Creates a new instance of Gray16LinComb which will form the linear combination of
two images by calculating (nA * first image + nB * second image) / nC.
Gray32SubImage is used to represent a rectangular region extracted from
a larger Gray32Image, retaining the x and y position where the image was
extracted.
Gray8SubImage is used to represent a rectangular region extracted from a larger
Gray8Image, retaining the x and y position where the subimage was extracted.
Pipeline stage modifies a gray image's pixel values to make its histogram
match a target histogram (to the extent this is possible while uniquely
mapping each input grayvalue).