JP2015119350A - Image processing apparatus, image forming apparatus, image processing method, and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus that can reduce the amount of toner used in printing processed images, and collect a plurality of pieces of image data with the readability of character parts being favorably maintained without affecting parts other than the character parts.SOLUTION: An image processing apparatus 100 includes an output unit 3 that collects a plurality of pages of image data into one page of image data and outputs the collected image data, a character image extraction unit 5 that extracts a character image from the image data, and a γ-correction unit 25 that improves the readability of the character image, where the γ-correction unit 25 improves the readability of the character image extracted by the character image extraction unit 5 when the collection is performed.

Description

  The present invention relates to an image processing apparatus, an image forming apparatus, an image processing method, and an image processing program, and more particularly to an image processing apparatus, an image forming apparatus, an image processing method, and an image processing program for performing aggregate printing.

  Conventionally, in image forming apparatuses such as printers, copiers, and MFPs, there are cases where it is desired to reduce the number of printed sheets in order to reduce power consumption and printing paper consumption, or to keep the number of printed sheets within a desired number. In such a case, techniques such as aggregate printing and double-sided printing are already known as methods for printing with the number of printed sheets being reduced from the actual number of pages. In the collective printing, for example, an image of a document for a number of pages corresponding to two pages or four pages is printed on one page of paper.

  A ratio between the number of pages of the original image and the number of pages of the print result to be output in the aggregate printing is called an aggregation rate. Aggregating N original page images into one page is called Nin1, and the aggregation rate at this time is N. In the setting of the aggregate printing function, in general, many can be selected from a plurality of options such as “2 in 1, 4 in 1, 9 in 1. In the case of aggregation by Nin1, since the area of one page of the original image is reduced to 1 / N, the original page image is reduced and printed each time N increases.

  In the case of performing collective printing, it has been demanded to improve the visibility of printing results and reduce the printing cost rather than improving the printing quality. As a technique for reducing the printing cost, a toner save mode function for saving the amount of toner used is known in addition to aggregate printing. In order to improve the visibility and reduce the printing cost, the following technologies are disclosed.

  In the image forming apparatus disclosed in Patent Document 1, a lower limit character size for ensuring a certain degree of legibility is set in advance. When performing aggregate printing with a specified aggregation rate, if the character size becomes smaller than the lower limit character size when printing at the specified aggregation rate, the aggregation rate is such that the character size is greater than or equal to the lower limit character size. Change to

  In the image forming apparatus disclosed in Patent Document 2, printing is performed in the toner save mode when performing aggregate printing, and the amount of toner to be used can be adjusted according to the aggregation rate.

  In the image forming apparatus disclosed in Patent Document 3, it is possible to reduce the amount of toner used by not using color components that are not dominant among colors used in image data.

  In collective printing, when the toner density of the character portion increases, toner bleeding may occur and the character may be crushed. In addition, color misregistration occurs due to an increase in toner amount, the color changes, and the legibility of characters deteriorates.

  In the image forming apparatus of Patent Document 1, it is possible to ensure the legibility of characters by reducing the aggregation rate, but there is a problem that aggregate printing may not be performed at the aggregation rate requested by the user.

  The image forming apparatus disclosed in Patent Document 2 has a problem in that although the entire toner usage amount is limited by the toner save mode and the collapse of characters can be prevented, the print quality of portions other than the characters is deteriorated.

  In the image forming apparatus disclosed in Patent Document 3, the amount of toner to be used can be reduced, but the reduction in the amount of toner used in aggregate printing is not considered.

  The object of the present invention is to reduce the amount of toner used when printing processed images, and to collect image data with good readability of character parts without affecting other parts than characters. Is to provide a simple image processing apparatus.

  The image processing apparatus according to the present invention improves the legibility of the character image by aggregating means for aggregating a plurality of pages of image data into one page of image data, a character image extracting means for extracting a character image from the image data, and A legibility improving means for improving the legibility of the character portion extracted by the character image extracting means when the aggregating means performs aggregation. It is characterized by making it.

  According to the present invention, the amount of toner used when printing a processed image can be reduced, and image data can be consolidated with good readability of character portions without affecting portions other than characters. An image processing apparatus can be provided.

1 is a block diagram showing a configuration of Embodiment 1 of an image processing apparatus of the present invention. It is a flowchart figure which shows the flow of a process of Embodiment 1 of the image processing apparatus of this invention. It is a figure which shows the flow of the character image determination process of the character image extraction means of Embodiment 1 of the image processing apparatus of this invention. 6 is a comparison of input density and output density for each aggregation rate by γ correction of the image processing apparatus according to the first embodiment of the present invention. It is a figure which shows the dot formed in Embodiment 1 of the image processing apparatus of this invention. It is a block diagram which shows the structure of Embodiment 2 of the image processing apparatus of this invention. It is a figure which shows the area | region of the color which Embodiment 2 of the image processing apparatus of this invention reduces. It is a figure which shows the color plate formed in Embodiment 2 of the image processing apparatus of this invention. It is a block diagram which shows the structure of Embodiment 3 of the image processing apparatus of this invention.

<Configuration of Embodiment 1>
The configuration of the first embodiment of the image processing apparatus of the present invention will be described with reference to FIG. The image processing apparatus 100 includes an image input unit 1, an image processing unit 2, an image output unit 3, an aggregation condition acquisition unit 4, and a character image extraction unit 5. The image input unit 1 receives an image from a scanner or the like, and the image output unit 3 outputs the image to a printer or the like. The image output unit 3 can aggregate and output images of a plurality of pages into one page, and also functions as an aggregation unit. The character image extraction unit 5 functions as an image extraction unit.

  The image processing unit 2 includes a scanner γ processing unit 21, a filter processing unit 22, a color correction unit 23, an inking process unit 24, a γ correction unit 25, and a gradation processing unit 26.

<Operation of Embodiment 1>
The overall operation flow will be described with reference to the flowchart shown in FIG. First, acquisition of aggregation conditions set by user settings or the like (step S1) and image input (step S2) are performed. Either order may be sufficient as the order which performs step S1 and step S2. Next, a character image is determined and extracted from the input image (step S3). If no character image exists (step S4, No), normal image processing is performed (step S5). If there is a character image in step S3 (step S4, Yes), image processing including character image density adjustment is performed (step S6).

  In the image processing (step S5 and step S6), first, as shown in FIG. 1, the scanner γ processing unit 21 applies the scanner γ to the input image. The image data at this time is passed to the character image extraction unit 5. Thereafter, the filter processing unit 22 smoothes and enhances the image, the color correction unit 23 and the inking processing unit 24 convert the image data from the RGB color space to the CMYK color space, and the γ correction unit 25 performs γ correction of the printer. The gradation processing unit 26 creates an output pattern.

  There is a difference in processing in the γ correction unit 25 between image processing without density adjustment (step S5) and image processing with density adjustment (step S6), and the γ correction unit 25 serves as a legibility improving unit. Function. Details of processing contents of the γ correction unit 25 will be described later.

  An example of a method for determining and extracting a character image from image data by the character image extracting unit 5 will be described with reference to FIG. From the results of the edge determination means, the white background determination means, and the halftone dot determination means (not shown), the white background character edge determination means 51 determines a character edge candidate pixel. In the white background character edge determination means 51, when the determination result of the edge determination means is an edge, the determination result of the white background determination means is a white background, and the determination result of the halftone dot determination means is a non-halftone dot, the target pixel is a character edge candidate. It is determined that it is a pixel.

  The aforementioned edge determining means detects 1 dot at a time for both the inner edge and the outer edge as character edge candidate pixels. The total of 2 dots for 1 dot each inside and outside is insufficient for the filter processing. Therefore, the expansion processing is performed by the expansion processing 52, and the result is set as “character edge”. The dilation process 52 is a process for referring to a 3 × 3 pixel edge candidate pixel centered on the pixel of interest and setting the pixel of interest as a character edge if there is at least one character edge candidate pixel. In this embodiment, the expansion amount is 3 × 3.

  In the black character / color character determination 53, it is determined that the character edge is a chromatic color and is a “color character”, and if the character edge is an achromatic color, it is determined that the character is a “black character”. This method is an example of a character image extraction method, and character images may be extracted by other methods.

  Here, the description returns to the image processing flow shown in FIG. The aforementioned γ correction unit 25 determines the accuracy of character image determination and the degree of γ correction for the character image extracted by the character image extraction unit 5 with reference to the aggregation condition acquired by the aggregation condition acquisition unit 4.

  Processing performed by the γ correction unit 25 will be described with reference to FIG. A printer γ correction table stored in a storage means (not shown) stores the density of the output image with respect to the density of the input image. FIG. 4 illustrates the relationship between the density of the input image and the density of the output image stored in the printer γ correction table.

  Γ correction is performed on the density of the input image shown on the horizontal axis in FIG. 4 so that the density of the output image becomes the density shown on the vertical axis. As shown in FIG. 4, the relationship between the density of the input image and the density of the output image varies depending on the aggregation condition. In particular, as the aggregation rate increases, the density of the high density portion is greatly reduced. Also, in any aggregation condition, a solid density is set, so that no matter what the input density is, the density is not higher than the solid density. For example, in 4in1 printing, the solid density is 1.4, which is smaller than that in normal printing and larger than that in 8in1 printing.

  FIG. 5 shows a schematic diagram of black character formation patterns when the density is lowered and when it is not lowered. Normally, when outputting black characters, the character pattern is output as shown in FIG. 5 (a) unless the density is specified. Next, in the case where the high density is lowered, for example, when the solid density is lowered to 1.3 and output, the black character portion is adjusted to the output density. Therefore, a dither pattern is used to match the density of the black character portion, and the character portion is formed with halftone dots as shown in FIG. The pattern shape varies depending on the dither pattern, but the interval and size of the halftone dot shape are set according to the output density.

<Operation / Effect of Embodiment 1>
As described above, the first embodiment is characterized in that the gamma correction unit 25 adjusts the density to improve the legibility of characters in the aggregated image. As shown in FIG. 4, for example, the density of the solid portion where the density is the maximum under normal output conditions is 1.5, but the solid density is 1.4 for 4in1, and the solid density is 1.3 for 8in1. .

  At that time, the normal γ is maintained because the legibility decreases when the density is lowered from the highlight to the medium density. The standard for maintaining γ in the normal state is, for example, an input density of 1.0. If the input density is greater than 1.0, γ may be set stepwise so that the solid density is matched to each aggregation rate. If the density is 1.0 or more, there is no problem in legibility even if the density is somewhat reduced.

  Since the size of the character image changes depending on the aggregation condition, the density of the high-density part of the printer γ is lowered according to the aggregation rate, so that the toner adhesion amount is reduced, the character blur is suppressed, and the character readability is maintained. I can do it.

<Configuration and Operation of Second Embodiment>
The configuration of the image processing apparatus according to the second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in that the extraction result in the character image extraction unit 5 is sent to the inking unit 24 instead of the γ correction unit 25, and the inking unit 24 functions as a legibility improving unit. Is different.

  Processing performed in the inking processing unit 24 in the second embodiment will be described with reference to FIG. FIG. 7 is a color space graph showing examples of primary colors of Y, M, and C in Lab. The primary color is based on the toner color to be output, and each CMY exists in the direction as shown in the figure.

  The image data is converted from RGB to CMYK after color correction. However, in the case of aggregation, for a portion determined to be a character image, a secondary color distributed at a position close to the primary color of CMY is a color that is not dominant. Reduce. The portion where the density of the secondary color close to the primary color is high is located at a location away from the origin as indicated by the hatched portion in FIG.

  FIG. 7 schematically shows the deleted area. For example, when the color conversion from RGB to CMY is performed, the portion where the ratio of the color that does not dominate the dominant color is 10% or less is shown. The color data is set to 0. As an example, if there is a color where C is 90 and M is 10, this is converted so that C is 90 and M is 0 and becomes the primary color. The same processing is performed for the colors after the tertiary color.

  The above processing method is one example. For example, when the color conversion from RGB to CMY is performed, the color ratio of the least dominant color with an emphasis on gradation is 5% or less. The data may be set to 0, or the colors after the tertiary color may be reduced and converted to the secondary color. Further, referring to the aggregation condition, the rate of reduction may be increased as the aggregation rate increases.

  However, it is desirable that the inking process is performed and the calculated K is not subject to reduction. In the inking process, the portion where C, M, and Y are equal is replaced with K in consideration of the CMY balance. Therefore, if K is temporarily reduced, the color balance is greatly lost.

<Operation and Effect of Embodiment 2>
8A shows an example of a color plate formation state in the case of printing with a secondary color, and FIG. 8B shows an example of a color plate formation state in the case of printing with a primary color. As shown in FIG. 8A, when a color shift occurs between the color plate 241a of the dominant color and the color plate 241b of the non-dominant color, the color changes at the end portion. In the case of characters, it causes blurring. Therefore, by reducing the color plate as shown in FIG. 8B, this edge blur can be prevented, and the character readability is improved.

<Configuration and Operation of Embodiment 3>
The configuration of the third embodiment of the image processing apparatus of the present invention will be described with reference to FIG. The third embodiment is different from the other embodiments in that the extraction result in the character image extraction unit 5 is sent to the gradation processing unit 26 and the gradation processing unit 26 functions as a legibility improving unit.

  The image data is converted into a dither pattern by the gradation processing unit 26 and output from the image output unit 3. At this time, the resolution setting at the time of output is changed in accordance with the aggregation rate and whether there is a character image. For example, when a character image exists, the resolution is 600 dpi if the aggregation rate is 2 or less, and the resolution is 1200 dpi if the aggregation rate is greater than 2.

<Operation and Effect of Embodiment 3>
When the gradation processing unit 26 changes the image data to a dither pattern, the distribution of the dither pattern differs depending on the resolution setting at the time of output. For example, when the aggregation rate is set to 4 in 1 or 8 in 1, the character size is reduced to 1/4 or 1/8 as compared with the normal size. Since the line width is also reduced in proportion thereto, a crowded image such as a character is easily crushed.

  Since the reproducibility of details is improved at 1200 dpi with respect to 600 dpi, the reproducibility of details and the readability of characters when the aggregation rate is large can be improved by applying the third embodiment.

  The above-described embodiment is a preferred embodiment of the present invention, and the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

  For example, γ correction by the γ correction unit 25, reduction in the number of colors in the inking processing unit 24, and change in resolution in the gradation processing unit 26 are cited as means for improving the legibility of characters. You may employ | adopt as a property improvement means.

  The image processing apparatus 100 may be used by being provided in an image forming apparatus. Each operation of the image processing apparatus 100 may be executed by an image processing program installed in the image processing apparatus 100 or a terminal connected to the image processing apparatus 100.

DESCRIPTION OF SYMBOLS 1 Image input part 2 Image processing part 3 Image output part 4 Aggregation condition acquisition part 5 Character image extraction part 21 Scanner gamma processing part 22 Filter processing part 23 Color correction part 24 Inking process part 25 γ correction part 26 Tone processing part

JP 2012-060234 A JP 2002-169417 A JP 2007-243376 A

Claims (7)

Aggregating means for aggregating multiple pages of image data into one page of image data;
A character image extracting means for extracting a character image from the image data;
Readability improving means for improving the readability of the character image;
An image processing apparatus comprising:
The legibility improving means is:
An image processing apparatus characterized by improving the legibility of the character image extracted by the character image extraction unit when the aggregation is performed by the aggregation unit. The legibility improving means is:
2. The image according to claim 1, wherein when the aggregation is performed by the aggregating unit, the readability is improved by performing γ correction so that the density of the image data is smaller than when the aggregation is not performed. Processing equipment. The legibility improving means is:
3. The image processing according to claim 1, wherein when the aggregation is performed by the aggregation unit and a plurality of colors are used, the legibility is improved by deleting a color having a small use ratio. apparatus. The legibility improving means is:
The readability is improved by increasing the resolution of the image data when the aggregation is performed by the aggregation unit as compared with the case where the aggregation is not performed. Image processing apparatus.   An image forming apparatus comprising the image processing apparatus according to claim 1. A character image extraction step for extracting a character image from the image data;
A legibility improving step for improving the legibility of the character image;
An aggregation step of aggregating multiple pages of image data into one page of image data;
An image processing method. In the image processing device,
An image processing program for executing image processing using the image processing method according to claim 6.

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