Identification of Annotations for Circuit Symbols in Electrical Diagrams of Document Images

Though annotations are integral part of symbols in drawings, due attention is yet to be given for their identification, interpretation, and storage. A reconstructed drawing from the vector format is thus deficient in the complete description of the original, and hence requires costly and time-consuming manual intervention. This paper presents a method for segmentation and identification of annotations associated with electrical symbols in a circuit diagram, which may be used with the vectorizer to make it complete. The proposed method first separates the text region around an intended circuit symbol, and then identifies the annotation part of the segmented text corresponding to that particular symbol. Morphological operations are used in identification phase. Finally, an efficient OCR is used to get the numerical values of the symbols along with their units. The performance of the algorithm is tested on a variety of images with ample variations in annotation. Some of the results are presented in this paper to demonstrate its efficiency.