Fig. 2.
Example shrinkage functions, x̂(y) = y + yΣgθ(y), for various subbands of an undecimated Haar decomposition, as optimized for SURE in the subband domain (dashed line) and in the image domain (solid line). For midrange bands (a)–(c), the image-domain estimation functions show more shrinkage of low amplitude coefficients, with a compensatory amplification of midrange values. The high frequency band (d) shows more shrinkage. Note that all functions are equal to the identity for large values, beyond the location of the last bump.