Patent ID: 7778479

Claim:
A Gabor filter comprising: a first mask generator that generates a modified Gabor mask function by shifting a core frequency of an original Gabor mask function along at least one of an X-axis and an Y-axis by π; and a first filter that performs a convolution of an image with the modified Gabor mask function to generate a first filtered image, wherein modification of the original Gabor mask function to the modified Gabor mask function reduces a number of calculations during the convolution within the first filter; and wherein the modified Gabor mask function has a zero-value for half of coordinate points, and wherein the first filter does not perform a calculation for the zero-values of the modified Gabor mask function during the convolution; and wherein the modified Gabor mask function is expressed as: g 1 ⁢ L ⁡ ( x , y , θ i , f j ) = 1 2 ⁢ { h ⁡ ( x , y , θ i , f j ) + ( ⅇ jπ ) x + y ⁢ h ⁡ ( x , y , θ i , f j ) } ⁢ ⁢ with ⁢ ⁢ h ⁡ ( x , y , θ i , f j ) being the original Gabor mask function that is expressed as: exp ⁢ { - 1 2 ⁡ [ ( x ⁢ ⁢ cos ⁢ ⁢ θ i ) 2 δ x 2 + ( y ⁢ ⁢ sin ⁢ ⁢ θ i ) 2 δ y 2 ] } ⁢ cos ⁢ { 2 ⁢ π ⁢ ⁢ f j ⁡ ( x ⁢ ⁢ sin ⁢ ⁢ θ i + y ⁢ ⁢ cos ⁢ ⁢ θ i ⁢ ) } ; with x and y respectively denoting X and Y coordinates; θ i and f j respectively denoting an orientation and a frequency; and δ x and δ y respectively denoting Gaussian standard deviations along the X and Y coordinates.