Editing images of text

went advances in image scanning, storage, and retrieval have stimulated interest in incorporating scanned documenu within elecaonic document systems. Integrating scanned documents with structured documenu is an important step toward making electronic document processing universally available. Most approaches to this problem are based on one of two paradigms-bitmap editing and format conversion. Conventional bitmap editors and paint programs treat scanned images as simple pixel arrays without internal structure. A major strength of this approach is that bitmap editors are applicable to an open-ended class of images. Moreover, almost by definition they preserve the detailed format and typographic design of the input material. In particular, if distortions due to scanning and printing are ignored, a bitmap editor behaves as an identity system if no editing operations are performed. There are numerous scenarios in which editing an image while preserving the appearance of unedited material is important. In general, such scenarios involve documenrs that originate in image form and are to be retained in image form after modification. Examples include last-minute correction of spelling mistakes before photocopying, modiing viewgraphs at meetings, exchange of document drafts by fax, and recreational forgery (the construction of obvious parodies for humorous purposes). While it would seem that bitmap editors are ideally suited to such applications, in practice their utility is often limited. The primary problem is that current bitmap editon support only relatively low-level editing operations. Typical facilities include selection of polygonal regions; cutting, pasting and copying selected regions; and painting operations such as bit setting, clearing, and complementation. No attempt is made to classify the content of the image (e.g., as text or line art) and no operations are pm tided that assist higher-level content-specific operations. Thus, for example, using a paint program to delete a character from the middle of a word