Bed area extraction method and bed area extraction apparatus

1. A non-transitory computer-readable recording medium having stored therein a program that causes a computer to execute a process, the process comprising:

specifying a first part of a bed candidate area in an image based on first line segments which are extracted from the image;

setting a search range for searching a second line segment with reference to the bed candidate area which is determined based on the specified first part of the bed candidate area;

selecting the second line segment from among one or more first line segments, which are included in the first line segments and the search range, based on a disposition of the one or more first line segments; and

correcting the bed candidate area based on a disposition of the second line,

wherein the specifying includes specifying, as a part of the bed candidate area, a second part including one of short sides of the bed candidate area, the one of short sides corresponding to a head board attached to one end of a bed,

wherein the head board has a certain thickness in a longitudinal direction of the bed candidate area, and wherein the setting includes setting, to the search range, an area surrounded by lines, the lines including a long side of the bed candidate area after rotation in which the bed candidate area is rotated by an angle depending on the thickness of the head board around a point corresponding to a midpoint of the one of short sides corresponding to a short side of the bed to which the head board is attached.

2. The non-transitory computer-readable recording medium according to claim 1 , wherein the second part corresponding to the head board is a U-shaped portion.

3. The non-transitory computer-readable recording medium according to claim 1 , further comprising acquiring a contour segment in the search range, the contour segment being determined to be a part of a contour of the bed in a case where an inclination of the contour segment with respect to a long side of the bed candidate area is equal to or larger than a predetermined angle, wherein the correcting includes correcting the bed candidate area in a case where the contour segment is acquired.

4. The non-transitory computer-readable recording medium according to claim 3 , wherein the setting includes setting a search range for each of the long sides of the bed candidate area, and wherein the correcting includes correcting the bed candidate area in a case where the contour segment is acquired from each of the set search ranges when an angular difference between the inclination of the contour segment and a rotation angle of the bed candidate area is less than a predetermined value.

5. The non-transitory computer-readable recording medium according to claim 3 , wherein the contour segment includes a line segment having a length equal to or longer than a predetermined length and being the longest line segment in the search range.

6. The non-transitory computer-readable recording medium according to claim 3 , wherein the correcting includes correcting the bed candidate area by rotating the bed candidate area so that the long side is parallel to a direction of the contour segment.

7. The non-transitory computer-readable recording medium according to claim 1 , wherein the angle depending on the thickness of the head board is an angle formed by a side, of the head board, corresponding to the one of short sides of the bed candidate area and a diagonal line in a cross section of the head board.

8. The non-transitory computer-readable recording medium according to claim 1 , wherein a misalignment between a position, in the image, corresponding to the bed and the bed candidate area is represented by an angle of a difference between a direction of the head board and a direction of a line obtained by connecting two line segments which corresponds respectively to parts of two long sides of the head board, the two long sides being parallel to each other.

9. A bed area extraction method, comprising:

specifying, by a computer, a first part of a bed candidate area in an image based on first line segments which are extracted from the image;

setting a search range for searching a second line segment with reference to the bed candidate area which is determined based on the specified first part of the bed candidate area;

selecting the second line segment from among one or more first line segments, which are included in the first line segments and the search range, based on a disposition of the one or more first line segments; and

correcting the bed candidate area based on a disposition of the second line segment,

wherein the specifying includes specifying, as a part of the bed candidate area, a second part including one of short sides of the bed candidate area, the one of short sides corresponding to a head board attached to one end of a bed,

wherein the head board has a certain thickness in a longitudinal direction of the bed candidate area, and wherein the setting includes setting, to the search range, an area surrounded by lines, the lines including a long side of the bed candidate area after rotation in which the bed candidate area is rotated by an angle depending on the thickness of the head board around a point corresponding to a midpoint of the one of short sides corresponding to a short side of the bed to which the head board is attached.

10. The bed area extraction method according to claim 9 , wherein the second part corresponding to the head board is a U-shaped portion.

11. The bed area extraction method according to claim 9 , further comprising: acquiring a contour segment in the search range, the contour segment being determined to be a part of a contour of the bed in a case where an inclination of the contour segment with respect to a long side of the bed candidate area is equal to or larger than a predetermined angle, wherein the correcting includes correcting the bed candidate area in a case where the contour segment is acquired.

12. The bed area extraction method according to claim 9 , further comprising: wherein the setting includes setting a search range for each of the long sides of the bed candidate area, and wherein the correcting includes correcting the bed candidate area in a case where the contour segment is acquired from each of the set search ranges when an angular difference between the inclination of the contour segment and a rotation angle of the bed candidate area is less than a predetermined value.

13. A bed area extraction apparatus, comprising:

a processor configured to:

specify a first part of a bed candidate area in an image based on first line segments which are extracted from the image;

set a search range for searching a second line segment with reference to the bed candidate area which is determined based on the specified first part of the bed candidate area;

select the second line segment from among one or more first line segments, which are included in the first line segments and the search range, based on a disposition of the one or more first line segments; and

correct the bed candidate area based on a disposition of the second line segment,

wherein the processor is configured to specify, as a part of the bed candidate area, a second part including one of short sides of the bed candidate area, the one of short sides corresponding to a head board attached to one end of a bed,

wherein the head board has a certain thickness in a longitudinal direction of the bed candidate area, and wherein the computer configured to set, to the search range, an area surrounded by lines, the lines including a long side of the bed candidate area after rotation in which the bed candidate area is rotated by an angle depending on the thickness of the head board around a point corresponding to a midpoint of the one of short sides corresponding to a short side of the bed to which the head board is attached.

14. The bed area extraction apparatus according to claim 13 , wherein the part including one of the short sides of the bed candidate area corresponding to the head board is a U-shaped portion.