the algorithm detect face image work realtime develop Paul Viola Michael Jones 2001 a algorithm procedure compute Haar feature as task consider simplify model conceptlet consider rectangular image represent table size nm the table element integer specify brightness pixel imageA feature rectangular table size nm each cell feature paint black whiteTo calculate value give feature give image perform follow step first table feature table image rotation reflection pixel entirely cover black white cell the value feature image value WB W total brightness pixel image cover white feature cell b total brightness pixel cover black feature cellssome example popular Haar feature give your task determine number operation require calculate feature socalled prefix rectanglesA prefix rectangle rectangle image upper leave corner coincide upper leave corner imageYou variable value value initially zero in operation count sum pixel value prefix rectangle multiply integer add variable valueyou give feature it necessary calculate minimum number operation require calculate value attribute arbitrary image for well understanding statement read explanation sample