JP2005260559A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor capable of easily controlling an amount of color material usage while preventing image quality deterioration at the time of reducing the amount of color material usage by performing an AND operation of image data and a mask pattern. <P>SOLUTION: This image processor comprises a first halftone processing means for performing screen processing for inputted image data and generating a pseudo halftone image, a control value acquiring means for acquiring a control value for controlling a signal value of the pseudo halftone image, a control data generating means for generating control data from the control value acquired by the control value acquiring means, a second halftone processing means for performing screen processing for the control data generated by the control data generating means and generating a mask pattern, and a logic operation processing means for performing a logic operation of the pseudo halftone image and the mask pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus that controls the amount of color material used by performing an AND operation between image data and a mask pattern.

  In an image processing apparatus having a printing function, an opportunity to print data created by a personal computer or the like is increasing. At this time, since the consumption of the color material such as toner and ink greatly affects the running cost, an image processing apparatus having a function for the purpose of reducing the consumption of the color material used is conventionally known. As a general technique for realizing such a color material saving function, there is a process of thinning out dots by performing a logical product operation with image data of the entire page with a certain mask pattern.

  Further, in an electrophotographic image processing apparatus represented by a laser beam exposure type laser printer, an image is formed by attaching toner, but there are various types of media used for printing. At this time, depending on the type of media, the toner may not be fixed completely, and the toner may be scattered, or the toner may be lost at portions where the dot density is high.

  As a countermeasure against the above-mentioned problem, a method of reducing the amount of toner adhesion is adopted. Specifically, a logical operation with a certain mask pattern is performed on image data for image formation, and dot thinning processing is performed. This is generally realized by doing.

  Also, when creating image data with a personal computer or the like, some applications have a function of rendering a figure translucent. When there is such a function, the image processing apparatus performs a logical operation with a certain mask pattern on the image data to be rendered translucently. A semi-transparent figure can be drawn by drawing a dot of image data when the bit of the mask pattern is ON and a dot of data serving as the background when the bit is OFF.

  As described above, it is common to perform a dot thinning process by performing a logical operation with a certain mask pattern in an image processing apparatus. However, in the conventional example, the types of mask patterns that can be used are limited, and the thinning rate is unique to the mask pattern. Therefore, it has not been easy to flexibly control the thinning rate. That is, the control of the amount of reduction of the color material, the control of the adhesion amount of the color material according to the medium to be printed, and the control of the transparency with respect to the image data cannot be easily realized.

  Furthermore, the problem of image quality degradation has been pointed out in the past when performing logical operations with mask patterns. Such a decrease in image quality has a greater effect on the lower density portion of the image data. For example, as shown in FIG. 1, the logical product of the 100% density image data 101 and the 25% density image data 102 with a mask pattern for performing 50% thinning processing as indicated by 103 and 104 in the figure. I take the. In this case, the 100% density image data becomes 50% density image data 105, whereas the 25% density data disappears as indicated by 106 in the figure.

  Further, when printing image data, many image processing apparatuses perform halftone processing. Screen processing is an example of general halftone processing, but when performing thinning processing by taking the logical product of the mask pattern on the screen-processed image data, the screen pattern and mask used in the screen processing are used. Interference may occur with the pattern, and moire may occur, resulting in a reduction in image quality.

As a means of controlling the thinning rate while preventing such image quality deterioration, by preparing a plurality of color material reduction mask patterns for saving the color material at the time of printing, the user specifies a desired mask pattern, There has been proposed a method of adjusting the amount of reduction of the color material while preventing deterioration in image quality (see, for example, Patent Document 1). Also, by preparing multiple thinning processing patterns with different thinning rates according to the density of image data, and changing the thinning pattern to be used according to the density of image data, it is possible to prevent image quality deterioration, especially in low density areas. However, it has been proposed to implement a thinning process (see, for example, Patent Document 2).

JP 09-245150 A Japanese Patent Laid-Open No. 2000-203010

  However, in the above-described conventional technique, a mask pattern to be used in advance must be registered in a storage means such as a ROM, and a ROM capacity is required to register a plurality of patterns. Further, since the mask pattern to be used is selected from the registered mask patterns, the selectable thinning rate is fixed with respect to the mask pattern, and it is not easy to control the thinning rate more finely.

  The present invention has been made in view of the above-described problems. When reducing the amount of color material used by performing an AND operation between image data and a mask pattern, it is possible to easily reduce color while preventing deterioration in image quality. An object of the present invention is to provide an image processing apparatus capable of controlling the amount of material used.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a first halftone processing means for generating a pseudo halftone image by performing screen processing on input image data, and a signal of the pseudo halftone image. Control value acquisition means for acquiring a control value for controlling the value, control data generation means for generating control data from the control value acquired by the control value acquisition means, and control data generated by the control data generation means The image processing apparatus includes a second halftone processing unit that performs screen processing and generates a mask pattern, and a logical operation processing unit that performs a logical operation of the pseudo halftone image and the mask pattern. And

  According to a second aspect of the present invention, in the first aspect of the present invention, the second halftone processing means for generating the mask pattern is a screen pattern used by the first halftone processing means during the screen processing. It is characterized by using the same screen pattern.

  According to a third aspect of the present invention, in the first aspect of the invention, the second halftone processing means for generating the mask pattern is a screen pattern used by the first halftone processing means during the screen processing. It is characterized by using different screen patterns.

  According to a fourth aspect of the present invention, first halftone processing means for performing screen processing on the input first image data and generating a first pseudo halftone image, and the input second image data Second halftone processing means for generating a second pseudo halftone image by performing screen processing, and control value obtaining means for obtaining a control value for controlling a signal value of the first pseudo halftone image; A control data generating unit that generates control data from the control value acquired by the control value acquiring unit; and a first mask pattern that generates a first mask pattern by performing screen processing on the control data generated by the control data generating unit. 3 halftone processing means, reversal processing means for performing a reversal process on the first mask pattern to generate a second mask pattern, the first pseudo halftone image, and the first mask pattern Theory While performing an operation, characterized in that constitute an image processing apparatus include a logic processing means for performing a logical operation of said second pseudo halftone image second mask pattern.

  According to the present invention, when the color material usage is reduced by performing an AND operation between the image data and the mask pattern, it is possible to easily control the color material usage while preventing deterioration in image quality. become.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
As an embodiment according to the present invention, a case where the present invention is applied to a color laser printer having a colorant of CMYK will be described below. The present invention can be applied to an image processing apparatus such as a color printer or a color facsimile apparatus.

  A first embodiment of the present invention will be described with reference to the block diagram of FIG.

  In FIG. 2, reference numeral 201 denotes an image data input unit, from which image data to be printed is input.

  The image data input method may be a method of sending through an application such as a driver on a PC connected to an image processing apparatus equipped with the system of the present invention, or a method obtained by scanning using a scanner unit, etc. Any means can be used.

  Reference numeral 202 denotes a color conversion processing unit. Here, the image data input from the image data input unit 201 is converted into color component data of a plurality of different color materials suitable for the target image processing apparatus using the color conversion table. Convert. For example, when the input image data is RGB data and the image processing apparatus is a general color laser printer using CMYK toner, conversion processing from RGB to CMYK is performed by this color conversion processing unit. At the same time, processing such as masking processing and UCR (Under Color Removal) processing is also performed.

  In the figure, reference numeral 203 denotes a control value acquisition unit, which acquires the control value for the amount of color material used at the time of output. The control value acquisition method is determined by the type of media used for printing, even if the method is input by a user through an application such as a driver on a PC connected to an image processing apparatus equipped with the system of the present invention. Even if the value is fixed, the means is not limited. Also, different control values may be given for the color materials of CMYK.

  Reference numeral 204 denotes a control data generation unit, which generates control data for generating a mask pattern to be used for color material usage amount control. The control data is image data based on the control value acquired by the control value acquisition unit 203. That is, when the control value is 75%, image data having a density of 75% on the entire surface is the control data. Note that control data is generated from the control values set for each of the CMYK color materials acquired by the control value acquisition unit 203. If the CMYK control values are the same, one control is performed to further reduce the memory usage. It is also possible to generate only data. The size of the control data may be the same size as the input image data, but the screen pattern information used in the halftone processing described later is acquired, and the control data of the same size as each CMYK screen pattern is created. May be.

  In the figure, reference numeral 205 denotes a halftone processing unit, which performs halftone processing on the image data color-converted by the color conversion processing unit and control data generated based on the control value. Although detailed processing of the halftone processing unit will be described later, normal screen processing is considered as the halftone processing. By performing halftone processing, pseudo halftone image data is generated from the image data subjected to color conversion processing, and a mask pattern is generated from the control data.

  In the figure, reference numeral 206 denotes a logical operation processing unit which takes a logical product of pseudo halftone image data subjected to halftone processing and a mask pattern and performs dot thinning processing. Details of the processing of the logical operation unit will also be described later. As a result of the logical operation processing with the mask data, the image data subjected to the halftone processing cannot take a density value higher than the control value acquired by the control value acquisition means, and controls the amount of color material used. It becomes possible.

  FIG. 3 shows a flowchart of the color material usage amount control process according to the first embodiment of the present invention, and FIG. 4 shows a more detailed data flow regarding the halftone processing unit 205 and the logical operation processing unit 206 of the present invention. A detailed flow of color material usage amount control processing according to the present invention will be described with reference to FIGS. 3 and 4.

  First, screen processing is performed on the image data input in S301 of FIG. 3 using a certain screen pattern. In FIG. 4, the halftone processing unit 205 performs screen processing on the input image data 401 using screen pattern 1 (402). As a result, pseudo halftone image data 403 subjected to halftone processing is generated from the image data 401. Next, in S302, it is determined whether or not a control value for the amount of color material used in printing is determined. At this time, if the control value is not defined, the screen-processed pseudo halftone image data 403 is output as it is.

  On the other hand, if it is determined that the control value is determined, control data is first generated from this control value (S304). For example, when the control value 404 is 75% in FIG. 4, control data 405 having a gradation of 75% per pixel is generated for all pixels. Next, screen processing is performed on the generated control data 405 using the same screen pattern 1 (402) as the screen pattern used in the screen processing of S301 (S305). As a result, a mask pattern 406 for density control is generated. Controlled image data 407 in which the usage amount of the color material is controlled by performing a logical operation on the pseudo halftone image data 403 subjected to the screen processing and the generated mask pattern 406 by the logical operation processing unit 206 (S306). Is generated and output as processing data.

  In the first embodiment of the present invention, the same screen pattern is used for image data and control data for each color material of CMYK as the screen pattern used in the screen processing. That is, the same screen pattern as that applied to the C plane of the image data is also applied to the C plane of the control data, and the same processing is performed for the MYK plane. The mask pattern is a mask pattern with an area gradation based on the screen pattern. By using the same screen pattern when creating the image data and the mask pattern data, the mask pattern is turned on in the low density portion. On the other hand, in the high density portion, the mask pattern is OFF for the control value or more.

  A specific example of the image processing process in the first embodiment of the present invention is shown in FIG.

  FIG. 5 shows a process when halftone processing is performed using the same screen pattern and the same control value is given. FIG. 5A shows an example in which the density of the input image data is 87.5%, which is a relatively high density, and FIG. 5B shows an example in which the density is 25%, which is a relatively low density. Both density control values are 75%. It is said.

  In FIG. 5A, the image data 501a having 87.5% density is first subjected to screen processing using the screen pattern 502, thereby generating pseudo-halftone image data 503a having 87.5% density. On the other hand, when the control value 505 is given as 75%, first, control data 506 that is image data with 75% density is generated.

  Next, in the screen processing, the screen processing is performed on the control data using the same screen pattern 502 as that used for the image data. As a result, a mask pattern 507 is generated, and controlled image data 508a is generated by calculating a logical product of the mask pattern 507 and the pseudo halftone image data 503a. At this time, since the mask pattern has a control value of 75%, in the example of 87.5% density in which the image data exceeds the control value, dots are thinned out as a result of the logical operation.

  On the other hand, in FIG. 5B, the 25% density image data 501b is first subjected to screen processing using the screen pattern 502, thereby generating 25% density pseudo halftone image data 503b. Similarly to the description of FIG. 5A, when the control value 505 is given as 75%, the control data 506 is generated, and the mask pattern 507 is generated by performing screen processing. Controlled image data 508b is generated by calculating the logical product of the mask pattern 507 and the pseudo halftone image data 503b. At this time, the mask pattern has a control value of 75%. However, since the image data has a control value of the following 25% density, dots are not thinned out even if a logical operation is performed, and the density is saved. become.

  FIG. 6 shows the density characteristics of the data controlled by the first embodiment of the present invention.

  In FIG. 6, a thick line 601 indicates the density characteristic of the data controlled according to the first embodiment of the present invention, and a dotted line 602 indicates the density characteristic when there is no control. As can be seen from FIG. 6, the density characteristics of the lower density part than the control value are not changed. As a result, it is possible to prevent the image quality deterioration in the low density portion, which is a problem in the thinning process using the mask pattern. Further, in the high density portion, the dot thinning process is performed on data that is equal to or higher than the control value, and the use amount of the color material can be controlled by controlling the density.

  In the figure, reference numeral 206 denotes an image data output unit, which performs modulation processing on the controlled image data in which the amount of color material used is controlled by logical operation processing with a pulse width corresponding to the irradiation time of laser exposure, thereby generating a latent image. Form data. Further, the latent image data is sent to the printer engine to print out as an output image.

  As described above, in Embodiment 1 of the present invention, when the amount of color material used is reduced by performing an AND operation between image data and a mask pattern, it is used for halftone processing of image data. A mask pattern generated using a screen pattern is used. As a result, it is possible to easily control the usage amount of the color material by controlling the usage amount of the color material only in the high density portion while preventing the deterioration of the image quality in the low density portion.

<Embodiment 2>
In the first embodiment, the screen processing in the halftone processing unit is realized with only one screen pattern for the image data. On the other hand, when halftone processing is performed, a screen pattern corresponding to the characteristics of the data is often applied to each normal object. In other words, a screen pattern that emphasizes low gradation with a low number of lines is applied to an image object such as a natural image, while a screen pattern that emphasizes a resolution with a high number of lines is applied to a text object that is character data. Therefore, the second embodiment corresponds to the case where the screen pattern is different for each object.

  Also in the second embodiment, the image data input unit and the image data output unit are the same as those in the first embodiment, and detailed description thereof is omitted.

  FIG. 7 shows a more detailed data flow regarding the halftone processing unit, the logical operation unit, and the integration processing unit according to the second embodiment of the present invention. This corresponds to FIG. 4 showing the flow of processing in the first embodiment. The second embodiment will be described with reference to the drawings.

  In FIG. 7, the halftone processing unit 702 performs screen processing on the input image data 701 using a screen pattern corresponding to the type of each object. At this time, screen processing is performed using the screen pattern (703) for the graphic object, screen pattern 2 (704) for the image object, and screen pattern 3 (705) for the text object. As a result, pseudo halftone image data 706 subjected to halftone processing for each object is generated from the image data 701. Next, when a control value is determined for each object, control data 708 is generated from the control value 707. Here, even when the control value is not given for each object, the processing may be performed assuming that the same control value is given for all the objects.

  Screen processing is performed on the control data 708 generated for each object using the same screen pattern as that used in the screen processing of the corresponding object. That is, screen processing is performed using screen pattern 1 (703) for graphic object control data, screen pattern 2 (704) for image object control data, and screen pattern 3 (705) for text object control data. As a result, a mask pattern 709 for each object is generated from the control data. The logical operation processing unit 710 performs logical operation on the screen-processed pseudo halftone image data 706 and the generated mask pattern 709 for each object, so that object data whose color material usage is controlled is obtained. Generated. The integrated processing unit 711 integrates the individual object data whose color material usage is controlled into one image data, thereby generating controlled image data 712, which is output as processed data.

  The density characteristics of the controlled image data in the second embodiment are the same as those shown in FIG. 6 of the first embodiment. Therefore, since the density characteristic of the low density portion is not changed from the control value, it is possible to prevent the image quality deterioration in the low density portion, which is a problem in the thinning process using the mask pattern. Further, in the high density portion, the dot thinning process is performed on data that is equal to or higher than the control value, and the use amount of the color material can be controlled by controlling the density.

  As described above, according to the second embodiment of the present invention, when the color material usage amount is reduced by performing the logical product operation between the image data and the mask pattern, for each object in the halftone processing of the image data. Even when different screen patterns are used, it is possible to easily control the usage amount of the color material by controlling the usage amount of the color material only in the high density portion while preventing the image quality deterioration in the low density portion.

<Embodiment 3>
In the first and second embodiments, the same screen pattern is used in the screen processing performed on the image data and the screen processing when generating the mask pattern. On the other hand, in the third embodiment, the screen pattern used in the screen processing when generating the mask pattern is different from that used in the screen processing performed on the input image data. In the third embodiment, a screen pattern that is applied to input image data and a screen pattern that does not cause interference due to interference are used when generating a mask pattern.

  Also in the third embodiment, the image data input unit and the image data output unit are the same as those in the first embodiment, and detailed description thereof is omitted.

  FIG. 8 shows a more detailed data flow regarding the halftone processing unit and the logical operation unit according to the third embodiment of the present invention. This corresponds to FIG. 4 showing the flow of processing in the first embodiment. The third embodiment will be described with reference to the drawings.

  In FIG. 8, screen processing is performed on the input image data 801 using the screen pattern 1 (803) in the halftone processing unit 802. As a result, pseudo halftone image data 804 subjected to halftone processing is generated from the image data. Next, when a control value is determined for the image data, control data 806 is generated from the control value 805. Screen processing is performed on the generated control data 806 using a screen pattern 2 (807) different from the screen pattern 1 (803) used in the screen processing for the image data. At this time, it is desirable that the screen pattern 1 (803) and the screen pattern 2 (807) are patterns that do not interfere with each other. As a result, a mask pattern 808 for density control is generated. The logical operation processing unit 809 performs logical operation on the screen-processed pseudo halftone image data 804 and the generated mask pattern 808 to generate controlled image data 810 in which the amount of color material used is controlled. Is output as processing data.

  In the third embodiment, unlike the first and second embodiments, the amount of toner used can be controlled in all input density ranges. At this time, it is possible to avoid the problem of image quality degradation by using a screen pattern that does not interfere with a screen pattern applied to input image data when generating a mask pattern.

  As described above, in the third embodiment of the present invention, when the amount of color material used is reduced by performing an AND operation between image data and a mask pattern, it is used for halftone processing of image data. A mask pattern generated using a screen pattern that hardly interferes with the screen pattern is used. As a result, it is possible to easily control the amount of color material used while preventing image quality deterioration in the entire density range.

<Embodiment 4>
The third embodiment can be applied to the drawing of a translucent figure as well as the control of the amount of color material to be used. However, the third embodiment is based on the premise that the background of a graphic is not drawn when drawing a translucent graphic, and no consideration is given to the case where an image exists in the background. Therefore, the method corresponding to the drawing of the background image when drawing the translucent figure is the fourth embodiment.

  Also in the fourth embodiment, the image data input unit and the image data output unit are the same as in the first embodiment, but the input data is the image data to be rendered translucent and the background of the image data. There are two types of background image data.

  FIG. 9 shows a more detailed data flow regarding the halftone processing unit, the logical operation unit, and the integration processing unit according to the fourth embodiment of the present invention. This corresponds to FIG. 4 showing the flow of processing in the first embodiment. The fourth embodiment will be described with reference to the drawings.

  In FIG. 9, the halftone processing unit 902 performs screen processing on image data 901 to be translucently drawn using screen pattern 1 (903). As a result, pseudo halftone image data 904 subjected to halftone processing is generated from the image data.

  Next, screen processing is performed using the screen pattern 3 (906) in the halftone processing unit 902 on the background data 905 that is the background of the figure to be translucently rendered. As a result, pseudo halftone background image data 907 subjected to halftone processing is generated from the background image data. At this time, it is desirable that the screen pattern 1 (903) and the screen pattern 3 (906) are patterns that do not interfere with each other. The screen pattern 1 and the screen pattern 3 may be the same screen pattern.

  Next, the transparency for the image data to be rendered semi-transparent is used as a control value, and control data 909 is generated from this control value 908. A screen pattern 2 (910) different from the screen pattern 1 (903) and screen pattern 3 (906) used in the screen processing for the image data and the background image data is used for the generated control data 909. Process. At this time, the screen pattern 2 (910) is desirably a pattern that does not interfere with the screen pattern 1 (903) and the screen pattern 3 (906). As a result, a mask pattern 910 for controlling transparency is generated.

  First, a logical operation is performed on the pseudo halftone image data 904 subjected to the screen processing and the generated mask pattern 910 by the logical operation processing unit 912, so that the image data is first made transparent. Further, the reversal processing unit 911 performs reversal processing on the mask pattern 910, and the logical operation processing unit 912 performs logical operation on the mask pattern after the reversal processing and the pseudo halftone background image data 907 to make the background image transparent. Processing is also performed. The inversion processing is processing that turns OFF when the mask pattern bit is ON and turns ON when the bit is OFF. The image data and the background image data that have been subjected to the logical operation processing are integrated by the integration processing unit 913, thereby generating translucent image data as if the background is seen through.

  As described above, in the fourth embodiment, it is possible to control the amount of color material used for data by performing a logical operation on the image data and the background data on which the mask pattern is subjected to inversion processing. Further, since the mask pattern is generated based on the transparency, it becomes possible to draw a translucent figure flexibly with respect to the transparency.

  The present invention is particularly useful for an image processing apparatus that controls the amount of color material used by performing an AND operation between image data and a mask pattern.

It is a figure explaining the problem in the logical operation process with the conventional mask pattern. It is a block diagram explaining Embodiment 1 of this invention. It is a flowchart for demonstrating the usage-amount control process of the coloring material of this invention. It is the figure which showed the detailed data flow of Embodiment 1 of this invention. It is a figure explaining the specific example of the image processing process in Embodiment 1 of this invention. It is a figure explaining the specific example of the image processing process in Embodiment 1 of this invention. It is the figure which showed the density | concentration characteristic of the data controlled by embodiment of this invention. It is the figure which showed the detailed data flow of Embodiment 2 of this invention. It is the figure which showed the detailed data flow of Embodiment 3 of this invention. It is the figure which showed the detailed data flow of Embodiment 4 of this invention.

Explanation of symbols

201 Image data input unit 202 Color conversion processing unit 203 Control value acquisition unit 204 Control data generation unit 205 Halftone processing unit 206 Logical operation processing unit

Claims (4)

  First halftone processing means for performing screen processing on the input image data and generating a pseudo halftone image; and a control value obtaining means for obtaining a control value for controlling a signal value of the pseudo halftone image; A control data generating unit that generates control data from the control value acquired by the control value acquiring unit, and a second halftone that generates a mask pattern by performing screen processing on the control data generated by the control data generating unit. An image processing apparatus comprising: processing means; and logical operation processing means for performing a logical operation of the pseudo halftone image and the mask pattern.   2. The second halftone processing means for generating the mask pattern uses the same screen pattern as the screen pattern used in the first halftone processing means at the time of screen processing. Image processing device.   2. The second halftone processing means for generating the mask pattern uses a screen pattern different from the screen pattern used in the first halftone processing means at the time of screen processing. Image processing device.   Screen processing is performed on the input first image data and first halftone processing means for generating a first pseudo halftone image, and screen processing is performed on the input second image data to perform the first processing. Acquired by a second halftone processing means for generating two pseudo halftone images, a control value obtaining means for obtaining a control value for controlling a signal value of the first pseudo halftone image, and obtained by the control value obtaining means Control data generating means for generating control data from the control values, and third halftone processing means for generating a first mask pattern by performing screen processing on the control data generated by the control data generating means, Reversing processing means for performing reversal processing on the first mask pattern to generate a second mask pattern, and performing logical operations on the first pseudo halftone image and the first mask pattern, The image processing apparatus characterized by comprising: a logic operation means and the second pseudo-halftone image performing a logic operation of the second mask pattern.

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