I'm working with a grey-scale data-collection of Hebraic tombstones in content-based image retrieval CBIR). For example an image like this tombstone. I'm going to reduce the content of the image to the centered tombstone. And after some other processing steps I'm trying to find a suitable representation of this image to enable CBIR. So far SIFT and SURF were good detectors but others like MSER fail to produce good results. The problem is the heterogeneity of the data-collection (6.700 picture of different tombstone with different shapes, symbols, ornaments and Hebraic letters).
Does anyone can give me a hint which pattern-recognition approach might be suitable? OCR won't do.
Thank for your help! If you need more picture, take a look around at the institue of German-Jewish history.