www.emgu.com/wiki
result = val - this, using a mask

Declaration Syntax
Public Function SubR ( _
val As TColor, _
mask As Image(Of Gray, Byte) _
) As Image(Of TColor, TDepth)

Parameters
- val (TColor)
- the value which subtract this image
- mask (Image<(Of <(Gray, Byte>)>))
- The mask for substraction

Return Value
val - this, with mask
Assembly:
Emgu.CV (Module: Emgu.CV) Version: 1.3.0.0 (1.3.0.0)