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Description  |
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BACKGROUND OF THE INVENTION
The present invention generally relates to a character region extracting
method and an apparatus capable of implementing the method which are
adapted to character recognition.
As is well known, characters or character strings on a document are
extracted as a preprocess of character recognition. To meet this
requirement, projection of a document image in a direction of alignment of
characters is extracted. Then a region in which the projection is
continuous in a direction perpendicular to the character strings is
segmentated as a character line. Subsequently, projection of the document
image for each of the segmentated character lines is extracted. Then a
region in which the projection is continuous in the direction of the
character strings is segmentated as a region of a rectangular shape.
However, the conventional character region segmentating or extracting
method has a disadvantage that it is impossible to correctly segment
character lines on a document such that characters of relatively small
sizes constituting a character string are located adjacent, in the
direction of the character string, to a character of a relatively large
size or a character string composed of relatively large sizes. This is
because projection of the character string composed of characters of
relatively small sizes is included in projection of the character of the
relatively large size or the character string composed of characters of
relatively large sizes, so that it is impossible to discriminate the
projection of the characters of the relatively small sizes against the
projection of the relative large size character or character string.
Therefore, recognition of characters becomes impossible.
In general, in the character recognition for a language such as Japanese
having a number of characters of similar patterns, it is difficult to find
one candidate character out of a plurality of candidate characters with
high accuracy by using a character recognition process per character unit.
Therefore, an improved character recognition method is being studied in
which a candidate of the character string is compared with character lines
which are related to categories and are stored in a knowledge dictionary,
and one candidate character is identified for each character included in
the character string, by referring to the compared result. In general,
information for indicating the category represented by characters included
in character strings is provided on the document, so that the collating
sequence with the knowledge dictionary can be facilitated.
However, the processing speed of the collating sequence is not high at
present.
SUMMARY OF THE INVENTION
Accordingly, a general object of the present invention is to provide a
character region extracting method in which the above disadvantages of the
conventional method have been eliminated.
A more specific object of the present invention is to provide a character
region extracting method in which character segmentation can be carried
out with accuracy even for a document in which character strings of
characters of different sizes are mixed.
The above objects of the present invention are achieved by a character
region extracting method comprising the following steps of segmentating a
first region (BL1) from a document image by extracting projection of the
document image in a first direction parallel to a character string and
detecting a range in which the projection is continuous in a second
direction perpendicular to the first direction, the range defining the
first region; segmentating a second region (sBL1) from the first region by
extracting projection of the first region in the second direction and
detecting a range in which the projection is continuous in the first
direction, the range defining the second region; and segmentating a third
region (BL2) from the second region by extracting projection of the second
region in the first direction and detecting a range in which the
projection is continuous in the second direction, the range defining the
third region.
Another object of the present invention is to provide a character region
extracting method in which segmentated character lines are combined with
each other in order to facilitate the character identification using the
knowledge dictionary.
The above object of the present invention is achieved by a character region
extracting method comprising in addition to the above steps, the step of
joining third regions in the first direction in accordance with a
relationship of a relative location between the third regions and a
relationship of a relative size between the third regions, so that a
fourth region (BL3) containing characters or character strings is
extracted. Preferably, the method further comprises the step of joining
fourth regions in the second direction in accordance with a relationship
of a relative location between the fourth regions and a relationship of a
relative size between the fourth regions, so that a fifth region (BL4)
containing characters or character strings is extracted.
Yet another object of the present invention is to provide a character
region extracting apparatus which can implement the above character region
extracting methods.
The above object of the present invention is achieved by a character region
extracting apparatus comprising the following constituents. An optical
scanning part extracts a document image in the form of an electric signal
by optically scanning a document. An image memory stores the document
image extracted by the optical scanning part. A projection extracting part
extracts projection of the document image in a first and second direction.
The first direction corresponds to a scanning direction in the optical
scanning part, and the second direction is perpendicular to the first
direction. A projection buffer stores the projection in each of the first
and second direction extracted by the projection extracting part. A region
segmentating part segmentates a region by using the projection stored in
the projection buffer. The region segmentating part further comprises a
first part for segmentating a first region (BL1) from the document image
by using the extracted projection of the document image in the first
direction and detecting a range in which the projection is continuous in
the second direction, said range defining the first region; a second part
for segmentating a second region (sBL1) from the first region by using the
extracted projection of the first region in the second direction and
detecting a range in which the projection is continuous in the first
direction, the range defining the second region; and a third part for
segmentating a third region (BL2) from the second region by using the
extracted projection of the second region in the first direction and
detecting a range in which the projection is continuous in the second
direction, the range defining the third region. A memory part stores the
extracted third region.
Other objects, features and advantages of the present invention will become
apparent from the following detailed description when read in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are views for showing character arrangements on a document
to be optically scanned;
FIG. 2 is a block diagram of an apparatus capable of implementing a first
preferred embodiment of the present invention;
FIG. 3 is a flowchart of a general sequence of the embodiment of the
present invention;
FIG. 4 is a view for explaining a first region segmentating process shown
in FIG. 3;
FIG. 5 is a flowchart of a second region segmentating process shown in FIG.
3;
FIG. 6 is a view for explaining a part of the second region segmentating
process shown in FIG. 3;
FIG. 7 is a view for explaining the remaining part of the second region
segmentating process shown in FIG. 3;
FIG. 8 is a flowchart of a first region joining process shown in FIG. 3;
FIG. 9 is a flowchart of a second region joining process shown in FIG. 3;
FIGS. 10A through 10C are views for explaining a region rearranging process
in a second preferred embodiment of the present invention;
FIG. 11 is a flowchart of the second embodiment of the present invention;
and
FIG. 12 is a flowchart of the region rearranging process shown in FIG. 11.
DETAILED DESCRIPTION
FIG. 1A shows a plurality of characters of different sizes on a document to
be optically scanned. As described previously, the conventional character
region segmentating method cannot segment each of character lines composed
of relatively small size characters "abcd", "efghi" and "jklm". This is
because projection in which the direction of the character strings is
continuous in the vertical direction is within a range 10 due to the
presence of relatively large characters "ABC". Therefore, the characters
included in the character strings "abcd". "efghi" and "jklm" cannot be
identified.
FIG. 1B shows a plurality of characters on a document to be optically
scanned. Areas 12, 13 and 14 on the document is concerned with an address,
and areas 15 and 16 are concerned with a telephone number. An area 11 is
filled with a character or symbol having a size corresponding to a hatched
rectangular shape. It can be easily seen from the above description that
the conventional method cannot segment character lines of the areas 12
through 16 due to the presence of the area 11.
If the area 11 did not exist on the document, the character lines 12
through 16 could be segmentated. As described above, the character lines
12 through 14 are concerned with the address information and the character
lines 15 and 16 are concerned with information of the telephone number. In
some documents, areas on the document are predetermined so as to be filled
with characters of specific categories, as in the document of FIG. 1B. As
described before, the use of the knowledge dictionary can facilitate the
process for determining one candidate character. In this case, each of the
character lines 12 through 16 is compared with the character lines
registered in the knowledge dictionary. If the separated areas 12, 13 and
14 belonging to the category of address can be segmentated as one
continuous character line, the identifying process could be more easily
performed. However, the conventional method does not have such a process
that character lines of the same information category are joined together
to form one continuous character line.
A description is given of a preferred embodiment of the present invention.
FIG. 2 is a block diagram of a configuration of an apparatus which can
implement the character region extracting process of the present
invention. An image scanner 20 optically scans the document and supplies a
document image of binary values 0 and 1 to an image memory 23 through a
scanner interface part 22. A projection extracting part 24 carries out
raster scan for the document image stored in the image memory 23 in
response to instructions from a central processing unit (hereafter simply
referred to as a CPU), and extracts projection of the document image in
the main scanning direction (,or the raster scanning direction) or the
sub-scanning direction. A projection buffer 25 is used for temporarily
storing the projection extracted by the projection extracting part 24.
FIG. 3 is a flowchart indicating an overall sequence of the character
region extracting process of the embodiment. As shown, the character
region extracting process comprises character region segmentating
processes #1 and #2, and region joining processes #1, #2 and #3.
A description is now given of the region segmentating process #1 (step
101). After the document image is stored in the image memory 23, the
projection extracting part 24 is activated by the CPU 21. The projection
extracting part 24 begins extracting projection of the document image in
the main scanning direction (identical to an X direction) and sends
projection data to the projection buffer 25, which stores the projection
data therein. The projection data have binary values of 1 and 0 which
represent the presence/non-presence of a back pixel, respectively.
Alternatively, the number of black pixels on the main scanning direction
may be used as the projection data.
When the projection extracting process is terminated, the CPU 21 refers to
the projection data stored in the projection buffer 25, and segments a
region BL1 in which the projection is continuous in the sub-scanning
direction. Then, the CPU 21 finds a Y address at the top (start) and a Y
address at the bottom (end) of the segmentated region BL1, and sends these
data to a region table T1 provided in a main memory 26 shown in FIG. 2. In
a case where the projection data is represented by binary values of 1 and
0 which denotes the presence/non-presence of black pixels, a range in
which black pixels are continuous in the sub-scanning direction is
segmentated as a region BL1. On the other hand, in a case where the
projection data is represented by the number of black pixels, a range in
which projection having a value exceeding a predetermined threshold value
is continuous in the sub-scanning direction, is segmentated as a region
BL1.
FIG. 4 is a view for explaining the region segmentating process #1 which is
carried out for the characters shown in FIG. 1A. The projection extraction
for the document image is performed in a direction indicated by an arrow
30, i.e., the main scanning direction. The projection extracting process
segments the document image of FIG. 4 in the manner described above, so
that three regions BL1-1, BL1-2 and BL1-3 shown in FIG. 4 are obtained. A
Y address at the top (start) of each of the regions BL1-1, BL1-2 and
BL1-3, and a Y address at bottom (end) of each of the regions BL1-1, BL1-2
and BL1-3 are stored in the region table T1 in the main memory 26.
Subsequently, a region segmentating process #2 following the region
segmentating process #1 at step 101 is performed (step 102). The region
segmentating process #2 is carried out for each of the segmentated regions
BL1-1, BL1-2 and BL1-3.
FIG. 5 shows a detailed flowchart of the region segmentating process #2 at
step 102. At the commencement of the process #2, the CPU 21 supplies the Y
addresses at the top and bottom of the region BL1-1 to the projection
extracting part 24, and instructs the projection extraction in the
sub-scanning direction. The projection extracting part 24 carries out the
extraction of projection in the sub-scanning direction for the region
BL1-1, and sends the projection data to the projection buffer 25, which
stores the same (step 201). This projection data corresponds to the number
of black pixels or the presence/non-presence of black pixels in
sub-scanning lines.
Then, the CPU 21 initializes a program counter k which is a software
counter provided in the main memory 26 (step 202). The counter k is used
for counting the number of regions which are segmentated by the projection
in the sub-scanning direction.
Thereafter, the CPU 21 refers to the projection data stored in the
projection buffer 25, and detects a region in which projection is
continuous in the main scanning direction (step 203). When a region is
detected, the CPU 21 calculates addresses Ws and We of the detected region
in the X direction at the start and end points thereof, and sends these
addresses to the region table T1 in the main memory 26. And the counter k
is incremented every time when one continuous projection region is
detected (step 203). A region segmentated by this step is hereafter
referred to as a sub-region sBL1. In a case where the projection data is
represented by binary values denoting the presence/non-presence of black
pixels, a range in which binary ones continues is defined as a sub-region
sBL1. In a case where the projection data is represented by the number of
black pixels, a range in which projection having a value exceeding a
predetermined threshold value is defined as a sub-region sBL1. Step 203 is
repeatedly carried out until all the projection data has been processed
(step 204).
FIG. 6 is a view for explaining the steps 201 through 204 shown in FIG. 5.
As shown, three sub-regions sBL1(1), sBL1(2) and sBL1(3) are obtained for
the region BL1-1. As described above, the X addresses Ws and We at the
start and end points of each of the sub-regions sBL1(1), sBL1(2) and
sBL1(3) are stored in the region table T1. When the sequence of the steps
201 through 204 is carried out for the region BL1-2, four sub-regions
sBL1(1), sBL1(2), sBL1(3) and sBL1(4) are obtained. Similarily, seven
sub-regions sBL1(1) through sBL1(7) are obtained when the sequence of the
steps 201 through 204 is carried out for the region BL1-3.
When the discrimination result at step 204 is affirmative, i.e., it is
found that all the projection data has been processed, a program counter j
which is a software counter provided in the main memory 26 is initialized
(step 205). The program counter j is used for counting the number of
sub-regions sBL1 included in one region BL1.
Thereafter, the CPU 21 provides the projection extracting part 24 with the
addresses Ws and We at the start and end points of i-th sub-region sBL1(i)
and instructs the projection extracting part 24 to extract projection of
the i-th sub-region sBL1(i) in the main scanning direction (step 206). The
projection extracting part 24 extracts projection of the sub-region in the
main scanning direction and sends the extracted projection data to the
projection buffer 25.
The CPU 21 refers to the projection data stored in the projection buffer 25
and segmentates a region BL2 in which continuous projection is obtained in
the sub-scanning direction. Then, the CPU 21 detects a start address Hs
and an end address He in the Y-direction and sends these addresses to the
region table T1. Then, when it is found that all the sub-region sBL1 have
not been processed (step 207), the CPU 21 increments the value of the
counter j by one every time when the region segmentating process for one
sub-region sBL1 terminated (step 208). In this manner, all the sub-regions
sBL1 are subjected to the segmentating process described above, and
regions BL2 are obtained for each of the sub-regions sBL1. Address
information (i, Hs, He, Ws, We) of each of the regions sBL2 are registered
in the region table T1 in the main memory 26 where "i" indicates one of
the region BL2 which is counted by a counter i which is a software counter
provided in the main memory 26. When the value of the counter j becomes
equal to the value of the counter k (step 207), the region segmentating
process # 2 is terminated.
FIG. 7 shows regions BL2 obtained by subjecting sub-regions sBL1 to the
region segmentating process composed of steps 206 through 208 shown in
FIG. 5. As shown, regions of BL2(1), BL2(2) and BL2(3) having characters
`t`, `h`, and `e`, respectively are obtained by subjecting the sub-regions
sBL1(1), sBL1(2) and sBL1(3) to the region segmentating process composed
of steps 206 through 208. Likewise, three regions BL2(1), BL2(2) and
BL2(3) each having character strings, as well as three regions BL2(4),
BL2(5) and BL2(6) having large capital characters `A`, `B` and `C`,
respectively are obtained. Similarily, seven regions BL2(1) through BL2(7)
having characters `o`, `p`, `q`, `r`, `x`, `y` and `z`, respectively are
obtained.
When the region segmentating process #2 is terminated, regions of
individual characters or character lines are segmentated for the documents
shown in FIG. 1A. Then, each of characters included in each of the
character lines BL2(1) through BL2(3) in the region BL1-2 can be
segmentated by extracting projection thereof in the Y direction.
It is noted that in the above region segmentating process, a character
composed of more than two separated parts such as `i`, `j` may be divided
into individual parts. For example, a character `i` is divided into two
parts `.` and `1`. In general, Chinese characters are composed of
separated parts, and the division into parts occurs much more frequently.
In addition, in a case where it is desired that the character recognition
is carried out per character line comprising a plurality of characters, a
plurality of segmentated regions of characters must be joined so as to
form one character line related to a specific category such as address
information, telephone information and so on. For these reasons, region
joining processes #1, #2 and #3 executed at steps 104, 106 and 108,
respectively are provided in the present embodiment.
A description is given of the region joining process #1, by referring to
FIG. 8.
The CPU 21 shown in FIG. 2 refers to the region table T1 and calculates an
absolute value of a difference between the X address Hs at the start point
of the region BL2(i) and the X address Hs at the start point of the region
BL2(i+1) adjacent to the region BL2(i) in the X direction. Then the CPU 21
compares the calculated absolute value of the difference with a
predetermined threshold value Th.sub.1 (step 301). That is, the CPU 21
checks whether or not .vertline.BL2(i, Hs)-BL2(i+1,
Hs).vertline.<Th.sub.1. When the absolute value of the difference is equal
to or larger than the threshold value Th.sub.1, the process proceeds to
step 311. Adversely, when the absolute value of the difference is smaller
than the threshold value Th.sub.1, step 302 is executed. At step 302, an
absolute value of a difference between the height H(i) of the region
BL2(i) and the height H(i+1) of the region BL2(i+1) is compared with a
predetermined threshold value Th.sub.2. That is, the CPU 21 checks whether
or not .vertline.H(i)-H(i+1)<Th.sub.2. When the absolute value of the
difference is equal to or larger than the threshold value Th.sub.2, the
process proceeds to step 311. Alternatively when the absolute value of the
difference is smaller than the threshold value Th.sub.2, step 303 is
executed. At step 303, an absolute value of a difference between the width
of the region BL2(i) and the width of the region BL2(i+1) is compared with
a predetermined threshold value Th.sub.3. That is, the CPU 21 checks
whether or not .vertline.BL2(i, We)-BL2(i+1, Ws).vertline.<Th.sub.3. When
the absolute value of the difference is equal to or larger than the
threshold value Th.sub.3, the process proceeds to step 304.
A case where the process reaches step 304 means that the regions BL2(i) and
BL2(i+1) adjacent to each other in the X direction have been decided to be
joined together (step 304). An address information register for storing
address information of regions to be joined is provided in the main memory
26. Additionally, a joint flag FLAG is provided in the main memory 26. The
CPU 21 registers the address information of the regions B23(i) and
BL2(i+1) which are to be joined together in the address information
register. Simultaneously, the CPU 21 sets the joint flag FLAG to ON.
At step 303, when the discriminated result is negative, step 306 is
executed. At step 306, a ratio of the height H(i) to the width W(i) of the
region BL2(i) is compared with a predetermined threshold value Th.sub.4.
When the ratio is equal to or larger than the threshold value Th.sub.4 the
process proceeds to step 307. At step 307, a ratio of the width W(i) to
the height H(i) of the region BL2(i) is compared with the threshold value
Th.sub.4. When the ratio is equal to or larger than the threshold value
Th.sub.4, the process proceeds to step 308. At step 308, a ratio of the
height H(i+1) to the width W(i+1) of the region BL2(i+1) is compared with
the threshold value Th.sub.4. When the ratio is equal to or larger than
the threshold value Th.sub.4, the process proceeds to step 309. At step
309, if a ratio of the width W(i+1) to the height H(i+1) of the region
BL2(i+1) is equal to or larger than the threshold value Th.sub.4, the
process proceeds to step 310. At each of steps 306 thought 309, when the
ratio is smaller than the threshold value Th.sub.4, the process proceeds
to step 304. When the process reaches step 310, the adjacent regions
BL2(i) and BL2(i+1) are decided not to be joined together. At step 310,
the address information of each of the adjacent regions BL2(i) and
BL2(i+1) is registered in a joint table T2 provided in the main memory 26.
At step 311, the CPU 21 checks whether the joint flag FLAG has been set or
not. When the result is affirmative, this means that there is a region
such as the region BL2(i-1) to be joined which is obtained by the previous
process with respect to the process for the region BL2(i). Therefore, the
proceeding region BL2(i-1) and current region BL2(i) are joined together.
At this time, address information of the joined region is stored in the
joint table T2 in the main memory 26. The address information of the
joined region is calculated by using the address information of the
preceding region BL2(i-1) registered in the address information register
and the address information of the region BL2(i). Alternatively, when the
result at step 311 is negative, which means that there is no region to be
joined, the process proceeds to step 310.
Subsequent to steps 304, 310 and 312, it is checked whether there is no
region to be processed (step 313). When the result at step 313 is YES, the
process is terminated. Adversely when the result is NO, the counter i is
incremented by 1 (step 314), and the process returns to step 301.
In the region joining process #1 described above, regions which are decided
to be joined together are joined together in the X direction. Hereafter, a
joined region by the region joining process #1 is denoted by BL3. It is
noted that the region joining process #1 cannot join regions BL2 together
in the Y direction. For example, characters `i` and `j` are still
separated into parts even after the execution of the region joining
process #1.
A region joining process #2 subsequent to the region joining process #1
enables regions BL3 to be joined together in the Y direction.
A description is given of the region joining process #2 at step 106 shown
in FIG. 3, by referring to FIG. 9 which shows a detailed flowchart of the
step 106.
At step 401, the width W(i) to the region BL3(i) is compared with a
predetermined threshold value Th.sub.5. When the width W(i) is equal to or
larger than the threshold value Th.sub.5, the width W(i+1) of the region
BL3(i+1) adjacent to the region BL3(i) included in the region BL1 is
compared with the threshold value Th.sub.5 (step 402). When the width
W(i+1) is equal to or larger than a predetermined threshold value
Th.sub.5, an absolute value of a difference between the width W(i) and the
width W(i+1) is compared with the threshold value Th.sub.6 (step 403).
When the absolute value of the difference is equal to or larger than the
threshold value Th.sub.6, an absolute value of a difference between the X
address at the start point of the region BL3(i) and the X address at the
start point of the region BL3(i+1), i.e., .vertline.BL3(i, Ws)-BL3(i+1,
Ws).vertline. is compared with the threshold value Th.sub.6 (step 404).
When the the absolute value of the difference is equal to or larger than
the threshold value Th.sub.6, the process proceeds to step 405. It can be
seen from the above description that the adjacent regions BL3(i) and
BL3(i+1) are decided to be joined together when both the widths W(i) and
W(i+1) are smaller than the threshold value Th.sub.5, the absolute value
of the difference in width between the adjacent regions is smaller than
the threshold value Th.sub.6, and the absolute value of the difference in
the X address at the start point is smaller than the threshold value
Th.sub.6. Additionally, address information of the regions to be joined
together is registered and simultaneously the joint flag is set. When one
of the conditional expressions at steps 401 through 404 is not satisfied,
the process proceeds to step 406.
At step 406, it is checked whether or not the joint flag FLAG has been set.
If the result at step 406 is YES, which means that there is at least a
region to be joined which is obtained by the previous process, the process
proceeds to step 408. At step 408, an address of the joined region is
calculated by using the registered address information obtained at step
405 and the address of the region BL3(i), and is then registered in the
joint table T3 provided in the main memory 26. If the result at step 406
is NO, the process proceeds to step 407. In this case where there is no
region to be joined, the address information of the region BL3(i) is
stored in the joint table T2.
At step 409, it is checked whether all the regions BL3 have been processed
or not. If the result is NO, the counter i is incremented by 1 at step
410, and the process returns to step 401, so that the next BL3 is
processed.
In the region joining process #2, a region of the character string `the`, a
region of the character string `ABC` and regions of five remaining strings
are finally extracted. That is, regions of characters or character strings
belonging to one character line are extracted as one region. The extracted
region may be subjected to the conventional projection manner, so that
each character may be segmentated for character recognition process per
character. Hereafter a region obtained by joining regions BL3 together is
represented by BL4.
Regions BL3 which should be joined together are mostly joined together when
the region joining process #2. However there is a probability that regions
to be joined still remain without being joined. For this reason, the
region joining process #3 is executed at step 108 in the present
embodiment. The region joining process #3 is carried out for each of the
regions BL1. In operation the joint table T3 is referred to and a process
for joining regions BL3 together in the X direction is performed. This
process is the same as the region joining process #1.
Therefore, it becomes possible to extract regions of characters having
similar sizes and character lines composed of characters having similar
sizes from the document having characters of different sizes such as the
document of FIGS. 1A and 1B. In other words, the regions can be extracted
depending on the sizes of the characters on the document.
When the region extracting process described above is carried out for the
document shown in FIG. 1B, regions BL4(1) through BL4(6) corresponding to
the regions 11 through 16, respectively are obtained in this sequence as
shown in FIG. 10A, and are stored in a region stored in the main memory 26
as shown in FIG. 10B. The region BL4(1) has a large character or symbol,
the region BL4(2) is concerned with the address information, the region
BL4(3) is concerned with the information of a telephone number, the
regions BL4(4) BL4(5) are concerned with the address information, and the
region BL4(6) is concerned with the information of the telephone number.
According to the process of FIG. 3, the regions BL4(2) and BL4(4) in one
character line are separately extracted. Similarly, the regions BL4(3) and
BL4(6) in the same character line are also separately extracted. However,
it is noted that the regions BL4(2) and BL4(4) belong to the same category
of the address information, and the regions BL4(3) and BL4(6) belong to
the same category of the telephone number information. Therefore, it is
desirable to join the regions BL4(2) and BL4(4) together in order to carry
out character recognition per character line in which the knowledge
dictionary prepared for each of the categories is used. Likewise it is
desirable to join the regions BL4(3) and BL4(6). That is, character lines
belonging the same category are joined together so as to form one
character line. The category of the joined character line can be presumed
by obtaining information such as positions of regions to be joined so as
to form the one character line region and the size of the characters
contained therein. In this regard, it is desirable to interchange the
regions BL4 with each other so as to form one character line region of a
specific category in the main memory 26.
FIG. 11 is a flowchart of another embodiment of the present invention
including a process for rearranging regions BL4 by interchanging those
regions with each other. In the embodiment of FIG. 11, a region
rearranging process 110 and a subsequent discrimination step 111 are added
to the flowchart of FIG. 3.
FIG. 12 shows a detailed flowchart of steps 110 and 111. Firstly, the
number of regions BL4 in the region BL1 is detected (step 501). When only
one region BL4 exists in the region BL1, the process ends. When the number
of regions is equal to or more than 2, the flag FLAG is reset and the
counter k is cleared (step 502). Then step 503 is performed.
It is now assumed that two regions BL4 to be compared for deciding whether
or not they are to be joined together are indicated by R1 and R2, an Y
address at the start point of the region R1 is indicated by Hs.sub.1, a Y
address at the end point of the region R2 is indicated by He.sub.2, an X
address at the start point of the region R1 is indicated by Ws.sub.1, and
an X address at the start point of the region R2 is indicated by Ws.sub.2.
At step 503, a comparison between Hs.sub.1 and He.sub.2 and a comparison
between Ws.sub.1 and Ws.sub.2 are carried out. When Hs.sub.1 >He.sub.2
(which means that the uppermost end of the region R1 is not located at
upper position with respect to the lowermost end of the region R2) and
when Ws.sub.1 <Ws.sub.2 (which means that the left-hand side of the region
R1 is positioned at the left-hand side of the left-hand side of the region
R2), the regions R1 and R2 are interchanged with each other and the flag
FLAG is set. Alternatively, the conditional expression at step 503 is not
satisfied, the process proceeds directly to step 505.
At step 505, it is checked whether or not the value of the counter k has
reached the number of the regions BL4 in the region BL1. When the result
is negative, the process proceeds to step 506, at which the value of the
counter k is incremented by 1. Alternatively when the result at step 505
is affirmative, the process proceeds to step 507, at which it is checked
whether the flag FLAG has been set. When the result is affirmative, the
process returns to the step 502. Adversely when the result is negative,
the process ends.
The process of FIG. 12 is repeatedly carried out until all the regions BL4
have been processed. Then the region rearranging process is carried out
for the regions BL4 in the next region BL1.
When the region rearranging process is carried out for the sequence of the
regions BL4(1) to BL4(6) shown in FIG. 10B, the sequence of the
arrangements of the regions as shown in FIG. 10C are obtained. Then, the
region joining process #3 is carried out for the rearranged regions BL4.
In this case it is checked whether or not regions BL4 should be joined
together by referring to the relative positional relationship and the
relative size. The two regions BL4(2) and BL4(4) are joined together to
form one region, and two region BL4(3) and BL4(6) are joined together to
form one region. As a result, two regions BL4(2) and BL4(4) concerning the
address information are joined together to form one region concerning the
address information, and the two regions BL4(3) and BL4(6) are joined
together to form one region concerning the telephone number.
In this manner, it becomes possible to extract a joined region in which
characters or character strings belonging to the same category in one
character line are joined together. Therefore, it is possible not only to
easily segment each character from the joined region by the conventional
projection process but also to presume the category of the joined region
by finding information of the location of the character line and the size
of the characters included in the character line and to carry out the
character recognition per character line in which the knowledge dictionary
is used.
The present invention is not limited to the above embodiments, but various
variations and modifications may be made without departing from the scope
of the present invention. For example, the region joining process #2 may
be carried out before the region joining process #1.
* * * * *
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