# Noise Reduction

Gilles
Caulier

    caulier dot gilles at free.fr

2004-11-07
0.7.0

The digiKam image plugin Noise reduction is a tool for to reduce the image noise. It use the Despeckle algorithm taken from the Gimp, and copyrighted by Michael Sweet.

KDE
Digikam

# Introduction

This plugin provides selectable image filters to remove specs or other artifacts caused by junk such as dust or hair on the lens. Too, it can be used to remove small defects due to dust, or scratches, on a scanned image, and also Moire Effect on image scanned from a magazine. The following filters are available:

- Non-recursive median.

- Recursive median.

- Non-recursize adaptive median.

- Recursive adaptive median.

## Using the plugin

The image pannel and the original preview help you to pan within the image. 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. This window moves over image, and the color in it is smoothed, so imperfections are removed.

The Black Level and White Level controls adjust the levels used by the adaptive filter to adjust the filter radius. Black Level Removes pixels darker than set value, and White Level the pixels whiter.

The Adaptive button selects the adaptive median filter. This method varies the window size based upon the image content and sometimes improves the clarity of filtered images. It renders a result smoother than with Radius alone.

The Recursive buttons selects a recursive median filter for repeat filter action which gets stronger. This method generally provides smoother results, but may cause additional unwanted blurring.

## The plugin in action

This is an example of how the noise reduction can change your life. The original image is (1) and the corrected image is (2). The noise reduction was applied with Adaptive and Recursive filtering and a Radius of 3.

Noise reduction filter preview