JP2008221673A - Image processing device - Google Patents

Abstract

When performing monochrome printing, appropriate image processing is performed according to an object.
A command analysis unit 202 for determining raster data from print data described in a page description language, a color space determination unit 203 for determining whether raster data is a color image or a monochrome image, and a color image are determined. A color space conversion unit 204 that converts the raster data into the YCbCr color space, and an attribute determination unit 205 that determines whether the attribute of the image data is a natural image or a solid image from each pixel of the raster data. An intermediate data generation unit 206 and a rendering unit 207 that process print data based on the object attributes and generate image data for monochrome printing.
[Selection] Figure 3

Description

  The present invention relates to an image processing apparatus such as a copying machine capable of monochrome printing, a printer, and a printing machine.

  Currently, many image processing apparatuses such as printers have a technique for obtaining an optimal print result by switching color conversion processing or halftone pattern according to the type of object (text, graphics, raster, etc.) to be printed. I have. For example, for vector images such as characters and graphics, the number of screen lines is set to a high resolution so that the edges of the characters are clear and the gradation pattern is not conspicuous. Also, for raster images such as photographs, importance is given to the gradation property by reducing the number of screen lines, setting the resolution low, and smoothing the color change. In addition, for color conversion processing, text and graphics use a color table that emphasizes saturation, and for photos, a color table that emphasizes gradation so that natural colors can be expressed, Color conversion is performed.

  However, although it is drawn as text or graphics on the screen of a personal computer, it may be generated as raster data depending on the type of PDL (Page Description Language). The raster data included in the PDL command data transmitted to the image processing apparatus is not only photographic data (natural image). Even if image processing is performed according to the type of object, the print result may not be optimal.

Here, the technique disclosed in Patent Document 1 discloses a method of determining raster data of interest from the type of image and the number of pixels, and performing optimal image processing according to the determination result.
JP 2005-335372 A

  Image data created by a personal computer and image data output from a digital camera are data having color information. As a result, a full color image is printed in the image processing apparatus. However, when an image processing apparatus is used in an office, the cost of monochrome printing is lower than that of color printing, so even a color image is often printed in monochrome.

  The print data input from the data processing apparatus such as a personal computer to the image processing apparatus includes color information. In the image processing apparatus, when such print data is input, conversion from color image data to monochrome image data is performed, and monochrome printing is performed. At this time, image processing corresponding to the object is not performed as in printing a color image. For this reason, in a raster image such as a photograph or painting, the gradation change corresponding to the original color change is not smooth, and a natural image cannot be obtained.

  In view of the above, an object of the present invention is to provide an image processing apparatus capable of performing image processing suitable for monochrome printing in accordance with an object.

  The present invention relates to a type determination unit that determines the type of an object from print data described in a page description language, and a color space conversion unit that converts image data of an object from a first color space to a second color space. And an attribute determination unit for determining the attribute of the image data of the object or the image data subjected to color space conversion, image processing of the print data based on the type of the object and the attribute of the image data, and image data for monochrome printing And an image processing unit to be generated.

  As a result, the type of object and the attributes of the image data are known, so that it is possible to select an optimal image processing for monochrome printing. That is, the type determination unit determines whether the type of the object is a raster image or a vector image. If it is determined as a vector image, the attribute determination unit determines the attribute of the object as character / graphics.

  When it is determined as a raster image, it is determined whether the image data of the object uses the first color space. When it is used, it is determined as a color image, and when it is not used, it is determined as a monochrome image. When the image data of the object uses the first color space, the color space conversion unit converts the image data to the second color space. Note that when the first color space is not used, the image data is not converted to the second color space. The first color space is composed of an RGB color space, and the second color space is composed of a YCbCr color space.

  Specifically, a color space determination unit that determines whether the image data is configured in the first color space when the type determination unit determines that the image is a raster image. When the color space determination unit determines that the color space is the first color space, the color space conversion unit converts the image data into the second color space.

  The attribute determination unit determines the attribute of the image data from each pixel of the image data. That is, the attribute determination unit determines whether the attribute of the image data subjected to the color space conversion is a solid image or a natural image when the object image data uses the first color space, that is, a color image. If the image data of the object does not use the first color space, that is, if it is a monochrome image, it is determined whether the attribute of the image data of the object that has not been color space converted is a solid image or a natural image.

  Here, the attribute determination unit determines whether the attribute of the image data is a solid image or a natural image based on the luminance information of the image data. Depending on whether or not the luminance value of each pixel is constant, the attribute of the raster data is determined. If it is constant, it is a solid image, and if it is not constant, it is a natural image. The image processing unit selects image processing based on the raster image and the vector image. Further, in the case of a raster image, image processing for monochrome printing is generated by selecting image processing according to a combination of a color image, a monochrome image, a solid image, and a natural image.

  According to the present invention, it is possible to perform optimum image processing when monochrome printing is performed on an object by determining whether the image is a natural image or a solid image from the attribute of the image data as well as the type of the object. . Therefore, a printed image with a clear outline can be obtained in a character or graphic image, and a smooth gradation change can be obtained in a photograph or painting image, and a printed image with a natural expression can be obtained.

  An image processing apparatus of this embodiment is shown in FIG. This image processing apparatus is a digital multi-function peripheral, and outputs a paper Pb on which a full color or monochrome image is formed on a paper Pa based on image data given from the outside of the apparatus. The image processing apparatus includes an exposure unit 19, photosensitive drums 12a to 12d, developing devices 13a to 13d, toner cartridges 23a to 23d, an intermediate transfer belt 11 for forming an image, a secondary transfer roller 14, and A fixing unit 21 including a primary transfer roller, a heating roller (also referred to as a fixing roller) and a pressure roller, a paper separating roller 16, and a paper discharge tray 18 are provided. In FIG. 1, the sheet conveyance path is indicated by a one-dot chain line, and the sheet is guided along the conveyance path by a predetermined roller including a conveyance roller. However, detailed description thereof is omitted.

  This image processing apparatus forms an image based on image data corresponding to each hue of four colors including black (K) and three subtractive primary colors, cyan (C), magenta (M), and yellow (Y). I do. For example, the image processing apparatus includes a photosensitive drum 12a, a developing device 13a, a charging roller, and a cleaning unit for forming a black image, and a similar configuration (photosensitive) for performing image formation for the other three colors. Body drums 12b to 12d and developing devices 13b to 13d). These components are arranged in a line as shown in FIG. 1 along the moving direction of the intermediate transfer belt 11.

  The charging roller is a contact-type charger that uniformly charges the surfaces of the photosensitive drums 12a to 12d, which are image carriers, to a predetermined potential. In this embodiment, the charging roller is used as a charging device. However, the charging device to be used is not limited to the charging roller. For example, a fur brush, a magnetic brush, or a corona wire is used. As long as it has a sawtooth shape or an ion generator, it can be used as long as it imparts a desired charging potential to the photoreceptor.

  The exposure unit 19 that is a laser beam scanning device includes a semiconductor laser, a polygon mirror 15, a plurality of reflection mirrors, and the like. Each of the four laser beams modulated based on the image data corresponding to the hues of black, cyan, magenta, and yellow is irradiated onto the surfaces of the corresponding photosensitive drums 12a to 12d. As a result, electrostatic latent images based on image data corresponding to the hues of black, cyan, magenta, and yellow are formed on the surfaces of the photosensitive drums 12a to 12d. Instead of the semiconductor laser, for example, a well-known write head in which EL or LED is arranged in an array may be used.

  The toner cartridges 23a to 23d are detachably attached near the upper portions of the developing devices 13a to 12d, and store toner that is a developer corresponding to a hue of black, cyan, magenta, or yellow.

  The developing devices 13a to 13d supply toner to the surfaces of the photosensitive drums 12a to 12d on which the electrostatic latent images are formed, and visualize the electrostatic latent images into toner images that are developer images. Specifically, the developing devices 13a to 13d receive toner corresponding to the hue from a supply port (not shown) of the toner cartridges 23a to 23d mounted on the upper portion, and the hue formed on the photosensitive drums 12a to 12d by the toner. The electrostatic latent image corresponding to 1 is visualized as a toner image corresponding to the hue of black, cyan, magenta, or yellow. The cleaning unit 17 removes and collects toner remaining on the surfaces of the photosensitive drums 12a to 12d after development and image transfer.

  The intermediate transfer belt 11 has a structure in which a film having a thickness of about 100 to 150 μm is formed in an endless manner. The intermediate transfer belt 11 is stretched between a driving roller and a driven roller and looped as shown in FIG. Forming a pathway. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 12d, the photosensitive drum 12c, the photosensitive drum 12b, and the photosensitive drum 12a. The intermediate transfer belt 11 rotates in this order so as to face the photosensitive drums 12a to 12d. A primary transfer roller is disposed at a position facing each of the photosensitive drums 12a to 12d with the intermediate transfer belt 11 interposed therebetween. These primary transfer rollers are rollers having a shaft made of a metal (for example, made of stainless steel) having a diameter of 8 to 10 mm as a base, and the surface thereof being covered with a conductive elastic material (for example, EPDM or urethane foam). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 11. In addition, although it shall be a roller shape here, a brush etc. may be sufficient.

  When forming a full-color image, the primary transfer roller has a reverse polarity to the toner charging polarity (-) in order to transfer the toner image carried on the surface of the photosensitive drums 12a to 12d onto the intermediate transfer belt 11. A primary transfer bias having a constant voltage of (+) is applied. Further, the primary transfer roller is pressed against the inner peripheral surface of the intermediate transfer belt 11 with a predetermined nip pressure. As a result, the toner images corresponding to the respective hues formed on the photosensitive drums 12a to 12d are transferred so as to be sequentially superimposed on the outer peripheral surface of the intermediate transfer belt 11, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. It is formed. When a monochrome image is formed, only the primary transfer roller arranged at a position facing the black photosensitive drum 12a is charged, and the primary arranged at a position facing the other photosensitive drums 12b to 12d. The transfer roller is not charged and is separated from the intermediate transfer belt 11 by a predetermined distance by a predetermined separation / contact mechanism. As a result, only a black toner image is formed on the outer peripheral surface of the intermediate transfer belt 11.

  The toner image transferred onto the outer peripheral surface of the intermediate transfer belt 11 in this way is conveyed to a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. At the time of image formation, the secondary transfer roller 14 is pressed against the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller with a predetermined nip pressure. In the case of such pressure contact, one of the pair of rollers is made of a hard material such as metal, and the other is made of an elastic material such as an elastic rubber roller or a foamed resin roller.

  The paper Pa is fed by a paper handling roller 16 that pulls out the paper Pa one by one from the paper feed cassette. When the paper Pa passes between the secondary transfer roller 14 and the intermediate transfer belt 11, a high voltage having a polarity opposite to the charging polarity of the toner is applied by the secondary transfer roller 14. As a result, a full-color or monochrome toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the surface of the paper Pa. The toner remaining on the intermediate transfer belt 11 without being transferred onto the paper among the toner adhering to the intermediate transfer belt 11 includes a cleaning blade provided so as to be in sliding contact with the driven roller in order to prevent color mixing. Collected by the unit.

  The paper Pa on which the toner image, which is a full-color or monochrome image, is transferred is guided to the fixing unit 21 and passes between a heating roller and a pressure roller constituting the fixing unit 21 and is heated and pressed. The heating roller is set to have a predetermined fixing temperature by the control unit based on a signal from a temperature detector (not shown). By the operation of the fixing unit 21, the toner image is firmly fixed on the surface of the paper Pa. The paper Pb on which the toner image is fixed is discharged onto the paper discharge tray 18 (with the printing surface facing downward) by the paper discharge roller.

  The image forming operation as described above is performed by a plurality of driving units including an electric motor and gears (not shown) and a control unit that controls these driving units. The function of the control unit is realized by a microcomputer that receives information such as a sensor and an operation input unit (not shown).

  As shown in FIG. 2, print data is created in a data processing apparatus 2 that is an external computer terminal. The image processing apparatus 10 receives print data transmitted from the data processing apparatus 2 via a predetermined communication line, and outputs an image corresponding to the received print data on a predetermined sheet.

  The print data is a file including data described in a page description language (PDL) that can be interpreted by the image processing apparatus 10. Further, the image processing apparatus 10 and the data processing apparatus 2 are connected so as to be able to communicate with each other by a LAN (Local Area Network) 5 including a predetermined cable or a hub. Instead of the LAN 5, a known mutual communication network such as a WAN (Wide Area Network) or the Internet, or a communication connection means such as a USB (Universal Serial Bus) connection or various parallel interfaces may be used.

  The image processing apparatus 10 includes an operation display including a CPU 101, a memory (semiconductor memory) 102, a printer controller 100 including various interfaces, a display device including a liquid crystal display and an input device including a touch panel and buttons. Unit 20, a hard disk storage device (hereinafter abbreviated as "hard disk" or "HDD") 30 including a disk-shaped magnetic storage medium, and image formation for forming an image on a sheet and discharging the sheet to the outside of the apparatus Part 40.

  The image forming unit 40 receives bitmap data for printing via the video controller 115 and forms a corresponding image on a predetermined sheet. The detailed configuration of the image forming mechanism in the image forming unit 40 is as described above.

  The printer controller 100 which is a control unit includes a CPU 101, a memory 102, an operation display unit interface 112 which is a connection interface with the operation display unit 20, a hard disk interface 113 which is a connection interface with the hard disk 30, and band data which will be described later. A compression / expansion circuit 114 that compresses or expands the image, a video controller 115 that is a connection interface with the image forming unit 40, and a network interface 116 that communicates with the data processing apparatus 2 via the LAN 5.

  The CPU 101, a RAM 102 that is a freely readable / writable memory and a ROM 102 that is a read-only memory, and the various interfaces are each a predetermined bus (such as a memory bus, a system bus, or a peripheral bus). Connected with. Since the connection by these buses is a well-known configuration in a general computer, detailed description thereof is omitted.

  The printer controller 100 optically reads an image of a target document, and receives an image read by a scanner unit (not shown) formed on a predetermined sheet and output from a so-called copying function or an external data processing device 2. The printer has various known functions such as a so-called printer function for forming and outputting print data (image data) on a predetermined sheet.

  These functions are typically realized by the CPU 101 executing a predetermined program built in the ROM of the memory 102 or expanded in the RAM. Here, the program is provided by a recording medium such as a CD-ROM in which the program is recorded. That is, a CD-ROM serving as a recording medium for the program is mounted on a CD-ROM driving device (not shown) built in the image processing apparatus 10 as an auxiliary storage device, and the program is read from the CD-ROM to obtain a hard disk. 30 installed. The program may be provided via a recording medium other than a CD-ROM or a communication line. When a predetermined operation for starting the image processing apparatus 10 is performed, the predetermined program installed in the hard disk 30 is transferred to the RAM, expanded there, and executed by the CPU 101. Thereby, the various functions described above are realized.

  The printer controller 100 has a PDL interprinter 200 shown in FIG. The PDL interpreter 200 includes an input interface unit 201, a command analysis unit 202, a color space determination unit 203, a color space conversion unit 204, an attribute determination unit 205, an intermediate data generation unit 206, a rendering unit 207, and a print processing unit 208. ing.

  The input interface unit 201, the command analysis unit 202, the color space determination unit 203, the color space processing unit 204, the attribute determination unit 205, the intermediate data generation unit 206, the rendering unit 207, and the print processing unit 208 are realized by software, It is stored in the memory 102 in the form of a code. All or a part of these can be realized by hardware.

  The input interface unit 201 acquires the PDL command data sent from the data processing device 2 such as a host computer and temporarily stores it. The PDL command data stored in the input interface unit 201 is transferred to the command analysis unit 202 and sequentially analyzed. If the analyzed PDL command is raster data, the color space determination unit 203 determines whether the raster data is in RGB space. When it is determined that the color space is the RGB color space (first color space), the color space conversion unit 204 converts the color space into the YCbCr color space (second color space). The attribute determination unit 205 determines the attribute of the raster data based on the information on the YCbCr color space. The intermediate data generation unit 206 generates intermediate data classified in units of objects and bands based on the analyzed PDL command. The intermediate data describes an object to be drawn and its attributes (object type, coordinates, color information, etc.). The rendering unit 207 generates print image data based on the intermediate data for each band. The print processing unit 208 transmits the print image data generated by the rendering unit 207 to the print engine.

  For example, when the same red rectangle is drawn by an application, when PDL command data is generated by graphics (vector image), a print image as shown in FIG. 4 is obtained. When PDL command data is generated with raster data (raster image), a print image as shown in FIG. 5 is obtained. As described above, since different color tables and halftones are used in the image processing apparatus that has received the PDL command data, objects that look the same on the screen of the personal computer are different in the print result.

  Here, the command analysis unit 202 functions as a type determination unit that determines the type of an object from print data described in a page description language, and determines whether the type of the object is a raster image or a vector image. The color space determination unit 203 determines whether or not the raster image is configured in the RGB color space. The attribute determination unit 205 determines the attribute of the raster data depending on whether or not the luminance value of each pixel is constant among the raster data configured in the YCbCr color space, and the color difference value of each pixel of the raster data. Depending on whether or not is constant, the attribute of the raster data is determined. The intermediate data generation unit 206 and the rendering unit 207 function as an image processing unit that performs image processing on print data based on the type and attribute of the object and generates image data for printing.

  In the present image processing apparatus, in order to perform appropriate image processing when performing monochrome printing regardless of the object, the attribute determination unit 205 determines whether the attribute is a natural image or a solid image in the case of raster data. judge. In this determination, the color space determination unit 205 first determines whether the raster data is a color image or a black and white image depending on whether or not the RGB color space is used. If the image is a color image, the attribute is determined for the raster data color space converted by the color space conversion unit 204. If the image is a monochrome image, the attribute is determined without color space conversion.

Next, a method for determining what kind of image the raster data is based on the characteristics of the raster data image will be described.
When Y is luminance, Cb is color difference (blue), Cr is color difference (red), and each value is in the range of 0 to 255, conversion from RGB to YCbCr is performed by the following conversion formula.

Y = 0.2990R + 0.5870G + 0.1140B
Cb = −0.1687R−0.3313G + 0.5000B + 128
Cr = 0.5000R-0.187G-0.0813B + 128
For example, when red (R = 255, G = 0, B = 0) is converted to a YCbCr value,
Y = 0.299x255 = 76
Cb = −0.1687 × 255 + 128 = 85
Cr = 0.5 × 255 + 128 = 255
It becomes.

In the case of the bitmap in FIG. 5, since the total pixel value Y is 76, if Y is a constant value, it is determined as a solid image. For example, when 50% gray (R = 128, G = 128, B = 128) is converted into a YCbCr value,
Y = 0.299x128 + 0.5870x128 + 0.114x128 = 143
Cb = −0.1687 × 128−0.3313 × 128 + 0.5 × 128 + 128
= 128
Cr = 0.5 × 128−0.4187 × 128−0.0813 × 128 + 128
= 128
It becomes.

  In the case of gray, Cb = Cr = 128. Therefore, if Cb = Cr = 128, it is determined as a gray image. In this way, it is determined what kind of image the raster data is.

  Next, image processing of PDL command data given from the data processing device 2 via the LAN 5 will be described in detail with reference to FIGS. The PDL data sent from the data processing device 2 to the image processing device is sequentially analyzed by the PDL interpreter 200 (S101). The type of object is determined from the type of command (S102).

  If it is determined that the object of interest is not a raster image, that is, a vector image, the attribute of the object is set to character / graphics (S116), and the process proceeds to S201 in FIG.

  If it is determined that the object is raster data (bitmap), the color space used by the raster data is confirmed (S103). The color space used in the raster data includes RGB color and black and white, and is raster data corresponding to the color space.

  If the color space of the raster data is determined to be RGB in S103, that is, if it is determined to be a color image, the object attribute is first set to character / graphics and the color attribute is set to gray (S104). Next, it is checked whether the attribute of the object is raster (bitmap) (S105). Initially, since the attribute is set to character / graphics, one pixel of raster data is converted from the RGB color space to the YCbCr color space by the above-described conversion formula (S106).

  If the attribute of the object is not raster, the Y (luminance) value is referred to and compared with the Y value of the previous pixel (S107). If the Y value is not the same value as the previous pixel, it is determined that the raster data attribute is not a solid image, that is, a natural image, and the object attribute is set to raster (S108). If the Y value is the same as that of the previous pixel, the object attribute is determined to be a solid image, and the process proceeds directly to S109. Steps 105 to S109 are repeated until there are no more pixels to be converted. If the attribute of the object has already been set to raster during the repetition, it is not necessary to compare the Y values thereafter, and the process proceeds to S201 in FIG.

  If the color space is not RGB, it is determined that the raster data is black and white. First, the attribute of the object is set to character / graphics (S110). Next, it is checked whether or not the attribute of the object is a raster (bitmap) (S111). Initially, since the attribute is set to character / graphics, one pixel is read out from the raster data (S112). In the case of black-and-white raster data, since only the brightness component is data, color space conversion is not performed. The Y value of the previous pixel is compared (S113).

  If the Y value is not the same as the previous pixel, it is determined that the attribute of the raster data is not a solid image, that is, a natural image, and the attribute of the object is set to raster (S114). If the Y value is the same as that of the previous pixel, the object attribute is determined to be a solid image, and the process proceeds directly to S115. Steps 111 to S115 are repeated until there are no more pixels to be converted. If the attribute of the object is already set to raster during the repetition, the process proceeds to S201 in FIG. 7 without comparing the Y value thereafter.

  The attribute of the object is determined as described above according to the type of the object and the attribute of the image data. Object types include raster and character / graphics. As attributes of image data, there are color or black and white, natural image or solid image. The attribute of the object is determined by these combinations. When a color raster image is a natural image, the attribute is a raster. Even in the case of a natural image such as a monochrome raster image, the attribute is a raster. In the case of a color or monochrome raster image and a solid image, the attribute is character / graphics. In the case of a vector image, the attribute is character / graphics.

  When the attribute of the object is determined, as shown in FIG. 7, the attribute of the object is read in order to determine the image processing mode of the currently processed object (S201). Tone curve processing and halftone processing are switched depending on the attribute of the object. FIG. 8 shows a drawing mode of image processing for each object.

  The attribute of the object is read (S201), and it is confirmed whether the attribute is raster (bitmap) or character / graphics (S202). For characters / graphics other than rasters, the drawing mode is set to mode 1 (S204). If it is a raster, the drawing mode is set to mode 2 (S203).

  After setting the mode, an intermediate code of the object currently being processed is generated (S205). It is checked whether there is a PDL command to be processed (S206). If there is a PDL command, the processing from S101 to S206 is repeated. When all the PDL commands have been processed, the generated intermediate code is converted into bitmap data for monochrome printing (S207). Thereafter, the printing process is executed (208), and the printing process is terminated.

  As a result, in order to perform monochrome printing, optimum image processing can be performed by changing halftone processing, output gamma characteristics, and the like according to the object. For example, for characters and graphics images, the number of screen lines is increased and the resolution is set high. The edge of the character becomes clear and the gradation pattern becomes inconspicuous. For raster images such as photographs and paintings, the number of screen lines is reduced and the resolution is set low. The change of the original color is expressed smoothly and the tone is improved. By changing the characteristics of the output gamma, the contrast is enhanced in characters and graphics images. A natural expression can be obtained in the raster image by correcting the tone curve.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. The image processing apparatus is not limited to a multifunction machine, and may be a color printer or a monochrome printer. In addition, even for an object in which photographs and characters are mixed, an attribute is determined for each image and appropriate image processing is performed on each image data. Thereby, monochrome printing can be performed without impairing the characteristics of each image.

The figure which shows schematic structure of the image processing apparatus which concerns on this Embodiment. Control block diagram of image processing apparatus The figure which shows the structure of a PDL interprinter The figure which shows the details of the PDL command and the print image when the object is described in vector graphics The figure which shows the detail and print image of a PDL command when an object is described by raster data Flowchart showing image processing procedure for input print data Flowchart showing image processing procedure for input print data The figure for demonstrating the drawing mode of the image processing for every object

Explanation of symbols

2 Data processing device 10 Image processing device 20 Operation display unit 30 Hard disk 40 Image forming unit 100 Printer controller 200 PDL interprinter 201 Input interface unit 202 Command analysis unit 203 Color space determination unit 204 Color space conversion unit 205 Attribute determination unit 206 Intermediate data Generation unit 207 Rendering unit 208 Print processing unit

Claims (7)

A type determination unit that determines the type of an object from print data described in a page description language, a color space conversion unit that converts the image data of an object from a first color space to a second color space, An image determination unit that determines an attribute of image data or image data that has undergone color space conversion, and image processing that generates image data for monochrome printing by performing image processing on the print data based on the type of object and the attribute of the image data And an image processing apparatus. The type determining unit determines whether the type of the object is a raster image or a vector image, and when the type is determined to be a raster image, if the image data of the object uses the first color space, the color space converting unit The image data is converted from the first color space to the second color space, and the attribute determination unit determines whether the attribute of the image data subjected to the color space conversion is a solid image or a natural image, and the image data of the object is the first image data. 2. The image processing apparatus according to claim 1, wherein when the color space is not used, the attribute determination unit determines whether the attribute of the image data of the object is a solid image or a natural image. The image processing apparatus according to claim 2, wherein the attribute determination unit determines whether the attribute of the image data is a solid image or a natural image based on luminance information of the image data.
Science device. 4. The image processing apparatus according to claim 2, wherein the first color space is composed of an RGB color space, and the second color space is composed of a YCbCr color space. When the object type is a raster image, the attribute determination unit determines whether the image is a color image or a black-and-white image depending on whether or not the first color space is used. In the case of a color image, the color space conversion unit 5. The image processing apparatus according to claim 4, wherein the data is converted from the first color space to the second color space. The attribute determination unit determines whether the attribute of the image data is a solid image or a natural image depending on whether or not the luminance value of each pixel is constant among the image data configured in the second color space. 6. The image processing apparatus according to claim 5, wherein the determination is made. In the case of a monochrome image, the attribute determination unit determines whether the attribute of the image data is a solid image or a natural image depending on whether or not the luminance value of each pixel of the image data is constant. The image processing apparatus according to claim 5.

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