Figure 1 shows the despeckle plug-in window. The scrollbars allow you to pan within the image (in this case to the back of the duck in the foreground). The preview window shows the filter output using the current settings.

The Radius control selects the window size used for the filter, from 1 (3x3) to 20 (41x41). Larger values increase the amount of time needed to filter each pixel in the image and can cause blurring.

The Adaptive button selects the adaptive median filter - this filter varies the window size based upon the image content and sometimes improves the clarity of filtered images. The Black Level and White Level controls adjust the levels used by the adaptive filter to adjust the filter radius.

Figure 1 - The despeckle plug-in window

The Recursive buttons selects a recursive media filter. The recursive algorithm generally provides smoother results, but may cause additional unwanted blurring.

Figures 2-4 show how a corrupted image can be restored to almost the same clarity as the original. The despeckle settings for figure 4 were adaptive and recursive filtering with a radius of 3.

By using the Sharpen plug-in, you can also restore much of the original image detail as well.

Figure 2 - Original image

Figure 3 - Image with added noise

Figure 4 - Noisy image with recursive adaptive median filter applied