Table 4 Mean values of the optimal SURE LD-SigShrink parameters, for the denoising of the "Lena" image corrupted by AWGN. The DWT with the "sym8" wavelet is used. The SURE LD-SigShrink parameters are obtained by applying a SURE optimization at every detail (Hori. for Horizontal, Vert. for Vertical, Diag. for Diagonal) subimage located at the different resolution levels concerned. We remark first that the threshold height, as well as the attenuation degree, tends to be increasing functions of the noise standard deviation . In addition, for every considered, the attenuation degree as well as the threshold tends to decrease when the resolution level increases.

Hori.

Vert.

Diag.

Hori.

Vert.

Diag.

0.2864

0.2738

0.3172

3.1072

2.3829

4.2136

0.2298

0.1722

0.3057

1.8747

1.4181

2.1687

0.0863

0.0657

0.1868

0.7361

0.4852

1.3251

0.1154

0.1558

0.4071

0.4957

0.4867

1.4383

Hori.

Vert.

Diag.

Hori.

Vert.

Diag.

0.5397

0.4517

0.9361

4.9893

4.0930

4.6560

0.4209

0.3767

0.4641

2.9436

2.4534

3.1053

0.2622

0.1794

0.3481

1.9541

1.3087

2.2195

0.2128

0.3161

0.4528

1.0539

1.0125

1.8657

Hori.

Vert.

Diag.

Hori.

Vert.

Diag.

0.8934

0.5412

0.9712

4.5129

5.0167

4.4367

0.4633

0.4217

0.5209

3.5723

2.8134

3.8653

0.3294

0.2642

0.4135

2.4032

1.7920

2.5764

0.2644

0.3264

0.4655

1.5004

1.3231

2.0720

Hori.

Vert.

Diag.

Hori.

Vert.

Diag.

0.8772

0.8785

0.9575

4.6843

4.5268

4.6499

0.4963

0.4389

0.5746

4.2031

3.2062

4.5700

0.3643

0.2745

0.4424

2.6642

1.9881

2.8343

0.2700

0.3119

0.4743

1.6543

1.3744

2.2185