When involved in the visual design of graphical user interfaces, graphic designers can do more than providing static graphics for programmers to incorporate into applications. We describe a technique that allows them to provide examples of graphical objects at various key sizes using their usual drawing tool, then let the system interpolate their resizing behavior. We relate this technique to current practices of graphic designers, provide examples of its use and describe the underlying inference algorithm. We show how the mathematical properties of the algorithm allows the system to be predictable and explain how it can be combined with more traditional layout mechanisms. ACM Classification: H5.2 [Information Interfaces and Presentation] User Interfaces — GUI; D2.2 [Software Engineering] Design Tools and Techniques; D2.6 [Software Engineering] Programming Environments. General terms: Design, Human Factors, Languages