| 摘要 |
<p>A sequence of complete video frames (V1) to (Vn) are compared with a corresponding sequence of mask frames (M1) to (Mn) according to an automatic background extraction process (55) to from a single background frame (60). Each mask frame (M1) to (Mn) includes an opaque part (51) and a transparent part (52). Each frame comprises MxN pixels arranged in (M) columns 1,2,3,…,M and (N) rows 1,2,3,… ,N. Where a pixel takes the value associated with transparency, it indicates that the corresponding pixel in the corresponding complete video frame is a visible background pixel. Similarly, where a pixel in a mask frame takes the corresponding to an opaque pixel, it indicates that the corresponding pixel in the corresponding complete video frame is a pixel associated with the foreground 'object'. All of the mask frames (M1) to (Mn) are considered in turn to identify all of the background pixels visible in at least one complete video frame of the sequence. As soon as a background pixel is visible for the first time, the value of the background pixel (ie brightness, colour, etc) at that time is stored in a reference background frame until all possible pixels within the reference background frame have been set to the corresponding values of background pixels in the complete video frames at which point the reference background frame is outputted as the single background frame (60).</p> |
