1. A method of detecting and correcting blur in a digital image stored in a digital file as a sequence of DCT coefficients arranged in a plurality of blocks representing a grid of frequency components, each said block representing a portion of said image, said method comprising: (a) reading a plurality of DCT coefficients from said sequence of DCT coefficients, said plurality of DCT coefficients comprising at least two DCT coefficients from each of said plurality of blocks; (b) calculating from said plurality of DCT coefficients a first blur indicator that quantifies the amount of blur in the block having the least amount of blur among all of said plurality of blocks; (c) calculating from said plurality of DCT coefficients a second blur indicator that quantifies the amount of blur throughout said digital image; and (d) selectively applying a filter to said digital image based upon the value of said first blur indicator and said second blur indicator.