Image processing system

An image processor operable to receive a video signal from a camera representative of a scene as viewed by the camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern comprising a plurality of alternately coloured elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the coloured elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and on the calibration surface, the first group of lines being orthogonal to the second group of lines, the image processor being operable

• to detect from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern,
• to extrapolate the lines from each group of lines to determine a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of scene as viewed by the camera at which the extrapolated lines from the second group intersect, and
• to estimate from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein the detection of the corner locations by the image processor comprises identifying from the video signal a plurality of potential corner locations, defining an area of the scene as viewed by the camera centred around each potential corner location, analysing a colour of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location.

A method of estimating camera parameters from a captured image, the method comprising

• generating a video signal representative of a scene as viewed by a camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern comprising a plurality of alternately coloured elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the coloured elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and with respect to the calibration surface, the first group of lines being orthogonal to the second group of lines,
• detecting from the video signal at least some of the corner locations and to identify the first and second group of lines of the calibration pattern,
• extrapolating the lines from each group of lines,
• determining from the extrapolated lines a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of the scene as viewed by the camera at which the extrapolated lines from the second group intersect,
• estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein the detecting the corner locations, comprises
• identifying from the video signal a plurality of potential corner locations,
• defining an area of the scene as viewed by the camera centred around each potential corner location, and
• analysing a colour of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location.

A computer graphics generation system, comprising

• a camera for generating video images of a scene captured by the camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern comprising a plurality of alternately coloured elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the coloured elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and on the calibration surface, the first group of lines being orthogonal to the second group of lines, and
• an image processor arranged in operation to receive the video signal from the camera, and to combine the video images with rendered computer generated objects, the computer generated objects being rendered in accordance with a position and orientation of the camera determined by
• detecting from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern,
• extrapolating the lines from each group of lines to determine a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of scene as viewed by the camera at which the extrapolated lines from the second group intersect, and
• estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein
• the detection of the corner locations by the image processor comprises identifying from the video signal a plurality of potential corner locations, defining an area of the scene as viewed by the camera centred around each potential corner location, analysing a colour of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location.

A computer program product having computer executable instructions stored on a storage medium, which when loaded on to a computer causes the computer to perform a method of estimating camera parameters from a captured image, the method comprising

• generating a video signal representative of a scene as viewed by a camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern comprising a plurality of alternately coloured elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the coloured elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and with respect to the calibration surface, the first group of lines being orthogonal to the second group of lines,
• detecting from the video signal at least some of the corner locations and to identify the first and second group of lines of the calibration pattern,
• extrapolating the lines from each group of lines,
• determining from the extrapolated lines a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of the scene as viewed by the camera at which the extrapolated lines from the second group intersect,
• estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein the detecting the corner locations comprises
• identifying from the video signal a plurality of potential corner locations,
• defining an area of the scene as viewed by the camera centred around each potential corner location, and
• analysing a colour of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location.

An apparatus for estimating camera parameters from a captured image, the apparatus comprising

• means for generating a video signal representative of a scene as viewed by a camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern comprising a plurality of alternately coloured elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the coloured elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and with respect to the calibration surface, the first group of lines being orthogonal to the second group of lines,
• means for detecting from the video signal at least some of the corner locations and to identify the first and second group of lines of the calibration pattern,
• means for extrapolating the lines from each group of lines,
• means for determining from the extrapolated lines a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of the scene as viewed by the camera at which the extrapolated lines from the second group intersect,
• means for estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein the means for detecting the corner locations comprises
• means for identifying from the video signal a plurality of potential corner locations,
• means for defining an area of the scene as viewed by the camera centred around each potential corner location, and
• means for analysing a colour of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location.