JP2007110468A - Printer, image processor and processing method, and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To print an image whose dots are inconspicuous whatever image is printed. <P>SOLUTION: Two image processing conditions differing in inconspicuousness of printed dots are stored and an image is printed by performing image processing in which dots are conspicuous first. For an area where dots are conspicuous, image processing wherein dots are inconspicuous is performed to obtain a final printed image. Consequently, the image can be printed by performing the image processing in which dots are inconspicuous for a part where dots are conspicuous whatever image is printed, so the image whose dots are inconspicuous can surely be printed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for printing an image by forming dots on a print medium, and more particularly to a technique for printing a good image in which dots are not noticeable.

  A so-called dot printer that prints an image by forming dots on a print medium is widely used as an output device for an image created by a computer or an image taken by a digital camera. The images printed by these dot printers are expressed using dots, and if the dots are conspicuous, they give the viewer a rough impression and become an image with poor so-called graininess.

  Therefore, a technique has been proposed in which a plurality of types of dots having different sizes can be formed, and an image is printed while properly using dots according to the gradation value of an image region to be expressed (Patent Document 1). According to the proposed technology, small dots are formed in areas where dots are conspicuous so that images can be printed while avoiding deterioration of graininess. Form and print the image. In a gradation region that cannot be expressed only with small dots, the dots are relatively inconspicuous, so even if large dots are formed, the graininess of the image does not deteriorate. In this way, it is possible to print an image with greatly improved graininess by properly using dots having different sizes.

JP-A-6-286138

  However, even when an image is printed using different sizes of dots, there is a problem that dots may still be conspicuous in a partial area of the printed image. This is because not only the size of a dot is conspicuous, but also the dot color and the background color and brightness on which the dot is formed. Although the conditions for switching the thickness are determined in consideration of these effects, the print image has a wide variety of combinations of color and lightness, so it is difficult to actually consider all the situations. It is done.

  The present invention has been made to solve the above-described problems in the prior art, and is a technique capable of printing a high-quality image in which dots are not conspicuous when printing any image. For the purpose of provision.

In order to solve at least a part of the problems described above, the printing apparatus of the present invention employs the following configuration. That is,
A printer that prints an image by performing predetermined image processing on the image data and converting it into dot data that indicates the presence or absence of dot formation for each pixel, and then forming dots on a print medium according to the dot data. And
Image processing condition storage means for storing a first image processing condition and a second image processing condition that differ in the degree of difficulty of conspicuous dots in the image when the image is printed;
An image quality confirmation image printing unit for printing an image quality confirmation image for confirming the image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
Position designation for receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the conspicuousness of dots as a result of confirming the image quality confirmation image Information receiving means;
Image quality improvement region extraction means for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. Image quality improvement dot data generation means for generating data as image quality improvement dot data;
The gist of the present invention is to provide an image quality improvement image printing means for printing an image quality improvement image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium according to the image quality improvement dot data.

Also, the printing method of the present invention corresponding to the above printing apparatus is
This is a printing method in which image data is subjected to predetermined image processing and converted into dot data representing the presence or absence of dot formation for each pixel, and then an image is printed by forming dots on a print medium according to the dot data. And
A first step of storing a first image processing condition and a second image processing condition in which the degree of difficulty of conspicuous dots in the image is printed when the image is printed;
A second step of printing an image quality confirmation image for confirming image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
As a result of confirming the image quality confirmation image, a position designation information designated for identifying the occurrence position of the image quality improvement region determined to require improvement of the difficulty of conspicuous dots on the image quality confirmation image is received. And the process of
A fourth step of receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. A fifth step of generating data as image quality improvement dot data;
The present invention includes a sixth step of printing an image quality improved image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium according to the image quality improved dot data.

  In the printing apparatus and the printing method of the present invention, the image quality confirmation image is printed by performing image processing under the image processing condition (first image processing condition) that makes dots more conspicuous. Next, the designation of the generation position of an area (image quality improvement area) that is determined to require improvement in the dot inconspicuousness in the image quality confirmation image is received, and for the image quality improvement area, the image processing condition for the dot inconspicuous Image processing is performed under (second image processing conditions), and an image (image quality improved image) is printed.

  The image quality improvement image obtained in this way is printed as it is in an image area where dots are not noticeable, and is printed in a state where dots are less noticeable in image areas where dots are conspicuous, so that the dots are not noticeable in all areas. ing. In addition, since the image quality improvement image can be printed after actually printing the image and confirming the image area where the dots are conspicuous, the dots are conspicuous in some areas, regardless of what image is printed. It is possible to surely avoid this.

  Such a printing apparatus receives RGB image data expressed by gradation values of red, green, and blue colors, and forms dots of cyan, magenta, yellow, and black colors on a print medium, thereby forming a color image. Can be printed, the following conditions may be stored as the first image processing condition and the second image processing condition, respectively. That is, as the first image processing condition, the first color conversion table referred to convert RGB image data into CMYK image data expressed by gradation values of each color of cyan, magenta, yellow, and black. Remember. In addition, as the second image processing condition, a second color conversion table in which the black tone value is suppressed as compared with the first color conversion table may be stored.

  Since black dots are more conspicuous than cyan, magenta, and yellow dots, the first color can be obtained by performing color conversion with reference to the second color conversion table in which black gradation values are suppressed. An image with less conspicuous dots can be printed than when referring to the conversion table. Therefore, if the first color conversion table and the second color conversion table are stored as the first image processing condition and the second image processing condition, respectively, the dot is conspicuous in any image. It is possible to print a non-image.

  Further, when the printing apparatus prints an image by forming a plurality of types of dots having different sizes on the print medium, the first image processing condition and the second image processing condition are respectively The following conditions may be stored. That is, as the first image processing condition, a first conversion table that is referred to in order to convert image data into formation density for various dots is stored. Further, as the second image processing condition, a second conversion table in which formation of large dots is suppressed as compared with the first conversion table may be stored.

  Since the dots become more conspicuous as they become larger, if the second conversion table in which the formation of large dots is suppressed is referred to, an image in which the dots are less conspicuous is printed than when the first conversion table is referred to. Can do. Accordingly, if the first conversion table and the second conversion table are stored as the first image processing condition and the second image processing condition, respectively, an image in which dots are not noticeable in any image. Can be printed.

  In the various printing apparatuses described above, the image quality improvement dot data may be generated as follows. That is, first, the improved area dot data is generated by converting the image data for the image quality improved area into dot data in accordance with the second image processing condition. Next, the image quality improvement dot data may be synthesized by replacing the dot data for the image quality improvement region in the dot data generated for printing the image quality confirmation image with the improvement region dot data.

  In this way, it is sufficient to generate the improvement area dot data only for the image quality improvement area, and for the areas other than the image quality improvement area, image processing for generating the image quality improvement dot data is not required, so the image quality improvement dots can be quickly generated. Data can be generated, and as a result, an image in which dots are not noticeable can be quickly printed.

  Alternatively, in the various printing apparatuses described above, the image quality improvement dot data may be generated as follows. That is, image processing is performed on the entire image data. As the image processing conditions at that time, the second image processing condition is applied to the image quality improvement region, and the first image processing is applied to the region other than the image quality improvement region. The image quality improvement dot data may be generated while applying the conditions.

  In this way, it is possible to generate image quality improvement dot data simply by switching the image processing conditions. In particular, since image processing of the entire image data is performed in the image quality confirmation image printing process, switching image processing conditions makes it possible to generate image quality improvement dot data while utilizing such processing, which is preferable. .

In addition, the above-described printing apparatus and printing method according to the present invention performs predetermined image processing on image data in order to print an image by forming dots on a print medium, thereby determining whether or not dots are formed for each pixel. If attention is paid to the point that the represented dot data is generated, the present invention can be grasped as an image processing apparatus and an image processing method as follows. That is, the image processing apparatus of the present invention
An image processing apparatus that performs predetermined image processing on image data representing an image and generates dot data representing the presence or absence of dot formation for each pixel in order to form dots on a print medium and print the image Because
Image processing condition storage means for storing a first image processing condition and a second image processing condition that differ in the degree of difficulty of conspicuous dots in the image when the image is printed;
The image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous, and the obtained dot data is output to print an image quality confirmation image for confirming the image quality Dot data output means;
Position designation for receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the conspicuousness of dots as a result of confirming the image quality confirmation image Information receiving means;
Image quality improvement region extraction means for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. The gist of the present invention is that the image quality improvement dot data generation means for generating data as image quality improvement dot data is provided.

The image processing method of the present invention corresponding to the above image processing apparatus is
An image processing method for performing dot image formation on a print medium and printing image data representing the image with predetermined image processing to generate dot data representing the presence or absence of dot formation for each pixel Because
A step (A) of storing a first image processing condition and a second image processing condition having different degrees of difficulty of conspicuous dots in the image when the image is printed;
Converting the image data into the dot data in accordance with a first image processing condition in which the dots are conspicuous, and outputting the obtained dot data for printing an image quality confirmation image for confirming image quality ( B) and
A step of receiving position designation information designated for identifying, on the image quality confirmation image, an occurrence position of an image quality improvement area that is determined to require improvement in the conspicuousness of dots as a result of confirming the image quality confirmation image ( C) and
Receiving the position designation information and extracting the image quality improvement region (D);
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. And a step (E) of generating data as image quality improvement dot data.

  Also in the image processing apparatus and the image processing method of the present invention, the image quality improvement region designated based on the image quality confirmation image is subjected to image processing under image processing conditions in which dots are not noticeable, and image quality improved dot data is generated. be able to. For this reason, if an image is printed based on the image quality improvement dot data obtained in this way, it is possible to reliably prevent dots from being conspicuous in some areas, regardless of what image is printed. Become.

Furthermore, the present invention can be realized using a computer by causing a computer to read a program for realizing the above-described printing method or image processing method and executing a predetermined function. Therefore, the present invention includes the following program or a mode as a recording medium on which the program is recorded. That is, the program of the present invention corresponding to the printing method described above is
A method of printing an image by performing predetermined image processing on image data and converting the data into dot data representing the presence or absence of dot formation for each pixel, and then forming dots on a print medium according to the dot data. A program for realizing using
A first function for storing a first image processing condition and a second image processing condition in which the degree of difficulty of conspicuous dots in the image is different when the image is printed;
A second function of printing an image quality confirmation image for confirming the image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
As a result of confirming the image quality confirmation image, a position designation information designated for identifying the occurrence position of the image quality improvement region determined to require improvement of the difficulty of conspicuous dots on the image quality confirmation image is received. Functions and
A fourth function for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. A fifth function for generating data as image quality improvement dot data;
The gist is to realize a sixth function for printing an image quality improved image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium according to the image quality improved dot data.

The recording medium of the present invention corresponding to the above program is
A program that prints an image by performing predetermined image processing on image data and converting it into dot data that indicates the presence or absence of dot formation for each pixel, and then forming dots on a print medium according to the dot data. A recording medium recorded so as to be readable by
A first function for storing a first image processing condition and a second image processing condition in which the degree of difficulty of conspicuous dots in the image is different when the image is printed;
A second function of printing an image quality confirmation image for confirming the image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
As a result of confirming the image quality confirmation image, a position designation information designated for identifying the occurrence position of the image quality improvement region determined to require improvement of the difficulty of conspicuous dots on the image quality confirmation image is received. Functions and
A fourth function for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. A fifth function for generating data as image quality improvement dot data;
According to the image quality improvement dot data, a program for realizing, using a computer, a sixth function for printing an image quality improvement image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium. It is a summary.

Furthermore, the program of the present invention corresponding to the image processing method described above is
In order to form dots on a print medium and print an image, a method of performing predetermined image processing on image data representing the image and generating dot data representing the presence or absence of dot formation for each pixel, A program for realizing using a computer,
A function (A) for storing a first image processing condition and a second image processing condition having different degrees of difficulty in conspicuous dots in the image when the image is printed;
A function of converting the image data into the dot data in accordance with a first image processing condition in which the dots are conspicuous, and outputting the obtained dot data for printing an image quality confirmation image for confirming image quality ( B) and
A function of receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the difficulty of conspicuous dots as a result of confirming the image quality confirmation image ( C) and
A function (D) for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. The gist is to realize a function (E) for generating data as image quality improvement dot data.

The recording medium of the present invention corresponding to the above program is
In order to form dots on a printing medium and print an image, a program that performs predetermined image processing on image data representing the image and generates dot data representing the presence or absence of dot formation for each pixel, A recording medium recorded in a computer-readable manner,
A function (A) for storing a first image processing condition and a second image processing condition having different degrees of difficulty in conspicuous dots in the image when the image is printed;
A function of converting the image data into the dot data in accordance with a first image processing condition in which the dots are conspicuous, and outputting the obtained dot data for printing an image quality confirmation image for confirming image quality ( B) and
A function of receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the difficulty of conspicuous dots as a result of confirming the image quality confirmation image ( C) and
A function (D) for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. The gist is that a program for realizing the function (E) for generating data as image quality improvement dot data using a computer is stored.

  If these programs are read into a computer and the various functions described above are realized, it is possible to print a high-quality image in which dots are not conspicuous for any image.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Summary of Examples:
B. Device configuration:
B-1. overall structure:
B-2. Internal configuration:
B-2-1. Internal configuration of the scanner unit:
B-2-2. Internal configuration of the printer unit:
C. First embodiment:
C-1. Image quality confirmation image printing process:
C-2. Image quality improved image printing process:
C-3. Modification of the first embodiment:
D. Second embodiment:
D-1. Image quality improved image printing process:

A. Summary of Examples:
Prior to detailed description of the embodiment, an outline of the embodiment will be described with reference to FIG. FIG. 1 is an explanatory diagram showing an overview of a printing apparatus 10 according to the present embodiment. The illustrated printing apparatus 10 prints an image by forming ink dots on the print medium P by ejecting ink droplets from the print head 12 while reciprocating the print head 12 on the print medium P. It is a printer.

  Since an inkjet printer prints an image by forming dots at an appropriate density according to the gradation value of the image data, first, when printing an image, predetermined image processing is performed on the image data. As a result, it is determined whether or not to form a dot for each pixel. Next, an image is printed based on the dot data thus obtained. Further, if the dots become conspicuous, an image having a so-called graininess is deteriorated. Therefore, appropriate image processing conditions are set in advance so as to appropriately perform image processing.

  However, since there are a wide variety of images to be printed, it is difficult to set appropriate image processing conditions assuming all images. Therefore, dots are conspicuous in some areas of the printed image. It can happen. In view of these points, the printing apparatus 10 shown in FIG. 1 prints an image as follows.

  First, the image data is supplied to the “image quality confirmation image printing module” to print an image (image quality confirmation image) for confirming the print image quality. Here, the “module” refers to a series of processing that is internally performed by the printing apparatus 10 to print an image, focusing on the function. Therefore, the “module” can be realized as a part of the program, or can be realized by combining a logic circuit having a specific function or the like. The “image quality confirmation image printing module” prints an image quality confirmation image on the print medium P by performing predetermined image processing on the received image data and then driving the print head 12 according to the obtained dot data. To do.

  As image processing conditions for performing image processing, a plurality of processing conditions are stored in advance in the “image processing condition storage module”. Among these, the first image processing condition is set so as to satisfy all points that should be considered in printing of the image including the difficulty of conspicuous dots in a well-balanced manner. The second image processing condition is an image processing condition that is set with emphasis on the difficulty of conspicuous dots. The “image quality confirmation image printing module” performs image processing according to the first image processing condition set in the “image processing condition storage module”, and prints an image quality confirmation image based on the obtained dot data.

  The operator of the printing apparatus 10 confirms the presence or absence of a portion where dots are conspicuous and graininess is deteriorated by observing the image quality confirmation image printed in this way. On the other hand, the image data is also supplied to the “position designation information receiving module”, and an image to be printed is displayed on the monitor 14 connected to (or incorporated in) the printing apparatus 10. "Is displayed. The operator of the printing apparatus 10 designates on the monitor 14 an image area (image quality improvement area) that has been determined that the graininess has deteriorated and needs to be improved. When specifying the image quality improvement region, various methods are applied, for example, by moving the cursor on the monitor 14 to specify the region, or by inputting the coordinate values of the vertices of the rectangle with the shape of the region being rectangular. be able to. Upon receiving the position designation information designated by the operator of the printing apparatus 10, the “position designation information receiving module” supplies the “position designation information receiving module” to the “image quality improvement area extraction module”, and the “image quality improvement area extraction module” receives the position designation information. Based on the above, an image quality improvement region is extracted from the image quality confirmation image (or image data).

  When the extracted image quality improvement area is received, the “image quality improvement dot data generation module” generates image quality improvement dot data. Here, the image quality improvement dot data means that the image quality improvement area is subjected to image processing according to the second image processing condition set with emphasis on the inconspicuousness of dots, while the area other than the image quality improvement area is , Dot data subjected to image processing in accordance with the first image processing condition. The image quality improvement dot data can be generated by converting the image data into dot data while switching the image processing conditions depending on whether or not the image quality improvement region. Alternatively, when the “image quality confirmation image printing module” prints the image quality confirmation image, if attention is paid to the fact that the image data has already been converted into dot data in accordance with the first image processing condition, only the image quality improvement region portion is changed. Dot data is generated in accordance with the image processing conditions of No. 2, and only the portion of the image quality improvement area in the dot data generated by the “image quality confirmation image printing module” is replaced with dot data based on the second image processing conditions. It is also possible to generate image quality improvement dot data.

  The “image quality improved image printing module” drives the print head 12 in accordance with the image quality improved dot data thus obtained, and forms dots on the print medium P, thereby printing an image quality improved image.

  In this way, by actually observing the image quality confirmation image that has been printed, and for the image area that is determined to require improvement in graininess, image processing is performed under conditions that emphasize graininess, and the image is printed. Can do. For this reason, it is possible to print a high-quality image in which dots are not conspicuous for any image. Below, such a printing apparatus 10 is demonstrated in detail based on an Example.

B. Device configuration :
B-1. overall structure :
FIG. 2 is a perspective view showing the external shape of the printing apparatus 10 according to the present embodiment. As illustrated, the printing apparatus 10 according to the present exemplary embodiment includes a scanner unit 100, a printer unit 200, an operation panel 300 for setting operations of the scanner unit 100 and the printer unit 200, and the like. The scanner unit 100 has a scanner function of reading a printed image and generating image data, and the printer unit 200 has a printer function of receiving image data and printing an image on a print medium. . Further, if an image (original image) read by the scanner unit 100 is output from the printer unit 200, a copy function can be realized. That is, the printing apparatus 10 according to the present embodiment is a so-called scanner / printer / copy combined apparatus (hereinafter referred to as an SPC combined apparatus) that can independently realize a scanner function, a printer function, and a copy function.

  FIG. 3 is an explanatory diagram showing a state in which the document table cover 102 provided on the upper part of the printing apparatus 10 is opened in order to read a printed document image. As shown in the drawing, when the document table cover 102 is opened upward, a transparent document table glass 104 is provided, and various mechanisms to be described later for realizing the scanner function are mounted therein. . When the printed document image is read, the document table cover 102 is opened as shown in the figure, the print image is placed on the document table glass 104, the document table cover 102 is closed, and then a button on the operation panel 300 is displayed. To operate. In this way, it is possible to immediately convert the document image into image data.

  The scanner unit 100 is entirely housed in an integrated case, and the scanner unit 100 and the printer unit 200 are coupled by a hinge mechanism 204 (see FIG. 4) on the back side of the printing apparatus 10. ing. For this reason, by lifting the front side of the scanner unit 100, it is possible to rotate only the scanner unit 100 at the hinge portion.

  FIG. 4 is a perspective view illustrating a state in which the front side of the scanner unit 100 is lifted and rotated. As shown in the figure, in the printing apparatus 10 of the present embodiment, the upper surface of the printer unit 200 can be exposed by lifting the front side of the scanner unit 100. Inside the printer unit 200, various mechanisms to be described later for realizing the printer function, a control circuit 260 to be described later for controlling the operation of the entire printing apparatus 10 including the scanner unit 100, and the scanner unit 100 are further described. And a power supply circuit (not shown) for supplying power to the printer unit 200 and the like. Also, as shown in FIG. 4, an opening 202 is provided on the upper surface of the printer unit 200, which makes it easy to replace consumables such as ink cartridges, handle paper jams, and perform minor repairs. It is possible to do it.

B-2. Internal configuration:
FIG. 5 is an explanatory diagram conceptually showing the internal configuration of the printing apparatus 10 of this embodiment. As described above, the printing apparatus 10 includes the scanner unit 100 and the printer unit 200, and various configurations for realizing the scanner function are mounted in the scanner unit 100. Is equipped with various configurations for realizing the printer function. Hereinafter, the internal configuration of the scanner unit 100 will be described first, and then the internal configuration of the printer unit 200 will be described.

B-2-1. Internal configuration of the scanner unit:
The scanner unit 100 includes a transparent platen glass 104 for setting a printed document image, a document table cover 102 for holding the set document image, a reading carriage 110 for reading the set document image, A driving belt 120 that moves the reading carriage 110 in the reading direction (main scanning direction), a driving motor 122 that supplies power to the driving belt 120, a guide shaft 106 that guides the movement of the reading carriage 110, and the like. The operations of the drive motor 122 and the reading carriage 110 are controlled by a control circuit 260 described later.

  When the driving motor 122 is rotated under the control of the control circuit 260, the movement is transmitted to the reading carriage 110 via the driving belt 120, and as a result, the reading carriage 110 is guided to the guide shaft 106 while being driven by the driving motor 122. It moves in the reading direction (main scanning direction) according to the rotation angle. Further, the drive belt 120 is constantly adjusted to be in a moderately tensioned state by the idler pulley 124. Therefore, if the drive motor 122 is rotated in the reverse direction, the reading carriage 110 is moved in the reverse direction by a distance corresponding to the rotation angle. It is also possible to make it.

  Inside the reading carriage 110, a light source 112, a lens 114, a mirror 116, a CCD sensor 118, and the like are mounted. Light from the light source 112 is applied to the platen glass 104 and reflected by a document image set on the platen glass 104. The reflected light is guided to the lens 114 by the mirror 116, collected by the lens 114, and detected by the CCD sensor 118. The CCD sensor 118 includes a linear sensor in which photodiodes that convert light intensity into an electrical signal are arranged in a row in a direction orthogonal to the moving direction (main scanning direction) of the reading carriage 110. Therefore, if the original image is irradiated with light from the light source 112 while the reading carriage 110 is moved in the main scanning direction and the reflected light intensity is detected by the CCD 118, an electrical signal corresponding to the original image can be obtained.

  Further, the light source 112 is composed of light emitting diodes of three colors of RGB, and can sequentially irradiate light of R color, G color, and B color at a predetermined cycle. In the CCD 118, the reflected light of R color, G color, and B color is sequentially detected. In general, the red portion of the image reflects R light, but hardly reflects G or B light, so the R reflected light represents the R component of the image. Similarly, the reflected light of G color represents the G component of the image, and the reflected light of B color represents the B component of the image. Accordingly, if the original image is irradiated while switching the light of three colors of RGB at a predetermined cycle and the reflected light intensity is detected by the CCD 118 in synchronization therewith, the R component, G component and B component of the original image can be detected. It is possible to read a color image. Note that since the reading carriage 110 is moved even while the color of the light emitted by the light source 112 is switched, the position of the image for detecting each component of RGB corresponds to the movement amount of the reading carriage 110 strictly. However, this deviation can be corrected by image processing after reading each component.

B-2-2. Internal configuration of the printer unit:
Next, the internal configuration of the printer unit 200 will be described. The printer unit 200 includes a control circuit 260 that controls the overall operation of the printing apparatus 10, a print carriage 240 that prints an image on a print medium, a mechanism that moves the print carriage 240 in the main scanning direction, and printing. A mechanism for feeding media is mounted.

  The print carriage 240 includes an ink cartridge 242 that stores K ink, an ink cartridge 243 that stores various inks of C ink, M ink, and Y ink, a print head 241 provided on the bottom surface side, and the like. The print head 241 is provided with an ink discharge head for discharging ink droplets for each ink. When the ink cartridges 242 and 243 are mounted on the print carriage 240, each ink in the cartridge is supplied to the ink discharge heads 244 to 247 for each color through an introduction pipe (not shown). In the printer unit 200 shown in FIG. 5, the C ink, the M ink, and the Y ink are described as being integrally stored in one ink cartridge 243, but these inks are formed separately. It can also be stored in a dedicated ink cartridge. In addition to these inks, low-density C ink (LC ink), low-density M ink (LM ink), and low-density K ink (LK ink) can also be mounted.

  The mechanism that moves the print carriage 240 in the main scanning direction includes a carriage belt 231 for driving the print carriage 240, a carriage motor 230 that supplies power to the carriage belt 231, and an appropriate tension is constantly applied to the carriage belt 231. And a carriage guide 233 for guiding the movement of the print carriage 240, an origin position sensor 234 for detecting the origin position of the print carriage 240, and the like. When the carriage motor 230 is rotated under the control of the control circuit 260 described later, the print carriage 240 can be moved in the main scanning direction by a distance corresponding to the rotation angle. Further, if the carriage motor 230 is rotated in the reverse direction, the print carriage 240 can be moved in the reverse direction.

  The mechanism for feeding the print medium includes a platen 236 that supports the print medium from the back side, a paper feed motor 235 that feeds the paper by rotating the platen 236, and the like. By rotating the paper feed motor 235 under the control of the control circuit 260 described later, the print medium can be fed in the sub-scanning direction by a distance corresponding to the rotation angle.

  The control circuit 260 has a CPU, a ROM, a RAM, a D / A converter that converts digital data into an analog signal, and a peripheral device interface PIF for exchanging data with peripheral devices. It is composed of The control circuit 260 controls the overall operation of the printing apparatus 10, and controls these operations while exchanging data with the light source 112, the drive motor 122, and the CCD 118 mounted on the scanner unit 100.

  Further, the control circuit 260 drives the carriage motor 230 and the paper feed motor 235 to supply the drive signals to the ink discharge heads 244 to 247 of the respective colors while performing the main scanning and the sub scanning of the printing carriage 240, thereby generating ink droplets. Control to discharge is also performed. The drive signals supplied to the ink discharge heads 244 to 247 are generated by reading image data from the computer 20 or the digital camera 30 and performing image processing to be described later. Of course, it is also possible to generate a drive signal by performing image processing on the image data read by the scanner unit 100. In this way, under the control of the control circuit 260, the ink droplets are ejected from the ink ejection heads 244 to 247 to form the ink dots of the respective colors on the printing medium while the print carriage 240 is moved in the main scan and the sub scan. It is possible to print an image. Of course, instead of performing image processing in the control circuit 260, the ink ejection heads 244 to 247 receive data on which image processing has been performed from the computer 20, and perform main scanning and sub-scanning of the print carriage 240 according to this data. Can also be driven.

  The control circuit 260 is also connected to the operation panel 300 so as to be able to exchange data. By operating various buttons provided on the operation panel 300, detailed operation modes of the scanner function and the printer function are set. It is possible to set. Further, it is possible to set a detailed operation mode from the computer 20 via the peripheral device interface PIF.

  In addition, a monitor screen is incorporated in the operation panel 300 mounted on the printing apparatus 10 of the present embodiment, and image data of an image to be printed is supplied from the control circuit 260 and displayed on the monitor screen. Alternatively, image data can be supplied to the computer 20 via the peripheral device interface PIF and displayed on the monitor screen of the computer 20. When an area of the image is designated by moving a cursor or the like on the operation panel 300 or the monitor screen of the computer 20, the control circuit 260 can detect information indicating the position of the area.

  FIG. 6 is an explanatory diagram showing a state in which a plurality of nozzles Nz for ejecting ink droplets are formed on the ink ejection heads 244 to 247 of each color. As shown in the figure, on the bottom surface of the ink discharge head for each color, four sets of nozzle rows for discharging ink droplets for each color are formed, and for each set of nozzle rows, 48 nozzles Nz have a nozzle pitch. They are arranged in a zigzag pattern at intervals of k. A drive signal is supplied from the control circuit 260 to each of these nozzles Nz, and each nozzle Nz ejects an ink droplet of each ink according to the drive signal.

  In addition, the printing apparatus 10 according to the present exemplary embodiment can also form dots having different sizes on the print medium by controlling the size of the ink droplets to be ejected. Hereinafter, the principle of forming dots having different sizes will be described.

  FIG. 7 is an explanatory diagram showing the principle of forming ink dots having different sizes by controlling the size of the ejected ink droplets. FIG. 7A is an explanatory diagram showing an internal structure of a nozzle for ejecting ink droplets and a method for ejecting ink droplets. Each of the ink discharge heads 244 to 247 for each color is provided with a plurality of such nozzles. As shown in the figure, each nozzle is provided with an ink passage 255 and an ink chamber 256, and a piezo element PE is provided on the upper surface of the ink chamber. When the ink cartridges 242 and 243 are mounted on the carriage 240, the ink in the cartridge is supplied to the ink chamber 256 via the ink gallery 257.

  As is well known, the piezo element PE is an element that performs electro-mechanical energy conversion at a very high speed because the crystal structure is distorted when a voltage is applied. In this embodiment, the side wall of the ink chamber 256 is deformed by applying a voltage having a predetermined waveform between the electrodes provided at both ends of the piezo element PE. As a result, the volume of the ink chamber 256 is reduced, and ink corresponding to the reduced volume is ejected from the nozzle Nz as ink droplets Ip. The ink droplet Ip soaks into the printing paper P mounted on the platen 236, whereby ink dots are formed on the printing paper.

  FIG. 7B is an explanatory diagram showing the principle of changing the size of the ink droplets discharged by controlling the voltage waveform applied to the piezo element PE. In order to eject the ink droplet Ip from the nozzle, a voltage is applied to the piezo element PE, the ink is once sucked into the ink chamber 256 from the ink gallery 257, and then a positive voltage is applied to the piezo element PE. The ink chamber volume is reduced and the ink droplet Ip is ejected. Here, if the ink suction speed is appropriate, ink corresponding to the amount of change in the ink chamber volume is sucked, but if the suction speed is too fast, there is a passage resistance between the ink gallery 257 and the ink chamber 256. For this reason, the inflow of ink from the ink gallery 257 is not in time. As a result, the ink in the ink passage 255 flows back into the ink chamber, and the ink interface near the nozzle is largely retracted. A voltage waveform a indicated by a solid line in FIG. 7B indicates a waveform for sucking ink at an appropriate speed, and a voltage waveform b indicated by a broken line indicates an example of a waveform for suctioning at a speed larger than the appropriate speed. .

  When a positive voltage is applied to the piezo element PE in a state where sufficient ink is supplied into the ink chamber 256, an ink droplet Ip having a volume corresponding to the volume reduction of the ink chamber 256 is ejected from the nozzle Nz. On the other hand, when a positive voltage is applied in a state where the ink supply amount is insufficient and the ink interface is largely retracted, the ejected ink droplets become small ink droplets. As described above, in the printer unit 200 mounted in the printing apparatus 10 of the present embodiment, the ink droplets to be ejected are controlled by changing the suction speed of the ink by controlling the negative voltage waveform applied before the ink droplets are ejected. Control the size of. This makes it possible to form three types of ink dots, large dots, medium dots, and small dots.

  Of course, not only three types but also more types of dots can be formed. Furthermore, the size of the ink dots formed on the printing paper may be controlled by using a method in which a plurality of fine ink droplets are ejected at a time and the number of ejected ink droplets is controlled.

  Various methods can be applied to the method of ejecting ink droplets from the ink ejection head. That is, a method of ejecting ink using a piezoelectric element, a method of ejecting ink droplets by generating bubbles in the ink passage with a heater arranged in the ink passage, and the like can be used. Also, instead of ejecting ink, use a method that forms ink dots on printing paper using phenomena such as thermal transfer, or a method that attaches toner powder of each color onto the printing medium using static electricity. Is also possible.

C. First Example:
As described above, the printer unit 200 of the printing apparatus 10 prints an image by forming dots on a print medium. For this reason, when printing an image, it is necessary to perform image processing on the image data in advance to convert the image into data expressed by the presence or absence of dot formation. In addition, when the dots are conspicuous, the image becomes rough, and in order to avoid such a situation, appropriate image processing conditions are set in advance in order to appropriately perform image processing.

  However, since there are a wide variety of images to be printed, it is difficult to set appropriate image processing conditions assuming all images. Therefore, dots are conspicuous in some areas of the printed image. It can happen. In view of these points, the printing apparatus 10 described above prints an image in the following manner so that a high-quality image in which dots are not noticeable can be obtained regardless of the image.

  FIG. 8 is a flowchart showing the flow of the image printing process of the first embodiment. As shown in the figure, the printing apparatus 10 prints an image roughly in two stages. First, in the image quality confirmation image printing process (step S10), which is the first stage process, an image (image quality confirmation image) for confirming the image quality is printed. Then, the operator of the printing apparatus 10 observes the obtained image quality confirmation image to confirm the presence / absence of an area that requires improvement in graininess (image quality improvement area).

  Next, in the image quality improved image printing process (step S20), which is the second stage process, an image quality improved area is extracted, and image processing is performed on this area under conditions that further improve the graininess. Print. In this way, it is possible to print a high-quality image in which dots are not conspicuous for any image. Hereinafter, the contents of the first stage process (image quality confirmation image printing process) and the second stage process (image quality improved image printing process) will be described in detail. The printing apparatus 10 according to the present embodiment is described as performing all image processing within the control circuit 260 incorporated in the printer unit 200. However, all or part of image processing is performed by the computer 20 provided outside. It is also possible to read the processed data from the peripheral device interface PIF and form dots.

C-1. Image quality confirmation image printing process:
FIG. 9 is a flowchart showing a flow of processing for printing an image (image quality confirmation image) for confirming image quality based on image data to be printed. Hereinafter, it demonstrates according to a flowchart. When the image quality confirmation image printing process is started, first, a process of reading image data of an image to be printed is performed (step S100). In this process, an image created by the computer 20 or image data of an image taken by the digital camera 30 may be taken in via the peripheral device interface PIF, or by driving the scanner unit 100, Image data may be read. In the following description, it is assumed that RGB image data is read. However, the format of the read image data is not limited to RGB image data, and the following description also applies to image data expressed in other formats. A process substantially similar to the process to be performed can be applied.

  Next, a process of converting the resolution of the read image data into a resolution (printing resolution) for printing by the printer unit 200 is performed (step S102). When the resolution of the read image data is lower than the print resolution, the image data is converted to a higher resolution by performing interpolation calculation between adjacent pixels and setting new image data. Conversely, when the resolution of the read image data is higher than the print resolution, the image data is converted to a lower resolution by thinning out the image data at a certain rate from between adjacent pixels. In the resolution conversion process, the read resolution is converted into the print resolution by generating or thinning out the image data at an appropriate ratio with respect to the read image data.

  When the resolution of the image data is converted to the printing resolution in this way, the control circuit 260 starts color conversion processing (step S104). The color conversion process is a process of converting RGB image data expressed by a combination of R, G, and B gradation values into data corresponding to the amount of each color ink used in the printer. As described above, since the printer unit 200 prints an image using four colors of C, M, Y, and K, in the color conversion process of the present embodiment, RGB image data is converted into C, M, and so on. , Y, and K are converted into gradation value data corresponding to the amount of ink used. Of course, in addition to the four colors C, M, Y, and K, low density C ink (LC ink), low density M ink (LM ink), or low density K ink (LK ink) are installed. In such a case, the RGB image data may be converted into gradation value data corresponding to the amount of ink used for each color including these light inks.

  The color conversion process is performed by referring to a three-dimensional numerical table called a color conversion table (LUT). FIG. 10 is an explanatory diagram conceptually showing a color conversion table (LUT) referred to for color conversion processing. Considering a color space in which gradation values of R, G, and B colors are taken on three orthogonal axes as shown in FIG. 10, the gradation values of RGB colors can take values from 0 to 255. . Then, all the RGB image data can be associated with points inside a cube (color solid) whose origin is the vertex and whose length of one side is 255. From this point of view, when a plurality of grid points are generated in the color space by changing the way of viewing and subdividing the color solid into a grid shape at right angles to the RGB axes, each grid point corresponds to the RGB image data. Can be considered. Therefore, a combination of gradation values corresponding to the usage amount of each color ink such as C, M, Y, and K is stored in advance at each grid point. By doing this, it is possible to quickly convert the RGB image data into data corresponding to the amount of ink used for each color by reading the gradation values stored in the grid points.

  For example, if the R component of the image data is RA, the G component is GA, and the B component is BA, this image data is associated with point A in the color space (see FIG. 10). Therefore, a cube dV containing point A is detected from the fine cubes that subdivide the color solid, and the gradation values of the respective color inks stored in the respective lattice points of the cube dV are read out. Then, if the interpolation calculation is performed from the gradation values of these grid points, the gradation value at the point A can be obtained. As described above, the color conversion table LUT is a gradation value corresponding to the use amount of each color ink such as C, M, Y, and K at each grid point indicated by a combination of gradation values of RGB colors. The RGB image data can be quickly color-converted into gradation data corresponding to the usage amount of each color ink by referring to the color conversion table. Become.

  When the color conversion process is completed as described above, as shown in FIG. 9, halftone processing is performed in the image quality confirmation image printing process (step S106). Halftone processing is the following processing. The gradation data corresponding to the ink usage of each color of CMYK obtained by the color conversion process is data that can take a value from gradation value 0 to gradation value 255 for each pixel. On the other hand, since the printer unit 200 displays an image by forming large, medium, and small dots, for each pixel, “form a large dot”, “form a medium dot”, “small” Only four states are possible: “form dots” and “do not form dots”. Therefore, it is necessary to convert CMYK gradation data having 256 gradations into 4-gradation data (dot data) corresponding to the presence / absence of formation of large, medium, and small dots. Halftone processing is processing for converting CMYK gradation data into dot data in this way.

  As a method for performing the halftone process, various methods such as an error diffusion method and a dither method can be applied. The error diffusion method is to determine whether or not dots are formed for a certain pixel so as to diffuse an error in gradation expression generated in that pixel to surrounding pixels and to eliminate the error diffused from the surroundings. This is a method of determining the presence or absence of dot formation for each pixel. In the dither method, a threshold value randomly set in the dither matrix and CMYK gradation data are compared for each pixel, and it is determined that a dot is formed in a pixel having a larger CMYK gradation data. This is a method of obtaining dot data for each pixel by determining that no dot is formed for a pixel having a larger threshold value. In the following description, it is assumed that halftone processing is performed using the dither method.

  Further, as described above, the printing apparatus 10 of this embodiment can form large, medium, and small dots. Corresponding to this, in the halftone process (step S106 in FIG. 9) of the present embodiment, a process of determining whether or not dots are formed is performed for each of the large dots, medium dots, and small dots. The following describes the process of generating dot data by determining whether large dots, medium dots, and small dots are formed by using the dither method. Briefly explain the law.

  FIG. 11 is an explanatory diagram illustrating an enlarged part of the dither matrix. In the illustrated matrix, threshold values that are uniformly selected from the range of gradation values 0 to 255 are randomly stored in a total of 4096 pixels, 64 pixels in the vertical and horizontal directions. Here, the threshold gradation value is selected from the range of 0 to 255. In this embodiment, the CMYK gradation data is 1-byte data, and the gradation value can take a value of 0 to 255. It corresponds to. Note that the size of the dither matrix is not limited to 64 pixels in the vertical and horizontal directions as illustrated in FIG. 11, and can be set to various sizes including those having different numbers of vertical and horizontal pixels. It is.

  FIG. 12 is an explanatory diagram conceptually showing a state in which the presence / absence of dot formation is determined for each pixel with reference to the dither matrix. This determination is made for each color of CMYK, but in the following, in order to avoid complicated explanation, each color of the CMYK gradation data is simply referred to as gradation data without being distinguished.

  When determining the presence or absence of dot formation, first compare the gradation value of the gradation data for the pixel of interest (the pixel of interest) as the object of determination with the threshold value stored at the corresponding position in the dither matrix. To do. The thin broken arrow shown in the figure schematically represents that the gradation data of the pixel of interest is compared with the threshold value stored at the corresponding position in the dither matrix. If the gradation data of the pixel of interest is larger than the threshold value of the dither matrix, it is determined that a dot is formed for that pixel. On the other hand, when the threshold value of the dither matrix is larger, it is determined that no dot is formed in the pixel. In the example shown in FIG. 12, the gradation data of the pixel at the upper left corner of the image is “97”, and the threshold value stored at the position corresponding to this pixel on the dither matrix is “1”. Accordingly, for the pixel in the upper left corner, the gradation data is larger than the threshold value of the dither matrix, and therefore it is determined that a dot is formed in this pixel. The arrows indicated by solid lines in FIG. 12 schematically show that it is determined that a dot is to be formed in this pixel and the determination result is written in the memory. On the other hand, for the pixel on the right side of this pixel, the gradation data is “97” and the threshold value of the dither matrix is “177”, and the threshold value is larger, so it is determined that no dot is formed for this pixel. . Thus, by comparing the gradation data with the threshold value set in the dither matrix, it is possible to determine whether or not dots are formed for each pixel.

  When the processing as described above is performed, it can be determined whether or not one type of dot is formed. However, the printer unit 200 of this embodiment can form various dots of large, medium, and small sizes. Therefore, it is necessary to determine whether or not dots are formed. Corresponding to this, in the halftone process (step S106 in FIG. 9) performed during the image quality confirmation image printing process of the present embodiment, the presence / absence of formation for large, medium, and small dots is determined as follows. ing.

  FIG. 13 is a flowchart showing a flow of processing for determining the presence or absence of dot formation for various large, medium, and small dots by applying a dither method to gradation data corresponding to ink of each color. Hereinafter, it demonstrates according to a flowchart.

  When the halftone process is started, first, the gradation data for each ink color is converted into the formation density (formation density data) for each of the large, medium, and small dots (step S200). Here, the formation density data indicates that dots are formed at a higher density as the value increases. For example, the value “255” of the formation density data indicates that dots are formed in all pixels. ing. Such conversion to formation density data can be performed by referring to the following conversion table.

  FIG. 14 is an explanatory diagram conceptually showing a conversion table referred to in the halftone process of this embodiment. As shown in the drawing, formation density data for large, medium, and small dots is set in advance in the conversion table in association with the gradation data after color conversion. By referring to such a conversion table, it is possible to immediately convert the gradation data obtained by the color conversion processing into the formation density data of each dot. Hereinafter, a specific description will be given with reference to FIG. 14. In the conversion table, as the gradation data increases from the gradation value “0”, the gradation data decreases in the range where the gradation data after color conversion takes a small value. The dot formation density is set to increase linearly. When the small dot formation density data increases to a certain extent, the formation of medium dots is started, and the small dot formation density data is set to decrease by the amount of medium dot formation. Further, when the medium dot formation density data increases to a certain extent, the formation of large dots is now started, and the medium dot formation density data is decreased by the amount of large dots formed. .

  In general, a region where the gradation data after color conversion takes a small value is a region where the brightness is high (bright), and thus dots are easily noticeable. Therefore, in such a region, by forming small dots, it is avoided that the dots are conspicuous and the image quality is deteriorated. Further, when the gradation data after color conversion becomes large, the brightness of the image becomes low (dark) and the dots are not conspicuous. Therefore, even if medium dots are formed, the dots do not stand out. Therefore, in such an area, an image is printed by forming medium dots. If the gradation data after color conversion becomes larger, the brightness of the image will become lower (darker), so even if a large dot is formed, the dot will not stand out. In such an area, a large dot is formed. Print the image. Therefore, if the dots formed according to the gradation data after color conversion are properly used as small dots, medium dots, and large dots in this way, a high-quality image in which dots are not noticeable can be obtained.

  In the conversion table shown in FIG. 14, the reason why the upper limit value of the formation density data of small dots or medium dots is suppressed to a value smaller than the maximum gradation value 255 is as follows. It is. Dots that are smaller than or similar to the size of a pixel, such as small dots and medium dots, are called so-called banding when dots are formed with too high density, and white streaks occur in the image. As a result, a phenomenon of deteriorating image quality may occur. Therefore, in order to prevent this from occurring, the formation density of small dots and medium dots is limited to a low formation density with a certain margin for banding.

  In step S200 of the halftone process shown in FIG. 13, the gradation data of each color of CMYK after the color conversion process is converted into the formation density for each of the large, medium, and small dots with reference to the conversion table illustrated in FIG.

  When the formation density data for each of the large dots, medium dots, and small dots is obtained in this way, first, it is determined whether or not the large dots are formed (step S202). Such a determination is made by comparing the formation density data of large dots with the threshold value set in the dither matrix. That is, if the formation density data is larger, it is determined that a large dot is to be formed, and conversely, if the threshold is larger, it is determined that a large dot is not to be formed.

  Then, a process of writing data “11” is performed on the pixel determined to form a large dot (step S202: yes) (step S206). Here, the data “11” is data indicating that a large dot is formed on the pixel. On the other hand, for a pixel determined not to form a large dot (step S202: no), a process for determining whether to form a medium dot is started.

  The determination of whether or not the medium dot is formed is performed as follows. First, medium dot formation density data is added to large dot formation density data to calculate intermediate data for determining whether or not medium dots are formed (step S208). By comparing the intermediate data thus calculated with the threshold value of the dither matrix, it is determined whether or not a medium dot is formed (step S210). That is, it is determined that medium dots are formed for pixels whose intermediate dot intermediate data is larger than the threshold value, and medium dots are determined not to be formed for pixels whose threshold value is larger. Then, for a pixel that forms a medium dot (step S212: yes), a process of writing data “10” representing the formation of a medium dot is performed (step S214). For a pixel determined not to form a medium dot (step S212: no), a process for determining whether or not to form a small dot is started.

  Whether or not small dots are formed is determined using intermediate data for small dots. The intermediate data for small dots is calculated by adding the formation density data for small dots to the intermediate data for medium dots (step S216). Next, by comparing the calculated intermediate data for small dots with the threshold value of the dither matrix, it is determined whether or not small dots are formed (step S218). Then, it is determined that the small dot intermediate data is larger than the threshold value, so that a small dot is formed. For the pixel forming the small dot (step S220: yes), the data “ “01” is stored (step S222). On the contrary, it is determined that no small dot is formed on a pixel having a larger threshold value than the intermediate data for small dots (step S220: no), and data indicating that no dot is formed on this pixel. “00” is stored (step S224).

  In step S106 of the image printing process shown in FIG. 9, the above-described processing is performed on the gradation data of each color of CMYK obtained by color conversion, and the presence / absence of formation of each large / medium / small dot is determined for each pixel. Thus, processing for generating dot data is performed.

  As described above, after the gradation data of each color of CMYK is converted into dot data, the interlace process is started (step S108). The interlace process is a process in which the print head 241 rearranges the dot data in the order in which dots are formed and supplies them to the ink discharge heads 244 to 247 for each color. That is, as shown in FIG. 6, the nozzles Nz provided in the ink discharge heads 244 to 247 are provided with an interval of the nozzle pitch k in the sub-scanning direction. When droplets are ejected, dots are formed at intervals of the nozzle pitch k in the sub-scanning direction. Therefore, in order to form dots in all the pixels, the relative position between the print carriage 240 and the print medium is moved in the sub-scanning direction, and new dots are formed in the pixels between the dots separated by the nozzle pitch k. Necessary. As described above, when an image is actually printed, dots are not formed in order from the upper pixel on the image. Furthermore, for pixels in the same row in the main scanning direction, instead of forming dots in a single main scan, the dots are divided into a plurality of main scans in response to image quality requirements. In this main scanning, dots are also widely formed on the pixels at the skipped positions.

  Thus, when an image is actually printed, dots are not formed according to the order of pixel arrangement on the image, so C, M, Y before actually starting the dot formation. , K, it is necessary to rearrange the dot data obtained for each color in the order in which the ink ejection heads 244 to 247 form dots. Such a process is a process called interlace.

  In the image copying process, when the interlace process is completed, a process for actually forming dots on the print medium (dot formation process) is started based on the data obtained by the interlace process (step S110). That is, while the carriage motor 230 is driven to cause the print carriage 240 to perform main scanning, the rearranged dot data is supplied to the ink ejection heads 244 to 247. As described above, since the dot data is data indicating whether or not to form a dot in each pixel, the ink discharge heads 244 to 247 can appropriately ink each pixel by discharging ink droplets according to the dot data. Dots can be formed.

  When one main scan is completed, the paper feed motor 235 is driven to feed the print medium in the sub-scanning direction, and then the carriage motor 230 is driven again to cause the print carriage 240 to perform the main scan. The dot data whose order has been rearranged is supplied to the ink discharge heads 244 to 247 to form dots. By repeating such an operation, dots of each color of C, M, Y, and K are formed on the print medium with an appropriate distribution according to the gradation value of the image data, and correspond to the image data. A printed image can be obtained. The image thus obtained is an image quality confirmation image. When the image quality confirmation image is obtained, the image quality confirmation image printing process of the first embodiment shown in FIG. 9 is terminated, and after returning to the image printing process of FIG. 8, the image printing process is also terminated.

  As described above, the image quality confirmation image is an image printed while using large, medium, and small dots in accordance with the conspicuousness of the dots, and as a whole, the image is a high-quality image in which the dots are not conspicuous. However, the visibility of dots is not determined only by the size of the dots, but is also affected by the color of the dots and the color or brightness of the background on which the dots are formed. The color and brightness of the varieties vary. Therefore, in all cases, it is not easy to properly use the appropriate dot size. Depending on the image to be printed, the dots may be conspicuous in some areas of the image. Can happen. In view of these points, in the printing apparatus 10 according to the present exemplary embodiment, the image quality improvement image printing process described below is performed after the image quality confirmation image printing process, so that any image has no dots. This makes it possible to print inconspicuous high-quality images.

C-2. Image quality improved image printing process:
FIG. 15 is a flowchart showing the flow of the image quality improved image printing process of the first embodiment. Such a process is a process executed by the control circuit 260 mounted on the printing apparatus 10 in the image printing process of the first embodiment shown in FIG. Hereinafter, it demonstrates according to a flowchart.

  When starting the image quality improved image printing process of the first embodiment, the control circuit 260 first performs a process of displaying an image quality confirmation image on the monitor (step S300). The image quality confirmation image is an image printed by the image quality confirmation image printing process described above. In step S300, after the image data read for printing the image quality confirmation image is converted into a video signal of the NTSC system or the like, a liquid crystal display monitor provided on the operation panel 300 or various devices connected to the printing apparatus 10 are used. By supplying it to the monitor, a process for displaying the same image as the image quality confirmation image is performed.

  On the other hand, the operator of the printing apparatus 10 observes the image quality confirmation image printed in the previously performed image quality confirmation image printing process (step S10 in FIG. 8) to improve the difficulty of conspicuous dots (granularity). Check if there is a part that requires. Then, an area (image quality improvement area) in which the granularity is deteriorated in the image and it is determined that the image quality needs to be improved is designated on the monitor. Since the image quality confirmation image is displayed on the monitor, the image quality improvement region can be easily specified by moving the cursor on the monitor and specifying the region.

  FIG. 16 is an explanatory diagram showing a state in which an image quality improvement region is set on the liquid crystal display monitor incorporated in the operation panel 300. In the example shown, an image of a yacht floating in a quiet summer sea is displayed on the monitor as an image quality confirmation image. A portion that changes to deep blue is designated as an area (image quality improvement area) where the graininess should be improved. A broken-line rectangle shown in the drawing indicates that this area is designated as an image quality improvement area. In FIG. 16, a rectangle is used to designate the image quality improvement area. However, the present invention is not limited to this. For example, the image quality improvement area may be designated using a circle or a closed polygon. good.

  In the image quality improvement image printing process shown in FIG. 15, when an image quality confirmation image is displayed on the monitor (step S300), a process of acquiring the image quality improvement area designated from the monitor by the operator of the printing apparatus 10 is performed (step S300). S302). In the example shown in FIG. 16, since the image quality improvement region is designated by a rectangle, the granularity of which part of the printed image quality confirmation image can be improved by detecting the coordinates of the vertices on the diagonal of the rectangle. You can know what to do.

  When the designated image quality improvement region is acquired in this way, color conversion processing is performed so that the granularity of the designated region is improved (step S304).

  FIG. 17 is a flowchart showing the color conversion process performed during the image quality improved image printing process of the first embodiment. In the color conversion process during the image quality improvement image printing process, first, one pixel to be subjected to the color conversion process is selected (step S350), and then it is determined whether or not the pixel is a pixel in the image quality improvement area (step S350). Step S352). As described above, which part of the image to be printed is designated as the image quality improvement region is acquired in advance in the process of step S302, so one pixel of interest is selected. Then, it can be easily determined whether or not the pixel is included in the image quality improvement region.

  If it is not included in the image quality improvement region (step S352: no), the RGB image data is converted into gradation data of each color of CMYK by referring to the first color conversion table (step S354). Here, the first color conversion table is the color conversion table referred to in step S104 of the image quality confirmation image shown in FIG. That is, the fact that the target pixel is not included in the image quality improvement region means that sufficient image quality can be obtained even if the same processing as that for printing the image quality confirmation image is performed. For the pixels, color conversion processing is performed with reference to the same color conversion table as the image quality confirmation image printing processing of FIG.

  On the other hand, if it is determined that the target pixel is included in the image quality improvement region (step S352: yes), the second color conversion table is referred to and the RGB image data is converted into the CMYK gradation data. Conversion is performed (step S356). Here, the second color conversion table differs from the first color conversion table only in the CMYK gradation values set for each grid point, and is set for the grid point of the second color conversion table. The CMYK gradation values are set to gradation values that make dots less noticeable than the CMYK gradation values set in the first color conversion table.

  FIG. 18 shows the CMYK gradation values set at each grid point of the second color conversion table by comparing with the CMYK gradation values set at each grid point of the first color conversion table. FIG. The difference between the first color conversion table and the second color conversion table appears most greatly in the CMYK gradation values set at the grid points on the achromatic color axis. Here, the achromatic color axis includes coordinate points (0, 0, 0) corresponding to K (black) and coordinate points (255, 255, 255) corresponding to W (white) in the RGB color space. It becomes a straight line connecting. In FIG. 18A, the achromatic color axis in the RGB color space is displayed by a thick dashed line. Therefore, here, the CMYK gradation values set at the grid points of the first color conversion table and the grid points of the second color conversion table on the achromatic color axis indicated by the alternate long and short dash line in the figure. A description will be given by comparing the CMYK gradation values set to “1”.

  FIG. 18B is an explanatory diagram showing how the gradation values of each color of CMYK set at each grid point of the first color conversion table change as it moves on the achromatic color axis. Here, a description will be given on the assumption that the color axis moves from the W (white) point to the K (black) point on the achromatic color axis. First, at the W (white) point, the gradation values of each color of CMYK are all gradation values. 0 and no dot is formed (ground color state of the printing paper). From this state, if the gradation value of K is increased little by little, and K dots are formed little by little, the brightness of the image becomes gradually darker and can be brought closer to the K (black) point. However, since K dots are conspicuous, if K dots are suddenly formed on the printing paper with the background color, the graininess is greatly deteriorated. Therefore, instead of K dots, C dots, M dots, and Y dots are formed in approximately equal amounts to K dots. According to the theory of subtractive color mixing, it is known that if CMY is mixed in almost equal amounts, it becomes K. Instead of forming K dots, C dots, M dots, and Y in approximately equal amounts with K dots. Dots may be formed. In addition, since C dots, M dots, and Y dots are less conspicuous than K dots, forming CMY dots instead of K dots makes the dots noticeable and deteriorates graininess. Can be avoided. For these reasons, the gradation value of K is not increased near the W (white) point, but instead, the gradation values of the CMY colors are increased by almost equal amounts.

  However, when forming CMY dots instead of K dots, it is necessary to form approximately three times as many dots. If the dot formation density is too high, the ink may bleed or the printing paper may swell and the surface may become wavy, which may adversely affect image quality. Therefore, instead of increasing the gradation value of each color of CMY indefinitely, when the image becomes dark to some extent (when the brightness decreases to a certain level), the gradation value of each color of CMY is replaced with the gradation value of K, and otherwise In addition, the gradation value of K is gradually increased. Then, at a certain stage, the CMY gradation values are all replaced with K gradation values, and thereafter, as the image becomes darker, the K gradation values increase. When the K (black) point is reached, the K level is increased. The adjustment value reaches the upper limit (255).

  FIG. 18C is an explanatory diagram showing how the gradation values of the CMYK colors set at the grid points of the second color conversion table change when moving on the achromatic color axis. As apparent from a comparison between FIG. 18B and FIG. 18C, the second color conversion table is an area in which the gradation values of the CMY colors are increased as compared to the first color conversion table. The tone value of K is generated only after the image is considerably dark (lightness is low). As described above, since each dot of CMY is less conspicuous than K dot, in order to obtain a print image that is as inconspicuous as possible, CMY dots are formed instead of K dots until the image is sufficiently dark. It is desirable to do. Also, if the image is sufficiently dark, even if the CMY dots are replaced with K dots, the dots will not stand out. Therefore, if color conversion is performed with reference to the second color conversion table, an image with less conspicuous dots can be obtained than when the first color conversion table is referred to.

  In the color conversion process shown in FIG. 17, when it is determined that the target pixel is included in an area where it is determined that the granularity needs to be improved (step S <b> 352: yes), the granularity of the print image is changed. In order to improve, color conversion processing is performed with reference to the second color conversion table (step S356).

  As described above, after the RGB image data of the target pixel is converted into the gradation data of each color of CMYK, it is determined whether or not the color conversion processing has been completed for all the pixels (step S358). If pixels that have not yet been processed remain (step S358: no), the process returns to step S350, a new pixel is selected, and the series of processes described above are performed. When it is determined that the processes for all the pixels have been completed (step S358: yes), the color conversion process shown in FIG. 17 is ended, and the image quality improved image of the first embodiment shown in FIG. Return to print processing.

  In the image quality improved image printing process of the first embodiment, when returning from the color conversion process, an image is printed by performing a halftone process, an interlace process, and a dot forming process. This process is the same as the image quality confirmation image printing process described above with reference to FIG.

  First, the gradation data of each color of CMYK obtained by the color conversion process is data that can take gradation values from 0 to 255, whereas the printer unit 200 of the printing apparatus 10 uses “large dots”. , “Form medium dots”, “form small dots”, and “do not form any dots”. Therefore, halftone processing is performed in order to convert the gradation data of each color of CMYK having 256 gradations into data of 4 gradations corresponding to the presence / absence of dot formation (step S306 in FIG. 15).

  In the halftone process, with reference to the conversion table shown in FIG. 14, the gradation data of each color of CMYK is converted into the formation density data for each of the large, medium, and small dots (step S200 in FIG. 13). Next, the presence / absence of large dots is determined by comparing the large dot formation density data with the threshold value of the dither matrix (step S202). For pixels that do not form large dots, intermediate data for medium dots is calculated from the formation density data for large dots and the formation density data for medium dots (step S208), and the intermediate data is compared with the threshold value of the dither matrix. Thus, it is determined whether or not medium dots are formed (step S210). For pixels that do not form medium dots, intermediate data for small dots is calculated from the intermediate data for medium dots and the formation density data for small dots (step S216), and the intermediate data for small dots and the threshold of the dither matrix To determine whether or not a small dot is formed (step S218).

  In step S306 in FIG. 15, it is determined whether to form a large dot, a medium dot, a small dot, or no dot for all the pixels by performing the above operation. As a result, dot data is generated.

  Subsequent to the halftone processing, interlace processing is performed in order to rearrange the obtained dot data in the order in which the print head 241 actually forms dots (step S308 in FIG. 15). Then, the rearranged dot data is supplied to the ink ejection heads 244 to 247, and ink droplets are ejected from the respective ink ejection heads (step S310). Thus, an image with improved image quality can be printed by forming dots on all pixels in accordance with dot data representing whether large, medium, and small dots are formed.

  The image quality improved image obtained in this way is an image printed using the same image data as the image quality confirmation image obtained by the image quality confirmation image printing process of FIG. However, for a region (image quality improvement region) in which it is determined that improvement in graininess is required in the printed image quality confirmation image, color conversion is performed using the second color conversion table set with emphasis on graininess. Processing has been performed, and the image has greatly improved graininess in the image quality improvement region. In other words, since the image quality is confirmed once with the image quality confirmation image and the image quality of the portion that is determined to need improvement in graininess is improved and printed, no matter what the image is, the dots are not noticeable. It is possible to print an image with high image quality.

  As described above, although the second color conversion table is set with emphasis on graininess, on the other hand, consideration for other image quality deterioration factors such as ink bleeding and printing paper swelling is as follows. Not as good as the color conversion table. Therefore, when such a color conversion table is applied to the entire image region, it cannot be said that there is no possibility of causing trouble in image quality in terms other than graininess. However, since the image quality improvement area occupies only a part of the entire image, there is no possibility that some problems will occur even if the second color conversion table is applied to such a small area. It becomes possible to improve the graininess of the image area.

C-3. Modification of the first embodiment:
In the image quality improved image printing process of the first embodiment described above, the image quality improvement area has been described as performing the color conversion process with reference to the second color conversion table (see FIG. 17). Since the second color conversion table is a table set with an emphasis on the difficulty of conspicuous dots, it is possible to improve graininess by performing color conversion processing while referring to the second color conversion table. Can do. However, as long as the granularity of the image quality improvement region can be improved, other methods may be used instead of the method of switching the color conversion table. For example, during halftone processing, it is possible to switch the conversion table that is referred to in order to convert gradation data after color conversion processing into formation density data for each type of dot.

  That is, in the halftone process of the first embodiment described above, the conversion table referred to for converting the gradation data of each color of CMYK after the color conversion process into the formation density data for each type of dot is shown in FIG. As shown, the formation of medium dots is started before the small dots reach the upper limit value 255 of the formation density, and the formation of large dots is also started for the medium dots before the upper limit value 255 of the formation density is reached. Was set to be. This is because, as described above, if these dots are formed at a very high density, white stripes called so-called banding may occur and the image quality may be deteriorated. Therefore, the formation density with a certain margin is limited. It was because.

  However, since medium dots are more conspicuous than small dots, it is desirable to delay the generation of medium dots as much as possible in order to make the dots less noticeable. Similarly, since large dots are more conspicuous than medium dots, it is desirable that large dots be generated as late as possible from the viewpoint of graininess. Therefore, with regard to the image quality improvement area determined to require improvement in graininess, by referring to a conversion table in which medium dots (and preferably large dots) are generated as late as possible, the graininess in the image quality improvement area can be reduced. It is possible to improve.

  FIG. 19 is an explanatory diagram conceptually showing a conversion table that is referred to in order to obtain formation density data in the image quality improvement region during the halftone process of the modified example. As apparent from a comparison between the conversion table (see FIG. 14) referred to in order to obtain the formation density data in the area other than the image quality improvement area and the conversion table shown in FIG. 19, the modification shown in FIG. In the conversion table, the formation density of small dots has increased (in the illustrated example, it has increased to nearly the upper limit value 255), and accordingly, the formation of medium dots has started more than the conversion table of FIG. It is late. Similarly, the formation density of medium dots has also increased (in the example shown, it has increased to almost the upper limit value 255), and accordingly, the start of formation of large dots is delayed. For this reason, it is possible to improve the graininess of the image quality improvement region.

  Of course, as shown in FIG. 19, if the formation density of small dots or medium dots becomes too high, the margin for the occurrence of so-called banding is reduced, but even if there is no margin at all, the banding is immediately performed with only that. It does not occur. Further, only a small area designated as the image quality improvement area is printed in such a state with no margin. For this reason, even when halftone processing is performed using a conversion table as shown in FIG. 19, there is no problem in image quality due to banding.

D. Second embodiment:
In the first embodiment described above, the color conversion table (or conversion table) set with emphasis on the graininess is referred to for the image area determined to require the graininess improvement in the image quality confirmation image. The other areas have been described as printing images with improved image quality by performing image processing with reference to the color conversion table (or conversion table) used in printing the image quality confirmation image. However, for areas other than the image quality improvement area, the image processed data (dot data) for printing the image quality confirmation image can be used as it is, so image processing is performed only for the image quality improvement area and the image quality is improved. The printed image may be printed. Hereinafter, the image quality improved image printing process of the second embodiment will be described.

D-1. Image quality improved image printing process:
FIG. 20 is a flowchart illustrating the flow of image quality improvement image printing processing according to the second embodiment. This process is performed following the image quality confirmation image printing process (see FIG. 9) during the image printing process shown in FIG. 8, similarly to the image quality improved image printing process of the first embodiment described above with reference to FIG. Process. However, the image quality improved image printing process of the second embodiment is only for the image area (image quality improved area) that is determined to require improvement in graininess compared to the image quality improved image printing process of the first embodiment described above. Dot data is generated by performing color conversion processing and halftone processing, and the other image areas are greatly different in that the image is printed using the dot data generated for printing the image quality confirmation image as it is. . In the following, the contents of the image quality improved image printing process of the second embodiment will be described focusing on these differences.

  In the image quality improved image printing process of the second embodiment, the control circuit 260 of the printing apparatus 10 first displays the image quality confirmation image on the monitor when the process is started, as in the first embodiment. Is performed (step S400). As described above, the image quality confirmation image is an image printed by the image quality confirmation image printing process performed prior to the image quality improved image printing process. The image quality confirmation image can be displayed on a liquid crystal display monitor provided on the operation panel 300 or various external monitors connected to the printing apparatus 10.

  Next, the control circuit 260 performs a process of acquiring designation of the image quality improvement area set by the operator of the printing apparatus 10 (step S402). Similar to the first embodiment described above, in the image quality improved image printing process of the second embodiment, the operator of the printing apparatus 10 actually prints the image quality confirmation image and needs to improve the graininess (image quality). Check if there is any improvement area. When the image quality confirmation image is displayed on the monitor of the operation panel 300 by the control circuit 260 (step S400), the operator designates an image quality improvement region on the monitor (see FIG. 16). In response, in step S402 of the image quality improved image printing process of the second embodiment, which area in the image quality confirmation image is designated as the image quality improved area is acquired.

  In this way, when the designated image quality improvement region is acquired, color conversion processing is performed (step S404). Here, in the image quality improved image printing process of the first embodiment described above, the color conversion process is performed on the entire image data, the color conversion table referred to when performing color conversion, and the second color conversion table for the image quality improved area. (Table set with emphasis on graininess) and the other areas are switched to the first color conversion table (table set to satisfy all image quality including graininess). On the other hand, in the image quality improved image printing process of the second embodiment, the color conversion process is performed with reference to the second color conversion table only for the image quality improved area, and the color conversion process is not performed for the other areas. Thus, it is very different from the processing of the first embodiment.

  Next, in the image quality improved image printing process of the second embodiment, a halftone process is performed by applying a dither method (step S406). Again, in the image quality improved image printing process of the first embodiment described above, halftone processing is performed on the entire image data. However, in the second embodiment, halftone processing is performed only for the image quality improving area, and the others. This area is greatly different from the first embodiment in that halftone processing is not performed.

  As described above, in the image quality confirmation image printing process and the image quality improved image printing process of this embodiment, the halftone processing method is not limited to the dither method, and various known methods such as an error diffusion method can be applied. it can. However, when halftone processing is performed using the error diffusion method, it is difficult to accurately estimate the diffusion error from the surroundings even if only the image quality improvement region is extracted and processed. Instead of performing tone processing, it is desirable to perform halftone processing on the entire image including other areas. On the other hand, in the dither method, as described above with reference to FIGS. 11 and 12, the comparison result between the gradation data set in the pixel and the threshold value set in the corresponding position in the dither matrix. Halftone processing is performed based on the above. For this reason, in principle, the halftone processing result for a certain pixel is not affected by the processing results in the surrounding pixels, and only the image quality improvement region is extracted and the halftone processing is performed appropriately. It is possible. Therefore, even if the halftone process is performed only on the image with improved image quality, the image data of each color of CMYK can be converted into data (dot data) representing the presence or absence of dot formation for each pixel.

  When the dot data for the image quality improvement region is obtained as described above, the dot data is incorporated into the dot data generated during the image quality confirmation image printing process in order to print the image quality confirmation image first. (Step S408). This is the following process.

  First, in the image quality improved image printing process of the first embodiment described above with reference to FIG. 15, the color conversion process and the halftone process are performed on the entire image. Color conversion processing (or halftone processing) is performed with reference to the set color conversion table (or conversion table for generating formation density data), and an image quality confirmation image is printed in an area other than the image quality improvement area. Using the color conversion table and the conversion table used in the above, color conversion processing and halftone processing were performed, respectively. In this way, almost all of the processing for printing the image quality confirmation image is diverted, and the granularity is improved over the image quality confirmation image in the image quality improvement region by simply switching the table to be referenced, and the image quality is improved in the other regions. An image equivalent to the confirmation image could be printed.

  However, since the dot data exactly the same as the dot data obtained by the image quality confirmation image printing process is obtained for the area other than the image quality improvement area, it is not necessary to repeat the same process again. Therefore, if the dot data obtained in the image quality confirmation image printing process described above is replaced with dot data with improved graininess, only the portion of the image quality improvement area is replaced with that of the first embodiment described above. The same data can be obtained from the dot data obtained by the image quality improvement image printing process. In addition, since it is not necessary to perform the color conversion process and the halftone process for the areas other than the image quality improvement area, it is possible to obtain dot data as quickly as possible.

  In step S408 in the image quality improvement image printing process of the second embodiment shown in FIG. 20, the graininess is improved only for the image quality improvement region with respect to the dot data generated by the image quality confirmation image printing process performed previously. A process of replacing with dot data is performed.

  When dot data with improved graininess in the image quality improvement region is obtained as described above, interlace processing is performed so that the dot data is rearranged in the order in which the print head 241 actually forms dots ( Step S410). Next, the interlaced dot data is supplied to the ink discharge heads 244 to 247, and dots are formed by the respective ink discharge heads (step S412). Thus, an image with improved image quality can be printed by forming dots on all pixels in accordance with dot data representing whether large, medium, and small dots are formed.

  Also in the image quality improved image printing process of the second embodiment described above, an image with improved graininess in the image quality improved region can be printed. For areas other than the image quality improvement area, it is confirmed that there is no problem in image quality by printing an image quality confirmation image in advance, so if the granularity is improved only for the image quality improvement area, the area where dots are conspicuous in all areas It is possible to print a high-quality image without any image. In addition, in the image quality improved image printing process of the second embodiment, the color conversion process or the halftone process is performed only for the image quality improved area, and the data generated for printing the image quality confirmation image is directly used for the other areas. Since it is used, the time required for image processing can be shortened, and as a result, an image can be printed quickly.

  Although the printing apparatus of the present embodiment has been described above, the present invention is not limited to all the above-described embodiments, and can be implemented in various modes without departing from the scope of the present invention.

It is explanatory drawing which showed the outline | summary of the printing apparatus of a present Example. It is a perspective view which shows the external appearance shape of the printing apparatus of a present Example. FIG. 3 is an explanatory diagram showing a state in which a document table cover provided at the upper part of the printing apparatus is opened in order to read a printed document image. It is the perspective view which showed a mode that the front side of the scanner part was lifted and rotated. It is explanatory drawing which showed notionally the internal structure of the printing apparatus of a present Example. It is explanatory drawing which showed a mode that the several nozzle which discharges an ink drop to the ink discharge head of each color was formed. It is explanatory drawing which showed the principle which forms the ink dot from which a magnitude | size differs by controlling the magnitude | size of the ink droplet to discharge. 3 is a flowchart illustrating a flow of image printing processing according to the first embodiment. It is a flowchart which shows the flow of the process which prints the image quality confirmation image for confirming an image quality based on the image data which it is going to print. It is explanatory drawing which showed notionally the color conversion table referred for a color conversion process. It is explanatory drawing which expanded and illustrated a part of dither matrix. It is explanatory drawing which showed notionally the mode that the presence or absence of dot formation was judged for every pixel, referring a dither matrix. It is the flowchart which showed the flow of the process which judges the dot formation presence or absence about various large / medium / small dots by applying the dither method to the gradation data corresponding to the ink of each color. It is explanatory drawing which showed notionally the conversion table referred in the halftone process of a present Example. 4 is a flowchart illustrating a flow of image quality improvement image printing processing according to the first embodiment. It is explanatory drawing which shows a mode that the image quality improvement area | region is set on the liquid crystal display monitor integrated in the operation panel of the printing apparatus. 3 is a flowchart illustrating a flow of color conversion processing performed during image quality improvement image printing processing according to the first embodiment. It is explanatory drawing which showed the CMYK gradation value set to each grid point of the 2nd color conversion table compared with the 1st color conversion table. It is explanatory drawing which showed notionally the conversion table referred in order to obtain | require the formation density data in the image quality improvement area | region in the halftone process of a modification. It is a flowchart which shows the flow of the image quality improvement image printing process of 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 12 ... Ink discharge head, 100 ... Scanner part,
200: Printer unit, 240: Print carriage, 241: Print head,
242 ... Ink cartridge, 243 ... Ink cartridge,
260 ... control circuit, 300 ... operation panel

Claims (10)

A printer that prints an image by performing predetermined image processing on the image data and converting it into dot data that indicates the presence or absence of dot formation for each pixel, and then forming dots on a print medium according to the dot data. And
Image processing condition storage means for storing a first image processing condition and a second image processing condition that differ in the degree of difficulty of conspicuous dots in the image when the image is printed;
An image quality confirmation image printing unit for printing an image quality confirmation image for confirming the image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
Position designation for receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the conspicuousness of dots as a result of confirming the image quality confirmation image Information receiving means;
Image quality improvement region extraction means for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. Image quality improvement dot data generation means for generating data as image quality improvement dot data;
A printing apparatus comprising: an image quality improvement image printing unit that prints an image quality improvement image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium according to the image quality improvement dot data. The printing apparatus according to claim 1,
The image quality confirmation image printing unit and the image quality improvement image printing unit respectively print the image quality confirmation image and the image quality improvement image by forming dots of each color of cyan, magenta, yellow, and black on the print medium. Means,
The image processing condition storage means
RGB image data expressed by gradation values of red, green, and blue colors is referred to for conversion into CMYK image data expressed by gradation values of cyan, magenta, yellow, and black colors. Is stored as the first image processing condition, and the second image processing condition is a second in which a black tone value is suppressed as compared with the first color conversion table. A printing apparatus which is means for storing a color conversion table. The printing apparatus according to claim 1,
The image quality confirmation image printing means and the image quality improvement image printing means are means for printing the image quality confirmation image and the image quality improvement image, respectively, by forming a plurality of types of dots having different sizes on the print medium. ,
The image processing condition storage means
A first conversion table that is referred to for converting the image data into formation densities for a plurality of types of dots having different sizes is stored as the first image processing condition, and the second A printing apparatus which is a means for storing a second conversion table in which formation of larger dots is suppressed than the first conversion table as the image processing conditions. A printing apparatus according to any one of claims 1 to 3,
The image quality improvement dot data generation means includes
Improved area dot data generating means for generating improved area dot data by converting the image data for the image quality improved area into dot data according to the second image processing conditions;
Image quality improvement dot data composition for synthesizing the image quality improvement dot data by replacing the dot data for the image quality improvement area in the dot data generated for printing the image quality confirmation image with the improvement area dot data And a printing apparatus. A printing apparatus according to any one of claims 1 to 3,
The image quality improvement dot data generation means applies the second image processing condition to the image quality improvement area, and applies the first image processing condition to an area other than the image quality improvement area, while the image data A printing apparatus which is means for generating the image quality improvement dot data by performing predetermined image processing on the image. An image processing apparatus that performs predetermined image processing on image data representing an image and generates dot data representing the presence or absence of dot formation for each pixel in order to form dots on a print medium and print the image Because
Image processing condition storage means for storing a first image processing condition and a second image processing condition that differ in the degree of difficulty of conspicuous dots in the image when the image is printed;
The image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous, and the obtained dot data is output to print an image quality confirmation image for confirming the image quality Dot data output means;
Position designation for receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the conspicuousness of dots as a result of confirming the image quality confirmation image Information receiving means;
Image quality improvement region extraction means for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. An image processing apparatus comprising: image quality improvement dot data generation means for generating data as image quality improvement dot data. This is a printing method in which image data is subjected to predetermined image processing and converted into dot data representing the presence or absence of dot formation for each pixel, and then an image is printed by forming dots on a print medium according to the dot data. And
A first step of storing a first image processing condition and a second image processing condition in which the degree of difficulty of conspicuous dots in the image is printed when the image is printed;
A second step of printing an image quality confirmation image for confirming image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
As a result of confirming the image quality confirmation image, a position designation information designated for identifying the occurrence position of the image quality improvement region determined to require improvement of the difficulty of conspicuous dots on the image quality confirmation image is received. And the process of
A fourth step of receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. A fifth step of generating data as image quality improvement dot data;
And a sixth step of printing an image quality improved image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium according to the image quality improved dot data. An image processing method for performing dot image formation on a print medium and printing image data representing the image with predetermined image processing to generate dot data representing the presence or absence of dot formation for each pixel Because
A step (A) of storing a first image processing condition and a second image processing condition having different degrees of difficulty of conspicuous dots in the image when the image is printed;
Converting the image data into the dot data in accordance with a first image processing condition in which the dots are conspicuous, and outputting the obtained dot data for printing an image quality confirmation image for confirming image quality ( B) and
A step of receiving position designation information designated for identifying, on the image quality confirmation image, an occurrence position of an image quality improvement area that is determined to require improvement in the conspicuousness of dots as a result of confirming the image quality confirmation image ( C) and
Receiving the position designation information and extracting the image quality improvement region (D);
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. And (E) generating data as image quality improvement dot data. A method of printing an image by performing predetermined image processing on image data and converting the data into dot data representing the presence or absence of dot formation for each pixel, and then forming dots on a print medium according to the dot data. A program for realizing using
A first function for storing a first image processing condition and a second image processing condition in which the degree of difficulty of conspicuous dots in the image is different when the image is printed;
A second function of printing an image quality confirmation image for confirming the image quality after the image data is converted into the dot data in accordance with the first image processing condition in which the dots are conspicuous;
As a result of confirming the image quality confirmation image, a position designation information designated for identifying the occurrence position of the image quality improvement region determined to require improvement of the difficulty of conspicuous dots on the image quality confirmation image is received. Functions and
A fourth function for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. A fifth function for generating data as image quality improvement dot data;
A program that realizes a sixth function of printing an image quality improved image in which dots are less noticeable than the image quality confirmation image by forming dots on the print medium according to the image quality improved dot data. In order to form dots on a print medium and print an image, a method of performing predetermined image processing on image data representing the image and generating dot data representing the presence or absence of dot formation for each pixel, A program for realizing using a computer,
A function (A) for storing a first image processing condition and a second image processing condition having different degrees of difficulty in conspicuous dots in the image when the image is printed;
A function of converting the image data into the dot data in accordance with a first image processing condition in which the dots are conspicuous, and outputting the obtained dot data for printing an image quality confirmation image for confirming image quality ( B) and
A function of receiving position designation information designated for identifying on the image quality confirmation image the occurrence position of the image quality improvement area determined to require improvement in the difficulty of conspicuous dots as a result of confirming the image quality confirmation image ( C) and
A function (D) for receiving the position designation information and extracting the image quality improvement region;
The extracted image quality improvement region is subjected to the image processing according to the second image processing condition, and the region other than the image quality improvement region is subjected to the image processing according to the first image processing condition. A program that realizes the function (E) for generating data as image quality improvement dot data.

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