This function computes and (by default) displays a histogram
of the pixel values in the image x.
An object of class "im"
describes a pixel image. See im.object)
for details of this class.
The function hist.im is a method for the generic
function hist for the class "im".
Any arguments in ... are passed to hist.default.
For example, such arguments control the axes, and may be used to
suppress the plotting.