Motion History Images
# Motion History Images

The motion history image (MHI) is a static image template helps in understanding the motion location and path as it progresses. In MHI, the temporal motion information is collapsed into a single image template where intensity is a function of recency of motion. Thus, the MHI pixel intensity is a function of the motion history at that location, where brighter values correspond to a more recent motion. Using MHI, moving parts of a video sequence can be engraved with a single image, from where one can predict the motion flow as well as the moving parts of the video action.

Some important features of the MHI representation are:

* It represents motion sequence in a compact manner. In this case, the silhouette sequence is condensed into a grayscale image, where dominant motion information is preserved.
* MHI can be created and implemented in low illumination conditions where the structure cannot be easily detected otherwise.
* The MHI representation is not so sensitive to silhouette noises, holes, shadows, and missing parts.
* The gray-scale MHI is sensitive to the direction of motion because it can demonstrate the flow direction of the motion.
* It keeps a history of temporal changes at each pixel location, which then decays over time.
* The MHI expresses the motion flow or sequence by using the intensity of every pixel in a temporal manner.
