Optically scanned data forms an image stored in a computer memory represented as an array having at least two dimensions. The stored image is subjected to virtual scanning. Thus a subset of the array is defined as a portion of the image having first and second dimensions. The value of the subset is derived, the subset is then incremented, and the value of the incremented subset is determined. The steps of incrementing and deriving the value of the incremented subset are repeated. The derived values of the data are compared to a calibrated standard, to create adjusted values of data. The adjusted data values, in the case of electrophoresis, represent the scanned sample which has been subjected to electrophoresis. Thereafter, the adjusted data values can be integrated or otherwise processed.