4.9. Despeckle

4.9.1. Overview

This filter is used to remove small defects due to dust, or scratches, on a scanned image, and also moiré effects on image scanned from a magazine. You should select isolated defects before applying this filter, in order to avoid unwanted changes in other areas of your image. The filter replaces each pixel with the median value of the pixels within the specified radius.

4.9.2. Activating the filter

You can find this filter through Filters → Enhance → Despeckle….

4.9.3. Options

Figure 17.47. “Despeckle” filter options

Preview

If checked, parameter setting results are interactively displayed in preview.

Median

• Adaptive

  Adapts the radius to image or selection content by analyzing the histogram of the region around the target pixel. The adapted radius will always be equal to or smaller than the specified radius.

  Recursive

  Repeats filter action which gets stronger.

Radius

Sets size of action window from 1 (3x3 pixels) to 20 (41x41). This window moves over the image, and the color in it is smoothed, so imperfections are removed.

Black level

Only include pixels brighter than the set value in the histogram (-1-255).

White level

Only include pixels darker than the set value in the histogram (0-256).