Come applicare un DCT a un'immagine in Python?

Question

Voglio applicare una Trasformata Coseno Discreta (e l'inverso) a un'immagine in Python e mi chiedo quale sia il modo migliore per farlo e come. Ho guardato PIL e OpenCV ma ancora non capisco come usarlo.

Answer 1

Da OpenCV:

 
DCT(src, dst, flags) → None 

    Performs a forward or inverse Discrete Cosine transform of a 1D or 2D 
    floating-point array. 

    Parameters: 

     src (CvArr) – Source array, real 1D or 2D array 
     dst (CvArr) – Destination array of the same size and same type as the source 
     flags (int) – 

     Transformation flags, a combination of the following values 
      CV_DXT_FORWARD do a forward 1D or 2D transform. 
      CV_DXT_INVERSE do an inverse 1D or 2D transform. 
      CV_DXT_ROWS do a forward or inverse transform of every individual row of 
the input matrix. This flag allows user to transform multiple vectors simultaneously 
and can be used to decrease the overhead (which is sometimes several times larger 
than the processing itself), to do 3D and higher-dimensional transforms and so forth. 

Here is an example of it being used.

Il DCT è disponibile anche in scipy.fftpack.