Kantenerhaltende Filter
Siril offers two edge preserving filters: OpenCV's implementation of the Bilateral Filter, and a Guided Filter. Both of these filters can be used to reduce noise, and both preserve sharp edges and strong gradients in the image. The bilateral filter acts on a single image whereas the guided filter filters the image using a guide image to identify structures. In the simplest use, the guided filter acts in a self-guided manner by using the input image as the guide image.
Dialogbox Median Filter.
Der Aufbau des Fensterdialogs ist recht einfach und es sind nur wenige Einstellungen möglich.
Filter type: Choose between the bilateral filter and the guided filter.
Diameter: This defines the size of the filter kernel that will be used. When using the bilateral filter, setting a diameter of 0 will cause the filter kernel size to be set automatically based on the spatial sigma value. When using the guided filter this value must be set: a diameter of 0 will result in no filtering being done.
Sigma (spatial): This defines the spatial extent of the filter kernel. A larger value results in smoothing of noise over a greater image area, but is slower to compute. A smaller value results in more local smoothing and is faster to compute. Defaults are not set for the sigma values as the appropriate value may depend significantly on image characteristics, but it can be good to start with both sigma (spatial) and sigma (intensity) set to about 11.
Sigma (intensity): This defines the range of intensity variation to which the filter responds. A high value results in stronger filtering of noise but may result in loss of genuine detail; a low value reduces the filtering of noise, but will avoid loss of details with gentler gradients.
Guide image: This allows selection of an image to use as a guide image when performing a guided filter. If the "self guided" check box is checked, the filter acts in self-guided mode using the input image as the guide image.
Modulation: In Siril ist die Modulation ein Parameter zwischen 0 und 1, der das Originalbild und das bearbeitete Bild mischt. Bei einem Wert von 1 bleibt nur das verarbeitete Bild erhalten, bei einem Wert von 0 wird überhaupt kein kantenbewahrender Filter angewendet.
Showing the effect of changing the bilateral filter parameters. Note that the exact values required will depend on the noise characteristics of your data.
Tipp
The parameters to the two different filter types do not behave identically, so when changing between bilateral and guided filters with sigma parameters set, you should expect to see some change in the preview result. The code applies a bit of compensation to the parameters provided to minimize the difference in behaviour of the two filters for the same input parameters but this is not exact (nor is it intended to be).
Siril Kommandozeile
epf [-guided] [-d=] [-si=] [-ss=] [-mod=] [-guideimage=]