Vector-based segmentation of text connected to graphics in engineering drawings

Abstract

A method for segmentation of text that may be connected to graphics in engineering drawings is presented. It consists of three steps: growing individual characterbox regions, using a recursive merging scheme by stroke linking; merging the detected characterboxes into a textbox and determining its orientation; and re-segmenting the textbox back into the refined characterbox that can be input to an OCR subsystem. The method can segment dimensioning text as well as other classes of text. It handles both isolated and touching characters, aligned at any slant. The capability of segmenting characters that touch either themselves or graphics, which is an important feature in handling real life drawings, is obtained by focusing on intermediate vector information rather that on tile raw pixel data. We present tile details of tile algorithm and show both successful and unsuccessful exvanples from an experimental set of 36 dimensioning textboxes, in which 94% segmentation rate was achieved with 3% false alarm rate.