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Three fidelity criteria in image enhancement

The crucial issue in image quality enhancement is the fidelity issue. Three fidelity criteria (3FC) are proposed in image quality enhancement. FC 1 is that the information entropy of the enhanced image should not be bigger than the original image. FC 2 is that the constituents of the enhanced image should not be bigger than the original. FC 3 that the color relationship in the enhanced image is not changed when comparing with the original. Our studies point out that the image enhancement methods based on histogram equalization and Retinex do not meet three fidelity criteria in image quality enhancement.