Palimpsest: A layered language for exploratory image processing

• This paper presents a novel purely-visual programming paradigm for image manipulation with constraint semantics.
• The design rationale demonstrates a user-oriented approach to transition from direct manipulation to programming.
• The feasibility of the paradigm is illustrated with a description of system implementation and evaluation.
• The text-free constraint paradigm is well-suited to coming generations of visual touch interfaces.

Palimpsest is a novel purely-visual language intended to support exploratory live programming. It demonstrates a new paradigm for the visual representation of constraint programming that may be appropriate to future generations of keyboardless and touchscreen devices. The current application domain is that of creative image manipulation, although the paradigm can support a wider range of computational expression. The combination of constraint semantics expressed via a novel image-layering metaphor provides a new approach to supporting a gradual slope of abstraction from direct manipulation to behaviour specification. Exploratory evaluations with a range of users give an indication of likely audiences, and opportunities for future development and application.