How can I work with my own dataset in scikit-learn (for computer vision)?

How can I work with my own dataset in scikit-learn? Scikit Tutorial always take as example to load his dataset (digit dataset, flower dataset...)

http://scikit-learn.org/stable/datasets/index.html ie: from sklearn.datasets import load_iris

I have my images and I have no idea how create new one.

Particularly, for starting, i use this example i found (i use library opencv):

img =cv2.imread('telamone.jpg')

# Convert them to grayscale
imgg =cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

# SURF extraction
surf = cv2.SURF()
kp, descritors = surf.detect(imgg,None,useProvidedKeypoints = False)

# Setting up samples and responses for kNN
samples = np.array(descritors)
responses = np.arange(len(kp),dtype = np.float32)

I would like to extract features of a set of images, in a way useful to implement a machine learning algorithm!