code: void growCellArray(int imageWidth, int imageHeight) {
  		cellCols = imageWidth/ pixelsPerCell;
  		cellRows = imageHeight/ pixelsPerCell;
  
  		if( cellRows*cellCols > cells.length ) {
  			Cell[] a = new Cell[cellCols*cellRows];
  
  			System.arraycopy(cells,0,a,0,cells.length);
  			for (int i = cells.length; i < a.length; i++) {
  				a[i] = new Cell();
  				a[i].histogram = new float[ orientationBins ];
  			}
  			cells = a;
  		}
  	}
docs: Determines if the cell array needs to grow.  If it does a new array is declared.  Old data is recycled when
  possible