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ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

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pyramid. This pyramid is built by using the Gaussian filter and the derivation. A<br />

detailed description of the construction of the contrast pyramid is presented in [5].<br />

2.4 Synthetic image reconstruction<br />

In order to investigate the quantitative performance of the selected methods, an image<br />

with artificial speckle noise was employed. A synthetic speckled image used in [14]<br />

and modeled as d = f.v is commonly used where f is a reference noise-free image, and<br />

v is a unit mean random field.<br />

3. RESULTS<br />

a b c d<br />

e f g<br />

Figure 2. Synthetic image used to show the quality of filters used in this study. 2a. a noise free synthetic<br />

image. 2b. synthetic image after noise multiplication. 2c. filtering of 2b by WST method. 2d: filtering of<br />

2b by contrast enhancement method. In 2e shows the error map between the noisy image and the noise<br />

free one. In 2f. shows the error map between 2a and 2c. Figure 2g. shows the error map between 2a and<br />

2d.<br />

In figure 2a a synthetic image without any noise is presented. In 2b a generated noise<br />

with SNR of 8.3 db is shown. In 2c the result obtained with WST filter with proposed<br />

thresholding an SNR of 15.8 db was obtained from this image. In 2d the result from<br />

contrast enhancement method the SNR calculated from this image is 11.3 dB. Another<br />

criterion which was evaluated is the absolute difference (error) between the noise free<br />

image and the other three. This error image (map) shows us the location of error in the<br />

filtered image, if the resulting error map is all black (zeros) the implication is that the<br />

filtering is ideal. The image in 2.e shows resulting image of the difference between<br />

noisy and noise-free image, this difference shows the error image or the noise<br />

distribution and intensity. Figure 2.f shows error map between the filtered image using<br />

SWT method and the noise free one. Figure 2.g shows the error map between the<br />

contrast filtered image and the noise-free one. The table 1 summarizes the quantitative<br />

measure used for all three error maps.<br />

4

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