Nonlinear Techniques for Color Image Processing - Nonlinear Signal and Image Processing: Theory, Methods and Applications - page 496

(a) (b) (c)

FIGURE 12.16
Comparison of efficiency of the vector median with the DPAF: (a) test image (part of a scanned
map); (b) VMF (3 × 3mask); (c) DPAF ( β = 20 , α = 1 . 25 , η = 2; 3 iterations).

even enhanced. The VMF gives much worse results: raster texture is still
visible and image details are blurred.
Table 12.4 and Table 12.5 indicate that the new filters yield especially good
results in the case of images corrupted by mixed Gaussian and impulsive
noise. In addition to excellent noise attenuation properties, the new filters
restore the noisy images so that they have well-preserved and even enhanced
edges and corners, which make them interesting for many different computer
vision applications (Figure 12.17).
The best results for the Gaussian and mixed noise attenuation for the ma-
jority of existing filters were obtained after many iterations, while for filters
based on the digital paths concept the best results were achieved in the second
or third iteration (see Figure 12.15).
The comparison of the new filters' efficiency with some of the standard
filters is presented in Figure 12.14, where for different filters, the PSNR and
NCD dependence on the amount of mixed impulsive and Gaussian noise is
shown. As the intensity of the noise increases, the quantitative results obtained
using the new filters become significantly better than those obtained by the
standard filters (AMF, VMF, DDF).