JP2001103282A - Image processing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing method and its device that can superimpose additional information with visually less sense of incongruity on image information and can decrease an error rate for dot pattern detection in the case of reading the additional information. SOLUTION: A color conversion section 702 converts a received RGB image signal into a CMYK signal, a various correction processing section 703 corrects the CMYK signal, a pseudo gradation processing section 704 quantizes a noticing pixel of the image signal, an attached information superimposing section 706 superimposes the attached information consisting of two kinks of dot patterns for high gray level area and a low gray level area generated by an attached information generating section 705 selectively depending on the gray level around the quantized noticing pixel and a printer engine 707 outputs an output image where various information is superimposed on the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing method and apparatus for superposing and outputting additional information different from image information on image information.

[0002]

2. Description of the Related Art In recent years, color image recording apparatuses such as printers and copiers have made great progress in terms of both performance improvement and widespread use, and full-color image recording apparatuses are also of silver halide type, thermosensitive type, electrophotographic type. Devices using a large number of output methods such as an electrostatic recording method and an ink jet method have been developed, and high-quality images have been obtained and have begun to spread widely. However, this has created new problems.

The problem is that banknotes and securities can be easily forged using a full-color image recording apparatus.
Along with this, it has become necessary to install a function for preventing forgery in the recording apparatus, and various full-color image recording apparatuses in recent years are equipped with various forgery prevention functions. The most common method is to print a regular dot pattern representing the machine number of the recording device on the paper at the time of recording, and the dot pattern hit on the bill when a forged bill is found This is a so-called tracking pattern method in which a machine number is determined from the data and a recording device from which the data is output is specified. In addition, since this dot pattern is printed on all output images, it is general that the dot pattern is printed with yellow having the lowest visibility.

The outline of the additional information superimposing process will be described. FIG. 1 is a diagram illustrating a configuration of an image processing apparatus that performs a general additional information embedding process. In the figure, first, an input image signal represented by RGB components is
In step 1, the color components are converted into four color components of C (cyan), M (magenta), Y (yellow), and K (black), and each color component is subjected to a correction process in various correction processing units 102. Next, in the pseudo gradation processing unit 103,
Pseudo gradation processing is performed using a method such as an organized dither method or an error diffusion method.

[0005] For the image signal subjected to the above processing,
The additional information generated by the additional information generation unit 104 is superimposed (added) on the Y component, and each component is input to the printer engine 105 to print an image to which some information other than the image information is added. be able to.

[0006]

However, the above-mentioned conventional method has the following problems.

As a general method of superimposing additional information on an image, grid points existing at N pixel intervals in a printable area are defined as shown in FIG. 3, and predetermined on the grid points, The additional information is expressed depending on whether or not there is a dot pattern (FIG. 2) stored in a storage device in a computer or a printer that performs the processing.

At this time, in a method proposed conventionally, for example, a method described in Japanese Patent Application Laid-Open No. Hei 10-30416, the same dot pattern is generally used for all density regions on an image. Here, how a dot pattern is added to image information by a conventional method will be described with reference to the drawings. Now, as an example of an image before the additional information is superimposed, consider an image after pseudo gradation processing as shown in FIG. When the dot pattern shown in FIG. 2 is added to the image as shown in FIG. 5, the image becomes as shown in FIG.

Referring to FIG. 5, in a density area (particularly area A) where the pixel arrangement is similar to the pixel interval forming the dot pattern, it is determined whether or not the dot pattern exists in the process of reading the added information. This makes it difficult to determine whether the additional information is correctly read out.

In order to avoid such a situation, it is conceivable to form a dot pattern with pixels that are closer together as shown in FIG. 6, but a dot pattern in which pixels are densely arranged as shown in FIG. When added over
Conversely, in an area where the density is extremely low, an unnatural dot may be visually recognized even if yellow is a component that is hard to detect visually.

In order to avoid such a situation, when adding a certain dot pattern to the image information which has been subjected to the pseudo gradation processing, the density around the added area, that is, the pixel density is measured by some method. It is necessary to perform processing such as adding an appropriate dot pattern according to the result, but such a method has not been proposed so far.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to superimpose additional information with little visual discomfort, and to reduce the error rate of dot pattern detection when reading additional information. It is an object to provide a method and an apparatus.

[0013]

In order to achieve the above object, the present invention provides an image processing apparatus for superimposing additional information different from image information on image information and outputting the image information. Means, pseudo-tone processing means for quantizing a target pixel of the image information, and a plurality of pieces of additional information each having a specific dot pattern according to the density around the target pixel processed by the pseudo-tone processing means. And additional information superimposing means for switching and superimposing.

According to another aspect of the present invention, there is provided an image processing method for superimposing additional information different from image information on image information and outputting the image information. A pseudo gradation processing step of quantizing a target pixel of information; and an additional step of switching and superimposing a plurality of pieces of additional information each having a specific dot pattern according to the density around the target pixel processed in the pseudo gradation processing step. And an information superimposing step.

[0015]

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

The image processing apparatus according to the present embodiment
It is efficient to mainly incorporate it as printer driver software in a computer that creates image information to be output to a printer engine. For example, it is necessary to incorporate it as hardware and software in a copying machine, facsimile machine, printer body, etc. Is also possible.

Further, image information can be expressed by pseudo gradation processing used in an ink jet printer, a hot-melt transfer printer, a laser printer and the like.

[First Embodiment] FIG. 7 is a block diagram showing an additional information superimposing method of the image processing apparatus according to the first embodiment. First, an outline of the operation will be described with reference to FIG.
Next, details of each unit will be described.

In FIG. 7, reference numeral 701 denotes an input terminal.
A multi-tone RGB image signal is input. The input signal is converted into a CMYK signal by a color conversion unit 702, subjected to various corrections by various correction processing units 703, and then input to a pseudo gradation processing unit 704. This pseudo gradation processing unit 704
In this example, an input image signal is converted into a quantization level smaller than the number of input gradations by performing pseudo gradation processing, and gradation is expressed in terms of area by the quantization values of a plurality of pixels. In the present embodiment, as a method for performing the pseudo gradation processing, any of the existing systematic dither method and the error diffusion method may be used, but the quantization value is set to “ It is assumed that it is a binary value of “0” or “1”. Here, when the quantization value becomes “1”, dots (ink, toner, etc.) are printed on a recording medium such as paper. It should be noted that the CMYK components after the above-described pseudo gradation processing are performed are respectively represented by I _c (x, y) and _Im (x,
y), I _y (x, y), and I _k (x, y).

FIG. 8 is a diagram showing an image after the pseudo gradation processing in the first embodiment has been performed. The example shown in FIG. 8 is a diagram showing a Y (yellow) component I _y (x, y).

Next, the additional information generated by the additional information generation unit 705 shown in FIG. 7 is converted by the additional information superimposition unit 706 using a predetermined dot pattern.
The Y component I _y (x,
superimposed on y). This makes use of the characteristic that the Y component is more difficult to identify with the human eye than the other components. The information to be added in the additional information superimposing unit 706 may be various information such as a maker name, a model name, a machine number of the output device, or an output state when an image is output on paper, and these signals may be necessary. If encrypted, they are superimposed.

After performing the above processing, each of the CMYK components is sent to the printer engine 707, and as a result,
An output image on which various information is superimposed can be obtained.

The outline of the operation of the image processing apparatus according to the first embodiment has been described above. Hereinafter, the details of each unit described above will be described. First, the additional information generation unit 705 will be described.

As a general method of superimposing additional information on an image, grid points existing at N pixel intervals in a printable area are defined as shown in FIG. 9 and a predetermined grid point is defined on the grid points. The additional information is expressed depending on whether or not there is a dot pattern stored in a storage device in a computer or a printer that performs the processing.

FIG. 10 is a diagram showing an example of a dot pattern according to the first embodiment. In the figure, the places where dots (ink, toner, etc.) are printed on the paper are indicated by black dots. In the first embodiment, two types of dot patterns for a high density area and a low density area as shown in FIG. 10 are prepared, and are switched according to the peripheral density at the addition position. Further, since the origin of the coordinate axis is set at the center of the dot pattern in FIG. 10, for example, the number of pixels C constituting the dot pattern as shown in the table in FIG.
And the pixel position _{^{(P lx c, P ly c}} ), and _{^{(P hx c, P hy c}} ) is such data would be stored in the storage devices present in the computer or printer to perform the pre-processing.

In the dot patterns (a) and (b) shown in FIG. 10, the number of dots per unit area is larger in (b) shown in FIG. In other words, a basic unit composed of a plurality of dots (that is, 5 × 5 pixels in FIG. 10A and 3 × 3 pixels in FIG. 10B) is shown in FIG. ) Is smaller. That is, the density of the dot patterns constituting the basic unit is higher in FIG. 10B.

The additional information generation unit 705 obtains the position to which the above-mentioned dot pattern is added by using means for converting information to be superimposed (such as a printer body number) based on a certain rule. There are various rules for converting to position information. For example, the machine number and model name of the printer body are expressed in a binary series,
Although it is conceivable that each of 1, 0 is represented by the presence or absence of a dot pattern, any method may be used in the first embodiment. Here, the obtained information of the addition position is represented by the grid point interval N and the coordinates (L _x ^z , L _y ^z ) of the Z grid points to be added, as shown in, for example, a table shown in FIG. Are input to the additional information superimposing unit 706. The above is the description of the additional information generation unit 705.

Next, the additional information superimposing process of the additional information superimposing unit 706 will be described. FIG. 11 is a flowchart illustrating the additional information superimposing process according to the first embodiment.
First, in step S1101, two types of dot pattern data shown in the table in FIG. 10 are read, and in subsequent step S1102, the additional position information generated by the additional information generation unit 705 is read.

Next, in step S1103 and thereafter, a dot pattern is added to I _Y (x, y) using these pieces of information. First, in step S1103, in order to grasp the concentration state of the additional positions periphery, adding position ^{_{(L x z, L y z}} ) defines the S pixel square blocks around the, present in the region The number of pixels P is calculated. Hereinafter, the above-mentioned area will be referred to as a “density reference area”. FIG. 12 is a diagram illustrating a density reference area according to the first embodiment. Note that in the figure, S = 5. Also, the block size S characterizing the density reference area
Is determined in advance and stored in a computer that performs the processing in the first embodiment or a storage device in the printer main body.

Next, in step S1104, it is determined whether or not to switch the dot pattern using the number of pixels P in the density reference area calculated in step S1103. Specifically, a threshold value thres which is predetermined and held in a storage device in a computer or a printer that performs the processing in the first embodiment is used. If the dot pattern for low-density area (a) shown in FIG.
A dot pattern for high density area (b) shown in FIG. That is, the above operation can be expressed as the following equation.

[0031] _{if (P <thres) I y} (L x z + P lx c, L y z + P ly c) = 1,1 ≦ c ≦ C (1.1) else I y (L x z + P hx c, L y ^z + P _hy ^c ) = 1, 1 ≦ c ≦ C (1.2) FIG. 14 is a diagram showing an example of an image before and after adding a dot pattern using the processing in the first embodiment. In FIG. 13, the threshold value thres is set to 4 as shown in FIG. The threshold thres may be a fixed value for each system, or may be freely set by the user for each image. Looking at (b) shown in FIG. 14, it can be seen that a dot pattern for a high density area is added to areas A and B with high density (large number of pixels).

By performing the processing in the first embodiment described above, in the process of superimposing the dot pattern on the image, the dot pattern can be switched according to the density state around the additional position by relatively simple means. Becomes possible,
It is possible to easily superimpose the additional information with little visually uncomfortable feeling and to easily perform the dot pattern detection operation at the time of reading the additional information.

[Second Embodiment] Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

In the first embodiment described above, the case where the quantization value is binary (0 or 1) is assumed as the output result of the pseudo gradation processing unit 704 shown in FIG. In the embodiment, a case of three values (0, 1, 2) is assumed.

FIG. 15 is a diagram showing an image after the pseudo gradation process according to the second embodiment is performed. In the figure, pixels indicated by density levels 2 and 1 indicate locations where dots are printed on paper using ink, toner, or the like, and pixels indicated by density level 0 are: This indicates a place where nothing is printed. Further, it means that a pixel represented by density level 2 is printed at twice the density of a pixel represented by density level 1. In the second embodiment, the same processing as that described in the first embodiment is performed on the pseudo gradation image quantized to the multi-value level (two or more values). is there.

FIG. 16 is a flowchart showing the additional information superimposing process according to the second embodiment. First, in step S1601, similarly to the first embodiment, a predetermined dot pattern is read from a storage device of a computer or a printer that performs the processing of the second embodiment.

FIGS. 17 and 18 are diagrams showing dot patterns used in the second embodiment. In the second embodiment, these three types of dot patterns are used, but the dot patterns are for low-density, medium-density, and high-density regions, respectively.

Both the dot patterns (a) and (b) shown in FIG. 17 are composed of pixels of density level 1, and the dot pattern for the high density area shown in (c) of FIG. It is composed of two pixels. Further, it is assumed that these dot patterns are described by, for example, data as shown in the tables in the respective drawings and stored in the storage device. The difference from the first embodiment is that a density level when a dot pattern is added is described. Next, in step S1602, the position information added a dot pattern _{^{(L x z, L y z}} )
Read. This processing is the same as that described in the first embodiment.

Next, in step S1603 and subsequent steps, a dot pattern is added to I _y (x, y) using these pieces of information. First, in step S1603, in order to grasp the density state around the addition position, the first
Similar to the embodiment, the additional position ^{_{(L x z, L y z}} ) defines the concentration reference region of the S pixel square centered on, to calculate the sum D of the concentration of pixels existing in the region. FIG. 19 is a diagram illustrating a density reference area according to the second embodiment.
Note that, in the same figure, as in the first embodiment, S = 5
And

Next, in steps S1604 and S1605, it is determined whether or not to switch the dot pattern using the sum D of the densities in the density reference area calculated in step S1103. Specifically, two predetermined thresholds
Using thres1 and thres2, the sum D of the densities is equal to the threshold thres.
If it is less than one, the dot pattern for the low-density area shown in FIG. 17A is used. If the sum D is equal to or more than the threshold thres1 and less than the threshold thres2, the medium-density area shown in FIG. If the sum D is equal to or larger than the threshold thres2, the dot pattern for high density area shown in FIG. 18C is used. That is, the above operation can be expressed as the following equation.

[0041] _{if (D <thres1) I y} (L x z + P lx c, L y z + P ly c) = 1,1 ≦ c ≦ C (2.1) else if (D <thres2) I y (L x z ^{_{+ P mx c, L y z}} + P my c) = 1,1 ≦ c ≦ C (2.2) else I y (L x z + P hx c, L y z + P hy c) = 1,1 ≦ c ≦ C (2.3 FIG. 21 is a diagram illustrating an example of an image before and after a dot pattern is added using the processing in the second embodiment. In FIG. 20, two thresholds are set as thres1 = 4 and thres2 = 8, respectively, as shown in FIG. These threshold values may be fixed values for each system, or may be freely set by the user for each image.

By performing the processing in the second embodiment described above, in the process of superimposing the dot pattern on the image, the dot pattern can be switched according to the density state around the additional position by relatively simple means. Becomes possible,
It is possible to easily superimpose the additional information with little visually uncomfortable feeling and to easily perform the dot pattern detection operation when reading the additional information.

In the second embodiment, for simplicity, 3
Although only the types of dot patterns have been described, the present invention is not limited to this, and it goes without saying that the same processing can be performed even if the number of types of dot patterns increases further.

The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but can be applied to a single device (for example, a copier, a facsimile). Device).

An object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (CPU or MP) of the system or apparatus.
It goes without saying that U) can also be achieved by reading and executing the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk,
Hard disk, optical disk, magneto-optical disk, CD-
A ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

[0050]

As described above, according to the present invention, it is possible to superimpose additional information with little visual discomfort on input image information and to output the additional information. Can be reduced.

Further, by switching dot patterns having different densities according to the density of the image information and adding the dot patterns to the image information, it is possible to reduce the error rate of dot pattern detection when reading the additional information.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image processing apparatus that performs a general additional information embedding process.

FIG. 2 is a diagram illustrating an example of a dot pattern to be added.

[0052]

FIG. 3 is a diagram illustrating an example of an image to which a dot pattern has been added.

[0053]

FIG. 4 is a diagram illustrating an example of an image after pseudo gradation processing.

[0054]

FIG. 5 is a diagram illustrating an example of an image after a conventional dot pattern addition process.

[0055]

FIG. 6 is a diagram illustrating an example of a dot pattern in which pixel intervals are made closer.

[0056]

FIG. 7 is a block diagram illustrating an additional information superimposing method of the image processing apparatus according to the first embodiment.

[0057]

FIG. 8 is a diagram showing an image after pseudo gradation processing according to the first embodiment is performed.

[0058]

FIG. 9 is a diagram illustrating an example of generated additional position information.

[0059]

FIG. 10 is a diagram illustrating an example of a dot pattern according to the first embodiment.

[0060]

FIG. 11 is a flowchart illustrating additional information superimposition processing according to the first embodiment.

[0061]

FIG. 12 is a diagram illustrating a density reference area according to the first embodiment.

[0062]

FIG. 13 is a diagram illustrating a density threshold according to the first embodiment.

[0063]

FIG. 14 is a diagram illustrating an example of an image before and after adding a dot pattern using the processing in the first embodiment.

[0064]

FIG. 15 is a diagram illustrating an image after pseudo tone processing according to the second embodiment.

[0065]

FIG. 16 is a flowchart illustrating additional information superimposition processing according to the second embodiment.

[0066]

FIG. 17 is a diagram illustrating a dot pattern used in the second embodiment.

[0067]

FIG. 18 is a diagram illustrating a dot pattern used in the second embodiment.

[0068]

FIG. 19 is a diagram illustrating a density reference area according to the second embodiment.

[0069]

FIG. 20 is a diagram illustrating a density threshold value and a dot pattern to be used in the second embodiment.

FIG. 21 is a diagram illustrating an example of an image before and after adding a dot pattern using the processing in the second embodiment.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/40 H04N 1/40 Z (72) Inventor Nobutaka Miyake 3-30-2 Shimomaruko, Ota-ku, Tokyo F term in Canon Inc. (reference) 2C061 AP03 AP04 AQ04 AQ05 AQ06 AR01 AS02 CL10 HH00 HK11 HN15 2C087 AA03 AA09 AA15 AA16 AC05 AC07 AC08 BA02 BA03 BA07 BA12 BD07 DA13 5B057 AA11 CA01 CA08 CA12 CB01CB07CB07CB DB02 DB06 DB08 DB09 DC22 5C076 AA01 AA12 AA14 AA26 BA06 CA10 5C077 LL14 MP01 MP08 NN08 NN11 PP23 PP32 PP33 PP38 PP43 PP48 PP61 PP68 PP80 PQ08 PQ20 RR02 RR05 TT02 TT06

Claims (14)

[Claims] An image processing apparatus for superimposing additional information different from the image information on the image information and outputting the image information, an input means for inputting the image information, and a pseudo gradation for quantizing a pixel of interest of the image information Processing means; and additional information superimposing means for switching and superimposing a plurality of pieces of additional information each having a specific dot pattern according to the density around the target pixel processed by the pseudo gradation processing means. Image processing device. And generating means for generating two types of additional information for a low-density area and a high-density area each having a specific dot pattern. 2. The image processing apparatus according to claim 1, wherein a pixel interval of the dot pattern is short. 3. The method according to claim 1, wherein the generating unit generates at least two types of dot patterns suitable for each density level, and the pattern for the high-density area is smaller than the pattern for the low-density area. 3. The image processing apparatus according to claim 2, wherein the image density is short and the density level of the pixel is high. 4. The image processing apparatus according to claim 1, wherein the additional information superimposing means includes a density reference area determining means for determining an area for measuring the density of the image, and a pixel number calculating means for calculating the number of pixels existing in the density reference area. 2. The image according to claim 1, further comprising: comparing a predetermined threshold value with the number of pixels obtained by the pixel number calculation unit, and switching and superimposing the plurality of pieces of additional information according to a comparison result. 3. Processing equipment. 5. A density reference area determining means for determining an area for measuring the density of an image, and a total density for calculating a sum of density levels of pixels existing in the density reference area. A value calculating unit that compares a predetermined threshold value with a value obtained by the total density value calculating unit, and switches and superimposes the plurality of pieces of additional information according to a comparison result. 2. The image processing device according to 1. 6. An image processing method for superimposing and outputting additional information different from the image information on the image information, comprising: an input step of inputting the image information; and a pseudo gradation for quantizing a pixel of interest of the image information. A processing step; and an additional information superimposing step of switching and superimposing a plurality of pieces of additional information each having a specific dot pattern according to the density around the target pixel processed in the pseudo gradation processing step. Image processing method. 7. A generating step for generating two types of additional information for a low-density area and a high-density area each having a specific dot pattern, wherein the high-density area has a higher density than the low-density area. 7. The image processing method according to claim 6, wherein an interval between pixels forming the dot pattern is short. 8. The generating step includes generating at least two types of dot patterns suitable for each density level, wherein a pattern for a high-density area has a smaller interval between pixels constituting the dot pattern than a pattern for a low-density area. 8. The image processing method according to claim 7, wherein the image density is short and the density level of the pixel is high. 9. The additional information superimposing step includes: a density reference area determining step of determining an area for measuring the density of an image; and a pixel number calculating step of calculating the number of pixels existing in the density reference area. The image according to claim 6, wherein a predetermined threshold is compared with the number of pixels obtained in the pixel number calculation step, and the plurality of pieces of additional information are switched and superimposed according to a comparison result. Processing method. 10. The additional information superimposing step includes: a density reference area determining step of determining an area for measuring the density of an image; and a total density calculating a sum of density levels of pixels existing in the density reference area. A value calculating step of comparing a predetermined threshold value with the value obtained in the total density value calculating step, and switching and superimposing the plurality of pieces of additional information according to a comparison result. 7. The image processing method according to 6. 11. A computer-readable storage medium storing a program code of an image processing method for superimposing additional information different from the image information on the image information and outputting the superimposed information, wherein a code of an input step of inputting the image information is provided. A code of a pseudo gradation processing step of quantizing a pixel of interest of the image information; a code of a generation step of generating a plurality of pieces of additional information having a specific dot pattern; A code for an additional information superimposing step for performing switching and superimposing in accordance with the density around the target pixel processed in the gradation processing step. 12. An image processing apparatus for adding predetermined information to image information, comprising: input means for inputting image information; holding means for holding a plurality of dot patterns having different densities; An image processing apparatus comprising: an adding unit configured to switch the dot pattern according to a density and to add the dot pattern to the image information. 13. An image processing method for adding predetermined information to image information, comprising: an input step of inputting image information; a holding step of holding a plurality of dot patterns having different densities; An adding step of switching the dot pattern according to density and adding the dot pattern to the image information. 14. A computer-readable storage medium storing a program code of an image processing method for adding predetermined information to image information, wherein a code of an input step of inputting image information is different from a code of an input step for inputting the image information. A storage medium comprising: a code of a holding step of holding a dot pattern; and a code of an adding step of switching the dot pattern and adding the dot pattern to the image information according to the density of the image information.