Recognition of symbols in grey level line-drawings from an adaptation of the Radon transform

An adaptation of the Radon transform is proposed to recognize grey level symbols. We directly process on the grey level document in order to improve the recognition step. A tridimensional signature is defined which takes into account the variations of photometry and the shape of a symbol. The proposed signature also allows to keep fundamental geometric transformations (scale, translation and rotation). Experimental results on technical documents show the promising aspect of our approach.