### 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 images 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.

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If the image is in indexed mode, this menu entry is disabled.

#### 4.9.2. Activating the Filter

This filter is found in the main menu under Filters → Enhance → Despeckle….

#### 4.9.3. Options

شكل 17.51. “Despeckle” filter options

Preview

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

Filter Type
  Median

    The median value of the pixels within the set Radius around the target pixel is used to replace the target pixel value.

  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-Median

    Repeats the Median filter action to get a stronger effect.

  Recursive-Adaptive

    Repeats the Adaptive filter action to get a stronger effect.

Radius

  Sets size of action window from 1 (3×3 pixels) to 20 (41×41). 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).

4.8. Sharpen (Unsharp Mask) |  | 4.10. NL Filter

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