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Image applications require complex processing on large amounts of data. The application designer is presented with difficult challenges that are exacerbated on personal systems which have limited processor speed and constrained memory. This paper discusses the problems relevant to personal systems image application architecture and how these problems were solved in the ImagEdit® program. A virtual array manager (VAM) consisting of a virtual memory manager (VMM) and an access scheduler was used to solve the data management problem. The VAM divided each image into segments and transferred them to the VMM for storage. These segments were swapped between memory and disk in response to a sequence of access requests, controlled by the access scheduler using performance-maximizing heuristics. Object-oriented design was used to address the functional complexity problem. The processing functions were divided into two classes. The data-stream class included scanning, printing, and filing, with each data-stream function decomposed into a series of demand-driven pipe objects. The editing class included cut and paste, textual and graphical annotation, and freehand drawing.
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