1. A method for detecting a region in a digital image, said method comprising: a) in a region-detection system, applying a masking condition to a digital image thereby identifying masked pixels that satisfy said masking condition; b) in a feature extractor in said region-detection system, calculating an entropy feature associated with a pixel-of-interest in said digital image, wherein said calculating said entropy feature comprises: i) quantizing, according to a first quantization, a plurality of pixel values associated with a plurality of pixels in a region surrounding said pixel-of-interest, wherein said plurality of pixels in said region surrounding said pixel-of-interest does not include said masked pixels; ii) forming a first histogram of said first-quantization quantized pixel values; iii) calculating a first entropy measure for said first histogram; iv) quantizing, according to a second quantization, said plurality of pixel values associated with said plurality of pixels in said region surrounding said pixel-of-interest; v) forming a second histogram of said second-quantization quantized pixel values; and vi) calculating a second entropy measure for said second histogram; and c) classifying a neighborhood of said digital image based on a combination of said first entropy measure and said second entropy measure and said pixel-of-interest location.