 refers to the color tables of the unit bands # 5 and # 6 stored in the color table memory 630 and encodes the color of each pixel of the raster data. When the bit depth is set to 24 bits, each pixel of the raster data can represent the RGB gradation value as it is, and therefore encoding is not performed. Specifically, when a raster object that can express the number of colors equal to or greater than a predetermined threshold is included, such as an image in JPEG or TIFF format, the bit depth is set to 24 bits. Not done.

  The raster data created for each drawing band is transmitted to the printing apparatus 200 by the data transmission unit 540 together with the color table of the unit band included in each drawing band, and printing is performed in the printing apparatus 200.

  As described above, in the first embodiment, the bit depth is determined based on the number of colors of the unit band, and the drawing band is set so as to include more unit bands based on the bit depth. Therefore, an increase in the memory capacity allocated to the band memory 620 can be suppressed, and the development overhead associated with an increase in the number of divisions of raster data for one page can be reduced. In addition, by encoding the color of each pixel in the raster data, the amount of data transmitted from the computer 100 to the printing apparatus 200 can be reduced.

B. Second embodiment:
FIG. 9 is a schematic configuration diagram showing the configuration of the image printing system 10a of the second embodiment. The image printing system 10a of the second embodiment is different from the image printing system 10 of the first embodiment in the configuration of a computer 100a. Specifically, the high resolution raster data creation unit 560 includes a low resolution raster data creation unit 550 as a processing unit realized by the CPU 110, and a drawing band setting unit 520 and an instruction expansion unit 530. The instruction analysis unit 510 is replaced with an instruction analysis unit 510a having a different function, the low resolution page memory 650 is secured in the RAM 120, and the band memory 620 is replaced with the high resolution band memory 620a. This is different from the first embodiment. Other points are the same as in the first embodiment.

  FIG. 10 is an explanatory diagram showing how raster data is created from PDL data in the second embodiment. The upper diagram of FIG. 10 shows the creation of raster data in the first embodiment, and is the same diagram as FIG. In the second embodiment, as shown on the lower side of FIG. 10, high resolution raster data and low resolution raster data are created from PDL data.

  The high-resolution raster data is created for an object that can be refined by suppressing jaggies by increasing the resolution. On the other hand, the low resolution raster data is created for an object whose effect of improving the image quality is difficult to understand even when the resolution is increased. Specifically, high resolution raster data is created for vector objects such as characters and figures, and low resolution raster data is created for raster objects such as photos and illustrations. The generated high resolution raster data and low resolution raster data are combined in the print data generation unit 220 of the printing apparatus 200 (FIG. 9), and an image including all objects is printed by the printing unit 240.

  The instruction analysis unit 510a (FIG. 9) of the second embodiment analyzes a drawing instruction included in the PDL data, and associates each drawing instruction with a unit band of high resolution raster data and low resolution raster data. As described above, high resolution raster data is created for vector objects, and low resolution raster data is created for raster objects. Therefore, the command analysis unit 510a associates a rendering command representing a vector object with a unit band of high resolution raster data, and associates a rendering command representing a raster object with low resolution raster data.

  FIG. 11 is an explanatory diagram showing how the PDL data drawing command shown in FIG. 10 is associated with the unit band of the high resolution raster data and the low resolution raster data. As shown in FIG. 10, the drawing commands 1 and 3 both represent characters that are vector objects. Therefore, the rendering commands 1 and 3 are associated with the unit band of the high resolution raster data. Note that the association of the drawing command with the unit band is the same as in the first embodiment, and thus the description thereof is omitted here. On the other hand, the drawing commands 2 and 4 represent a photograph and an illustration, respectively. Since the photograph and the illustration are both raster objects, the rendering commands 2 and 4 representing them are associated with the low resolution raster data.

  The command expansion unit 552 of the low resolution raster data creation unit 550 (FIG. 9) expands the rendering commands 2 and 4 on the low resolution raster data representing a single page. The low resolution raster data in which the rendering commands 2 and 4 are expanded is stored in the low resolution page memory 650.

  On the other hand, as in the first embodiment, the drawing band setting unit 520 of the high resolution raster data creation unit 560 calculates the number of colors from the drawing command associated with each unit band and sets the drawing band. The instruction expansion unit 530 creates raster data in which pixel colors are encoded for each drawing band, and stores the created raster data in the high resolution band memory 620a.

  The data transmission unit 540 transmits the high resolution raster data stored in the high resolution band memory and the color table stored in the color table memory 630 to the printing apparatus 200 for each drawing band. The data transmission unit 540 also transmits raster data of an area corresponding to a drawing band among the low resolution raster data stored in the low resolution page memory 650 to the printing apparatus 200. In the printing apparatus 200, print data is created from the raster data transmitted in this way, and an image represented by PDL data is printed. In the second embodiment, the low resolution raster data is transmitted for each region corresponding to the drawing band. However, the entire low resolution raster data is transmitted to the printing apparatus 200 prior to the transmission of the high resolution raster data. It may be a thing. As a result, the print data creation unit 220 can sequentially perform processing such as color conversion and halftone processing from the low resolution raster data and the high resolution raster data transmitted via the data reception unit 210. Therefore, it is possible to speed up the processing in the printing apparatus 200 as compared with the case where the high resolution raster data is transmitted prior to the transmission of the low resolution raster data.

  As described above, according to the second embodiment, raster data is created for each drawing band for a vector object that can improve image quality by increasing resolution. In creating raster data, a drawing band is set based on the number of colors calculated from a drawing command, and raster data in which pixel colors are encoded is created. Thereby, even when the number of pixels of the raster data is increased due to the increase in resolution, it is possible to reduce the development overhead while suppressing an increase in the memory capacity secured as the high-resolution band memory 620a.

  In general, the number of colors used for vector objects such as characters and figures is smaller than the number of colors used for raster objects such as photographs and illustrations. Therefore, since the number of unit bands included in the drawing band can be increased, the development overhead can be reduced more effectively. Furthermore, the amount of data transmitted from the computer 100a to the printing apparatus 200 can be more easily suppressed by encoding the pixel color of the high resolution raster data.

C. Variations on how to create high resolution raster data:
FIG. 12 is a schematic configuration diagram showing the configuration of the image printing system 10b in a modification of the high resolution raster data creation method. The image printing system 10b according to this modification is different from the second embodiment in that the configuration of the computer 100b is different. Specifically, the instruction analysis unit 510a is replaced with an instruction analysis unit 510b having a different function, the configuration of the high resolution raster data creation unit 560b is different, and the high resolution band memory 620a includes a high resolution page. The second embodiment is different from the second embodiment in that the memory 620b is replaced. Other points are the same as in the second embodiment.

  In a modification of the high resolution raster data creation method, the high resolution raster data is created in units of pages, as is the case with the low resolution raster data. The instruction analysis unit 510b associates the vector object with single page high resolution raster data and associates the raster object with single page low resolution raster data.

  The color table creation unit 562 calculates the total number of colors of the entire vector object and creates a color table. Then, the instruction expansion unit 564 expands drawing commands for all vector objects with reference to the color table, and stores the expanded high resolution raster data in the high resolution page memory 620b. As in the first embodiment, the instruction expansion unit 564 encodes the color of each pixel with reference to the color table when creating high-resolution raster data.

  As described above, the number of colors used for vector objects such as characters and figures is smaller than the number of colors used for raster objects such as photographs and illustrations. Therefore, it is possible to sufficiently reduce the amount of high resolution raster data by encoding the color of the pixel. Therefore, even if the high-resolution raster data is created in units of pages, the memory capacity secured as the high-resolution page memory 620b that stores the high-resolution raster data can be sufficiently reduced. Also, by creating high resolution raster data in units of pages, it is possible to eliminate the development overhead. Furthermore, as in the second embodiment, the amount of data transmitted from the computer 100b to the printing apparatus 200 can be more easily suppressed by encoding the pixel color of the high resolution raster data.

10, 10a, 10b ... Image printing system 100, 100a, 100b ... Computer 110 ... CPU
120 ... RAM
130 ... HDD
DESCRIPTION OF SYMBOLS 140 ... Transmission interface 200 ... Printing apparatus 210 ... Data receiving part 220 ... Print data creation part 230 ... Printer control part 240 ... Printing unit 510, 510a, 510b ... Command analysis part 520 ... Drawing band setting part 522 ... Color table creation part 524 ... Bandwidth determination unit 530 ... Command development unit 540 ... Data transmission unit 550 ... Low resolution raster data creation unit 552 ... Command development unit 560, 560b ... High resolution raster data creation unit 562 ... Color table creation unit 564 ... Command development unit 610 ... Command memory 620 ... Band memory 620a ... High resolution band memory 620b ... High resolution page memory 630 ... Color table memory 640 ... Development memory 650 ... Low resolution page memory TL ... Transmission path

Claims (10)

An image processing apparatus,
An instruction expansion unit that creates raster data representing the result of drawing the object based on input data including an object drawing instruction;
A color table creating unit that creates a color table for encoding the color of each pixel in the raster data using a code corresponding to the number of colors used for drawing the object based on the drawing command;
The instruction expansion unit is an image processing apparatus that creates raster data in which the color of each pixel is encoded with reference to the color table. The image processing apparatus according to claim 1,
The input data includes a first type of rendering command corresponding to a first type of object, and a second type of rendering command corresponding to a second type of object having a different image representation format from the first type of object. Contains
The command expansion unit creates high-resolution raster data in which the color of each pixel is encoded when the drawing command is the first type of drawing command, and when the drawing type is the second type of drawing command. An image processing apparatus that creates low-resolution raster data in which the color of each pixel is not encoded. The image processing apparatus according to claim 2,
The instruction development unit is an image processing apparatus that creates the high resolution raster data by dividing it into a plurality of drawing bands, and creates the entire low resolution raster data at a time. The image processing apparatus according to claim 2 or 3,
The first type object is a vector object,
The image processing apparatus, wherein the second type object is a raster object. An image processing apparatus according to any one of claims 2 to 4,
A transmission unit for transmitting the raster data;
The transmission unit transmits the low-resolution raster data before transmitting the high-resolution raster data. The image processing apparatus according to claim 1,
The instruction processing unit is an image processing apparatus that creates the raster data by dividing it into a plurality of drawing bands. The image processing apparatus according to claim 1,
The instruction expansion unit is an image processing apparatus that creates the entire raster data at a time. A printing system,
An image processing apparatus according to any one of claims 1 to 7,
And a printing unit that performs printing based on raster data created by the image processing apparatus. An image processing method for creating raster data representing a result of drawing an object based on input data including an object drawing command,
Based on the drawing command, create a color table for encoding the color of each pixel in the raster data using a code corresponding to the number of colors used for drawing the object,
An image processing method for creating raster data in which the color of each pixel is encoded with reference to the color table. A computer program for image processing that creates raster data representing a result of drawing an object based on input data including an object drawing command,
A function of creating a color table for encoding the color of each pixel in the raster data using a code corresponding to the number of colors used for drawing the object based on the drawing command;
A computer program that causes a computer to realize raster data in which the color of each pixel is encoded with reference to the color table.

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