Method for determining orientation of contour line segment in local area and for determining straight line and corner

A computer readable product storing at least one program, for determining an orientation of a local line segment in a contour in a local area of a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels located in a plurality of orientations around one of plural pixels, located in the local area and having a first predetermined value, wherein the pixels are stored in a storage memory unit;
• a second step for determining whether or not the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in said each orientation when the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit.

A computer readable product storing at least one program, for determining an orientation of a local line segment in a contour in a local area of a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• and
• a second step for determining whether or not the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in said each orientation when the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit.

A computer readable product storing at least one program, for determining an orientation of a local line segment in a contour in a local area of a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels located in a plurality of orientations around one of plural pixels located in the local area and having a first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit.

A computer readable product storing at least one program, for determining an orientation of a local line segment in a contour in a local area of a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• and
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a first plurality of sectorial areas around each pixel having the first predetermined value and located at the center of each of a plurality of local areas, and counting the numbers of pixels each having the first predetermined value and located in each of a second plurality of sectorial areas around said each pixel having the first predetermined value and located at the center of each of the plurality of local areas, where the locations of the second plurality of sectorial areas are different from the locations of the first plurality of sectorial areas, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining for each of the first and second patterns a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• a third step for obtaining for each of the first and second patterns an orientation corresponding to one of the areas for which the difference is greater than a second predetermined value using the processing unit;
• and
• a fourth step for obtaining an overlapping area in which one of the first plurality of sectorial areas and one of the second plurality of sectorial areas are overlapped, where the number of pixels located in said one of the first plurality of sectorial areas is greater than the second predetermined value, and the number of pixels located in said one of the second plurality of sectorial areas is greater than the second predetermined value, respectively;
• and for determining that a local line segment exists in an orientation corresponding to said overlapping area using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in a certain orientation when the number of pixels located in the orientation is greater than a second predetermined value using the processing unit;
• a third step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the second step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fourth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the third step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in an orientation corresponding to one of the sectorial areas when the number of pixels located in the sectorial area is greater than a second predetermined value using the processing unit;
• a third step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the second step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fourth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the third step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a first plurality of sectorial areas around each pixel having the first predetermined value and located at the center of each of a plurality of local areas, and counting the numbers of pixels each having the first predetermined value and located in each of second plurality of sectorial areas around said each pixel having the first predetermined value and located at the center of each of the plurality of local areas, where the locations of the second plurality of sectorial areas are different from the locations of the first plurality of sectorial areas, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining an overlapping area in which one of the first plurality of sectorial areas and one of the second plurality of sectorial areas are overlapped, where the number of pixels located in said one of the first plurality of sectorial areas is greater than a second predetermined value, and the number of pixels located in said one of the second plurality of sectorial areas is greater than the second predetermined value, respectively;
• and for determining that a local line segment exists in an orientation corresponding to said overlapping area using the processing unit;
• a third step for determining in each of the plurality of local areas that a straight local line segment passing through said each pixel exists in the local area when two local line segments are determined to exist in the second step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fourth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the fourth step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the third step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fifth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the fourth step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each area and a sum of the numbers of pixels in orientations adjacent to said each areas on both sides thereof using the processing unit;
• a third step for determining that a local line segment exists in an orientation of one of the areas when the difference for the area is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the third step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fifth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the fourth step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A computer readable product storing at least one program, for detecting a position of a corner from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in an orientation corresponding to one of the sectorial areas when the number of pixels located in the sectorial area is greater than a second predetermined value using the processing unit;
• a third step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second step exceeds a predetermined angle value using the processing unit;
• a fourth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a fifth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a sixth step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• a seventh step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A computer readable product storing at least one program, for detecting a position of a corner from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in an orientation corresponding to one of the sectorial areas when the number of pixels located in the sectorial area is greater than a second predetermined value used in the processing unit;
• a third step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second step exceeds a predetermined angle value used in the processing unit;
• a fourth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously used in the processing unit;
• a fifth step for obtaining for each group representative values of the coordinates of the respective pixels in the group used in the processing unit;
• a sixth step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group used in the processing unit;
• and
• a seventh step for obtaining a representative value of the orientations of all of the pixels in each group used in the processing unit.

A computer readable product storing at least one program, for detecting a position of a corner from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a first plurality of sectorial areas around each pixel having the first predetermined value and located at the center of each of a plurality of local areas, and counting the numbers of pixels each having the first predetermined value and located in each of a second plurality of sectorial areas around said each pixel having the first predetermined value and located at the center of each of the plurality of local areas, where the locations of the second plurality of sectorial areas are different from the locations of the first plurality of sectorial areas, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining two overlapping areas in each of which one of the first plurality of sectorial areas and one of the second plurality of sectorial areas are overlapped, where the number of pixels located in said one of the first plurality of sectorial areas is greater than a second predetermined value, and the number of pixels located in said one of the second plurality of sectorial areas is greater than the second predetermined value, respectively;
• and for determining that a local line segment exists in each of orientations corresponding to said overlapping area using the processing unit;
• a third step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second step exceeds a predetermined angle value using the processing unit;
• a fourth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a fifth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a sixth step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• a seventh step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A computer readable product storing at least one program, for detecting a position of a corner from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the central processing unit;
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second and third steps exceeds a predetermined angle value using the processing unit;
• a fifth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a sixth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a seventh step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• an eighth step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A computer readable product storing at least one program, for detecting a position of a corner from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas-and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each sectorial area and a sum of the numbers of pixels in sectorial areas adjacent to said each sectorial area on both sides thereof using the processing unit;
• a third step for determining that a local line segment exists in an orientation corresponding to a sectorial area when the difference for the sectorial area is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second and third steps exceeds a predetermined angle value using the processing unit;
• a fifth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a sixth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a seventh step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• an eighth step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A computer readable product storing at least one program, for detecting a line segment from a contour in a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels having a first predetermined value and located in a plurality of sectorial areas which are arranged around each of a plurality of pixels located in the binary contour image and having the first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining for each of the plurality of pixels located in the binary contour image and having the first predetermined value, that a local line segment exists in an orientation, corresponding to one of the sectorial areas, from said each of the plurality of pixels, when the number of pixels located in the sectorial area is greater than a second predetermined value using the processing unit;
• a third step for determining for each of the plurality of pixels located in the binary contour image and having the first predetermined value, that first and second local line segments which are determined to exist in the second step constitute a straight local line segment passing through said each of the plurality of pixels when the orientations of said first and second local line segments differ by 180.degree. from each other using the processing unit;
• a fourth step for determining for each of the plurality of pixels located in the binary contour image and having the first predetermined value, that third and fourth local line segments constitute a nearly-straight local line segment corresponding to the straight local line segment obtained in the third step when the orientation of the third local line segment is within a predetermined range of azimuth from the orientation of one of the said first and second local line segments constituting the straight local line segment determined in the third step, the orientation of the fourth local line segment is within a predetermined range of azimuth from the orientation of the other of said first and second local line segments, and the difference between the orientations of the above third and fourth local line segments is not equal to 180.degree. using the processing unit;
• and
• a fifth step for determining a series of pixels as constituents of a candidate of a line segment when the pixels in the series are contiguously arrayed, at least one of the pixels in the series is the pixel through which the straight local line segment is determined in the third step to pass, the respective orientation of at least one straight local line segment which is determined to pass through said at least one of the pixels in the series is the same, and a nearly-straight local line segment, corresponding to said straight local line segment which is determined to exist in the third step for one of said at least one of the pixels, is determined in the fourth step for each of the pixels other than said at least one pixel in the series using the processing unit.

A computer readable product storing at least one program, for determining an orientation of a local line segment in a contour in a local area of a binary contour image, in a storage memory unit, where said at least one program when executed by a processing unit, causes the processing unit and its associated hardware to carry out the steps of:

• obtaining the numbers of pixels located in a plurality of orientations around one of plural pixels located in the local area and having a predetermined value, wherein the pixels are stored in the storage memory unit;
• obtaining a sum of the numbers of pixels in orientations adjacent to each of the plurality of orientations on both sides thereof;
• obtaining a difference between the number of pixels located in said each orientation and said sum using the processing unit;
• and
• determining that local line segments exist in two orientations among said plurality of orientations when said difference obtained in the third step is the largest and the second largest in said two orientations, respectively, using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels located in a plurality of orientations around one of plural pixels, located in the local area and having a first predetermined value, wherein the pixels are stored in a storage memory unit;
• a second step for determining whether or not the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in said each orientation when the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• and
• a second step for determining whether or not the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in said each orientation when the number of pixels located in each orientation is greater than a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels located in a plurality of orientations around one of plural pixels located in the local area and having a first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• and
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• and
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a first plurality of sectorial areas around each pixel having the first predetermined value and located at the center of each of a plurality of local areas, and counting the numbers of pixels each having the first predetermined value and located in each of a second plurality of sectorial areas around said each pixel having the first predetermined value and located at the center of each of the plurality of local areas, where the locations of the second plurality of sectorial areas are different from the locations of the first plurality of sectorial areas, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining for each of the first and second patterns a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• a third step for obtaining for each of the first and second patterns an orientation corresponding to one of the areas for which the difference is greater than a second predetermined value using the processing unit;
• and
• a fourth step for obtaining an overlapping area in which one of the first plurality of sectorial areas and one of the second plurality of sectorial areas are overlapped, where the number of pixels located in said one of the first plurality of sectorial areas is greater than the second predetermined value, and the number of pixels located in said one of the second plurality of sectorial areas is greater than the second predetermined value, respectively;
• and for determining that a local line segment exists in an orientation corresponding to said overlapping area using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in a certain orientation when the number of pixels located in the orientation is greater than a second predetermined value using the processing unit;
• a third step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the second step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fourth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the third step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in an orientation corresponding to one of the sectorial areas when the number of pixels located in the sectorial area is greater than a second predetermined value using the processing unit;
• a third step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the second step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fourth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the third step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a first plurality of sectorial areas around each pixel having the first predetermined value and located at the center of each of a plurality of local areas, and counting the numbers of pixels each having the first predetermined value and located in each of second plurality of sectorial areas around said each pixel having the first predetermined value and located at the center of each of the plurality of local areas, where the locations of the second plurality of sectorial areas are different from the locations of the first plurality of sectorial areas, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining an overlapping area in which one of the first plurality of sectorial areas and one of the second plurality of sectorial areas are overlapped, where the number of pixels located in said one of the first plurality of sectorial areas is greater than a second predetermined value, and the number of pixels located in said one of the second plurality of sectorial areas is greater than the second predetermined value, respectively;
• and for determining that a local line segment exists in an orientation corresponding to said overlapping area using the processing unit;
• a third step for determining in each of the plurality of local areas that a straight local line segment passing through said each pixel exists in the local area when two local line segments are determined to exist in the second step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fourth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the fourth step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the processing unit;
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the third step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fifth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the fourth step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each area and a sum of the numbers of pixels in orientations adjacent to said each areas on both sides thereof using the processing unit;
• a third step for determining that a local line segment exists in an orientation of one of the areas when the difference for the area is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that a straight local line segment passing through said each of the plurality of pixels exists in the local area when two local line segments are determined to exist in the third step, and the orientations of the two local line segments differ by 180.degree. from each other using the processing unit;
• and
• a fifth step for determining a group of pixels as a candidate of a line segment when the pixels in the group are contiguously arrayed and it is determined in the fourth step that local line segments in the same orientation pass through the respective pixels in the respective local areas using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in an orientation corresponding to one of the sectorial areas when the number of pixels located in the sectorial area is greater than a second predetermined value using the processing unit;
• a third step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second step exceeds a predetermined angle value using the processing unit;
• a fourth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a fifth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a sixth step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• a seventh step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining in each of the plurality of local areas that a local line segment exists in an orientation corresponding to one of the sectorial areas when the number of pixels located in the sectorial area is greater than a second predetermined value used in the processing unit;
• a third step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second step exceeds a predetermined angle value used in the processing unit;
• a fourth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously used in the processing unit;
• a fifth step for obtaining for each group representative values of the coordinates of the respective pixels in the group used in the processing unit;
• a sixth step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group used in the processing unit;
• and
• a seventh step for obtaining a representative value of the orientations of all of the pixels in each group used in the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels each having a first predetermined value and located in each of a first plurality of sectorial areas around each pixel having the first predetermined value and located at the center of each of a plurality of local areas, and counting the numbers of pixels each having the first predetermined value and located in each of a second plurality of sectorial areas around said each pixel having the first predetermined value and located at the center of each of the plurality of local areas, where the locations of the second plurality of sectorial areas are different from the locations of the first plurality of sectorial areas, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining two overlapping areas in each of which one of the first plurality of sectorial areas and one of the second plurality of sectorial areas are overlapped, where the number of pixels located in said one of the first plurality of sectorial areas is greater than a second predetermined value, and the number of pixels located in said one of the second plurality of sectorial areas is greater than the second predetermined value, respectively;
• and for determining that a local line segment exists in each of orientations corresponding to said overlapping area using the processing unit;
• a third step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second step exceeds a predetermined angle value using the processing unit;
• a fourth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a fifth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a sixth step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• a seventh step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in a plurality of orientations around each of a plurality of pixels respectively located at the centers of a plurality of local areas and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each orientation and a sum of the numbers of pixels in orientations adjacent to said each orientation on both sides thereof using the central processing unit;
• a third step for determining that a local line segment exists in a certain orientation when the difference for the orientation is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second and third steps exceeds a predetermined angle value using the processing unit;
• a fifth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a sixth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a seventh step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• an eighth step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for obtaining the numbers of pixels each having a first predetermined value and located in each of a plurality of sectorial areas around each of a plurality of pixels respectively located at the centers of a plurality of local areas-and each having said first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for obtaining a difference between the number of pixels located in each sectorial area and a sum of the numbers of pixels in sectorial areas adjacent to said each sectorial area on both sides thereof using the processing unit;
• a third step for determining that a local line segment exists in an orientation corresponding to a sectorial area when the difference for the sectorial area is greater than a second predetermined value using the processing unit;
• a fourth step for determining in each of the plurality of local areas that the pixel located at the center of the local area is a near-corner point when an absolute value of a difference between 180.degree. and a difference between the orientations of the two local line segments determined in the second and third steps exceeds a predetermined angle value using the processing unit;
• a fifth step for obtaining a group of pixels which are determined as the near-corner point, and are arrayed contiguously using the processing unit;
• a sixth step for obtaining for each group representative values of the coordinates of the respective pixels in the group using the processing unit;
• a seventh step for obtaining for each group as a corner orientation of the near-corner points a mean orientation of the orientations of the two local line segments in the local area containing at the center of the local area each pixel in the group using the processing unit;
• and
• an eighth step for obtaining a representative value of the orientations of all of the pixels in each group using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• a first step for counting the numbers of pixels having a first predetermined value and located in a plurality of sectorial areas which are arranged around each of a plurality of pixels located in the binary contour image and having the first predetermined value, wherein the pixels are stored in the storage memory unit;
• a second step for determining for each of the plurality of pixels located in the binary contour image and having the first predetermined value, that a local line segment exists in an orientation, corresponding to one of the sectorial areas, from said each of the plurality of pixels, when the number of pixels located in the sectorial area is greater than a second predetermined value using the processing unit;
• a third step for determining for each of the plurality of pixels located in the binary contour image and having the first predetermined value, that first and second local line segments which are determined to exist in the second step constitute a straight local line segment passing through said each of the plurality of pixels when the orientations of said first and second local line segments differ by 180.degree. from each other using the processing unit;
• a fourth step for determining for each of the plurality of pixels located in the binary contour image and having the first predetermined value, that third and fourth local line segments constitute a nearly-straight local line segment corresponding to the straight local line segment obtained in the third step when the orientation of the third local line segment is within a predetermined range of azimuth from the orientation of one of the said first and second local line segments constituting the straight local line segment determined in the third step, the orientation of the fourth local line segment is within a predetermined range of azimuth from the orientation of the other of said first and second local line segments, and the difference between the orientations of the above third and fourth local line segments is not equal to 180.degree. using the processing unit;
• and
• a fifth step for determining a series of pixels as constituents of a candidate of a line segment when the pixels in the series are contiguously arrayed, at least one of the pixels in the series is the pixel through which the straight local line segment is determined in the third step to pass, the respective orientation of at least one straight local line segment which is determined to pass through said at least one of the pixels in the series is the same, and a nearly-straight local line segment, corresponding to said straight local line segment which is determined to exist in the third step for one of said at least one of the pixels, is determined in the fourth step for each of the pixels other than said at least one pixel in the series using the processing unit.

A program executing machine containing a computer readable product storing at least one program, which when executed by the program executing machine, causes the program executing machine and its associated hardware to carry out the steps of:

• obtaining the numbers of pixels located in a plurality of orientations around one of plural pixels located in the local area and having a predetermined value, wherein the pixels are stored in the storage memory unit;
• obtaining a sum of the numbers of pixels in orientations adjacent to each of the plurality of orientations on both sides thereof;
• obtaining a difference between the number of pixels located in said each orientation and said sum using the processing unit;
• and
• determining that local line segments exist in two orientations among said plurality of orientations when said difference obtained in the third step is the largest and the second largest in said two orientations, respectively, using the processing unit.