best way to get the shape of the leaves

hello everybody, i need your suggestion now im using gabor filter meanAmplitude msEnerg and wavelet transformation to get the shape of the leaves and knn for classification

it gives a good result if you test the leaves with almost the same shape of leaves saved in the database but if the leaves is smaller than the leaves save in the database sometimes it gives wrong result and also if you rotate the leaf it will give wrong result also.

can you guys give me a suggestion on what should i do to resolve my problem?

i attached some leaf that are saved in my database