10. The method of claim 5 , wherein the comparison score is further based on a significance of the reference image, and wherein the significance of the reference image is a classification confidence g(x ij ) that can be computed according to g ⁡ ( x ij ) = l i ⁡ ( x ij ) - l i * ⁡ ( x ij ) max ⁢ { l i ⁡ ( x ij ) , l i * ⁡ ( x ij ) } , with ⁢ ⁢ i * = arg ⁢ ⁢ max k ≠ i ⁢ ⁢ l k ⁡ ( x ij ) .
10. The method of claim 5 , wherein the comparison score is further based on a significance of the reference image, and wherein the significance of the reference image is a classification confidence g(x ij ) that can be computed according to g ⁡ ( x ij ) = l i ⁡ ( x ij ) - l i * ⁡ ( x ij ) max ⁢ { l i ⁡ ( x ij ) , l i * ⁡ ( x ij ) } , with ⁢ ⁢ i * = arg ⁢ ⁢ max k ≠ i ⁢ ⁢ l k ⁡ ( x ij ) . 11. The method of claim 10 , wherein the comparison score κ(x,x ij ) can be described according to 
 κ( x,x ij )=λ·κ on ( x,x ij )+(1−λ)· g ( x ij ), where κ on (x,x ij ) is a function that compares the lower-dimensional reprentation of the query image to the combined representation of the reference image, where g(x ij ) is the classification confidence, and where γ is a weighting parameter.