Geometric transformation matrix estimating device, geometric transformation matrix estimating method, and program

A computer-implemented method for determining aspects of a shape representing a plane region in a space, the method comprising:

• receiving an input image, wherein the input image includes a shape with a side;
• identifying, based on a plurality of line segments in the input image, an original set of line segments;
• generating a first set of line segments from the original set of line segments, wherein the first set of line segments includes line segments that are either in parallel or perpendicular to a side of the shape in the input image;
• generating a remainder portion of line segments from the original set of line segments, wherein the remainder portion of line segments and the first set of line segments are distinct;
• generating, based on an angle of the first set of line segments relative to a reference direction of the input image as a rotational angle, affine transformation matrix data;
• generating, based on line segments that are either in parallel or perpendicular to the side of the shape in the input image and line segments obtained by transforming the remainder portion of line segments using the affine transformation matrix, a second set of line segments;
• determining, based on two line segments from the second set of line segments and upper and lower ends or left and right ends of the input image, a set of four intersection points;
• generating, based on correspondence between the determined set of four intersection points and four vertices of the shape in a reference image, a homography matrix;
• and
• determining, based on the homography matrix and the affine transformation matrix, the geometric transformation matrix.

A system for determining aspects of a shape representing a plane region in a space, the system comprises:

• a processor;
• and
• a memory storing computer-executable instructions that when executed by the processor cause the system to:
• receive an input image, wherein the input image includes a shape with a side;
• identify, based on a plurality of line segments in the input image, an original set of line segments;
• generate a first set of line segments from the original set of line segments, wherein the first set of line segments includes line segments that are either in parallel or perpendicular to a side of the shape in the input image;
• generate a remainder portion of line segments from the original set of line segments, wherein the remainder portion of line segments and the first set of line segments are distinct;
• generate, based on an angle of the first set of line segments relative to a reference direction of the input image as a rotational angle, affine transformation matrix data;
• generate, based on line segments that are either in parallel or perpendicular to the side of the shape in the input image and line segments obtained by transforming the remainder portion of line segments using the affine transformation matrix, a second set of line segments;
• determine, based on two line segments from the second set of line segments and upper and lower ends or left and right ends of the input image, a set of four intersection points;
• generate, based on correspondence between the determined set of four intersection points and four vertices of the shape in a reference image, a homography matrix;
• and
• determine, based on the homography matrix and the affine transformation matrix, the geometric transformation matrix.

A computer-readable non-transitory recording medium storing computer-executable instructions that when executed by a processor cause a computer system to:

• receive an input image, wherein the input image includes a rectangle with a side;
• identify, based on a plurality of line segments in the input image, an original set of line segments;
• generate a first set of line segments from the original set of line segments, wherein the first set of line segments includes line segments that are either in parallel or perpendicular to a side of the rectangle in the input image;
• generate a remainder portion of line segments from the original set of line segments, wherein the remainder portion of line segments and the first set of line segments are distinct;
• generate, based on an angle of the first set of line segments relative to a reference direction of the input image as a rotational angle, affine transformation matrix data;
• generate, based on line segments that are either in parallel or perpendicular to the side of the rectangle in the input image and line segments obtained by transforming the remainder portion of line segments using the affine transformation matrix, a second set of line segments;
• determine, based on two line segments from the second set of line segments and upper and lower ends or left and right ends of the input image, a set of four intersection points;
• generate, based on correspondence between the determined set of four intersection points and four vertices of the rectangle in a reference image, a homography matrix;
• and
• determine, based on the homography matrix and the affine transformation matrix, the geometric transformation matrix.