Used Filters:

• Gaussian filter (5 different sigma) = 5 feature dimensions
• Sobel filter (5 sigma) = 5 feature dimension
• Gabor filter (6 theta, 1 different sigma, 2 different frequencies) = 12 feature dimensions
• Hessian filter (1 sigma) = 3 feature dimensions (one for derivative in direction xx, one for derivative in direction xy and one for derivative in direction yy)