Texture transformation

Question

I am working on eigen transformation - texture to detect object from an image. This work was published in ACCV 2006 page number 71. Full pdf is available on chapter-3 in this pdf https://www.diva-portal.org/smash/get/diva2:275069/FULLTEXT01.pdf. I am not able to follow after getting texture descriptors. I am working on the attached image. The image size is 9541440. I took image patches of 3232 and for every patch calculated eigenvalues and got the texture descriptor. After that what to do with these texture descriptors is what I am not able to follow. Any help to unblock will be really appreciated. Code looks for calculating descriptors looks like below:

descriptors = np.zeros((gray.shape[0]//w, gray.shape[1]//w))
w = 32
for i in range(gray.shape[0]//w):
    temp = []
    for j in range(gray.shape[1]//w):
        sorted_eigen = -np.sort(-np.linalg.eigvals(gray[i*w: 
                                (i+1)*w,j*w:(j+1)*w]))
        l = i*w + 13
        k = (i+1)*w
        theta_svd = (1/(k-l+1))* np.sum([np.abs(val) for val in s[l:k]])
        descriptors[i,j] = theta_svd