Patent GB-1338867-A (GB)
Title: System for analysing engineering drawings or like documents
IPC: G06K9/00
Filed: 1972-03-30
Abstract: 1338867 Pattern recognition systems INTERNATIONAL BUSINESS MACHINES CORP 30 March 1972 [30 April 1971] 15244/72 Heading G4R A system for analysing a document, e.g., an engineering drawing, that carries both alphanumeric characters and other line images includes means for presenting the images as binary data and for examining the data to determine the area occupied by each respective image, an image then being classified as a character or as another form of line image according to the area occupied. As disclosed the document is scanned and binary signals representing the whole of the data on the document, or on a portion of it, are stored. For example, in the case of document 100, Fig. 3, a portion 101 is stored initially. In this portion there is graphic and character data as shown at 102, which represents the content of the input image store. The input image is examined in a sequence of horizontal scans starting at the top right hand corner. After a few blank scans the top of the graphic data is found. In this scan, e.g. scan 3, an unbroken sequence of black bits is found. These bits are erased from the input image store and transferred to a segment image store. At this point the input image is examined to determine whether there is any black bit vertically or diagonally contiguous to any of the black bits in scan 3. If there are two or more such bits separated by at least one white bit the scan line number (in this case 3) and the data in that scan line are recorded in an up and/or a down connection list as appropriate. The next scan, scan 4, now take place in a similar manner, but (as in all scans) only the right-most unbroken sequence of black bits is transferred to the segment image store. Scanning continues until a scan is reached at which no down connection is found. This scan must then be of the lowest part of the present segment of the image. The complete segment is in the segment image store as shown at 103 and has been erased from the input image which is now as at 105. The segment is transferred to a store 104 in which will be built up an object of which the present segment is a part. The down connection list is now examined to determine the starting point of the next rightmost segment, and this segment (shown at 106) is separated in a similar manner to the separation of the first segment, being deleted from the input image store as at 108 and added to the object store as at 107. Successive remaining right-most down connecting segments are similarly separated as in columns D, E, F. The up connection list is now examined and the up-connecting segments separated in turn as in columns G, H. At this point both the up and down connection lists are empty, indicating the completion of separation of the first object. Operations are now performed to determine whether the size of the object is such that it (a) can be fitted within a first square of preset size, in which case it is regarded as spurious data or noise, or (b) can be fitted within a second square larger than the first, in which case it is regarded as an alphanumeric character, or (c) can not be fitted within the second square, in which case it is regarded as a graphic object. Having been classified in this way the object image store content is read out to a data processor or character recognition unit. The segments of the image may be defined by their X, Y co-ordinates. There follows further scanning of the input image store in the manner described above to separate other objects. In the example shown numeral 4 at 113 is separated by two operations, indicated at J, K.  If the portion 100 of the document has only a small part of a line image within it, the remaining part of the image being in adjacent portions, the small part might be identified as spurious data. To prevent this successive portions to be scanned overlap (e.g., Fig. 10, not shown) so that the small part will be included in a subsequent portion.