Method and system for converting privacy zone planar images to their corresponding pan/tilt coordinates

A method for establishing a privacy zone in a video security system, the method comprising:

• receiving planar coordinate data defining a plurality of privacy zone corner points, the planar coordinate data taken from a still image, the still image having a focal length substantially equal to an image field of view at lx zoom divided by a current zoom magnification, the focal length being equal to the radius of the sphere, each privacy zone corner point being defined by respective Cartesian coordinates x and y;
• converting each privacy zone corner point to corresponding points on a sphere based on an origin point, the points on the sphere being defined by spherical coordinates, each of the spherical coordinates including a radius, a polar angle and an azimuth angle, where:
• if the Cartesian coordinate y is one of greater than zero and equal zero, the radius of the point on the sphere is determined to be equal to the radius of the origin point;
• and
• if the Cartesian coordinate y is less than zero, the radius of the point on the sphere is determined to be equal to a multiple of the radius of the origin point, the multiple being based on at least one of a vertical field of view, a zoom factor, and a screen height;
• converting each of the corresponding spherical coordinates to corresponding pan/tilt coordinates;
• and
• storing the corresponding pan/tilt coordinates in a storage device.

A camera surveillance system comprising:

• a pan/tilt/zoom (PTZ) camera assembly configured to:
• capture a first video stream;
• obtain a still image from the first video stream;
• a processor in communication with the PTZ camera assembly, the processor configured to:
• receive planar coordinate data corresponding to the privacy zone defined by a plurality of privacy zone corner points on the still image from the first video stream;
• covert each privacy zone corner point to corresponding points on a sphere based on an origin point, the points on the sphere and origin point being defined by spherical coordinates including a radial distance, a polar angle and an azimuth angle, where:
• if the azimuth angle between the point on the sphere and the origin point is less than 180 degrees, the radius of the point on the sphere is determined to be equal to the radius of the origin point;
• and
• if the azimuth angle between the point on the sphere and the origin point is not less than 180 degrees, the radius of the point on the sphere is determined to be equal to a multiple of the radius of the origin point, the multiple being based on at least one of a vertical field of view, a zoom factor and a screen height;
• convert each of the spherical coordinates to corresponding pan/tilt coordinates;
• cause a motor of a Pan Tilt Zoom (PTZ) camera to move according to the corresponding pan/tilt coordinates such that the privacy corner points appear in a second video stream;
• the pan/tilt/zoom (PTZ) camera assembly further configured to:
• capture the second video stream after the motor of the PTZ camera is caused to move according to the pan/tilt coordinates;
• the processor is further configured to:
• apply the privacy zone to the second video stream;
• and
• cause transmission of the second video stream with the applied privacy zone for display.

A non-transitory computer readable medium storing a computer program which when executed performs a method for converting a privacy zone point on a still image to its corresponding pan tilt coordinates, the method comprising:

• capturing a first video stream;
• obtaining a still image from the first video stream;
• receiving planar coordinate data corresponding to the privacy zone defined by a plurality of privacy zone corner points on the still image from the first video stream;
• converting each privacy zone corner point to corresponding points on a sphere based on an origin point, the points on the sphere and the origin point being defined by spherical coordinates including a radial distance, a polar angle and an azimuth angle, where:
• if the azimuth angle between the point on the sphere and the origin point is less than 180 degrees, the radius of the point on the sphere is determined to be equal to the radius of the origin point;
• and
• if the azimuth angle between the point on the sphere and the origin point is not less than 180 degrees, the radius of the point on the sphere is determined to be equal to a multiple of the radius of the origin point, the multiple being based on at least one of a vertical field of view, a zoom factor and a screen height;
• converting each of the corresponding spherical coordinates to corresponding pan/tilt coordinates;
• and
• causing a motor of a Pan Tilt Zoom (PTZ) camera to move according to the corresponding pan/tilt coordinates such that the privacy corner points appear in a second video stream;
• capturing the second video stream after the motor of the PTZ camera is caused to move according to the pan/tilt coordinates;
• applying the privacy zone to the second video stream;
• and
• transmitting the second video stream with the applied privacy zone for display.