2D Filter Options

Use

To...

Input, Output, Select region, Reset, Details,

Wavelengths

Specify input data and output parameters as shown in Image Input and Output.

Method

Select one of the following filters:

Median uses the image intensities within a box-shaped region around each pixel and selects the median value for the resulting image. The example below shows the results of a 3x3 median filter on a 4x4 image.

        Measured Image     Median Filtered Image

         1   3   2   2             2   2   2   2

         2   9   1   2             2   2   2   2

         3   3   2   2             2   2   2   2

         2   2   1   2             2   2   2   2

Use the median filter to remove pixels with noise-like intensity. In the example above, the pixel with intensity 9 is removed by the filter and doesn't affect the filtered image.

Mean is similar to the median filter except that the mean value is used instead of the median. For example, a 3x3 mean filter applied to the same measured image as above yields:

        Measured Image      Mean Filtered Image

         1   3   2   2             4   3   3   2

         2   9   1   2             4   3   3   2

         3   3   2   2             4   3   3   2

         2   2   1   2             3   2   2   2

The mean filter is sensitive to noise. The pixel with value 9 elevates the filtered intensities throughout the 3x3 region.

Variance calculates the statistical variance of the image about the mean intensity within the local region.

Weighted Mean is similar to the mean filter, except that mean is weighted by the variance.

Kernel Size

Specify the size, in pixels, of the square box used to calculate the filtered images. Increasing the kernel size increases the size of the local region that is used to calculate the filtered image. Kernel sizes of 3 and 5 are most useful.

Iterations

Specify the number of times to repeat the filter process.