When used as the Image.ColorModel operator, this operator uses its parent Image as the source, unless a different source image is provided in the optional parameter. If another image is passed as a parameter to one of its methods, it is used as the source of the operation. The result is usually a new image.
It can also be created independently using CreateOperator. In this case the operator does not have a parent and the parent image to be used as the source must be supplied in the parameter.
