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BACKGROUND OF THE INVENTION
Development is under way of an OCR which processes the image of a printed
document and codes the document contents through character recognition to
read them. For this type of OCR, it is a known method to analyze the image
of a document to segment it into objects such as character strings,
graphics, and tables, and structure the data for the objects as a tree
structure hierarchically expressing the layout relationship between the
objects. For example, the official gazette of PUPA No. 2-59880 discloses a
method for structuring the objects constituting a document and the layout
relationship between the objects as a tree structure in accordance with
the inputted document image and read characters in a desired area from the
present document image by specifying an object area whose layout is
displayed in accordance with the tree structure.
The official gazette of PUPA No. 3-17771 discloses a method for generating
a document in which character information and image information are laid
out as a tree structure of layout objects in order of a block, frame,
page, and page set from the bottom by a document processor. This method
makes it possible to edit a document covering different objects by
specifying an area to edit the document, generating a frame equivalent to
the specified area, detecting layout objects in the specified area,
generating a new layout object equivalent to an area combined with the
specified area, and connecting the new object to the lower rank of the
generated frame. These methods lay out each object of a document image by
using a hierarchical tree structure. However, the type of document is
restricted to which prepared tree structure or layout form can be directly
applied. To form a new tree structure or layout model each time, it is
necessary to define a complex hierarchical structure and, moreover, it is
difficult to intuitively understand the hierarchical structure. Therefore,
this is not easy for general users.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for simply
extracting and generating a tree structure to hierarchically express the
relationship between objects of any type of document from a document
image.
It is another object of the present invention to provide a method for
generating a flexible layout model by using image analysis results of an
actual document.
It is still another object of the present invention to provide an interface
for visually displaying the hierarchical structure of a complex model to
decrease the load of a user in generating a document image layout model.
For the present invention, a tree structure is automatically extracted
through image analysis before a user forms a new tree structure or layout
model by interactively executing graphical correction.
That is, a document image is physically analyzed to automatically extract a
separator with a high possibility to separate the objects of the document
and the document image is segmented into tree structure areas in
accordance with the information for the separator. Then, the area
segmentation of the tree structure is displayed on a display unit and a
user interactively executes necessary correction to define a desired tree
structure. A parameter is then set for each node of the tree structure to
complete a flexible layout model.
To describe the layout of a document image, a tree structure model
consisting of rectangular hierarchies horizontally and vertically arranged
is generally used. The layout model related to the present invention
basically comprises a rectangular hierarchical structure.
Following is the description of the method for generating the layout model
of a document image in accordance with the image analysis of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and the
advantages thereof, reference is now made to the Detailed Description
taken in conjunction with the attached Drawings, in which:
FIG. 1 shows the entire structure of the electronic filing system which is
an embodiment of the present invention;
FIG. 2 shows a processing flow of the layout model generation apparatus in
FIG. 1;
FIG. 3 shows the area segmentation of a document image;
FIG. 4 shows the flow for area segmentation by the automatic area
segmentation unit in FIG. 1;
FIG. 5 shows an example of the layout model of the tree structure obtained
through area segmentation;
FIG. 6 shows an example of area segmentation displayed on a screen display
unit;
FIG. 7 shows a flow for segmented area corrections;
FIG. 8 shows "grouping" and "ungrouping" for segmented area corrections;
FIG. 9 shows the processing by the command "MOVE RECTANGLE" for segmented
area correction;
FIG. 10 shows a flow for macroparameter specification and layout model
generation;
FIG. 11 shows the state for setting a macroparameter;
FIG. 12 shows the data format of the layout model in a storage unit;
FIG. 13 shows an example of definition for a layout model which is
expressed in the text format when it is stored in an external memory such
as ASCII file;
FIG. 14 shows the processing for a layout model by the command
"AUTOMATICALLY MODIFY";
FIG. 15 shows the processing for a layout model by the command
"SINGULARIZE";
FIG. 16 shows the processing for a layout model by the command "PLURALIZE";
FIG. 17 shows the layout model generated by correcting the area
segmentation displayed on the screen display unit in FIG. 6;
FIG. 18 shows another embodiment for automatically correcting area
segmentation;
FIG. 19 shows a flow for setting parameters to an image window as another
embodiment of the present invention; and
FIG. 20 shows the image window of the screen display unit showing the
results obtained by the method in FIG. 19.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the general structure of the electronic filing system which is
an embodiment of the present invention. In FIG. 1, reference numeral 1
generally indicates a layout model generation apparatus which comprises an
input unit 1A, processing unit 1B, recording unit 1C, and output unit 1D.
A document whose layout model is to be generated is scanned by an image
input unit 2 like an image scanner and its image information is recorded
in an image memory 3. The image information is sent to an automatic area
segmentation unit 4A of an area generation unit 4 where the image area is
automatically segmented. The results of area segmentation are recorded in
an area structure storage unit 9. The commands and data by which the user
executes various processings are selected and inputted by command and data
input units 5 using such as a mouse and sent to a corresponding section of
the processing unit 1B through an input judgment unit 6. For example, when
it is necessary to correct a segmented area as the result of area
segmentation, a correction command is sent to an area structure
modification unit 4B in accordance with the operation of the user. Numeral
7 indicates a layout model generation unit for generating a layout model
by applying necessary modification to the results of area segmentation of
the document image and setting a parameter. Numeral 10 indicates a layout
model storage unit for recording the data for the layout model. Numeral 8
indicates a macro specification unit for setting parameters by using the
data held in a macroparameter library 11. The situations of document image
area segmentation and layout model generation are successively displayed
on a screen display unit 13 through an output control unit 12 and used for
the interactive operation of the user. Each processing-result is outputted
to external memory 14 or printer 15. Numeral 16 indicates a character
recognition unit for reading characters from the image information of a
document image, and numeral 17 indicates a retrieval unit for retrieving
the-document image by using a layout model.
FIG. 2 shows a processing flow of the layout model generation unit 1 in
FIG. 1. First, a document image is scanned by the image input unit 2, and
character strings, vertical and horizontal black lines, and other black
pixel regions (picture-element) are extracted from the image and stored in
the image memory 3 (Step 21). Subsequent processing is executed in
accordance with extracted rectangle data. Then, area segmentation of the
document image is-automatically executed by the automatic area
segmentation unit 4A of the area generation unit 4 (Step.22). First, long,
wide, and White pixel regions and long black lines to serve as separators
for objects are extracted from the x,y-coordinates of the rectangle. Then,
graphic areas are removed before character areas are roughly segmented
using the extracted separator. Moreover, subseparators to serve as a
boundary between objects are obtained from the change of line pitch and
character size in the character areas and the areas are sub-divided in
accordance with the subseparators.
The area structure data thus obtained by analyzing the image, that is, the
x,y-coordinates of rectangles and areas, the relationship between the
areas, and tree structure data corresponding to the x,y-coordinates are
stored in the area structure storage unit 9. Then, the results are
displayed on the screen display unit 13.
The user graphically corrects the segmented areas of the area structure
data through the area structure modification unit 4B to form a desired
tree structure by viewing the display on the screen display unit 13 to
judge the necessity for correction and inputting a correction command when
necessary (Step 23 ).
Moreover, a parameter is set to each node of the tree structure by the
macro specification unit 8 (Step 24). Because the minimum and maximum
number of lines can approximately be specified for the objects of a
document image, parameters are not separately set but are set by using the
macroparameter previously held in the macroparameter library 11. As a
result, a layout model is generated by the model generation unit 7 (Step
25) and the data for the layout model is recorded in the layout model
storage unit 10. The layout model is also displayed on the screen display
unit 13, which is modified by the layout model generation unit 7 when the
user inputs a correction command (Step 26).
Each step of the processing flow shown in FIG. 2 is described below in
detail.
For the first image extraction (Step 21 in FIG. 2), the document image is
scanned by the image input unit 2, and then character strings and other
black rectangles are extracted and a document image data 30 consisting of
many rectangular areas shown in FIG. 3 is extracted to be stored in the
image memory 3. According to the known black components labeling method
and run-length combining method, it is possible to express all character
strings, black lines, and other black pixel regions from a document image
by expressing them in rectangles. Then, rectangle collection enclosing
white pixel regions 32A through 32N is obtained in accordance with the
rectangles of character strings (31a through 31n) and vertical and
horizontal black lines such as 31d. For this embodiment, description is
hereafter made by premising that all character strings (or sub-character
strings) are extracted as rectangular areas. Detailed description of the
character-string extracting method is shown in the following literature
which is incorporated herein by reference.
(1) "A Character String Extraction Algorithm Using Horizontal Boundaries",
Proc. SPIE/SPSE, vol. 1452-23, pp. 330-339, 1991, written by T. Amano, A.
Yamashita, and H. Takahashi
(2) Official gazette of PUPA No. 1-253077
The processing for area segmentation of a document image (Step 22) is
executed by the automatic area segmentation unit 4A in accordance with the
procedure illustrated in FIG. 4.
First, the document image data 30 is fetched from the memory 3 (Step 41).
Then, white pixel rectangles close to each other with approximately the
same height are unified before all rectangles with a length and width
larger than a certain value are extracted as vertical and horizontal
separators (reference numerals 33 and 34 in FIG. 3) to record the X,Y
coordinate values of them on the document image in the area structure
storage unit 9. However, horizontal separators whose both ends do not
contact a vertical separator are not recorded. A black line 31d with a
certain length or more is recorded as a black line separator 35 (Step 42).
It is preferable to dynamically determine the threshold values of width
and length by examining the distribution of the white pixel rectangle size
for each document image. Among the separators extracted here, only those
with a high reliability (wide and long separators) are recorded as
sub-separators in order to prevent errors of area segmentation to be
successively executed.
The character area is then segmented in accordance with vertical and
horizontal separators (reference numerals 33 and 34) (Step 43). Before
segmentation, an image area 36 is excluded from the processing objects by
specifying it with the distribution of the above separators, extracted
character strings, and rectangles other than character strings. The image
area can be separated from the character area by using a characteristic
value such as the neighborhood line density as reported in the existing
method.
Then, a tree structure is extracted from the hierarchical relationship
between the obtained rectangles, areas, and Separators (Step 44). The area
segmentation direction always appears vertically and horizontally by turns
as the tree structure hierarchy becomes deep. Each node of the tree
structure shows a rectangle enclosing objects. The child node of a node
shows a rectangle obtained by cutting the rectangle of the node
horizontally or vertically.
If a vertical separator 37 for segmenting the whole of an image excluding
the image area into several areas is found, the image is further segmented
by using the separator 37. Then, if a horizontal separator 38 capable of
segmenting each area into several areas is again found, it is further
segmented into smaller areas by using the separator. Thus, the whole of
the image is segmented into area groups constituting a tree structure by
repeating recursive segmentation while alternately using the vertical and
horizontal separators.
Then, lines, the character height for each line, and base lines are
obtained from the character string group Separated into each area to
estimate a line where the line pitch or character size changes in
accordance with them. The interlinear space on these lines is extracted as
a horizontal subseparator 39 to record the X,Y-coordinate values of the
subseparator 39 (Step 45). If a white pixel rectangle with a size larger
than a certain value (but smaller than a separator) for separating two
character-string groups regularly arranged in the vertical direction is
found, it is recorded as a vertical separator. The subseparator has a
function to compensate the boundary between objects which cannot serve as
separators.
Area segmentation is further repeated by using the subseparator for
separating an area vertically or horizontally (Step 46 ).
Then, from the results of the above area segmentation, a tree structure 61
as shown in FIG. 5 is extracted by segmenting the entire image (Step 47).
As the result of area segmentation, most rectangles appearing at the
terminal node of the bottom layer are character strings corresponding to
so-called lines. Obtained data is recorded in the area structure storage
unit 9 (Step 48).
The results of image segmentation are displayed in an image window 50 of
the display unit 13 as a document image 51 as shown in FIG. 6. A layout
model 80 schematically representing the tree structure 61 is displayed in
a model window 60. Each of areas (51A through 51G) of the document image
51 corresponds to each of nodes (61A through 61G) of the tree structure
61. For the layout model 80 at this point, no attribute data is assigned
to each node. The symbol shown at the top and bottom of each node of the
tree structure 61 shows a separator or subseparator. The separator is
segmented into separator 62, black line separator 63, or subseparator 64
in accordance with the type of the line. The terminal node of the tree in
the character area becomes a so-called character line. The tree of the
model in FIG. 6, however, shows only up to the parent node of the terminal
node. A tree including up to the terminal node is internally generated.
Subsequently, the object corresponding to the so-called terminal node is
called a rectangle and the parent node including the rectangle or
higher-rank parent node including the parent node and rectangle is called
an area.
Following is a description of the area segmentation correction by the area
structure modification unit 4B (see FIG. 2).
Because the previously-mentioned area segmentation (Step 22) is
automatically processed in accordance with the predetermined rule, the
objects of an individual document are not always correctly segmented. For
(A) in FIG. 8, for example, "title" areas 51b1 and 51b2 are not separated
from "author's name" areas 51b3 through 51b6 in the image area 51B. For
(A) in FIG. 9, the area of "body" portion 51E of the image 51 is
erroneously segmented.
In this case, graphical correction of the area is changed to correct
segmentation in accordances with interactive user operation. FIG. 7 shows
the procedure. First, the area-segmented document image 51 and data for
its tree structure 61 recorded in the area structure storage unit 9 are
read (Step 71) and displayed in the image window 50 and model window 60
respectively (Step 72). Separators and subseparators are also displayed in
the document image 51. The user compares the contents of the document
image with the results of area segmentation to judge the validity of area
segmentation. If an error is found in area segmentation, the user selects
a command to execute correction by specifying an area on the image window
50 through mouse operation. The area structure modification unit 4B
interprets the command inputted by the user to correct the tree structure
(Steps 73 and 74). The corrected data is recorded in the area structure
storage unit 9 (Step 75).
Following are the command for correcting the area structure. The correction
range (rectangle or area) and position are specified with a mouse.
"GENERATE RECTANGLE": Changes the rectangular area in the specified
document image 51 to a new rectangle and records the data (tree structure
and x,y-coordinate values).
DELETE RECTANGLE: Deletes the data for the specified rectangular area.
MODIFY RECTANGLE: Modifies X,Y-coordinates of the specified rectangular
area.
GROUPING: Unifies existing rectangles or areas by enclosing them and
generates a new area.
UNGROUPING: Specifies and separates the unified areas or rectangles.
MOVE RECTANGLE: Moves a rectangle in an area to another area or outside of
the area. The rectangle moved to outside of the area independently serves
as a new area.
Area segmentation is corrected by combining the above command operations.
For the example in FIG. 8, the areas 51b1 and 51b2 of the second
descendant node and the area 51B of the child node including 51b3 through
51b6 are "ungrouped" to delete the rectangle data for the child node 51B.
Then, the areas 51b1, 51b2 and 51b3 through 51b6 of a child node are
formed {(B) in FIG. 8} by adding theareas 51b1, 51b2, and 51b3 through
51b6 to parent node 51P to "re-group" them into the "title" area 51B (the
second descendant nodes 51b1 and 51b2) and the "author's name" area 51C
(second descendant nodes 51c1 through 51c4) {(C) in FIG. 8}.
For the example in FIG. 9, the-area segmentation of the "body" portion 51E
is-corrected by the command "MOVE RECTANGLE". That is, the data for "e21"
is deleted from the bottom of the second descendant node 51e2 by
specifying the rectangle of the third descendant node "e21" in (A) with a
mouse to move it to the second descendant node 51e1. Then, the second
descendant node 51e2 having no third descendant node is deleted to
generate a new tree structure shown in (B) by inserting the rectangle data
for the original third descendant node "e21" into the bottom of the second
descendant node 51e1 as the new third descendant node "e16".
The object for processing in the correction of area segmentation is not an
image but the collection of rectangles 51A through 51G obtained by
extracting character strings. Therefore, not "cut and paste" like image
processing, but processing similar to a graphic editor is possible.
These corrections are effective for a caption different from a body and
vice versa. Similarly, it is possible to correct an error by the command
"MOVE RECTANGLE".
Following is a description of specifications of the macroparameter and
generation of a layout model (Steps 24 and 25 in FIG. 2) by referring to
FIG. 10.
First, the data for document image and that for tree structure are read
from the area structure storage unit 9 and displayed in the image window
50 and model window 60 respectively (Steps 101 and 102).
As previously described, because the nodes (61A through 61G) of the tree
structure 61 are kept blank, it is necessary to set various parameters
including an area name to these nodes in order to complete the tree
structure as a layout model. From the results of analyzing an actual
image, it is possible to know whether the top, bottom, right, and left
separators are present and the number of rectangles. However, to generate
a model from the image, it is necessary to consider features varying for
each image (e.g. number of rectangles) and relatively stable features
(e.g. presence or absence of black line). Therefore, the macroparameter
set is previously defined as a default parameter set to record it in the
library 11. The user checks the set with the actual analysis results and
adds necessary modification before setting a parameter to each node (Step
103).
FIG. 11 shows the situation in which macroparameters are set. In FIG. 11,
numeral 65 is a macroparameter set window in which the default value of
each parameter displayed in macroparameter table 66 in the form of a table
by corresponding to tree structure 61 is set for typical objects of the
document. The macroparameter window 65 is displayed on the screen display
unit so that parameters can be set through mouse operation.
As examples of the macroparameter, "Man." indicates whether an object is
exactly present in the page, "Min." indicates the minimum number of child
nodes, "Max." indicates the maximum number of child;nodes, and "Separ."
indicates whether the top, bottom, right, and left separators are present.
These parameters are previously prepared in accordance with the type of
area which may appear.
Items showing a hierarchical structure (e.g. Nest., Name, and Dir.) among
the above items judge the parent-child relation with the analyzed tree
structure and set a new value. The items related to the separator (e.g.
Separ.) reset the value suitable for analysis results when a default value
does not coincide with the actual analysis result. The same is true for
the number of rectangles included in an area. Thus, a layout model is
defined by setting a macroparameter to an imitative tree node. It is also
possible to directly set each parameter without using the macroparameter.
Resultingly, layout model 80 (see FIG. 12) in which the macroparameter is
set to all nodes of a tree structure extracted from a document image and
recorded in the layout model storage unit 10. FIG. 12 shows the data
format of the layout model 80 in the layout model storage unit 10. As
shown in (A) of FIG. 12, the above macroparameter and the predetermined
data are recorded in each node 61 and the connection between nodes is
shown by child pointer 67 and brother pointer 68. As shown in (B) of FIG.
12 in detail, x,y-coordinate values are recorded in each node and details
of the separator are recorded by pointer 69.
The table in FIG. 13 shows a definition of a layout model which is
expressed in the text format to be stored in the external memory 14 as an
ASCII file. In the table of FIG. 13, the parameter "Nest" shows the depth
of the tree structure level, "Dir." shows the direction in which child
nodes are arranged, "Element" shows whether a child node is a rectangle
(String) or an area (Dummy), and "Reco" shows whether it should be
recognized by the character recognition unit (Yes) or not (No, N/A).
More detailed description of the layout model and its definition and area
segmentation method is given in the below literature.
A. Yamashita, T. Amano, K. Toyokawa and H. Takahashi, "A Model Based Layout
Understanding Method for Document Recognition System," Proc. 1ST INT.
Conf. on Document Analysis and Recognition, pp. 130-138, 1991.
Then, the commands to be mentioned later are selected and inputted in order
to increase the flexibility of the layout model according to necessity
(Step 104 in FIG. 10) to modify the layout model (Step 105) and the
modified results are recorded in the layout model (Step 106).
When the layout model is modified (Steps 104 and 105 in FIG. 10), it is
possible to define repetition of the child node. Thus, the layout model
increases its flexibility to cover many document images. Especially when a
layout model is generated from a document image as shown in the present
invention, a flexible model should be generated by giving redundancy to
the model.
To give redundancy to the model, there is a method for setting a default
value by a macroparameter. It is also possible to prepare a method in
which the area included in an area can be repeatedly defined. The command
for modifying a layout model includes "AUTOMATICALLY MODIFY",
"SINGULARIZE", and "PLURALIZE".
The command "AUTOMATICALLY MODIFY" repeatedly executes definition
automatically. As shown in FIG. 14, when macroparameters with the same
name are set to a plurality of nodes, the display of the node is changed
to the display showing repetition of an area by the command "AUTOMATICALLY
MODIFY". That is, the second descendant nodes 61e1 through 61e3 specified
with the same parameter are deleted with the original tree structure
preserved {(A) in FIG. 14} and, instead, the variable number of third
descendant node "em1" and dummy second descendant node 61em are inserted
{(B) in FIG. 14}. In view of the definition of the model, when an area is
repeated, the dummy node 61em is always formed and a parameter including a
number of repetitions M is set.
The command "PLURALIZE" deletes the single second descendant node 61e1 with
the original tree structure preserved under the state of (A) in FIG. 15
and, instead, inserts a variable number of the third descendant node "em1"
and the dummy second descendant node 61em {(B) in FIG. 15}. When only one
area is produced as the result of image analysis, it is possible to select
the repetition display by using the command "PLURALIZE" by considering
flexibility.
As shown in FIG. 16, the command "SINGULARIZE" deletes the variable number
of the third descendant node "em1" and the dummy second descendant node
61em under the state of (A) and, instead, inserts the second descendant
nodes 61e1 through 61e3 of the original tree structure.
Because the information for the number of child nodes and that of second
descendant nodes of these tree structures 61 are recorded in the space for
the parent node of the macroparameter table, the parameter of the parent
node is internally determined when setting of the parameters of the
second-descendant and child nodes is completed. Parameters with a fine
number of repetitions can be reset any time by the command "SET".
As described above, an example of the layout model 80 finally generated by
generating a tree structure from the image 51 in FIG. 6 and correcting it
is shown in the model window 60 of FIG. 17. Thus, a flexible layout model
capable of covering the same type of document images can be graphically
generated from the results of analyzing one image.
The following is the description of an embodiment made by applying the
present invention to generation of a layout model for an address book in
accordance with FIG. 18. The area segmenting direction always appears
vertically and horizontally by turns as the depth of the tree structure
hierarchy increases. For the embodiment previously described, however, the
first segmenting direction is assumed as the vertical direction. This is
because the segmentation frequency in this direction is high in general.
As a result, when address book 90 in FIG. 18 is automatically
area-segmented by this method, the physical boundary becomes different
from the logical boundary. That is, the address book 90 is segmented into
areas (51A through 51D) by the vertical separator 33 serving as the
physical boundary. If the areas are directly used for a layout model,
definition results in a document consisting of four columns vertically
arranged in parallel {(B) in FIG. 18}. However, because a name, zip code,
and address are generally put in the address book in the horizontal
direction, horizontal area segmentation is logically significant.
To avoid the above trouble, it is necessary to prepare a macroparameter
suitable for processing the type of document having the above special
segmenting direction. For example, it is previously defined that the
macroparameter "address book" is followed by a child node "person" in
parameter specification and set to a parent node. When the macroparameter
is used, nodes under the "address book" are examined on a model. If a
corresponding node is present, insertion occurs to the node. If not,
insertion occurs to a child node. Then, modification occurs as shown in
(C) of FIG. 18. That is, because the child node "person" is not present
under parent node 61P in (B), a variable number of child nodes 61N is
inserted between the parent node 61P and child nodes 61A through 61D and
the tree structure is changed so that the original child nodes 61A through
61D serve as second descendant nodes 61a1 through 61a4 {(C) in FIG. 18}.
In this case, though the parameter Dir. showing the direction in which the
child nodes 61A through 61D are arranged is Ver. (vertical) in the
original analysis results, the direction in which the second descendant
nodes are arranged under child node 61N (person) newly inserted by the
parameter specification "address book" becomes Hor. (horizontal).
Therefore, it is preferable to prepare not only the Collection of
parameters but a macroparameter in which up to a hierarchical structure is
set in model definition for a document in which the physical analysis
result is different from the logical structure (e.g. table format document
such as a telephone directory or schedule table). The macroparameter has
the function to insert an imaginary node which does not appear in the
analysis result and to automatically change the arrangement of child nodes
in a direction different from the analysis result (vertical to horizontal
and vice versa). It is possible to generate a correct model by using the
macroparameter and forcibly modifying the actually obtained physical
structure. Approximately the same result can be obtained on a model by
re-enclosing individual data for one person on the image analysis result.
The present invention can also be used to retrieve and decode a document in
the same way as an electronic filing system. In this case, a usage is also
considered to specify only the text area of the image of a specific
document and directly read the area without generating a flexible layout
model.
FIGS. 19 and 20 show embodiments suitable for the above purpose. In this
case, parameters can be set to not only the model window 60 but the image
window 50. First, data for the tree structure is read (Step 191) and
displayed on the image window 50 together with a document image (Step
192). Then, a macroparameter is directly set to the text area (Step 193).
Subsequently, a layout model is generated by the same method as that shown
in the model window 60 and the results are recorded in the layout model
storage unit 10. The model in this case is not always flexible, but it is
peculiar to the page of an analyzed document.
Thus, a layout model 82 having a set of parameters (55A through 55H) is
generated in the image window 50 and stored together with the page (Step
195). Characters of a document image are recognized and read by the
character recognition unit 16 in FIG. 1 and stored in the storage unit by
relating the document image with the above layout model. Then, when
setting a parameter to be retrieved by using the layout model 82, it is
retrieved by the retrieval unit 17 and the character recognition results
at the portion concerned of the document image are read and outputted
(Step 196). According to this method, a retrieval range can easily be set.
It is also possible to execute the area segmentation of a document image
and the layout model generating function by a processor instead of the
layout model generation apparatus in FIG. 1 by storing a program including
the processing procedure described in FIG. 2 forward in the memory of a
general-purpose computer.
As described above, the present invention makes it possible to graphically
generate a flexible layout model through modification of hierarchical
structure and repetitive specification of area in accordance with actual
image analysis results. The user can therefore easily understand the
operation. For example, to read a document without a layout model and
without the necessity to set the layout model, the present invention can
also be used to segment an area, specify the area (node) to be read, and
convert it into a character code.
It is possible to easily generate the tree structure of a document by using
the image analysis results of the document. It is also possible to
generate a flexible layout model by processing only one tree structure
extracted by analyzing the image of an actual document.
Moreover, because the user can interactively generate or modify a tree
structure or layout model, he easily understand the operation.
Although the present invention has been particularly shown and described
with reference to the preferred embodiment, it will be understood by those
skilled in the art that various changes in form and detail may be made
without departing from the spirit and the scope of the invention.
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