Noise reduction in Showfoto

Tutorial by ChromaticOrb

Introduction

Showfoto is the stand alone photo editing program for digiKam. Among it's features, it allows us to apply noise reduction to digital photos in two ways:

  1. Fix -> Noise Reduction
    This is an implementation based on the dcamnoise2 GIMP plugin, modified to support 16bit images[1].
  2. Fix -> Restorarion
    This uses the GREYCstoration algorithm included in the CImg library.

In this simple tutorial we'll be using the dcamnoise2 approach as it's results are quite good and the GREYCstoration plug-in is really too slow to be comfortable to work with.

The process

The dcamnoise2 algorithm was implemented on digiKam 0.9 so we need this version or greater

cb_noise.jpg
100% crop from a noisy image

1. Open the dcamnoise2 noise reduction plug-in (Fix -> Noise Reduction)

showfoto_noise1.jpg

2. Adjust the settings in order to get the best results.

  • Radius sets the size of the blur kernel. Larger values mean more aggressive noise reduction but also mean a more blurry image.
  • Threshold limits the number of pixels that will be affected by the blur.
  • Texture
  • Sharpness controls the amount of sharpening to compensate the blur.
  • Edge Lookahead is used to limit the blurring. Higher numbers result in sharper images but reduce the amount of nosise reduction.
    • Erosion

3. I was satisfied by changing Radius=3.0, Threshold=0.07 and Sharpness=40.00, keeping all others values at default values.

Result

cb_noise.jpg cb_noise_removed.jpg
Before After
Bibliography
1. New image editor noise reduction plugin..., Gilles Caulier, digiKam-users mailing list.
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