Image processing apparatus, electronic medium, and image processing method

1. An image processing apparatus, comprising:

a storage unit storing an image of a processing target;

a tangent calculating unit extracting contours represented as sets of contour points from an image read from the storage unit and computing tangents with respect to the extracted contours;

a projecting unit projecting tangents computed by the tangent calculating unit to axes in the direction orthogonal to the corresponding tangent, and computing coordinates of intersections where the tangents and the corresponding axes intersect; and

a rectangle calculating unit selecting intersections with maximum values and minimum values of coordinates among intersections computed by the projecting unit for each direction of the axis, and computing a rectangle formed by a pair of parallel tangents passing through two intersections with maximum values and minimum values selected for a first axis and another pair of tangents passing through two intersections with maximum values and minimum values selected for a second axis orthogonal to the first axis.

2. The image processing apparatus according to claim 1 ,

wherein the tangent calculating unit computes a tangent in each of sections which are computed by dividing the contour into predetermined lengths.

3. The image processing apparatus according to claim 1 ,

wherein the tangent calculating unit computes a tangent for each of contour points on the contours.

4. The image processing apparatus according to claim 1 ,

wherein the tangent calculating unit comprises:

a contour tracing unit tracing contour points on the contour sequentially starting from a certain position on the contour;

a tangent range determining unit determining a direction in which the tangent is to be drawn, according to the tracing result of each contour point traced by the contour tracing unit; and

an in-range tangent calculating unit computing the tangent from the contour in the range of angles determined by the tangent range determining unit.

5. The image processing apparatus according to claim 4 ,

wherein the in-range tangent calculating unit comprises a tangent candidate enumerating unit chooses the direction of the tangent candidates from N directions dividing 360 degree evenly.

6. The image processing apparatus according to claim 1 , further comprising:

a weight calculating unit calculating a weight for each of the contours; and

a projection calculating unit calculating a projection of the image in each direction from a weights of contours calculated by the weight calculating unit and minimum bounding rectangles corresponding to the contours calculated for multiple directions by the rectangle calculating unit.

7. The image processing apparatus according to claim 6 , further comprising,

a character row estimating unit estimating the direction of a character row based on projections in multiple directions calculated by the projection calculating unit.

8. A non-transitory electronic medium configured to store an image processing program to execute image processes in an image processing apparatus, the image processing program providing functions of the image processing apparatus, the functions including: reading an image from a storage unit, extracting contours represented as sets of contour points from the read image, and computing tangents to the extracted contours; projecting computed tangents to an axes orthogonal to the tangents, and computing coordinates of an intersections where the tangents intersect the axis; and

selecting intersections with maximum values and minimum values of coordinates among intersections computed by the projecting unit for each direction of the axis, and computing a rectangle formed by a pair of parallel tangents passing through two intersections with maximum values and minimum values selected for a first axis and another pair of tangents passing through two intersections with maximum values and minimum values selected for a second axis orthogonal to the first axis.

9. An image processing method in an image processing apparatus having a storage unit storing an image of a processing target, the image processing method comprising:

extracting a contour represented as an sets of contour points from an image read from the storage unit and computing a tangents with respect to the extracted contours;

projecting a computed tangents to an axes orthogonal to the tangents, and computing coordinates of an intersections where the tangents intersect the axis; and

selecting intersections with maximum values and minimum values of coordinates among intersections computed by the projecting unit for each direction of the axis, and computing a rectangle formed by a pair of parallel tangents passing through two intersections with maximum values and minimum values selected for a first axis and another pair of tangents passing through two intersections with maximum values and minimum values selected for a second axis orthogonal to the first axis.

10. The image processing method according to claim 9 , further comprising,

computing a tangent in each of sections which are obtained by dividing the contour into predetermined lengths.

11. The image processing method according to claim 9 , further comprising,

computing a tangent for each of contour points on the contours.

12. The image processing method according to claim 9 , further comprising:

tracing contour points on the contour sequentially from a certain position on the contour;

determining a direction in which the tangent is to be drawn, according to the tracing result of each traced contour point; and

computing the tangent from the contour in the determined range of angles.

13. The image processing method according to claim 12 , further comprising,

choosing the direction of the tangent candidates from N directions dividing the 360 degree evenly.

14. The image processing method according to claim 9 , further comprising:

calculating a weight for each of the contours; and

calculating a projection of the image in each direction from a calculated weights of contours and minimum bounding rectangles corresponding to the contours calculated for multiple directions.

15. The image processing method according to claim 14 , further comprising,

estimating the direction of a character row based on calculated projections in multiple directions.