Parameter

Description

Smoothing

Selects how to smooth the image before the threshold values are set. The following methods are available:

-

None

The image is not smoothed.

-

Lowpass

Applies the Lowpass method. The lowpass filter compares the brightness of each pixel to the brightness of its neighboring pixels. If a pixel is brighter than its neighbors, the brightness of this pixel is reduced and the brightness of the neighboring pixels is increased. This suppresses sharp changes in brightness (i.e. contours) and leads to more gradual changes in brightness.

-

Gauss

Applies the Gauss method. Each pixel is replaced by a weighted average of its neighbors. The weighting depends on the sigma value. The Gaussian filter is particularly useful for contour enhancement, which is very sensitive to noise. Using a Gaussian filter before finding contours greatly improves the results.

-

Median

Applies the Median method. Each pixel is replaced by the median of its neighbors. The number of neighboring pixels taken into account depends on the size. In a set of values (in this case the pixel values taken into account), the median is the value for which the number of larger values is equal to the number of smaller values.

Size

Only visible, if you have selected Low Pass or Median.
Sets the size of the filter matrix in the X and Y direction, i.e. the number of neighboring pixels taken into account. The size should correspond to the pixel size of the contours to be reduced.

Sigma

Only visible, if you have selected Gauss.
Sets the sigma value that defines how much neighboring pixels contribute to the weighting. Larger values broaden the applied Gaussian distribution and lead to reduced noise but also to an increased loss of image information.