Foreground and background detection method

An imaging device for taking a chronological sequence of images comprising a data processing device configured to assign a pixel from an image of said chronological sequence of images to one of a foreground pixel set and a background pixel set using asynchronous semantic post processing to improve motion detection by the imaging device by reducing the rate of false positives, in which false positives represent an erroneous assignment of pixels to the foreground pixel set due to one or more of dynamic backgrounds, ghosting, shadows, reflections, camera jitter, panning, tilting, zooming, inclement weather, gradual or sudden lighting changes and background displacement in the sequence of images being taken by the imaging device, said data processing device being programmed to:

• initialize a baseline probability for the pixel as equal to a probability that a corresponding pixel in an initial image of the chronological sequence of images belongs to a foreground relevant object, said probability being calculated according to a semantic segmentation algorithm;
• assign the pixel to the background pixel set if the probability that the pixel belongs to a foreground-relevant object does not exceed a first predetermined threshold;
• assign the pixel to the foreground pixel set if the probability that the pixel belongs to a foreground-relevant object exceeds the first predetermined threshold and a difference between the probability that the pixel belongs to a foreground-relevant object and the baseline probability for the pixel equals or exceeds a second predetermined threshold;
• use a background subtraction algorithm to assign the pixel to the foreground pixel set or to the background pixel set if the probability that the pixel belongs to the foreground-relevant object exceeds the first predetermined threshold and a difference between the probability that the pixel belongs to a foreground-relevant object and the baseline probability for the pixel is lower than a second predetermined threshold;
• and
• use said asynchronous semantic post processing to assign the pixel to the foreground pixel set or the background pixel set according to the last enforced assignment provided by semantic segmentation algorithm for the given pixel position when an assignment rate of the semantic segmentation algorithm is too slow to calculate the probability that said pixel position belongs to a foreground-relevant object.

A non-transitory data storage medium comprising a set of instructions configured to be read by a data processing device, the set of instructions including a plurality of steps to be undertaken to assign a pixel, from an image of a chronological sequence of images taken by an imaging device, to one of a foreground pixel set and a background pixel set using asynchronous semantic post processing to improve motion detection by the imaging device, said plurality of steps in the set of instructions including initializing a baseline probability for the pixel as equal to a probability that a corresponding pixel in an initial image of the chronological sequence of images belongs to a foreground relevant object, said probability being calculated according to at a semantic segmentation algorithm;

• assigning the pixel to the background pixel set if the probability that the pixel belongs to a foreground-relevant object does not exceed a first predetermined threshold;
• assigning the pixel to the foreground pixel set if the probability that the pixel belongs to a foreground-relevant object exceeds the first predetermined threshold and a difference between the probability that the pixel belongs to a foreground-relevant object and the baseline probability for the pixel equals or exceeds a second predetermined threshold;
• using a background subtraction algorithm to assign the pixel to the foreground pixel set or to the background pixel set if the probability that the pixel belongs to the foreground-relevant object exceeds the first predetermined threshold and a difference between the probability that the pixel belongs to a foreground-relevant object and the baseline probability for the pixel is lower than a second predetermined threshold;
• using said asynchronous semantic post processing to assign the pixel to the foreground pixel set or the background pixel set according to a last enforced assignment provided by the semantic segmentation algorithm for a given pixel position when an assignment rate of the semantic segmentation algorithm is too slow to calculate the probability that said pixel position belongs to a foreground-relevant object;
• wherein the steps performed by the data processing device according to the set of instructions reduce a rate of false positives which represent an erroneous assignment of pixels to the foreground pixel set due to one or more of dynamic backgrounds, ghosting, shadows, reflections, camera jitter, panning, tilting, zooming, inclement weather, gradual or sudden lighting changes and background displacement in the sequence of images taken by the imaging device.