Digital Signal Processing Reference
In-Depth Information
Figure 6.9. Visual comparison of term-by-term (hard and soft) and block threshold-
ing on “Barbara” 512×512. (a) Original. (b) Noisy
σ
= 20. (c, f, i) Block denois-
ing (threshold
λ
∗
= 4
.
50524) with, respectively, DWT (PSNR = 28.04 dB), UDWT
(PSNR = 29.01 dB), and DCTG2 (PSNR = 30 dB). (d, g, j) Term-by-term hard thresh-
olding (threshold = 3
σ
) with, respectively, DWT (PSNR = 25.6 dB), UDWT (PSNR =
27.3 dB), and DCTG2 (PSNR = 28.93 dB). (e, h, k) Term-by-term soft thresholding
(threshold =
√
3
σ
) with, respectively, DWT (PSNR = 26.03 dB), UDWT (PSNR =
26.84 dB), and DCTG2 (PSNR = 28.24 dB).
