The core of this sample illustrates feature extraction for image processing. Using the edge information of each video frame allows you to estimate whether the current camera scene is blocked/tampered by the others or not. The modern academic community introduces many Edge Detection theories, for instance, Sobel operator and Canny Edge detector. Here, the Canny Edge detector is applied.
The pictures below show the result of using the edge detection algorithm for gathering edge information of an input image:
The next step is to quantize the edge image and then define a threshold value to judge whether a tampering event occurred or not. The significant difference between the original image and the edge one indicates that something is placed in front of a camera. The figure below illustrates the sample flowchart.
The further work is to combine this concept with OpenVX*. Since the concept is not complex, the implementation by OpenVX is not needed. This sample associates with the Motion Detection sample to demonstrate functionality of both algorithms together.