These kind of fundamental methods in computer vision are commonly called "image processing".
"Computer vision" typically refers to computations that have an interpretative component (image analysis), i.e. programs that actually "see" something. Interpretation basically refers to the inference of the state of the "world" (or a part thereof) from an image. Image processing is often used in pre-processing for computer vision applications, but it also has many other purposes which do not need image analysis, such as in photo and video editing, as well as in generative applications, e.g. 3D engines and video games (which can in some sense be seen as the inverse of vision). Therefore, image processing is not exactly a subset of computer vision.
