Geometry.GetRenderBounds Method (Pen)
Returns an axis-aligned rectangle that is exactly large enough to contain the geometry after it has been outlined with the specified Pen.
Assembly: PresentationCore (in PresentationCore.dll)
This method uses the default tolerance factor (described by the StandardFlatteningTolerance property) when processing the geometry. To specify your own tolerance factor, use the GetRenderBounds method.
Some Geometry methods (such as GetRenderBounds) produce or use a polygonal approximation of the geometry. The tolerance factor specifies the maximum distance between points in this polygonal approximation. Smaller tolerance values produce better approximations, but require more processing than an approximation with a large tolerance factor.