Preprocessing Operations
Dana H. Ballard · Birkhäuser Basel eBooks · 1976
In the appendix we describe the transformation of the image from á film transparency to an array of pixels. In this chapter we describe the preprocessing operations applied to that array. A preprocessing operation is one which modifies the scanned array of pixels in some way to facilitate subsequent processing. Characteristics of such an operation are that a) it is simple and b) it leaves the form of the image unchanged i.e. the resultant data structure is an array of numbers. The three types of preprocessing operations used in this dissertation are: a) consolidation, b) high frequency emphasis filtering and c) gradient processing. All these operations have parameters which specify the range of output images. The best way to choose values for these parameters would be to first define operations to achieve the desired characteristics of the preprocessed image. Then the transfer function for these cascaded operations should be derived and optimized. But because this task is difficult, it is not attempted in this dissertation.