JP4861251B2 - Image processing apparatus and control method thereof - Google Patents

Description

  The present invention relates to an image processing technique for extracting watermark information embedded in a document image based on line spacing of character strings in the document image.

In order to give information such as copyright and copy control to a document image, a method of embedding information using line spacing (hereinafter referred to as line spacing watermarking) as shown in the description on pages 198 to 199 of Non-Patent Document 1. Is known). FIG. 2 is a diagram illustrating the concept of the line spacing watermark. When extracting embedded information from a document image using a line spacing watermark, the line spacing between character strings in the document image is first obtained. In order to obtain the line spacing, generally, a document image is scanned all over to obtain a histogram, and the line spacing is derived from the histogram. Then, information is extracted according to the derived line spacing and the rules used at the time of embedding. For example, as shown in FIG. 2, the rule is to set U> D for the line intervals U and D when embedding “0” of binary information. On the other hand, when it is desired to embed “1” of the binary information, U <D is set for the line intervals U and D.
Kokoo Matsui “Basics of Digital Watermarking” Morikita Publishing Co., Ltd. 1998

  However, the above-described method for extracting embedded information from a document image using a line watermark has the following problems. That is, in order to measure the line spacing, it is necessary to perform a full scan on the document image and obtain a histogram, and the information extraction process takes time. In particular, if the information to be embedded is copy control information, copy control information is extracted in the copier, a determination is made as to whether or not copying is possible from the extracted information, and then a single document is copied to perform copy processing. Will have a considerable amount of time. Also, if the character string direction and the scanning direction of the input document image are inclined, the line spacing cannot be derived from the histogram. Therefore, a complicated operation such as re-inputting the document image or performing image processing such as rotation operation on the input document image is required.

In order to solve at least one of the above-described problems, the image processing apparatus of the present invention has the following configuration. That is, an image processing apparatus that inputs a document image and extracts embedded watermark information from line spacing of character strings in the document image, the input means for inputting the document image as image data, and the input first image reduction means for generating reduced image data, detecting means for detecting the end point of the character string existing area in the first reduced image data obtained by reducing with reduction ratio image data are predetermined in a first direction And, for the two sides facing the second direction orthogonal to the first direction in the quadrangle using the end points , the scanning start point is set on one side and the scanning end point is set on the other side. Setting means for setting, and extraction means for scanning the reduced image data along a line segment connecting the start point and end point set by the setting means, detecting character string line intervals, and extracting watermark information. Features .

In order to solve at least one of the above-described problems, the control method of the image processing apparatus of the present invention has the following configuration. That is, a control method of an image processing apparatus that inputs a document image and extracts embedded watermark information from line spacing of character strings in the document image, and an input step of inputting the document image as image data; An image reduction process for generating first reduced image data obtained by reducing the input image data in a first direction at a predetermined reduction ratio, and detecting an end point of a character string existing area in the first reduced image data And a scanning start point is set on one side and scanning is performed on the other side with respect to two sides opposed to the second direction orthogonal to the first direction in the quadrature using the end points. A setting step for setting the end point of the image, and an information extraction step for scanning the reduced image data along a line segment connecting the start point and the end point set in the setting step, detecting a character string line interval, and extracting watermark information And having And wherein the door.

  According to the present invention, it is possible to provide a technique capable of more efficiently extracting watermark information embedded in a document image based on the line spacing of character strings in the document image.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are merely examples, and are not intended to limit the scope of the present invention.

(First embodiment)
As a first embodiment of an image processing apparatus according to the present invention, an image processing apparatus that reads a paper document original with an image reading apparatus (scanner) and extracts watermark information from the read document image data will be described as an example. Explained.

<Device configuration>
FIG. 1 is a block diagram illustrating a main functional configuration of the image processing apparatus 11 according to the first embodiment. As illustrated in FIG. 1, the image processing apparatus 11 includes an image input unit 101, an image reduction unit 102, an information extraction unit 103, an inclination detection unit 104, a control unit 110, and an operation unit 111.

  The image input unit 101 is a functional unit that inputs image data corresponding to a document image in which the above-described watermark information is embedded. Specifically, image data based on a paper document original read and generated by an external scanner is input through an external device connection interface such as a USB. Of course, the image data may be input via a network such as Ethernet (registered trademark).

  The image reduction unit 102 performs a first direction (for example, the horizontal direction of the image) and a second direction (for example, a vertical direction of the image) orthogonal to the first direction with respect to the image data input by the image input unit 101. It is a functional part that reduces each. When the input image data is in the bitmap (raster) format, generally, the first and second directions described above coincide with the arrangement direction of the pixels constituting the image data. In addition, although it demonstrated that it was the structure reduced to two orthogonal directions here, it is good also as a structure reduced only to one direction so that it may mention later.

  The inclination detection unit 104 is a functional unit that detects the inclination of an area in which characters are recorded in the image data input by the image input unit 101. Specifically, from the reduced image data generated by the image reduction unit 102, an edge portion (side or vertex constituting the existing area) of the existing area of the significant pixel on the image data is detected.

  The information extraction unit 103 is a functional unit that extracts binary (binary) information corresponding to watermark information from the reduced image data generated by the image reduction unit 102. Specifically, it is executed by detecting the presence / absence of significant pixels in the reduced image data generated by the image reduction unit 102. Then, a portion where a significant pixel is detected is determined as a character string region, and a region where a significant pixel is not detected is determined as an interline portion. Then, a binary value (0 or 1) corresponding to each row is determined based on the length (number of continuous pixels) corresponding to each of the plurality of rows determined as the portion between the rows. It is assumed that the watermark information embedding algorithm such as the correspondence between the length of the line spacing portion and the binary value and the information amount (number of bits) is set in the information extraction unit 103 in advance.

  The control unit 110 is a functional unit for controlling the above-described functional units to operate in cooperation with each other. The operation unit 111 is a functional unit for receiving an instruction from the user. Details of the operation of each functional unit described above will be described later.

<Image data with embedded watermark information>
In the first embodiment, the watermark information embedding algorithm will be described as follows. Of course, other algorithms can be applied as long as the watermark information is embedded based on the line spacing of the character string.

FIG. 2 is a diagram exemplarily showing a document original in which watermark information is embedded. In FIG. 2, black characters are recorded on white paper. Also, binary information is embedded by using two types of U and D for each interval (line interval) of a character string composed of a plurality of lines. Specifically, the line spacing is set as follows with respect to the space between two consecutive rows (U _n and D _n : n is a natural number).

When embedding “0”: U _n > D _n
When embedding “1”: U _n <D _n
Then, the watermarked document original is read by a scanner having an optical sensor such as a charge coupled device (CCD), and image data I is generated. Here, the generated document image data I is described as a binary image in which the text portion of the paper document is black and the background portion is white. Hereinafter, the “black pixel” corresponding to the character portion may be referred to as a “significant pixel”.

  FIG. 3 is a diagram exemplarily showing binary image data in which watermark information is embedded. Here, FIG. 3A shows image data in which a horizontally written character document is recorded in the correct direction. On the other hand, FIG. 3B and FIG. 3C are tilted document images. As described above, when a paper document original is read by the scanner, image data as shown in FIGS. 3B and 3C is input due to a deviation from the reference direction or a misplacement of the paper original by the user. May be.

<Operation of the device>
Hereinafter, an operation in which the image processing apparatus 11 extracts watermark information from the image data I will be described in detail with reference to flowcharts.

  FIG. 10 is an operation flowchart of the image processing apparatus 11 according to the first embodiment. Note that the following flow is executed, for example, with an image reading instruction from the user via the operation unit 111 as a trigger.

  In step S <b> 1001, the image input unit 101 receives image data I corresponding to a document image with watermark information from the scanner, and supplies the image data I to the image reduction unit 102.

  In step S1002, the image reduction unit 102 reduces the image data I supplied from the image input unit 101 in the horizontal direction and the vertical direction, respectively, and generates horizontal reduced image data Ish and vertical reduced image data Isv. . Further, reduced image data Isvh, which is an image that has been reduced in the horizontal and vertical directions at an equal magnification with a predetermined reduction ratio, is generated. The reduced image data Ish (first reduced image data), reduced image data Isv (second reduced image data), and reduced image data Isvh (third reduced image data) are supplied to the information extraction unit 103.

  FIG. 4 is a diagram illustrating an example of reduced image data Ish obtained by reducing the image data I in the horizontal direction and reduced image data Isv reduced in the vertical direction. 4A is based on the document image in FIG. 3A, FIG. 4B is based on the document image in FIG. 3B, and FIG. 4C is based on the document image in FIG. 3C. Reduced image data generated in this way.

  Here, the reason why the reduced image is generated in the two directions of horizontal and vertical is to cope with the case where the image data I having a 90 degree inclination is input as shown in FIG. is there. Such a situation often occurs when reading with a scanner. Therefore, if the input direction of the image data I is guaranteed in advance, the image data I may be reduced in only one direction corresponding to the character string direction.

  From FIG. 4, it can be seen that a plurality of character strings are expressed as a group (object) of a plurality of significant pixels for a reduced image reduced in the character string direction by reduction by the image reduction unit 102. Hereinafter, the generation of the reduced image will be described in more detail.

  As a specific calculation method of the reduction process executed by the image reduction unit 102, reduction by simply thinning out pixels at a constant period with respect to input image data can be considered. However, in order to more accurately identify the character string portion and the line spacing portion, the following calculation using the bilinear method may be performed.

  In the bilinear method, the pixel value of the corresponding reduced image data pixel is calculated based on the pixel values of four adjacent pixels in the image data I. In this case, if at least one of the four pixels is black, the calculation result is halftone (gray) (left in FIG. 5). Specifically, the result of calculating white as 0 and black as 1 is a value greater than 0 and less than 1.

  Since there is no black pixel that is a significant pixel in the inter-line portion, if there is even one black pixel, it can be estimated that the portion where the four adjacent pixels are present is a character string region. Therefore, the character string area and the line space area can be divided with higher accuracy by converting the portion calculated as the halftone into black as a significant pixel (right in FIG. 5). In other words, there are cases where there are no significant pixels in the character string area (characters with a small number of strokes), but there is generally no significant pixel in the line spacing area.

  The reduction ratio in the horizontal and vertical directions by the image reduction unit 102 may be any reduction ratio that is large enough to recognize an object. The specific reduction ratio value may be a fixed value designated in advance, or may be determined as needed based on additional data (such as reading resolution information by a scanner) of input image data. Although the bilinear method is applied here as an example of an algorithm for generating a reduced image, the present invention is not limited to this. It can be reduced by using various calculation methods such as a near-less tray bar and bicubic.

  In step S1003, the inclination detection unit 104 detects four end points of the document area (character string existence area) in the document image from the reduced image data Isvh generated by the image reduction unit 102. Hereinafter, a specific method will be described.

  FIG. 8 is a conceptual diagram of a method for detecting end points (vertices) of a document area. As shown in FIG. 8 (a), the inclination detecting unit 104 generates the reduced image data Isvh in the horizontal direction (H1, H2, H3... In the figure) and the vertical direction (V1, V2, V3... In the figure). Scan sequentially. At that time, the end point is determined based on the line where the significant pixel is detected first and the line detected last. For example, in FIG. 8A, a circle (●) portion is determined as an end point from H1 and H30 which are horizontal lines and V1 and V25 which are vertical lines.

  Note that, depending on the layout of the document area, the reduced image data Isvh may be as shown in FIG. 8C. In this case as well, end points (circled portions in the figure) can be obtained in the same manner. Further, although the end point is detected from the reduced image data Isvh here, the edge of the document area may be extracted using the image data I to detect the end point.

  As another method of detecting the end point, the end point may be detected using the difference between the paper document original and the background (pressed plate or the like) when the image data I is created, that is, read by the scanner.

  In step S1004, the inclination detection unit 104 calculates the end point in the reduced image data Ish from the end point of the reduced image data Isvh determined in step S1003 and the reduction rate R used in step S1002. Then, the calculated result is supplied as end point data C to the information extraction unit 103 together with the reduced image data Ish.

  For example, it is assumed that the image data I is performed in the horizontal and vertical directions at a reduction ratio R = 1/100 in step S1002. Further, it is assumed that the end points in the reduced image data Isvh are coordinates (10, 10), (30, 20), (0, 90), (20, 100) as shown in FIG. In this case, since the reduced image data Ish is reduced only in the horizontal direction at a reduction ratio R = 1/100, the end point of the reduced image data Ish may be multiplied by 100 in the vertical coordinate Y. That is, the end points in the reduced image data Ish are calculated as (10, 1000), (30, 2000), (0, 9000), (20, 10000).

  Here, when calculating the end point of the reduced image data Ish, by using the reduced image data Isvh having a data amount smaller than the reduced image data Ish, there is an effect that the calculation can be performed with a small memory and at a high speed.

  In step S <b> 1005, the information extraction unit 103 uses the end point data C supplied from the inclination detection unit 104 to calculate the midpoint between each end point. When the document area is detected as a rectangular area (FIG. 8A), the calculated midpoint is present on each side of the rectangle.

  In step S1006, the information extraction unit 103 measures the length (line interval) between the character string regions using one of the reduced image data supplied from the image reduction unit 102.

  FIG. 12 is a diagram exemplarily showing the inclination of the document image. As shown in the figure, if the image data I is inclined in the direction indicated by white in the figure, it is desirable to use the reduced image data Ish which is a reduction in the horizontal direction. On the other hand, if the image is inclined in the direction indicated by gray, it is desirable to use the reduced image data Isv that is a reduction in the vertical direction. However, determining the arrangement direction of character strings in the character string existence area generally requires complicated processing. For this reason, it is assumed here that measurement is first performed on the reduced image data Ish reduced in the horizontal direction. The specific measurement method is as follows.

  The information extraction unit 103 scans significant pixels based on the reduced image data Ish and the calculated midpoint, and measures the distance (row interval) between objects.

  FIG. 9 is a diagram exemplarily showing the scanning direction in step S1006. As shown in FIG. 9A, scanning is performed in the direction of a line connecting the midpoints (between square marks (♦) in the figure) existing on the two opposing sides. In FIG. 9A, two scanning directions ((1) and (3)) are shown. This indicates the scanning direction corresponding to the inclination direction ((1) and (3)) of the image data I shown in FIG.

  Here, it is difficult to determine which of the document images (1) and (3) is in the correct direction. Therefore, here, first, scanning is performed in two directions. Although there are two scanning directions here, a configuration in which there is one scanning direction may be used depending on the watermark information embedding algorithm as described later.

  FIG. 6 is an enlarged view of the reduced image data Ish. First, the information extraction unit 103 detects the presence / absence of a significant pixel by scanning the reduced image data Ish in a direction (here, the vertical direction) orthogonal to the reduction direction (here, the horizontal direction). Then, the position where the presence / absence of the significant pixel is reversed is determined as the boundary between the character string region and the line spacing region.

For example, when the inversion position is detected along the arrow in FIG. 6, each pixel position of x _{1 to} x ₁₀ is detected. At this time, the length of each of _{U 1, D 1, U 2} , D 2 is a line _{spacing, U 1 = x 3 -x 2} , D 1 = x 5 -x 4, U 2 = x 7 -x ₆ , D ₂ = x ₉ -x ₈ (unit is pixel (pix)).

  As described above, as a result of the reduction process in step S1002, the character string area is reduced in the character arrangement direction, and at the same time, the halftone portion is converted into a significant pixel. As a result, the density of significant pixels (here, black) in the character string region is increased. As a result, the information extraction unit 103 can detect the boundary between the character string area and the line space area with higher accuracy, and can measure the line spacing with higher accuracy.

  In this example, scanning is performed in the direction connecting the middle points on the two opposite sides of the quadrangle using the four end points as the start point and the end point, respectively. It doesn't have to be minutes. For example, in the case of the document area shown in FIG. 9B, one place between the end points may be scanned in the tilt direction (arrow in the figure).

  Note that when the reduced image data using the above-described bilinear method is used, one scan is generally sufficient. However, when performing detection with higher accuracy, a plurality of scans may be performed on the reduced image, and an average value at a plurality of locations may be used as the line interval. Even when reduced image data is generated by thinning, scanning at a plurality of locations is effective. FIG. 7 is a diagram exemplarily showing a state in which a plurality of locations are scanned for the reduced image data Ish. In FIG. 7, the character string portion indicated by the black object is shown as being closer to the actual reduced image data. That is, it is shown as including an insignificant pixel (white pixel) instead of the ideal rectangular object as shown in FIG. For this reason, the measurement value between objects (line interval) differs slightly depending on the scanning position.

For example, as shown in the figure, values obtained by performing three scanning positions (arrows (1), (2), and (3))
Arrow (1): U ₁ = 10 [pix], D ₁ = 4 [pix], U ₂ = 4 [pix], D ₂ = 12 [pix]
Arrow (2): U ₁ = 8 [pix], D ₁ = 5 [pix], U ₂ = 6 [pix], D ₂ = 10 [pix]
Arrow (3): U ₁ = 6 [pix], D ₁ = 3 [pix], U ₂ = 5 [pix], D ₂ = 8 [pix]
Suppose that In that case, for example, the average value of each length,
U ₁ = 8 [pix], D ₁ = 4 [pix], U ₂ = 5 [pix], D ₂ = 10 [pix]
May be determined as the distance between objects (line spacing).

In step S1007, the information extraction unit 103 derives watermark information based on the line spacing derived in step S1006. Specifically, watermark information is calculated in association with an embedding algorithm preset in the information extraction unit 103. For example, in FIG. 6, since U ₁ <D ₁ , U ₂ > D ₂ , the watermark information is derived as “10 (binary)”.

  Note that, as shown in FIG. 9A, for the two scanning directions ((1) and (3)), the above-described measurement of the distance (row interval) between objects and the derivation of watermark information are performed. However, at this time, it cannot be determined which information is correct. Therefore, the determination is made from the derived watermark information. This is related to the watermark information embedding algorithm. In addition to the information to be embedded, a start bit and a stop bit are used, and the determination is made based on whether or not this is inverted.

  For example, if the start bit and the stop bit are set to the same “0”, when the watermark information is calculated, one of the start bits is “1”, so the watermark whose start bit is “0”. Determine that the information is correct.

It is also preferable to use an algorithm configured so as not to depend on the reading start direction as the watermark information embedding algorithm. For example, if the information to be embedded is “101 (binary)” or “11010 (binary)”, the start bit is “0”, and the stop bit is “11”, the information is “010111 (binary)”, “01101011 (binary)”. Furthermore, if information such as “010111000101 (binary)” and “0110101100101001 (binary)” is embedded so that reading can be performed from either of them, the information can be read only in one scan from top to bottom in (1) Extraction is possible. The latter part of the information is bit-inverted when the determination condition is embedded with “0”: U _n > D _n
When embedding “1”: U _n <D _n
In this case, reading from the opposite direction reverses the order of U _n and D _n and reverses the bit.
In addition to the above, if the start bit and the stop bit are set to the same “0”, the information to be embedded is “001010 (binary)” when the information to be embedded is “101 (binary)”. When read from the opposite direction, “101011 (binary)” and the start bit is “1”. Therefore, by reversing the information portion and rearranging “010100 (binary)” in the opposite direction, it becomes “001010 (binary)” and can be extracted.
If such a method is used, it is also possible to derive watermark information by only one without using two scanning directions.

  However, in step S1006, as already described with reference to FIG. 12, when measurement is performed on the reduced image data Ish shown in FIG. 4C, the distance between objects may not be measured. Therefore, there are cases where a watermark image cannot be extracted in step S1007.

In step S1008, the control unit 110 determines whether information has been extracted in step S1007. The determination as to whether or not the information has been extracted is, for example, when U _n and D _n can be measured, it is determined that the information has been extracted, and when U _n and D _n cannot be measured, it is determined that the extraction has failed. To do. Alternatively, it is assumed that information cannot be extracted when a value other than a value defined by a preset embedding algorithm is detected. Alternatively, the reading result may be determined by performing a pre-specified erroneous detection / non-detection determination.

  In step S1009, the inclination detecting unit 104 calculates the end point in the reduced image data Isv from the end point of the reduced image data Isvh determined in step S1003 and the reduction rate R used in step S1002. Then, the calculated result is supplied as end point data C to the information extraction unit 103 together with the reduced image data Ish.

  In step S <b> 1010, the information extraction unit 103 uses the end point data C supplied from the inclination detection unit 104 to calculate the midpoint between each end point.

  In step S <b> 1011, the information extraction unit 103 measures the length (line interval) between the character string regions using the reduced image data Isv supplied from the image reduction unit 102. A specific measurement method is the same as that in step S1006. However, it should be noted that the information extraction unit 103 detects the presence / absence of a significant pixel by scanning the reduced image data Isv in a direction substantially orthogonal to the scanning direction in step S1006.

  In step S1012, the information extraction unit 103 derives watermark information based on the line spacing derived in step S1011. A specific measurement method is the same as that in step S1007.

  Through the operation flow as described above, the image processing apparatus 11 extracts watermark information from the image data I.

  In the first embodiment, description has been made using an algorithm for embedding watermark information in correspondence with the relative length of one set (two) of line intervals as shown in FIG. However, as described first, the present invention is not limited to this embedding algorithm. For example, on the basis of the first line interval (between the first and second lines of the character string), the line interval after the second (between the second and third lines of the character string) An algorithm that embeds information corresponding to the relative length to the line spacing may be used. Further, instead of the binary information based on the relative line spacing, multi-value information based on the line spacing may be embedded. In other words, this is an effective technique for any arbitrary embedding algorithm using line spacing.

  As described above, according to the image processing apparatus according to the first embodiment, it is possible to extract watermark information with higher accuracy or higher speed. Further, even if the character string direction in the input image data is inclined with respect to the direction of the image data, information can be extracted without performing a complicated operation.

(Second Embodiment)
A second embodiment will be described in which an end point (vertex) of a character string area is detected using reduced image data. Since operations other than the end point detection operation are the same as those in the first embodiment, description thereof will be omitted.

  For example, as shown in FIG. 13, the inclination detection unit 104 sequentially scans the reduced image data Ish in the horizontal direction (H1, H2, H3... In the figure) and the vertical direction (V1, V2, V3... In the figure). Thus, the end point is a place where the black pixel is first detected and a place where the black pixel ends. Here, based on H1 and H10000 in the horizontal direction, and V1 and V25 in the vertical direction, end points indicated by circles (●) are detected. With this configuration, it is possible to detect the inclination directly from the reduced image data Ish. Therefore, the generation of reduced image data Isvh, which is an image reduced in the horizontal and vertical directions at the same magnification in the first embodiment, and the end point calculation processing in step S1003 can be omitted.

  In the first embodiment, both the reduced image data Ish and Is are generated at the same time in step S1002. However, first, only the reduced image data Ish in the horizontal direction may be generated, and end points may be detected from the reduced image data Ish to extract information. Then, only when information cannot be extracted, the reduced image data Isv in the vertical direction may be generated, and the end point may be detected from the reduced image data Isv to extract the information.

(Third embodiment)
In the third embodiment, a description will be given of a form in which watermark information is extracted from a document image read by a scanner or the like by a program that operates on a computer (PC).

<Equipment configuration>
FIG. 11 is a diagram showing an internal configuration of the PC.

  In the figure, reference numeral 1101 denotes a CPU, which realizes each part of the functional blocks shown in FIG. 1 based on programs and data stored in a RAM 1102 and a ROM 1103.

  Reference numeral 1102 denotes a RAM which stores programs and data loaded from the external storage device 1108. In addition, a program or data downloaded from another computer system 1114 via an I / F (interface) 1115 is temporarily stored. Furthermore, the CPU 1101 has an area necessary for performing various processes.

  Reference numeral 1103 denotes a ROM which stores computer function programs and setting data. Reference numeral 1104 denotes a display control apparatus, which performs control processing for displaying images, characters, and the like on the display 1105. Reference numeral 1105 denotes a display that displays images, characters, and the like. As a display, a CRT, a liquid crystal screen or the like can be applied.

  Reference numeral 1106 denotes an operation input device, which is a device such as a keyboard or a mouse that can input various instructions to the CPU 1101. Reference numeral 1107 denotes an I / O for notifying the CPU 1101 of various instructions input via the operation input device 1106.

  Reference numeral 1108 denotes an external storage device that functions as a large-capacity information storage device such as a hard disk, and stores an OS (operating system), various application programs, and input / output document images. Writing information to the external storage device 1108 and reading information from the external storage device 1108 are performed via the I / O 1109.

  Reference numeral 1110 denotes a printer for outputting documents and images. Output data is sent from the RAM 1102 or the external storage device 1108 via the I / O 1111. Examples of printers for outputting documents and images include ink jet printers, laser beam printers, thermal transfer printers, and dot impact printers.

  Reference numeral 1112 denotes a scanner for reading a document or an image. Input data is sent to the RAM 1102 or the external storage device 1108 via the I / O 1113.

  Reference numeral 1116 denotes a bus connecting the CPU 1101, ROM 1103, RAM 1102, I / O 1111, I / O 1109, display control device 1104, I / F 1115, I / O 1107, and I / O 1113.

<Operation of the device>
The external storage device 1108 stores an image processing program for realizing each functional unit and operation flow described in the first embodiment as an application program. The operation flow described in the first embodiment is started based on an instruction to start the image processing program via the operation input device 1106 by the user. Detailed operations are substantially the same as those in the first embodiment, and will not be described.

(Other embodiments)
Although the embodiments of the present invention have been described in detail above, the present invention may be applied to a system constituted by a plurality of devices or may be applied to an apparatus constituted by one device.

  The present invention can also be achieved by supplying a program that realizes the functions of the above-described embodiments directly or remotely to a system or apparatus, and the system or apparatus reads and executes the supplied program code. The Accordingly, the program code itself installed in the computer in order to realize the functional processing of the present invention by the computer is also included in the technical scope of the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  Examples of the recording medium for supplying the program include a floppy (registered trademark) disk, a hard disk, an optical disk (CD, DVD), a magneto-optical disk, a magnetic tape, a nonvolatile memory card, and a ROM.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. In addition, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can also be realized by the processing.

  Further, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program, and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the main function structures of the image processing apparatus 11 in 1st Embodiment. FIG. 3 is a diagram exemplarily showing a document original in which watermark information is embedded. It is a figure which shows exemplarily the binary image data in which watermark information was embedded. It is a figure which shows the example of the reduced image data Ish which reduced the image data I to the horizontal direction, and the reduced image data Isv reduced to the vertical direction. It is a figure which shows illustratively conversion to the black which is a significant pixel of the part calculated as a halftone. It is an enlarged view of reduced image data Ish. It is a figure which shows an example of a mode that multiple times scanning is performed with respect to the reduction image data Ish. It is a conceptual diagram of the method of detecting the end point (vertex) of a document area. It is a figure which shows the scanning direction of a significant pixel detection exemplarily. 3 is an operation flowchart of the image processing apparatus 11 according to the first embodiment. It is a figure which shows the internal structure of PC. It is a figure which shows the inclination of a document image as an example. It is a figure which shows the endpoint detection using the reduced image data Ish exemplarily.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Image processing apparatus 101 Image input part 102 Image reduction part 103 Information extraction part 104 Inclination detection part 110 Control part 111 Operation part

Claims (7)

An image processing apparatus that inputs a document image and extracts embedded watermark information from line spacing of character strings in the document image,
An input means for inputting a document image as image data;
Image reduction means for generating first reduced image data obtained by reducing the input image data in a first direction at a predetermined reduction rate ;
Detecting means for detecting an end point of a character string existing area in the first reduced image data;
With respect to two sides facing a second direction orthogonal to the first direction in a quadrangle using the end points, a scanning start point is set on one side and a scanning end point is set on the other side. Setting means;
An information extraction unit that scans the reduced image data along a line segment connecting the start point and the end point set by the setting unit, detects a line interval of a character string, and extracts watermark information;
An image processing apparatus comprising: It said image reduction means further generates a second reduced image data obtained by reducing by the reduction ratio the image data in the second direction,
When the effective character string line spacing is not detected by the information extraction means,
The detecting means detects an end point of a character string existing area in the second reduced image data,
The setting means sets a starting point of scanning on one side and an end point of scanning on the other side with respect to two sides facing the first direction in a quadrangle using the end points,
The extraction unit scans the second reduced image data along a line segment connecting the start point and the end point set by the setting unit, detects a line interval of a character string, and extracts watermark information. The image processing apparatus according to claim 1. The image processing apparatus according to claim 1, wherein the setting unit sets the start point at a midpoint of the one side and sets the end point at a midpoint of the other side. . It said image reduction means further generates a third reduced image data obtained by reducing each said reduction ratio of the image data in the first direction and the second direction,
The detecting means detects an end point of a character string existing area in the third reduced image data, and uses the reduction ratio in the image reducing means and the coordinates of the end point to use the character in the first reduced image data. The image processing apparatus according to claim 1, wherein an end point of the row existence area is detected. A method for controlling an image processing apparatus that inputs a document image and extracts embedded watermark information from line spacing of character strings in the document image,
An input process for inputting a document image as image data;
An image reduction step of generating first reduced image data obtained by reducing the input image data in a first direction at a predetermined reduction rate ;
A detecting step of detecting an end point of a character string existing area in the first reduced image data;
With respect to two sides facing a second direction orthogonal to the first direction in a quadrangle using the end points, a scanning start point is set on one side and a scanning end point is set on the other side. A setting process;
An information extraction step of scanning the reduced image data along a line segment connecting the start point and the end point set in the setting step, detecting a line interval of a character string, and extracting watermark information;
An image processing apparatus control method comprising: A step of generating second reduced image data obtained by reducing the input image data in the second direction at the reduction rate ;
A step of detecting an end point of a character string existing area in the second reduced image data when a line spacing of a valid character string is not detected in the information extracting step;
A step of setting a scanning start point on one side and a scanning end point on the other side with respect to two sides facing the first direction in a quadrangle using the end points;
Scanning the second reduced image data along a line connecting the set start point and end point, detecting line spacing of a character string, and extracting watermark information;
The image processing apparatus control method according to claim 5, further comprising:   A program for causing a computer to execute each step of the control method for an image processing apparatus according to claim 5 or 6.

Images