public function trainPoint(imgPtr:int, id:int, x:int, y:int, stride:int):void
        {
            var idx_ptr:int = ferns.leaves_index;
            var nf:int = numFerns;
            ferns.drop(imgPtr, x, y, stride);

            var ptr:int = __cint(number_of_samples_for_class + (id << 2));
            Memory.writeInt(__cint(Memory.readInt(ptr) + 1), ptr);

            for(var i:int = 0; i < nf; ++i)
            {
                ptr = __cint( leaves_counters + ((i * step2 + Memory.readInt(idx_ptr) * step1 + id) << 1) );
                Memory.writeShort(__cint(Memory.readUnsignedShort(ptr) + 1), ptr);
                idx_ptr = __cint(idx_ptr + 4);
            }
        }