hi thanks to IOhannes indications i'm feeding my pix_mulitblob output into the iemmatrix now. as long as there're enough blobs in the picture it works pretty nice. but as soon as there're less blobs than given in the argument to pix_multiblob i get: error: $43: argument number out of range error: $44: argument number out of range ... for all the arguments of undetected blobs. and as soon as there's no blob in the picture the pd-shell reports: matrix : corrupt matrix passed do i do something wrong? i was using the attached patch thanks for help & hints olsen