1. A method for classifying a pixel in a digital image, said method comprising: a) determining a pixel of interest in a digital image; b) evaluating a large-text-character condition for said pixel of interest and a first region substantially proximate to said pixel of interest, said first region comprising a first plurality of pixels and an associated first local background color estimate; c) classifying said pixel of interest as a first-category pixel when said large-text-character condition is satisfied; d) computing a dynamic threshold when said large-text-character condition is not satisfied, wherein said dynamic threshold is based on the color values in a second region substantially proximate to said pixel of interest, said second region comprising a second plurality of pixels and an associated second local background color estimate; e) calculating a first similarity measure between said second local background color estimate and the color of said pixel of interest; f) classifying said pixel of interest as a first-category pixel when said first similarity measure is greater than said dynamic threshold; and g) classifying said pixel of interest as a second-category pixel when said first similarity measure is not greater than said dynamic threshold.