12
10
8
12
45
23
10
64
12
10
50
Biomedical Signal and Image Processing
(a)
(b)
FIGURE 3.11 (a) Original image and (b) image after applying low-pass filter.
3.3.2 MEDIAN FILTERS
Median filters are statistical nonlinear filters that are often described in the space
domain. Median filters are known to reduce the noise without eliminating the edges and
other high-frequency contents. Median filters (also referred to as order statistics filters)
perform the following operations to find each pixel value in the processed image:
Step 1: All pixels in the neighborhood of the pixel in the original image (identified
by the mask) are inserted in a list.
Step 2: This list is sorted in ascending (or descending) order.
Step 3: The median of the sorted list (i.e., the pixel in the middle of the list) is
chosen as the pixel value for the processed image.
As defined earlier, median filter create pixel values of the filtered image based on the sorting of the gray level of pixels in the mask around the central pixels in the original image.
Example 3.5
The performance of a 3 × 3 median filter on a subimage is illustrated in Figure 3.12.
As can be seen from Figure 3.12, the median filter selects the median of the graylevel values in the 3 × 3 neighborhood of the central pixel and assigns this value as
the output. In this example, the median filter is to select the median of following set:
{8 10 10 12 12 23 45 64}. According to the sorted list, the response of the filter is 12.
FIGURE 3.12 Mask of median filter.
10
8
12
45
23
10
64
12
10
50
Biomedical Signal and Image Processing
(a)
(b)
FIGURE 3.11 (a) Original image and (b) image after applying low-pass filter.
3.3.2 MEDIAN FILTERS
Median filters are statistical nonlinear filters that are often described in the space
domain. Median filters are known to reduce the noise without eliminating the edges and
other high-frequency contents. Median filters (also referred to as order statistics filters)
perform the following operations to find each pixel value in the processed image:
Step 1: All pixels in the neighborhood of the pixel in the original image (identified
by the mask) are inserted in a list.
Step 2: This list is sorted in ascending (or descending) order.
Step 3: The median of the sorted list (i.e., the pixel in the middle of the list) is
chosen as the pixel value for the processed image.
As defined earlier, median filter create pixel values of the filtered image based on the sorting of the gray level of pixels in the mask around the central pixels in the original image.
Example 3.5
The performance of a 3 × 3 median filter on a subimage is illustrated in Figure 3.12.
As can be seen from Figure 3.12, the median filter selects the median of the graylevel values in the 3 × 3 neighborhood of the central pixel and assigns this value as
the output. In this example, the median filter is to select the median of following set:
{8 10 10 12 12 23 45 64}. According to the sorted list, the response of the filter is 12.
FIGURE 3.12 Mask of median filter.