JP2005135321A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device converting a color image including a vector object into a monochrome image without any reduction in visibility. <P>SOLUTION: This image forming device is provided with an object extraction part 11 extracting an object from a print target image and a monochrome conversion part 113 performing pallet type monochrome conversion, in which density is dispersed, at least on the vector object and density conservation type monochrome conversion, in which density is used without any change, at least on a bit-map object among the extracted objects. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that converts a color image into a monochrome image.

  In recent years, color printers are becoming popular in offices and the like, but the number of color printers is less than that of printers dedicated to monochrome images. Therefore, the user is often restricted from outputting to a color printer and forced to output to a printer dedicated to monochrome images. Even in the case of a color printer, there may be a case where a monochrome image is output from the viewpoint of saving ink or saving time.

  On the other hand, since the user creates and outputs a color image without considering the installation status of the printer, the printer must convert the color image into a monochrome image. Conversion to a monochrome image is performed by calculating the density of each pixel based on, for example, R, G, and B color components.

  However, as described above, when monochrome conversion is performed by simply calculating the density, there are cases where the calculated density approximates even if the colors are completely different. In this case, these colors are distinguished. There was a problem that became very difficult. In this case, the monochrome-converted color cannot be distinguished, causing a problem that the visibility of the image is lowered. In particular, for a vector image such as a graph, the visibility is likely to deteriorate.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that converts a color image including a vector object into a monochrome image without reducing visibility.

  An image forming apparatus according to the present invention is an image forming apparatus that converts a color image including a vector object including a vector image into a monochrome image, an object extracting unit that extracts an object constituting the color image from the color image, and Among the extracted objects, at least for the vector object, monochrome conversion means for performing monochrome conversion by calculating the density of each color so that the density difference value of each color to be subjected to monochrome conversion is increased, and monochrome conversion Output means for outputting the applied color image as a print image.

  Further, the monochrome conversion means, for the vector object, sets each color of the object to a low gradation scale having a gradation number lower than the gradation number of the object, based on the density of the object. It is preferable to assign the obtained density to the density of each color.

  The monochrome conversion unit preferably assigns each color of the vector object to the closest density on the low gradation scale.

  The monochrome conversion means is assigned when the density of the low gradation scale closest to the density of the color to be converted into monochrome is assigned to another color among the colors constituting the vector object. It is preferable to assign the closest low gradation scale density among the low gradation scale densities that are not.

  Further, it is preferable that the color image includes a bitmap object made up of a bitmap image, and the monochrome conversion means performs at least monochrome conversion using the density as it is for the bitmap object.

  According to the first aspect of the present invention, the objects constituting the color image are extracted, and among the extracted objects, the vector object is subjected to monochrome conversion so that the difference in density of each color becomes large. . For this reason, the density difference between the two types of colors with similar densities becomes large, and it is possible to suppress a decrease in the visibility of the vector image due to monochrome conversion.

  According to the second aspect of the present invention, since the vector object is converted into a monochrome image by mapping each pixel to the low gradation scale, the two colors having similar densities are clearly distinguished. Is converted to monochrome. For this reason, a decrease in visibility is suppressed.

  According to the third aspect of the present invention, the density can be dispersed reflecting the density.

  According to the fourth aspect of the present invention, it is possible to further disperse the density reflecting the magnitude of the density.

  According to the fifth aspect of the invention, the number of colors tends to be larger than that of a vector image, and it is difficult to perform monochrome conversion that increases the density difference. The bitmap image that may be incurred is subjected to monochrome conversion that employs the density as it is. Therefore, a color image in which a vector image and a bitmap image are mixed can be converted into a monochrome image without reducing visibility.

  FIG. 1 is a schematic side view mainly showing a mechanical configuration of an image forming apparatus according to the present invention. The image forming apparatus includes a main body unit 200, a sheet post-processing unit 300 disposed on the left side of the main body unit 200, an operation unit 400 for a user to input various operation commands and the like, and an upper part of the main body unit 200. The document reading unit 500 is disposed, and the document feeding unit 600 is disposed above the document reading unit 500.

  The operation unit 400 includes a touch panel 401, a start key 402, a numeric keypad 403, and the like. The touch panel 401 displays various operation screens and various operation buttons for the user to input various operation commands. The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of copies to be printed.

  The document feeding unit 600 includes a document placement unit 601, a document discharge unit 602, a paper feed roller 603, a document transport unit 604, and the like, and the document reading unit 500 includes a scanner 501 and the like. The paper feed roller 603 feeds out the original set on the original placement unit 601, and the original transport unit 604 transports the fed originals one by one on the scanner 501. The scanner 501 sequentially reads the conveyed document, and the read document is discharged to the document discharge unit 602.

  The main body 200 includes a plurality of paper feed cassettes 201, a plurality of paper feed rollers 202, a transfer roller 203, an intermediate transfer body roller 204, a photosensitive drum 205, an exposure device 206, and development for each color of yellow, magenta, cyan, and black. Devices 207Y, 207M, 207C, and 207K, a fixing roller 208, a discharge port 209, a discharge tray 210, and the like are provided.

  The photosensitive drum 205 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow. The exposure device 206 converts the modulation signal generated based on the image data of the original read by the original reading unit 500 into a laser beam and outputs it, and forms an electrostatic latent image on the photosensitive drum 205 for each color. The developing devices 207Y, 207M, 207C, and 207K supply each color developer to the photosensitive drum 205 to form a toner image for each color. Each pixel of the document image data is composed of R (red), G (green), and B (blue) color components, and each color component has a gradation of 0 to 255.

  The intermediate transfer roller 204 transfers the color toner images from the photosensitive drum 205, and forms a color toner image on the intermediate transfer roller 204.

  On the other hand, the paper feed roller 202 pulls out the recording paper from the paper feed cassette 201 in which the recording paper is stored, and feeds the recording paper to the transfer roller 203. The transfer roller 203 transfers the toner image on the intermediate transfer body roller 204 onto the conveyed recording paper, and the fixing roller 208 heats and fixes the transferred toner image on the recording paper. Thereafter, the recording paper is carried into the paper post-processing section 300 from the discharge port 209 of the main body section 200. The recording paper is also discharged to the discharge tray 210 as necessary.

  The paper post-processing unit 300 includes a carry-in port 301, a recording paper transport unit 302, a carry-out port 303, a stack tray 304, and the like. The recording paper transport unit 302 sequentially transports the recording paper carried into the carry-in port 301 from the discharge port 209 and finally ejects the recording paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to move up and down in the direction of the arrow in accordance with the number of recording sheets stacked from the carry-out port 303.

  FIG. 2 is a block diagram showing an electrical configuration of the copying machine shown in FIG. The control unit 10 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a dedicated hardware circuit. The ROM stores a control program for controlling the image forming apparatus, and the CPU causes the control unit 10 to function as the image processing unit 11 and the storage unit 12 by executing the control program. In FIG. 2, illustrations of portions that control other functions of the image forming apparatus such as a print controller and a scanner controller are omitted. The image processing unit 11 includes an object extraction unit 111, an object distribution unit 112, a monochrome conversion unit 113, an exposure control unit 114, and a CMYK conversion unit 115. The storage unit 12 includes an image memory 121 and a drawing campus memory 122.

  The external PC 30 is composed of a normal personal computer equipped with a LAN board, and is connected to the image forming apparatus via a LAN (local area network). Then, the external PC 30 outputs print data of the print target image created by the user using various application software to the image forming apparatus via the LAN. This print target image is composed of various objects such as a vector object, a bitmap object, and a character object. A vector object consists of a figure such as a graph, and image data is described in a command format. The bitmap object corresponds to an image such as JPEG (joint photographic experts group) or GIF (graphics interchange format), and the image data is expressed as an aggregate of dots. The character object is an image made up of characters created by a word processor or the like. The print data includes image data of each object, attribute data indicating what kind of object the image data of each object is, and monochrome designation data indicating whether or not to convert the print target image into monochrome. It is out.

  The storage unit 12 includes an image memory 121 and a drawing campus memory 122. The image memory 121 has a memory capacity capable of storing a plurality of pieces of image data, and stores print data output from the external PC 30 and various objects processed by the image processing unit 11.

  The drawing campus memory 122 has a memory area for each of C, M, Y, and K color components, and stores an output image printed on a recording sheet for each color component. Each address corresponds to each pixel of the output image. For example, the image data is stored in order from the upper left pixel to the lower right pixel of the output image. Note that the image memory 121 and the drawing campus memory 122 may be realized by using one RAM with separate address areas.

  The object extracting unit 111 extracts objects included in the print target image by analyzing attribute data included in the print data from the external PC 30. FIG. 3 is a diagram for explaining how an object is extracted from a print target image. The print target image shown in FIG. 3 includes a character object made up of characters such as “Hatsuyume”, “1/1” showing the scale of the graph, a bitmap object made up of a picture of Mt. Fuji, and a vector object made up of a line graph. And a background object corresponding to the background portion of the recording paper. Then, as shown on the right side of the arrow in FIG. 3, a background object, a character object, an image object, and a vector object are extracted from the print target image. The extracted object is stored in the image memory 121.

  The object distribution unit 112 identifies an object to be converted into a monochrome image and an object that is not to be converted into monochrome according to the type of each extracted object, outputs the object to be converted into monochrome to the monochrome conversion unit 113, and does not perform monochrome conversion. The object is output to the CMYK conversion unit 115.

  In the present embodiment, the vector object, the bitmap object, and the character object are monochrome-converted. However, an object designated to be monochrome-converted by the user may be monochrome-converted. Such designation may be performed for each attribute of an object such that a vector object is converted into monochrome but a bitmap object is not converted into monochrome, or a vector object of a certain print target image is converted into monochrome but a vector of another print target image. An object can be individually performed for each image to be printed so that monochrome conversion is not performed.

  The monochrome conversion unit 113 receives the object output from the object distribution unit 112, performs density preservation type monochrome conversion to be described later on an object having a certain attribute, and applies to another attribute object, Palette-type monochrome conversion described later is performed, and the monochrome-converted objects are stored in the drawing campus memory 122. In the present embodiment, palette type monochrome conversion is performed on vector objects, and density preservation type monochrome conversion is performed on other character objects and bitmap objects.

  In addition, the monochrome conversion unit 113 divides the vector object into primitives specified for each figure such as a line segment, a triangle, and a rectangle, and performs monochrome conversion processing for each primitive.

  The density preservation type monochrome conversion is a conversion in which a color expressed in the RGB color system is converted into, for example, a YUV color system, and the obtained Y (luminance) component value is used as the density when the monochrome conversion is performed. Refers to the method. In the present embodiment, the R, G, and B color components are each represented by 0 to 255 gradations, and thus the density when monochrome conversion is represented by 0 to 255.

  In the palette type monochrome conversion, the color to be converted is assigned to the number of gradations smaller than 256 gradations, for example, the density of a low gradation scale consisting of 8 gradations, according to the density, and the obtained density Is a conversion method that is used as the density of the color at the time of monochrome conversion.

  The exposure control unit 114 drives the image forming unit 20 to print the output image stored in the drawing campus memory 122 on recording paper. Here, the image forming unit 20 includes the transfer roller 203, the intermediate transfer member roller 204, the photosensitive drum 205, the exposure device 206, and the developing devices 207Y, 207M, and 207C for yellow, magenta, cyan, and black as shown in FIG. , 207K, and the fixing roller 208.

  The CMYK conversion unit 115 converts the object represented by the RGB color components output from the object distribution unit 112 into CMYK color components and stores them in the drawing campus memory 122.

  FIG. 4 is a block diagram for explaining an outline of processing by the image processing unit 11. The “print data” output from the external PC 30 is divided by the object extraction unit 111 into various objects such as “vector object”, “bitmap object”, and “character object”. Then, the object distribution unit 112 outputs the “vector object”, “bitmap object”, and “character object” to the monochrome conversion unit 113.

  The “vector object” is divided into primitives such as “line segments” and “triangles” by the monochrome conversion unit 113, and palette-type monochrome conversion is performed for each primitive and is written in the drawing campus memory 122. The bitmap image is subjected to density preservation type monochrome conversion for each primitive such as “JPEG” and “GIF” by the monochrome conversion unit 113 and is written in the drawing campus memory 122. The “character object” is subjected to density preservation type monochrome conversion by the monochrome conversion unit 113 and written to the drawing campus memory 122.

  FIG. 5 is a block diagram showing processing for line segment primitives by the monochrome conversion unit 113. The line segment primitive includes “color data” indicating the color of the line segment, “width data” indicating the width of the line segment, “start point end point data” indicating the coordinates of the start point and end point of the line segment, and the like. The “outline shape” of the line segment is generated by the “width data” and the “start point / end point data”. The “color data” is subjected to palette type monochrome conversion. Then, the “outline shape” and the “color data” after monochrome conversion are combined and stored in the drawing campus memory 122. When monochrome conversion is not performed, color data of four colors C, M, Y, and K is generated from the color data and synthesized with the outline shape.

  FIG. 6 is a flowchart illustrating processing when the image processing unit 11 performs monochrome conversion on the print target image. First, in step S1, the image processing unit 11 determines whether the print data from the external PC 30 is print data for which monochrome conversion is designated based on the monochrome designation data, and monochrome conversion is designated. If YES (YES in step S1), the process proceeds to step S2. If monochrome conversion is not specified (NO in step S1), the process is terminated.

  In step S <b> 2, the object extraction unit 111 extracts the objects included in the print data by analyzing the attribute data. In the example shown in FIG. 3, a background object, a character object, a bitmap object, and a vector object are extracted.

  The object distribution unit 112 outputs, to the monochrome conversion unit 113, objects for which monochrome conversion is designated among the objects extracted in step S2, that is, character objects, vector objects, and bitmap objects (YES in step S3 and steps in step S3). S4). On the other hand, an object for which monochrome conversion is not designated is output to the CMYK conversion unit 115 (step S5).

  In step S6, the monochrome conversion unit 113 performs palette type monochrome conversion on the vector object (YES in step S6 and step S7), and stores the monochrome converted object in the drawing campus memory 122 (step S9). On the other hand, the monochrome conversion unit 113 performs density preservation type monochrome conversion on objects other than vector objects, that is, bitmap objects and character objects (NO in step S6 and step S8), and converts the objects converted into monochrome. It is stored in the drawing campus memory 122 (step S9).

  In step S11, the CMYK conversion unit 115 converts the object represented by the RGB color components output from the object distribution unit 112 into CMYK color components (step S11), and stores them in the drawing campus memory (step S9).

  In step S <b> 10, the exposure control unit 114 drives the image forming unit 20 to print the output image stored in the drawing campus memory 122 on recording paper.

  7A and 7B are diagrams for explaining palette-type monochrome conversion. FIG. 7A is a chromaticity diagram of an XYZ color system, and FIG. 7B is a gradation scale employed in density-preserving monochrome conversion. (C) shows a low gradation scale employed in palette-type monochrome conversion. In the gradation scale shown in (b), the density of 0 to 255 is graduated from the top to the bottom. The low gradation scale shown in (c) has eight densities of 32, 64, 96,..., 192, 255 in the downward direction with the top as the origin. In this way, the low gradation scale is scaled so that the step size is larger than the gradation scale shown in (b). Can be prevented. It should be noted that the number of density levels on the low gradation scale is not limited to the above eight but may be seven or less or nine or more. However, if the step size is increased to reduce the number of densities, if the object to be converted consists of many colors, it will not be possible to assign all the colors to the density scaled on the low gradation scale. (Low gradation scale saturation). For this reason, the step size of the low gradation scale should be a value that does not cause saturation of the low gradation scale and does not deteriorate visibility due to the number of colors of the object to be converted. Is preferred. Further, in order to prevent saturation of the low gradation scale, the low gradation scale may be individually adopted for each object to be converted.

  FIG. 8 is a flowchart showing the subroutine of step S7. Of the colors included in the vector object, the density of the color to be converted into monochrome is calculated (step S71). Next, when the density of the closest low gradation scale is not assigned to the calculated density in another color (NO in step S72), the density of the closest low gradation scale is the density of the color. Allocated (step S73). Since the color P1 shown in the chromaticity diagram of FIG. 7A has a density of 171, among the densities graduated on the low gradation scale, 192 which is the density closest to 171 is adopted as the density of the color. Is done.

  On the other hand, when the density of the closest low gradation scale is assigned by another color (YES in step S72), among the densities of the low gradation scale to which no color is assigned, the color to be converted into monochrome is selected. The closest low-tone scale density is assigned as the density of the color (step S74).

  Since the color P2 shown in the chromaticity diagram of FIG. 7A has a density of 50, 64, which is the density of the low gradation scale closest to 50, is adopted as the density of the color. On the other hand, since the density of the color P3 is 65, the density of the low gradation scale closest to 65 is 64.

  However, since 64 is already assigned to the color P2, both colors are monochrome-converted to exactly the same density and cannot be distinguished. On the other hand, when density-preserving monochrome conversion is adopted, 50 and 65 are close to each other, so that it is difficult to distinguish both colors, leading to a decrease in visibility. Therefore, among the low gradation scale densities to which no color is assigned, 96, which is the density of the low gradation scale closest to 65, is assigned as the density of the color P3.

  In step S75, when the allocation of all the colors to be converted into monochrome is completed (YES in step S75), the process is terminated and the allocation is not completed (NO in step S75). The process proceeds to step S76.

  In step S76, when colors are assigned to all the densities of the low gradation scale and the low gradation scale is not saturated (NO in step S76), the process returns to step S71, and the density of the color to be assigned next is determined. Calculated. On the other hand, when the low gradation scale is saturated (YES in step S76), the density of the remaining colors is determined by density-conserving monochrome conversion (step S77).

  As described above, according to the present image forming apparatus, an object composed of a relatively small number of colors, such as a vector object, is subjected to palette-type monochrome conversion processing. An image is obtained. On the other hand, for objects that are made up of many colors, such as bitmap images, and for which palette-type monochrome conversion processing is difficult, density-preserving type monochrome conversion processing is performed, so the original color is distinguished. A monochrome image that can be obtained can be obtained.

  Further, according to the present image forming apparatus, since it is possible to designate whether or not monochrome conversion is performed for each object, so-called partial color printing in which some objects are printed in color can be performed.

  The present invention may adopt the following aspects.

  In the above embodiment, density preservation type monochrome conversion is performed on a character object. However, the present invention is not limited to this, and palette type monochrome conversion may be performed. As a result, it is possible to perform monochrome conversion so that a highlighted character expressed in a color other than black, for example, red, and a black character can be clearly distinguished.

1 is a schematic side view mainly showing a mechanical configuration of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the copying machine shown in FIG. 1. It is a figure explaining a mode that an object is extracted from a printing target image. It is a block diagram for demonstrating the outline | summary of the process by an image process part. It is the block diagram which showed the process with respect to the line segment primitive by a monochrome conversion part. It is the flowchart which showed the process when an image process part performs monochrome conversion with respect to a printing target image. It is a figure for demonstrating palette type monochrome conversion, (a) shows the chromaticity diagram of an XYZ color system, (b) shows the gradation scale employ | adopted by density preservation type monochrome conversion, c) shows a low gradation scale employed in palette-type monochrome conversion. It is a flowchart which shows the subroutine of step S7.

Explanation of symbols

10 control unit 11 image processing unit 12 storage unit 20 image forming unit 30 external PC
111 Object Extractor 112 Object Distributor 113 Monochrome Converter 114 Exposure Controller 115 CMYK Converter 121 Image Memory 122 Drawing Campus Memory

Claims (5)

An image forming apparatus for converting a color image including a vector object made up of vector images into a monochrome image,
Object extraction means for extracting an object constituting the color image from the color image;
Monochrome conversion means for performing monochrome conversion by calculating the density of each color so that the difference value of the density of each color to be subjected to monochrome conversion becomes large for at least the vector object among the extracted objects;
An image forming apparatus comprising: an output unit that outputs a color image subjected to monochrome conversion as a print image.   The monochrome conversion means assigns each color of the object to the vector object on a low gradation scale having a gradation number lower than the gradation scale number of the object based on the density of the vector object. 2. The image forming apparatus according to claim 1, wherein the obtained density is a density of each color.   3. The image forming apparatus according to claim 2, wherein the monochrome conversion unit assigns each color of the vector object to the closest density on the low gradation scale.   The monochrome conversion means is not assigned when the density of the low gradation scale closest to the density of the color to be converted from monochrome among the colors constituting the vector object is assigned to another color. 4. The image forming apparatus according to claim 3, wherein among the low gradation scale densities, the closest low gradation scale density is assigned. The color image includes a bitmap object consisting of a bitmap image,
The image forming apparatus according to claim 1, wherein the monochrome conversion unit performs monochrome conversion that employs a density as it is for at least the bitmap object.

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