Pre-processing 개념

Before a computer vision method can be applied to image data in order to extract some specific piece of information, it is usually necessary to process the data in order to assure that it satisfies certain assumptions implied by the method. Examples are 

Re-sampling in order to assure that the image coordinate system is correct.

Noise reduction in order to assure that sensor noise does not introduce false information.

Contrast enhancement to assure that relevant information can be detected.

Scale-space representation to enhance image structures at locally appropriate scales.
http://en.wikipedia.org/wiki/Computer_vision