JP2008146134A - Data restoration device and its method and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the precision of the restoration of data recorded on a printing medium when a region on the printing medium necessary for data recording is made smaller. <P>SOLUTION: This device for recording digital data on a printing medium converts digital data into code data showing a series of dot types by associating each of a plurality of values to be acquired by a bit column configuring the digital data with the dot types to be specified according to the combination of ink colors and dot sizes. The device for restoring the digital data obtains the gray levels (gray scale values) of nine reading pixels corresponding to each of print pixels from an image of a vision code showing the code data, and calculates the total sum of the gray levels of the nine reading pixels as a total gray level, and calculates a mean gray level per one reading pixel of every print pixel from the calculated total gray level. Then, the mean gray level is collated with a dot type association level DT, so that the dot type can be discriminated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for restoring digital data recorded in the form of a machine-readable visual code.

  2. Description of the Related Art Conventionally, for example, a technique for recording data on a print medium by performing printing in association with a bit string and a color, such as a color barcode, is known (for example, Patent Document 1).

JP 2000-67191 A

  However, in the conventional technique, when data is recorded on a print medium using a printer that expresses a plurality of colors with area gradations, such as an ink jet printer, a large amount of data for recording data on the print medium is required. There was a problem that an area was required.

  In addition, when ink dots are formed on a print medium so as to express a plurality of colors, it becomes difficult to distinguish colors due to the influence of blurring and the like, and data recorded on the print medium can be accurately restored. There was a problem that it might be difficult.

  The present invention has been made to solve the above-described conventional problems. When the area on the print medium necessary for data recording is further reduced, the accuracy of restoration of the data recorded on the print medium is improved. An object is to provide a technique that can be improved.

In order to solve at least a part of the above problems, the data restoration device of the present invention provides:
A data restoration device for restoring digital data recorded in the form of machine-readable visual codes,
An image reading means for reading a visual code printed on a print medium as a unit with at least a dot of a dot type specified by a dot size;
Code data generating means for generating code data representing a series of dot types by determining the dot type for each of a plurality of ink dots constituting the visual code based on the image of the read visual code; ,
Decoding means for converting the code data into the digital data by associating each of a series of dot types represented by the code data with a value that can be taken by a bit string;
The image reading means is configured to read the visual code at a resolution finer than the printing resolution of the visual code,
The code data generation means includes
Total density value calculating means for obtaining density values of a plurality of read pixels corresponding to each print pixel from the read visual code image and calculating a total density value for each print pixel from the density value;
Dot type discrimination means for discriminating the dot type based on the calculated total density value for each print pixel.

  In this data restoration device, code data representing a series of dot types is obtained by determining at least the dot type specified by the dot size for each of a plurality of ink dots constituting a visual code printed on a print medium. Generated. Further, the code data is converted into digital data by associating each of a series of dot types represented by the code data with a value that can be taken by the bit string. Thus, in this data restoration device, digital data can be restored from a visual code in which a bit string can be associated with a dot type itself, so that digital data recorded in a smaller area on a print medium can be restored. Can be restored.

  Further, in this data restoration device, digital data can be restored from a visual code in which a value that can be taken by a bit string is associated with the dot type itself, so that a plurality of ink dots are formed in the visual code. It is possible to improve the accuracy of restoration of data recorded on the print medium without making it difficult to determine the color due to the influence of blur or the like.

  Further, in this data restoration device, from the image of the read visual code, a density value of each of the plurality of read pixels corresponding to each print pixel is obtained, and a total density value for each print pixel is calculated from the density value. Since the dot type is determined based on the calculated total density value for each print pixel, the total density value for each print pixel even if the position where the ink dots are formed is shifted within the range of each print pixel. As a result, the dot type can be determined with high accuracy. For example, in an ink jet printer, there is a slight shift in the ink dot landing position, but even in the case of printing by this ink jet printer, the dot type can be determined with high accuracy. Therefore, it is possible to further improve the accuracy of restoration of data recorded on the print medium. In other words, even if the printing apparatus is inexpensive and inferior in landing position accuracy, according to the data restoration apparatus of the present invention, it is possible to sufficiently determine the dot type.

  In the data restoration apparatus, the dot type determination unit includes an average density value calculation unit that calculates an average density value per read pixel for each print pixel from the calculated total density value for each print pixel. The dot type may be determined based on the calculated average density value.

  According to this configuration, since the dot size is determined from the average density value per read pixel, the above calculation can be performed using the read pixel by the image reading apparatus as it is, and the processing is easy.

  In the data restoration apparatus configured to use the average density value, the print medium supports a machine-readable dot type that defines a correspondence between an average density value per pixel read by the image reading unit and the dot type. The information may be printed, and the image reading unit may read the dot type correspondence information, and the dot type determination unit may determine the dot type using the read dot type correspondence information. Good.

  According to this configuration, it is possible to obtain all information necessary for determining the dot size from the print medium. The printed dot type correspondence information may be information representing tabular table data.

  Alternatively, the printed dot type correspondence information is a dot test pattern in which all the dot types that can be used for the visual code are test printed, and one read by the image reading unit is performed from the printed dot test pattern. A table generation unit that generates a dot type correspondence table indicating a correspondence relationship between an average density value per pixel and the dot type, and the dot type determination unit uses the dot type correspondence information table to It is good also as a structure which performs discrimination.

  According to this configuration, the dot type correspondence table can be obtained from the dot test pattern without preparing the dot type correspondence information in advance by checking the relationship between the dot type and the average density value for each printing device that prints the visual code. Can be easily created.

  In the data restoration device of the present invention, the print medium is printed with machine-readable encoded information that defines correspondence between a plurality of values that can be taken by the bit string constituting the digital data and the dot type, The image reading unit may read the encoded information, and the decoding unit may convert the code data into the digital data using the read encoded information.

  According to this configuration, all the information necessary for the decoding means can be acquired from the print medium, and digital data can be restored. The printed encoded information may be information representing tabular table data.

  In the data restoration device of the present invention, the dot type may be specified by a combination of an ink color and the dot size. In this way, since more information can be included in one dot, it is possible to cope with a longer bit string.

The data restoration method of the present invention
A data restoration method for restoring digital data recorded in the form of a machine readable visual code, comprising:
(A) a step of reading a visual code printed on a print medium in units of at least dots of a dot type specified by a dot size as an image;
(B) generating code data representing a series of dot types by determining the dot types for each of a plurality of ink dots constituting the visual code based on the read visual code image; ,
(C) converting the code data into the digital data by associating each of a series of dot types represented by the code data with a value that can be taken by a bit string, and
The step (a) is configured to read the visual code at a resolution finer than the printing resolution of the visual code,
The step (b)
(B-1) obtaining density values of a plurality of read pixels corresponding to each print pixel from the read visual code image, and calculating a total density value for each print pixel from the density value;
(B-2) a step of determining the dot type based on the calculated total density value for each print pixel.

The computer program of the present invention is:
A computer program for restoring digital data recorded in the form of machine-readable visual codes,
(A) a function of reading, as an image, a visual code printed on a print medium with at least a dot of a dot type specified by a dot size;
(B) a function of generating code data representing a series of dot types by determining the dot types for each of a plurality of ink dots constituting the visual code based on the read visual code image; ,
(C) by causing a computer to realize a function of converting the code data into the digital data by associating each of a series of dot types represented by the code data with a value that can be taken by a bit string;
The function (a) is configured to read the visual code at a resolution finer than the printing resolution of the visual code,
The function (b) is
(B-1) a function of obtaining density values of a plurality of read pixels corresponding to each print pixel from the read visual code image, and calculating a total density value for each print pixel from the density value;
(B-2) A function of discriminating the dot type based on the calculated total density value for each print pixel.

  The data restoration method and the computer program have the same effects as the data restoration apparatus of the present invention.

  Next, embodiments of the present invention will be described based on examples.

A. First embodiment:
FIG. 1 is an explanatory diagram schematically showing the configuration of a data recording / restoring system as a first embodiment of the present invention. The data recording / restoring system 10 of this embodiment includes a computer 100, and a printer 300 and a scanner 400 connected to the computer 100.

  The computer 100 includes a CPU 110, a display unit 120 such as a liquid crystal monitor, an operation unit 130 such as a keyboard and a mouse, an external storage device 140 such as a hard disk drive, an interface unit (I / F unit) 150, a ROM and a RAM. And an internal storage device 200. Each component of the computer 100 is connected to each other via a bus 160.

  The interface unit 150 is connected to an external device such as the printer 300 and the scanner 400 via a cable, and exchanges information with the external device. For example, the interface unit 150 supplies print data for printing an image to the printer 300. Further, the interface unit 150 acquires image data generated by the scanner 400. The interface unit 150 may be connected to a network and exchange information via the network.

  The internal storage device 200 stores a data recording processing unit 210 and a data restoration processing unit 220. The data recording processing unit 210 and the data restoration processing unit 220 are computer programs for executing data recording processing and data restoration processing described later under a predetermined operating system. The CPU 110 reads out and executes these computer programs from the internal storage device 200, thereby realizing data recording processing and data restoration processing described later.

  The data recording processing unit 210 includes, as modules, an encoding processing unit 212 that encodes data and a printing processing unit 214 that controls the printer 300 to execute printing. The data restoration processing unit 220 also generates an image reading processing unit 222 that controls the scanner 400 to execute reading of an image, a code data generation processing unit 224 that generates code data based on the read image, and A decoding processing unit 226 that converts code data into digital data is included as a module. The code data generation processing unit 224 includes an average density value calculation processing unit 224a and a dot type determination processing unit 224b. Details of the functions of these units will be described in detail in the description of data recording processing and data restoration processing described later. Each module included in the data recording processing unit 210 and the data restoration processing unit 220 may have a configuration independent of the data recording processing unit 210 and the data restoration processing unit 220.

  The internal storage device 200 also stores a coding table CT and a dot type correspondence table DT. The encoding table CT defines a correspondence between a plurality of values that can be taken by the bit string constituting the digital data and a plurality of dot types that are specified by combinations of ink colors and dot sizes used for printing by the printer 300. It is a table in table format and is used by the encoding processing unit 212 of the data recording processing unit 210. On the other hand, the dot type correspondence table DT is a table in a table format used by the dot type discrimination processing unit 224b of the data restoration processing unit 220. Details of the encoding table CT and the dot type correspondence table DT will be described later.

  The printer 300 is an ink jet printer that performs printing by spraying ink droplets onto a print medium to form ink dots. The printer 300 according to the present embodiment has three dot sizes (six color inks (cyan (C), light cyan (LC), magenta (M), light magenta (LM), yellow (Y), and black (K))). It is possible to perform printing using ink dots of “small”, “medium”, and “large” in ascending order.

  The scanner 400 is an image scanner that reads images and characters formed on a printing medium such as printing paper and generates data representing the read images. The scanner 400 of this embodiment is a scanner that can read an image or the like with a resolution finer than the printing resolution when the printer 300 prints a data recording code DRC described later. How fine the resolution is read will be described later.

  FIG. 2 is a flowchart showing the flow of data recording processing by the data recording / restoring system 10 of this embodiment. The data recording process of the present embodiment is a process for recording digital data on a print medium.

  In step S110, the data recording processing unit 210 (FIG. 1) acquires target data. The target data is digital data to be recorded on the print medium. The target data is arbitrary digital data. For example, the target data may be image data representing an image (a still image or a moving image), voice data representing speech, or text data representing text. Good. The data recording processing unit 210 may acquire target data from the outside via the interface unit 150, or may acquire target data stored in the external storage device 140 or the internal storage device 200.

  In step S120, the encoding processing unit 212 (FIG. 1) of the data recording processing unit 210 encodes the target data. The encoding of the target data is performed by associating each of a plurality of values that can be taken by the bit string constituting the target data with the dot type specified by the combination of the ink color and dot size used for printing in the printer 300. This is a process of converting data into code data representing a series of dot types. The encoding of the target data is performed using the encoding table CT (FIG. 1) that defines the correspondence between the dot type and the values that can be taken by the bit string that forms the target data.

  FIG. 3 is an explanatory diagram illustrating an example of the encoding table CT. As shown in FIG. 3, in the coding table CT, dots specified by combinations of six ink colors (C, LC, M, LM, Y, K) and three dot sizes (small, medium, large). Each type is associated with a unique 4-bit bit string value. The ink color corresponds to a larger bit string value in the order of C, LC, M, LM, Y, and K. In each ink color, a larger bit string value corresponds to a larger dot size. Yes.

  For example, as shown in FIG. 3, in the encoding table CT of the present embodiment, a bit string having a value of “0000” is associated with a dot type of “none” for both ink color and dot size, and cyan (C). A bit string having a value of “0001” is associated with the “small” dot type, and a bit string having a value of “0010” is associated with the “medium” dot type of cyan. The type is associated with a bit string having a value of “0011”. A bit string having a value of “0100” is associated with the “small” dot type of light cyan (LC), and a bit string having a value of “0101” is associated with the “medium” dot type of light cyan. A bit string having a value of “0110” is associated with the “large” dot type.

  As a result, in the encoding table CT shown in FIG. 3, unique bit string values are associated with each of the 16 types of dots including “None” that does not form dots in the print pixel PX. For example, dot types that are not used, such as “small” dot type of light cyan (LC), “small” dot type of light magenta (LM), and “small” dot type of yellow (Y) are included. It is out. This is to improve the accuracy of dot discrimination by not using a dot type that is highly likely to cause a discrimination error in dot discrimination during data restoration processing (step S220 in FIG. 6). The types of dots that are likely to cause a determination error are, for example, dots with a relatively small ink color, such as yellow (Y), magenta (M), and light magenta (LM).

  Note that the dot types that are not used are only examples, and it is highly possible that a discrimination error will occur even for “large” dots of relatively high density ink colors such as cyan (C) and light cyan (LC). The dot type that is not used may be replaced with a dot having a relatively high density and a large ink color.

  FIG. 4 is an explanatory diagram illustrating an example of a method for encoding target data. The uppermost part of FIG. 4 illustrates a part of the bit string constituting the target data. In the example of FIG. 4, the target data is divided into 4-bit bit strings (hereinafter referred to as “unit bit string UBQ”), and each unit bit string UBQ is included in a plurality of dot types according to the encoding table CT (FIG. 3). It is converted into code data representing one. For example, the unit bit string UBQ “0110” is converted into code data representing the “large” dot type of light cyan (LC). Similarly, for example, a unit bit string UBQ having a value of “1001” is converted into code data representing a “medium” dot type of light magenta (LM), and a unit bit string UBQ having a value of “0011” is cyan (C). Is converted into code data representing the “large” dot type. By performing such conversion on all the unit bit strings UBQ constituting the target data, the target data can be encoded into code data representing a series of dot types.

  Note that the encoding of the target data by the encoding processing unit 212 is preferably performed using an error-correctable code. An example of a code that can be corrected is a Reed-Solomon code.

  In step S130 (FIG. 2), the print processing unit 214 (FIG. 1) prints the data recording code DRC based on the code data representing a series of dot types generated by the encoding in step S120. FIG. 5 is an explanatory diagram showing an example of the data recording code DRC. FIG. 5 shows an enlarged part of the data recording code DRC printed on the print medium PM. As shown in FIG. 5, the data recording code DRC is formed by a plurality of dot types of ink dots D formed on each of the printing pixels PX (enclosed by broken lines in FIG. 5), which is one pixel on the printing medium PM. A structured visual code. The print processing unit 214 controls the printer 300 to print the data recording code DRC by sequentially forming ink dots D on the print medium PM according to code data representing a series of dot types.

  Note that the data recording code DRC includes a reference mark (not shown) for positioning in the later-described data restoration process. The reference mark is printed using, for example, ink dots having an ink color or dot size that are not directly used for recording target data. In step S130, a machine-readable encoding table identifier CTI (see FIG. 5) for specifying the encoding table CT used for encoding in step S120 on the print medium PM, and a data restoration process described later. A machine-readable dot type correspondence table identifier DTI (see FIG. 5) for specifying the dot type correspondence table DT necessary for the printing is printed. The encoding table identifier CTI and the dot type correspondence table identifier DTI are configured by a two-dimensional code such as a QR code, for example.

  By the data recording process described above, the target data is recorded in the form of the data recording code DRC on the print medium PM.

  FIG. 6 is a flowchart showing the flow of data restoration processing by the data recording / restoring system 10 of this embodiment. The data restoration process of the present embodiment is a process for restoring the target data recorded on the print medium PM.

  In step S210, the image reading processing unit 222 (FIG. 1) controls the scanner 400 to read the data recording code DRC, the encoding table identifier CTI, and the dot type correspondence table identifier DTI printed on the printing medium PM. In the present embodiment, the reading of the data recording code DRC by the image reading processing unit 222 is performed at a resolution finer than the printing resolution when the printer 300 prints the data recording code DRC (FIG. 5). Specifically, reading of the data recording code DRC by the image reading processing unit 222 is performed at a resolution of 9 times (3 × vertical × 3 × horizontal) the print resolution of the printer 300. Image data generated by reading by the image reading processing unit 222 is stored in a predetermined area in the internal storage device 200.

  In step S220, the code data generation processing unit 224 (FIG. 1) determines the dot type using the image data generated by reading the data recording code DRC, and generates code data representing a series of a plurality of dot types. Code data generation processing is performed.

  FIG. 7 is a flowchart showing details of the code data generation processing in step S220. As shown in FIG. 7, the code data generation processing unit 224 first detects a reference mark included in the data recording code DRC from the image data generated by reading, and positions the data recording code DRC (step S310). ). Next, the average density value calculation processing unit 224a included in the code data generation processing unit 224 identifies each print pixel PX of the data recording code DRC that has been positioned, and per read pixel PY for each print pixel PX. An average density value is calculated (step S320). As described above, the reading of the data recording code DRC by the image reading processing unit 222 is performed at a resolution of 9 times the printing resolution of the printer 300 (3 times in length × 3 times in width). As described above, each print pixel PX corresponds to nine of the read pixels PY obtained by the image reading processing unit 222. In step S320, each print pixel PX is specified from the reference mark, and each density value (gradation value) for each of the nine read pixels PY corresponding to each specified print pixel PX is obtained. Is divided by 9 which is the number of read pixels PY, thereby obtaining an average density value per read pixel PY in each print pixel PX.

  The density value of each read pixel PY is composed of density values for each color of red (R), green (G), and blue (B), and the density value of each color is R of the read pixel of the scanner 400. , G, B gradation values can be easily obtained. The average density value is obtained as the average density values DAVr, DAVg, and DAVb for each color of R, G, and B. Each average density value DAVr, DAVg, DAVb is represented by a gradation value of 0-255.

  Next, the dot type determination processing unit 224b determines the dot type correspondence table DT based on the read data (image data) generated by reading the dot type correspondence table identifier DTI (step S330). The determination of the dot type correspondence table DT is a process of specifying the dot type correspondence table DT by decoding the QR code when the dot type correspondence table identifier DTI is, for example, a QR code.

  FIG. 9 is an explanatory diagram showing an example of the dot type correspondence table DT. As shown in the figure, in the dot type correspondence table DT, the dot types specified by combinations of six ink colors (C, LC, M, LM, Y, K) and three dot sizes (small, medium, large). Are associated with the gradation values of read pixels of R, G, and B colors.

  For example, as shown in FIG. 9, in the dot type correspondence table DT of the present embodiment, the ink type and the dot size of “None” have a value of 211 to 255 as R gradation values, Values 211 to 255 as G gradation values are associated with values 211 to 255 as B gradation values. The cyan (C) “small” dot types include values 141 to 175 as R gradation values, values 211 to 255 as G gradation values, and 211 as B gradation values. ˜255, the cyan “medium” dot types include values of 71 to 105 as R gradation values, values of 211 to 255 as G gradation values, and B The values of 211 to 255 as the tone values of C are associated with each other. For the “large” dot type of cyan, the values of 0 to 35 as the tone values of R and 211 as the tone value of G are included. The values of ˜255 and the values of 211 to 255 as the gradation values of B are associated with each other. Similarly, the R, G, and B gradation values are associated with the LC, M, LM, Y, and K dot sizes.

  That is, the dot type and the gradation value of the read pixel included in the dot type correspondence table DT are recorded as a dot type correspondence table identifier DTI in the form of a two-dimensional code such as a QR code. In step S330, Processing for obtaining the dot type correspondence table DT from the dot type correspondence table identifier DTI is performed.

  Returning to FIG. 7, when the above-described dot type correspondence table DT is specified in step S330, the dot type discrimination processing unit 224b then obtains the average density values DAVr, DAVg, and DAVb obtained in step S320 in step S330. The ink color and dot size determined from each average density value DAVr, DAVg, and DAVb by collating with the dot type correspondence table DT obtained in step 4 (matching with “gradation value of read pixel” in the right column in FIG. 9). Is determined (step S340). For example, when the average density values DAVr = “80”, DAVg = “230”, and DAVb = “240” obtained in step S222, matching is performed on the third line from the top in FIG. ) Of “medium”. For example, when the average density values DAVr = “220”, DAVg = “220”, and DAVb = “60” obtained in step S222, matching is performed on the fourth line from the bottom in FIG. ) Of “large” dot type.

  In step S340, the dot type is determined for each of all the printing pixels PX included in the data recording code DRC, and the result of the determination is the internal storage device as code data representing a series of a plurality of dot types. 200 is temporarily stored. After executing step S340, the process proceeds to “return”, and after exiting the code data generation process, the process proceeds to step S230 in FIG.

  As shown in FIG. 6, in step S230, the decoding processing unit 226 (see FIG. 1) determines the coding table CT based on the read data (image data) generated by reading the coding table identifier CTI. Do. The determination of the encoding table CT is a process of identifying the encoding table CT used for the data recording process by decoding the QR code when the encoding table identifier CTI is, for example, a QR code.

  In subsequent step S240, the decoding processing unit 226 (FIG. 1) converts each of a series of dot types represented by the code data generated in step S220 into a bit string using the encoding table CT specified in step S230. The target data is restored by associating with possible values. This process is a process opposite to the encoding of the target data in the data recording process (step S120 in FIG. 2). In addition, when the encoding of the target data in the data recording process is performed using a code capable of error correction, error correction is performed when the decoding processing unit 226 restores the target data.

  By the data restoration process described above, it is possible to restore the target data recorded in the form of the data recording code DRC on the print medium PM.

  As described above, in the data recording / restoring system 10 according to the present embodiment, the target data is obtained by associating each possible value of the unit bit string UBQ constituting the target data with the dot type using the encoding table CT. Encoding for converting into code data representing a series of dot types is performed. The target data can be recorded on the print medium PM by forming a series of dot types of ink dots D represented by the generated code data on the print medium PM and printing the data recording code DRC. . At this time, since the value of a predetermined bit string is associated with the dot type itself specified by the combination of the ink color and the dot size, an area on the print medium PM required for recording the target data (the data recording code DRC) Area) can be further reduced. That is, in the data recording / restoring system 10 of the present embodiment, the target data can be recorded on the print medium PM at a high density, and the target data recorded on the print medium PM at a high density can be restored. it can.

  Further, as shown in FIG. 5, in the data recording code DRC, only one ink dot D is formed for each print pixel PX, and a plurality of ink dots D are not formed overlapping each other. Therefore, it is possible to accurately restore the target data recorded on the print medium PM without making it difficult to determine the color due to the influence of bleeding or the like during the data restoration process.

  Further, in the data restoration processing unit 220 of this embodiment, the density values (gradation values) of the nine read pixels corresponding to the respective print pixels PX are obtained from the visual code image, and the density values of the nine read pixels are obtained. Is calculated as a total density value, and an average density value per read pixel PY for each print pixel PX is calculated from the calculated total density value. The average density value is checked against the dot type correspondence table DT to determine the dot type. For this reason, even if the position where the ink dots are formed is shifted within the range of each print pixel PX, the dot type can be determined with high accuracy.

  FIG. 10 is an explanatory diagram showing a state in which the positions where ink dots are formed are shifted within the range of the print pixel PX. 10A is an example in which an ink dot having a “small” dot size is shifted to the upper left side, and FIG. 10B is an example in which an ink dot having a “small” dot size is shifted to the lower right side. . (C) is an example in which an ink dot having a “medium” dot size is shifted to the lower left side, and (d) is an example in which an ink dot having a “medium” dot size is located near the center. (E) is an example in which an ink dot having a “large” dot size is shifted to the upper left side, and (f) is an example in which an ink dot having a “large” dot size is shifted to the lower right side. Note that the size of the printing pixel PX by the printer 300 is determined in consideration of the amount of deviation of the ink dot landing position. In other words, the ink dot landing position has a large shift as illustrated in FIGS. 10A to 10F, but falls within the range of one print pixel PX.

  In the ink jet printer that constitutes the printer 300, ink dot landing as illustrated in FIGS. 10A to 10F due to the amount of ink discharged from the printer head, uneven reading of the scanner 400, and the like. Deviation occurs in position. On the other hand, since the data restoration processing unit 220 of this embodiment determines the dot type based on the average density value per read pixel PY for each print pixel PX, (a) in FIG. And (b), or between (c) and (d), or between (e) and (f), the calculation result as the same average density value is obtained to distinguish the same dot type The result can be obtained.

  As a method for discriminating the dot type (ink color and dot size) from the image data generated by reading the data recording code DRC, an ink dot is detected from the image data (a reading pixel where an ink dot exists is detected). ), It is conceivable to determine the ink color and the dot size for each of the detected read pixels. However, if the deviation amount of the landing position of the ink dot is large, the detection of the ink dot may be missed, and the dot type There was a risk of misjudgment. On the other hand, in this embodiment, as described above, even if a deviation occurs in the landing position of the ink dot, the dot type determination result is accurate without change, so that the dot type is determined with high accuracy. be able to. In addition, since the displacement amount of the ink dot landing position is large in an ink jet printer having a simple configuration (that is, inexpensive), it is difficult to record digital data on a print medium using an inexpensive ink jet printer. However, as described above, the data restoration processing unit 220 according to the present embodiment can determine the dot type with high accuracy regardless of the deviation amount of the landing position of the ink dot, so that the digital data using an inexpensive ink jet printer can be used. There is also a secondary effect that data recording can be easily realized.

  Further, in the data recording / restoration system 10 of the present embodiment, at the time of data recording processing, an encoding table identifier CTI for specifying an encoding table CT used for encoding target data and a target data recovery are used. A dot type correspondence table identifier DTI for specifying the dot type correspondence table DT is printed on the print medium PM. In the data restoration process, the dot type correspondence table DT used for decoding the target data is specified based on the dot type correspondence table identifier DTI printed on the print medium PM, and the coding table identifier CTI is used as the coding table identifier CTI. Based on this, the coding table CT is specified. Therefore, in the data recording / restoration system 10 of the present embodiment, the target data can be accurately restored using the appropriate dot type correspondence table DT and the encoding table CT during the data restoration process.

  Further, in the data recording / reconstructing system 10 of this embodiment, when the target data is encoded using an error-correctable code during the data recording process, the error correction is performed during the data restoration process. Is done. In this case, even if a discrimination error occurs in the dot discrimination of the data restoration process (step S220 in FIG. 6), it is possible to correct the error and restore the target data accurately.

  Note that it is considered that the determination error in the dot determination (step S220 in FIG. 6) of the data restoration process is relatively likely to occur in the dot size determination rather than the ink color determination. As shown in FIG. 3, the encoding table CT used in the present embodiment is a table in which each of two dot sizes different in dot size by one level is associated with a bit string value that is different by only 1 bit. It has become. Therefore, even if the dot size is erroneously determined to be one size different in size, the error that occurs is only one bit. Therefore, the accuracy of error correction can be improved in the encoding table CT used in the present embodiment.

B. Second embodiment:
Next, a second embodiment of the present invention will be described. In the first embodiment, the dot type correspondence table identifier DTI used for the data restoration processing is composed of a two-dimensional code representing the contents of the dot type correspondence table DT (see FIG. 9). In the second embodiment, a dot test pattern obtained by test printing all dot types that can be used for visual codes is used as a dot type correspondence table identifier, and a dot type correspondence table DT is generated from the dot test pattern. Details will be described below.

  FIG. 11 is an explanatory diagram showing an example of a dot type correspondence table identifier DTI2 used for data restoration processing in the second embodiment of the present invention. As shown in the figure, the dot type correspondence table identifier DTI2 is a dot test pattern composed of a total of 18 ink dots, 3 in the horizontal direction and 6 in the vertical direction. Dotted lines and broken lines in the figure are shown for convenience of illustration and are not actually printed. In the dot type correspondence table identifier DTI2, each row from the first row to the sixth row includes cyan (C), light cyan (LC), magenta (M), light magenta (LM), yellow (Y), black ( K) Ink dots specified by each ink color are shown, and each column from the 1st column to the 6th column is specified by the dot size of “Small”, “Medium”, “Large” Ink dots are shown.

  The data recording processing unit performs processing for printing the dot type correspondence table identifier DTI2 having the above-described configuration when printing the data recording code. As a result, a dot test pattern is printed by the printer 300. In the figure, the reason why the ink dot is not positioned at the center of the print pixel PX is due to the positional deviation of the ink dot described above.

  FIG. 12 is a flowchart showing the dot type correspondence table specifying process. This dot type correspondence table specifying process is a process performed in place of step S330 of the code data generation process (FIG. 7) in the first embodiment. As shown in the figure, when the processing shifts to the dot type correspondence table specifying process, the CPU 110 first positions the dot type correspondence table identifier DTI2 (step S510), and specifies each print pixel of the dot type correspondence table identifier DTI2. Then, a process of calculating an average density value per read pixel for each print pixel is performed (step S520). The processing in steps S510 and S520 is the same as the processing in steps S310 and S320 in the first embodiment, and whether the processing target is image data generated by reading the data recording code, or a dot type correspondence table identifier. The only difference is whether the image data is generated by reading DTI2. That is, in step S520, the CPU 110 identifies each print pixel PX of the dot type correspondence table identifier DTI2, and each density value (gradation value) for the nine read pixels PY corresponding to the identified print pixel PX. Are obtained, and the total density value, which is the sum of the density values, is divided by 9, which is the number of read pixels PY, to obtain an average density value per read pixel PY in each print pixel PX. The average density value is obtained as the average density values DAVr, DAVg, and DAVb for each color of R, G, and B.

  Next, the CPU 110 obtains the brightness around one read pixel for each print pixel based on the average density values DAVr, DAVg, and DAVb of each color for each print pixel calculated in step S520, and sets each print pixel to the brightness. Then, ranking is performed (step S530). The brightness for each print pixel is obtained from the gradation value of each color of RGB, that is, the average density values DAVr, DAVg, and DAVb of each color, using the conversion formula (1) below. Here, the average density value of each color is expressed as R.D. G. B.

  y = 0.30DAVr + 0.59DAVg + 0.11DAVb (1)

  The ink colors are light in this order among cyan (C), magenta (M), yellow (Y), and black (K), but between cyan (C) and light cyan (LC) of the same color system and magenta (M) The lighter magenta (LM) is not necessarily brighter than the former. Between cyan (C) and light cyan (LC), in order of brightness, C is “small”, LC is “small”, C is “medium”, LC is “medium”, LC is “large”, LC The order of “Large”. Between magenta (M) and light magenta (LM), when arranged in order of brightness, M “small”, LM “small”, M “medium”, LM “medium”, LM “large”, The order of LM is “Large”.

  Thereafter, the CPU 110 sequentially calculates intermediate gradation values between two print pixels adjacent in the brightness order obtained in step S530 (step S540), and based on the calculated plurality of intermediate gradation values. Processing for generating a dot type correspondence table is performed (step S550).

  FIG. 13 is an explanatory diagram illustrating an example of the process of step S540. The illustration in the figure corresponds to a print pixel in which “small” ink dots of C are recorded and a print pixel in which “small” ink dots of LC are recorded as two print pixels having adjacent brightness orders. If you want to. In addition, it can be determined from the reading position when the dot type correspondence table identifier DTI2 is read which dot type of ink dot is recorded by each print pixel. As shown in FIG. 11, for example, if the reading position is in the first row and the first column, a print pixel in which “small” ink dots of C are recorded (hereinafter referred to as the first print pixel PX1). If the reading position is in the second row and the first column, it is a print pixel (hereinafter referred to as a second print pixel PX2) in which LC “small” ink dots are recorded.

  As shown in FIG. 13, the average density value DAVr = “158”, DAVg = “233”, and DAVb = “233” of the first print pixel PX1, and the average density value DAVr = “of the second print pixel PX2. In the case of 193 ”, DAVg =“ 233 ”, and DAVb =“ 233 ”, an intermediate value (intermediate gradation value) of the average density value DAVr for red (R), that is, an intermediate value between“ 158 ”and“ 193 ” Is obtained as R intermediate gradation value = “175”. The R intermediate gradation value = “175” is the boundary between the “small” ink dot of C and the “small” ink dot of LC. As described above, when the ink colors are C and LC, the boundary for R is obtained based on the intermediate value of the average density value DAVr for R of the two print pixels. Although not shown, for M and LM, a boundary for G is obtained based on an intermediate value of the average density value DAVg for G of the two print pixels. For Y, the boundary for B is determined based on the intermediate value of the average density value DAVb for B of the two print pixels. For K, the boundaries for R, G, and B are obtained based on the intermediate values of the average density values DAVr, DAVg, and DAVb of R, G, and B of the two print pixels.

  As described above, the dot type correspondence table DT illustrated in FIG. 9 is generated by obtaining the boundary. When the generation of the dot type correspondence table DT is finished, the process returns to “Return” and the dot type correspondence table specifying process routine is once finished. Using this dot type correspondence table DT, code data representing a series of a plurality of dot types recorded in the data recording code DRC is generated as in the first embodiment.

  According to the second embodiment configured as described above, even if the relationship between the dot type and the average density value is checked for each printer that prints the visual code, the dot type correspondence table is not created in advance. A dot type correspondence table can be easily created from a dot test pattern. For this reason, it becomes possible to cope with various printers and is excellent in versatility. The various printers are not limited to the RGB printer as in the above embodiments, and may be a Lab printer whose input data is Lab.

C. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C1. Modification 1:
The configuration of the data recording / restoration system 10 (FIG. 1) in each of the above embodiments is merely an example, and the configuration of the data recording / restoration system 10 may be other configurations. For example, the data recording / restoring system 10 may include a digital still camera or a digital video camera instead of the scanner 400. In this case, reading of the data recording code DRC and the encoding table identifier CTI (step S210 in FIG. 6) in the data restoration process is performed using a digital still camera or a digital video camera.

  In each of the above embodiments, both the data recording process and the data restoring process are executed by the data recording / restoring system 10, but each of the data recording process and the data restoring process is executed by another system. Also good. That is, the data recording process is executed by a data recording system including the data recording processing unit 210 (FIG. 1) and the printer 300, and the data recovery process is executed by a data recovery system including the data recovery processing unit 220 and the scanner 400. Good.

  In each of the above embodiments, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. Also good.

C2. Modification 2:
In each of the above embodiments, in step S130 of the data recording process (FIG. 2), the encoding table identifier CTI and the dot type correspondence table identifier DTI are printed on the print medium PM together with the data recording code DRC (FIG. 2). 5), machine-readable information indicating the content of the coding table CT itself may be printed on the print medium PM instead of the coding table identifier CTI, or the dot type instead of the dot type correspondence table identifier DTI. Machine-readable information indicating the contents of the correspondence table DT itself may be printed on the print medium PM.

  In addition, the encoding table CT and the dot type correspondence table DT are not individually provided as in the above embodiments, but the contents of both the tables CT and DT may be combined into one table. In the case of this configuration, there is also one table identifier printed on the print medium.

C3. Modification 3:
The dot types used in the printer 300 in each of the above embodiments are six ink colors and three dot sizes, but the dot types are not limited to this. The dot type is specified by the combination of the ink color and the dot size, and the number of ink colors and the number of dot sizes may be different from those in the above embodiments.

C4. Modification 4:
In each of the above embodiments, the visual code is configured to be printed in units of dots of the dot type specified by the ink color and the dot size. Instead, the dot type is specified only by the dot size. It can also be. The target data is divided into 2-bit bit strings. When the value of the bit string is “00”, there is no dot, when it is “01”, it is “small”, and when it is “10”, it is “medium”. In the case of “11”, the printing may be performed with a dot size of “large”. Also in this configuration, at the time of data restoration, the dot type can be determined based on the average density value per read pixel for each print pixel, as in the above embodiments.

  Although the dot types in Modification 4 are three dot sizes, the number of dot sizes may be a number other than three. Furthermore, the dot type may be specified by a combination of the dot size and a parameter (for example, shape) that defines other dots.

C5. Modification 5:
Further, the ink used for printing by the printer 300 may be dye ink or pigment ink.

C6. Modification 6:
In the embodiment, the density values (gradation values) of the nine read pixels corresponding to the print pixels PX are obtained from the visual code image, and the sum of the density values of the nine read pixels is calculated as the total density value. Then, the average density value per read pixel PY for each print pixel PX is calculated from the calculated total density value, and the dot type is discriminated by comparing the average density value with the dot type correspondence table DT. It was. Instead of this, the calculated total density value may be used as it is, and the dot type discrimination may be performed by comparing the total density value with the dot type correspondence table DT. In this case, the dot type correspondence table is not “the gradation value of the reading pixel”, but “the total density value” obtained by multiplying the value by the number of reading pixels per printing pixel (“9” in the above example). It is necessary to memorize as. Also with this configuration, the dot type can be determined with high accuracy, as in the above embodiments.

C7. Modification 7:
In the above-described embodiment, the reading of the data recording code DRC by the image reading processing unit 222 is performed at a resolution of 9 times the printing resolution of the printer 300 (3 times in the vertical direction and 3 times in the horizontal direction). It may be 16 times (4 times vertical x 4 times horizontal), 25 times (5 times vertical x 5 times horizontal), or the like. Any resolution can be used as long as the resolution is finer than the printing resolution of the data recording code DRC as the visual coat.

It is explanatory drawing which shows roughly the structure of the data recording / restoration system as 1st Example of this invention. 4 is a flowchart showing a flow of data recording processing by the data recording / restoring system 10. It is explanatory drawing which shows an example of encoding table CT. It is explanatory drawing which shows an example of the encoding method of object data. It is explanatory drawing which shows an example of the data recording code DRC. 4 is a flowchart showing a flow of data restoration processing by the data recording / restoring system 10. It is a flowchart which shows the detail of the code data generation process of step S220. It is explanatory drawing which shows the relationship between the printing pixel PX and the reading pixel PY. It is explanatory drawing which shows an example of the dot kind corresponding | compatible table DT. It is explanatory drawing which shows a mode that the position which forms an ink dot within the range of the printing pixel PX shifts | deviates. It is explanatory drawing which shows an example of the dot kind corresponding | compatible table identifier DTI2 used for the data restoration process in 2nd Example of this invention. It is a flowchart which shows a dot kind corresponding | compatible table specific process. It is explanatory drawing which shows an example of a process of step S540.

Explanation of symbols

10. Data recording / restoration system 100 ... Computer 110 ... CPU
DESCRIPTION OF SYMBOLS 120 ... Display part 130 ... Operation part 140 ... External storage device 150 ... Interface part 160 ... Bus 200 ... Internal storage device 210 ... Data recording process part 212 ... Encoding process part 214 ... Print process part 220 ... Data restoration process part 222 ... Image reading processing unit 224 ... Code data generation processing unit 224a ... Average density value calculation processing unit 224b ... Dot type discrimination processing unit 226 ... Decoding processing unit 300 ... Printer 400 ... Scanner PM ... Print medium CT ... Encoding table CTI ... Code Table identifier DT ... dot type correspondence table DTI ... dot type correspondence table identifier DRC ... data recording code PX ... print pixel PY ... read pixel

Claims (12)

A data restoration device for restoring digital data recorded in the form of machine-readable visual codes,
An image reading means for reading a visual code printed on a print medium as a unit with at least a dot of a dot type specified by a dot size;
Code data generating means for generating code data representing a series of dot types by determining the dot type for each of a plurality of ink dots constituting the visual code based on the image of the read visual code; ,
Decoding means for converting the code data into the digital data by associating each of a series of dot types represented by the code data with a value that can be taken by a bit string;
The image reading means is configured to read the visual code at a resolution finer than the printing resolution of the visual code,
The code data generation means includes
Total density value calculating means for obtaining density values of a plurality of read pixels corresponding to each print pixel from the read visual code image and calculating a total density value for each print pixel from the density value;
A data restoration device comprising: a dot type determination unit that determines the dot type based on the calculated total density value for each print pixel. The data restoration device according to claim 1,
The dot type discrimination means is
An average density value calculating unit that calculates an average density value per read pixel for each print pixel from the calculated total density value for each print pixel, and based on the calculated average density value, the dot A data restoration device that is configured to determine the type. The data restoration device according to claim 2,
The print medium is printed with machine-readable dot type correspondence information that defines a correspondence between an average density value per pixel read by the image reading unit and the dot type,
The image reading means reads the dot type correspondence information,
The dot type discrimination means is a data restoration device that discriminates the dot type using the read dot type correspondence information. The data restoration device according to claim 3, wherein
The data restoration device, wherein the printed dot type correspondence information is information representing table data in a tabular format. The data restoration device according to claim 3, wherein
The printed dot type correspondence information is a dot test pattern in which all dot types that can be used for the visual code are test printed,
A table generation unit that generates a dot type correspondence table indicating a correspondence relationship between an average density value per pixel read by the image reading unit and the dot type from the printed dot test pattern;
The dot type discrimination means is a data restoration device that discriminates the dot type using the dot type correspondence table. A data restoration device according to any one of claims 1 to 5,
The print medium is printed with machine-readable encoded information that defines the correspondence between a plurality of values that can be taken by the bit string constituting the digital data and the dot type,
The image reading unit reads the encoded information,
The data decoding device, wherein the decoding means is configured to convert the code data into the digital data using the read encoded information. The data restoration device according to claim 6,
The data restoration apparatus, wherein the printed encoded information is information representing table data in a tabular format. The data restoration device according to any one of claims 1 to 7,
The data restoration device, wherein the dot type is specified by a combination of an ink color and the dot size. A data restoration method for restoring digital data recorded in the form of a machine readable visual code, comprising:
(A) a step of reading a visual code printed on a print medium in units of at least dots of a dot type specified by a dot size as an image;
(B) generating code data representing a series of dot types by determining the dot types for each of a plurality of ink dots constituting the visual code based on the read visual code image; ,
(C) converting the code data into the digital data by associating each of a series of dot types represented by the code data with a value that can be taken by a bit string, and
The step (a) is configured to read the visual code at a resolution finer than the printing resolution of the visual code,
The step (b)
(B-1) obtaining density values of a plurality of read pixels corresponding to each print pixel from the read visual code image, and calculating a total density value for each print pixel from the density value;
(B-2) A step of determining the dot type based on the calculated total density value for each print pixel. The data restoration method according to claim 9, comprising:
The step (b-2)
A step of calculating an average density value per read pixel for each print pixel from the calculated total density value for each print pixel, and determining the dot type based on the calculated average density value. A data restoration method which is a configuration to be performed. A computer program for restoring digital data recorded in the form of machine-readable visual codes,
(A) a function of reading, as an image, a visual code printed on a print medium with at least a dot of a dot type specified by a dot size;
(B) a function of generating code data representing a series of dot types by determining the dot types for each of a plurality of ink dots constituting the visual code based on the read visual code image; ,
(C) by causing a computer to realize a function of converting the code data into the digital data by associating each of a series of dot types represented by the code data with a value that can be taken by a bit string;
The function (a) is configured to read the visual code at a resolution finer than the printing resolution of the visual code,
The function (b) is
(B-1) a function of obtaining density values of a plurality of read pixels corresponding to each print pixel from the read visual code image, and calculating a total density value for each print pixel from the density value;
(B-2) A computer program comprising: a function of determining the dot type based on the calculated total density value for each print pixel. A computer program according to claim 11,
The function (b-2) is
A function of calculating an average density value per read pixel for each print pixel from the calculated total density value for each print pixel, and determining the dot type based on the calculated average density value. A computer program that is configured to perform.

Images