JP2002171395A - Image processor, method for the same and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the deviation of the position, inclination or the like of image data by simple arithmetic. SOLUTION: A single image (partial image) included in an area (an area of a predecided size at a predecided position) supposed to be a partial image in image data of an original is fetched (S20). An image (sub-partial image) supposed to be a partial image is given fast Fourier transformation and a peak dot is obtained from obtained frequency data to be stored (S30). Next, phase component data of respective peak dots included in the sub-partial image is obtained to be stored (S40). The deviation of the position data of the peak dot from the ideal position data of the peak point is obtained to correct 'deviation' with respect to the whole image data of the original (S50). Next, deviation between the first pixel of the sub-partial image and that of the partial image is detected (S60) and electronic watermark data is read from the image data of the original in S70.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method for detecting and correcting a deviation of a read image and a storage medium.

[0002]

2. Description of the Related Art Recently, it has become possible to include information such as copyright in an original as a printed matter by using a technique called "digital watermark". That is,
By embedding the second digital information (sub-information) indicating the copyrighted work in the image data (electronic image information) as the original first digital information (main information), the copyright Image data (electronic image information) of a document containing information can be obtained.

Further, the copyright information (sub-information) can be extracted from the image data of the document containing the copyright information if the method of embedding is known. As a result, the embedded copyright information is extracted from the electronic image data obtained by reading the printed matter of the document created from the image data of the document containing the copyright information by a document reading device such as a color scanner. Since this is possible, the technique called “digital watermark” is attracting attention because it can be applied to applications for preventing copyright infringement or the like due to illegal duplication of a document as a printed matter.

[0004]

However, in the process of recognizing a copyrighted work, if the orientation (angle) or position of the original is not determined, various comparisons with pre-registered spectral data and image pattern data are performed. In order to be able to cope even in the case, the total amount of calculations tends to increase dramatically.

[0005] At this time, there is a problem that the time required for processing is drastically increased in accordance with the total amount of operations in copyright protection or the like using a digital watermark.

The present invention has been made in view of the above problems, and has as its object to correct a shift in image data, such as a position or an inclination, by a simple calculation.

[0007]

In order to achieve the object of the present invention, for example, an image processing apparatus of the present invention has the following arrangement. That is, a region extracting unit that extracts a second image of a predetermined size from the first image, a detecting unit that performs frequency conversion on the second image, and detects a coordinate position of a peak in a frequency region, Phase component calculation means for calculating phase component data in a phase region corresponding to a coordinate position of a peak in the second image frequency region; and a phase component calculating unit for calculating the first image based on the phase component data and a predetermined reference. A correction unit that detects a deviation from a reference position and corrects the image data.

In order to achieve the object of the present invention, for example, an image processing apparatus of the present invention has the following arrangement. That is,
An area extracting means for extracting a second image having a predetermined size from the first image; performing frequency conversion on the second image; and detecting phase data together with frequency data of the second image. Performing a geometric conversion on the first image based on frequency conversion means, position data of a pixel having a peak value from frequency data by the frequency conversion means, and reference position data of the pixel; Geometric conversion means, based on phase data corresponding to pixels constituting the first image subjected to the geometric conversion by the geometric conversion means, and phase data serving as a reference for the pixels. Detecting means for detecting a deviation of the second image from a reference position.

A correcting means for correcting the first image based on the displacement detected by the detecting means;
Extraction means for extracting digital watermark data from the first image corrected by the correction means.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail according to preferred embodiments with reference to the accompanying drawings.

[First Embodiment] A device that reads a document and generates image data of the document, such as a scanner, a facsimile machine, and a digital copying machine, does not read the document without any inclination or displacement of the document. It is extremely difficult, and a minute enlargement / reduction occurs when reading a document. For this reason, in order to reliably extract the digital watermark data embedded by the digital watermark technology from the read image data, it is necessary to detect the inclination, displacement, enlargement / reduction, etc. of the original as a pre-processing of the extraction, and read the original. First, it is necessary to consider the detection result. Further, how to quickly identify the position of the digital watermark data included in the image data of the document is a factor that can greatly reduce the overall processing speed.

In this embodiment, an image processing apparatus and method for extracting digital watermark data from image data in which digital watermark data is embedded will be described.

FIG. 2 shows a configuration of a personal computer (hereinafter, referred to as a PC) as an image processing apparatus and peripheral devices in the present embodiment. In FIG. 1, reference numeral 1 denotes a color image scanner (hereinafter referred to as a scanner) which reads a document and outputs image data of the document to a PC 2 described later. 2 is PC
Then, various processes including the processes described below are performed. A cable 3 connects the scanner 1 and the PC 2.

FIG. 3 is a block diagram showing the basic configuration of the PC 2. In the figure, reference numeral 11 denotes a CPU, a ROM 13,
Using the program codes and data stored in M12, the entire PC 2 is controlled, and various processes described later are performed.

Reference numeral 12 denotes a RAM, which has an area for storing program codes and data loaded from the external storage device 18, and also has a work area used when the CPU 11 executes various processes. 13 is a ROM,
In addition to storing program codes and data for controlling the entire PC 2, character codes and the like are also stored. A display control unit 14 controls the display 15. A display 15 displays various messages and the like. A pointing device 16 such as a keyboard and a mouse can input various instructions to the PC 2. Reference numeral 17 denotes an I / O for connecting the pointing device 16 and the bus 20. Reference numeral 18 denotes an external storage device including a hard disk for storing program codes and data installed by a CD-ROM, a floppy (registered trademark) disk, or the like. O. 22,
Reference numeral 23 denotes an I / O for connecting to the scanner 1 and the network, respectively. A bus 20 connects the above-described units.

FIG. 4 is a flowchart of a process for detecting a tilt or a positional shift of an image of a document read via the scanner 1. By storing a computer-executable program describing processing in accordance with the flowchart shown in the figure in a memory such as the ROM 13 or the RAM 12 in advance and executing the program by the CPU 11, the PC 2 can execute each processing described later. it can.

In the image of the document used below, four pixels having a peak value in the frequency space (hereinafter referred to as peak points) are embedded at predetermined positions, and an area including these peak points (hereinafter referred to as a peak point). , Partial area) are known in advance. In the present embodiment, the description will be made assuming that there are four peaks, but the number is not limited to four.

In step S10, the CPU 11 executes I / O
The scanner 1 is instructed via the unit 22 to read a document placed on a reading surface (not shown) of the scanner 1. As a result, the scanner 1 reads the document and outputs the image data of the document to the PC 2 via the I / O unit 22. The image data of the document input to the PC 2 is stored in the RAM 12
Is stored in

In step S20, R in step S10
In the image data read into the AM 12, one image included in an area considered to be a partial area (an area of a predetermined size at a predetermined position) is taken out (copied) and transferred to another area in the RAM 12. Store. In the present embodiment, the size of the partial image is 1024 × 1024 pixels.

In step S30, R in step S20
Images considered to be partial images stored in the AM 12 (hereinafter referred to as
Fast Fourier transform is performed on the quasi-partial image to obtain frequency data of the quasi-partial image. FIG. 5 shows peak points obtained as a result of performing the fast Fourier transform on the quasi-partial image. In the figure, points A, B, C, and D are peak points, and the positions of the peak points are stored in the RAM 12. Note that these points are stored as registration signals.

In step S40, the phase component data of each peak point included in the quasi-partial image obtained in step S30 is converted into points A (i) and B as shown in FIG.
(I), C (i), and D (i).
12 is stored. The phase component data at each peak point can be obtained by the fast Fourier transform in step S30.

In step S50, a deviation between the peak point position data generated in step S30 and stored in the RAM 12 and the peak point ideal position data stored in advance in a memory such as the ROM 13 or the RAM 12 is determined. This "shift" is corrected for the entire image data.
The ideal position data is local position data of a peak point in the quasi-partial image.

More specifically, when the original is read by the scanner 1, the information of the inclination or enlargement / reduction intentionally added by the operator is corrected as the "shift". FIG. 1 shows this correction processing. In the figure, points A, B, C, and D are the position data of the peak points generated in step S30 and stored in the RAM 12, and points A ', B', C ', and D' are points A, B, and This is the ideal position data described above for each of C and D. The point A will be described with reference to FIG.
And the angle θ formed by the distances d and d ′ are calculated.
Is subjected to a geometric transformation so as to match.

The above-described processing in steps S30 and S40 is implemented by a known technique as shown in US Pat.

In step S60, using the phase component data of each peak point stored in the RAM 12 generated in step S40, the first pixel of the quasi-partial image extracted in step S20 (the upper left pixel of the same image) ) Detects how many pixels are shifted from the first pixel of the partial image.

The above-described detection processing performed in step S60 will be specifically described. To embed the above-mentioned peak point data in the electronic data of the original image (step S30)
In order to detect the peak point in the above, a predetermined angle (45 degrees in the present embodiment, but not limited thereto) is attached to the image data of the document in the main scanning direction or the sub scanning direction. A wave having an arbitrary period as shown in FIG. 7 is embedded. Here, a wave in which one cycle is 8 pixels will be described.

As shown in the figure, the first pixel from which the quasi-partial image data is read in step S20 is
If it is the same as the first pixel of the partial image data, the phase component data corresponding to the peak point coordinates in the frequency space becomes 0 when the value of θ is taken as shown in FIG. Becomes Such a table is set such that X (0 ≦ X <8) in the main operation direction and Y (0 ≦ Y <8) in the sub operation direction.
The 64 tables (tables) at the time of the movement are registered in the ROM 13 or the RAM 12 in advance, and by referencing, how many pixels are shifted between the quasi-partial image and the partial image in the main operation direction or the sub operation direction is detected. can do. As a result, a position shift correction process is further performed on the document image using the detected shift.

As a result of the above processing, when the image data of the document is read by the scanner 120, image data obtained when there is no displacement, enlargement / reduction, inclination, etc. can be obtained.

Finally, in step S70, step S5
In step S60, digital watermark data is read from the image data of the document that has been preprocessed.

As described above, according to the image processing apparatus and method of the present embodiment, even when the original is read, the image data of the read original can be corrected even if the position or the inclination is shifted or enlarged or reduced. Can be. As a result, the position and direction of the image data of the document can be specified, and the position of the data embedded in the image data can be specified. For example, a process of extracting digital watermark data embedded in the image data Can be shortened.

[Second Embodiment] In the first embodiment,
The image data of the original is read by the scanner 1, but is not limited thereto. For example, the image data of the document read from the network via the interface 23 in FIG. 3 may be input to the image processing apparatus, or a removable storage medium (for example, smart media or CompactFlash (registered trademark)) Alternatively, the image data of the document stored in the storage medium can be read from a magneto-optical disk or the like by connecting a drive of the storage medium to the bus 20 via an I / O.

In this case, the processing procedure in the flowchart shown in FIG. 4 may be such that the image data of the document is read from the network or a removable storage medium and stored in the RAM 12 in step S10.

[Other Embodiments] The present invention is not limited to only the apparatus and method for realizing the above-described embodiment, and the computer (CPU or MPU) in the above-described system or apparatus may be used in the above-described embodiment. The scope of the present invention also includes a case where a program code of software for realizing the above is provided, and the computer of the system or the apparatus operates the above-described various devices to realize the above-described embodiment in accordance with the program code.

In this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, specifically, A storage medium storing the program code is included in the scope of the present invention.

As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM, etc. can be used.

In addition to the case where the computer controls the various devices according to only the supplied program code to realize the functions of the above-described embodiment, the above-described computer can be operated by the operating system running on the computer. Such a program code is also included in the scope of the present invention when the above embodiment is realized in cooperation with an (operating system) or other application software.

Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, the function expansion board or the function is stored based on the instruction of the program code. The case where the CPU or the like provided in the storage unit performs part or all of the actual processing, and the processing implements the above-described embodiment is also included in the scope of the present invention.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the above-described flowchart (shown in FIG. 4).

[0039]

As described above, according to the present invention, it is possible to correct the deviation of the image data, for example, the position and the inclination by a simple calculation.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a correction process.

FIG. 2 is a block diagram illustrating a configuration of a personal computer (hereinafter, referred to as a PC) as an image processing apparatus and peripheral devices according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a basic configuration of a PC.

FIG. 4 is a flowchart of a process for detecting a tilt or a position shift of an image of a document read via a scanner 1;

FIG. 5 is a diagram showing peak points obtained as a result of performing fast Fourier transform on a quasi-partial image.

FIG. 6 is a diagram illustrating phase data of peak points obtained as a result of performing a fast Fourier transform on a quasi-partial image.

FIG. 7 is a diagram illustrating a process when embedding a peak point in image data of a document.

Continued on the front page (72) Inventor Junichi Hayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) in Canon Inc. 5B057 AA11 BA02 CA08 CA12 CA16 CB08 CB12 CB16 CC03 CD01 CE09 CG09 DA07 DA08 DB02 DB09 DC08 DC22 DC36 5C076 AA02 AA14 AA23 AA40 BA06 5L096 AA06 BA08 DA01 EA35 FA14 FA23 FA66 FA67 FA69

Claims (14)

[Claims] 1. An area extracting means for extracting a second image of a predetermined size from a first image, and a frequency converting section for performing frequency conversion on the second image to detect a coordinate position of a peak in a frequency domain. Means, phase component calculation means for calculating phase component data in a phase region corresponding to a coordinate position of a peak in the second image frequency region, and the first component based on the phase component data and a predetermined reference. An image processing apparatus, comprising: a correction unit configured to detect a deviation of the image from a reference position and correct the image data. 2. An area extracting means for extracting a second image having a predetermined size from the first image, performing frequency conversion on the second image, and frequency data of the second image, Frequency conversion means for detecting phase data; position data of a pixel having a peak value from the frequency data by the frequency conversion means; and geometric data for the first image based on position data serving as a reference for the pixel. Transformation means for performing a geometric transformation, phase data corresponding to the pixels constituting the first image subjected to the geometric transformation by the geometric transformation means, and a reference phase of the pixel Based on the data
An image processing apparatus comprising: a detection unit configured to detect a deviation of the image from a reference position. 3. A correction unit for correcting the first image based on the shift detected by the detection unit, and extracting digital watermark data from the first image corrected by the correction unit. The image processing apparatus according to claim 2, further comprising an extraction unit. 4. The image processing apparatus according to claim 2, wherein the predetermined size is a size of a region including a pixel having the peak value. 5. The image processing apparatus according to claim 2, wherein said frequency conversion means performs frequency conversion using fast Fourier transform. 6. The image processing apparatus according to claim 2, wherein the desired position data of the pixel having the peak value is local position data in a region by the region extracting means. 7. The image processing apparatus according to claim 1, wherein the geometric conversion unit determines a position of the pixel having a peak value from a frequency component by the frequency conversion unit and the desired position data of the pixel. 3. The image processing apparatus according to claim 2, wherein a geometric transformation is performed. 8. The image processing device according to claim 1, wherein the detecting unit is configured to:
3. The image processing apparatus according to claim 2, wherein the shift is detected using a table in which phase data for one cycle each is registered for each pixel. 9. An area extracting step of extracting a second image of a predetermined size from a first image, and performing a frequency conversion on the second image to detect a coordinate position of a peak in a frequency domain. A phase component calculating step of calculating phase component data in a phase domain corresponding to a coordinate position of a peak in the second image frequency domain; and the first component based on the phase component data and a predetermined reference. A correction step of detecting a shift of the image from a reference position and correcting the image data. 10. A region extracting step of extracting a second image having a predetermined size from a first image, performing frequency conversion on the second image, and performing frequency conversion on the second image together with frequency data of the second image. A frequency conversion step of detecting phase data; a position data of a pixel having a peak value from the frequency data obtained by the frequency conversion step; and a geometric position of the first image based on position data serving as a reference of the pixel. Transformation step of performing a geometric transformation, phase data corresponding to a pixel constituting the first image subjected to the geometric transformation by the geometric transformation step, and a phase serving as a reference of the pixel Based on the data
A detection step of detecting a deviation of the image from a reference position. 11. A correcting step for correcting the first image based on the shift detected in the detecting step, and extracting digital watermark data from the first image corrected in the correcting step. The image processing method according to claim 10, further comprising an extraction step. 12. A computer-readable storage medium storing a program code, the program code of an area extracting step of extracting a second image of a predetermined size from a first image, and the second image A program code of a detection step of performing frequency conversion on the peak position in the frequency domain, and phase component data in the phase domain corresponding to the coordinate position of the peak in the second image frequency domain. A program code of a phase component calculating step of calculating the phase component data, and detecting a deviation from a reference position of the first image based on the phase component data and a predetermined reference, and correcting the image data. A storage medium comprising a program code. 13. A computer-readable storage medium storing a program code, the program code of an area extracting step of extracting a second image having a predetermined size from a first image; Frequency conversion for the image of the second image, together with the frequency data of the second image, a program code of a frequency conversion step of detecting phase data, and position data of a pixel having a peak value from the frequency data by the frequency conversion step A program code of a geometric conversion step of performing a geometric conversion on the first image based on position data serving as a reference of the pixel, and performing a geometric conversion by the geometric conversion step. Based on the applied phase data corresponding to the pixels constituting the first image and the reference phase data of the pixels, the second
And a program code for a detection step of detecting a deviation of the image from a reference position. 14. A program code for a correction step for correcting the first image based on the shift detected in the detection step, and digital watermark data from the first image corrected in the correction step. 14. The storage medium according to claim 13, further comprising: a program code for an extraction step of extracting the information.