imagetools.py 文件源码

def sparsify(x, percentage):
    """
    Keeps only as many entries nonzero as specified by percentage.
    Note that only the larges values are kept.

    --------------------------------------------------------------------------
    Usage:

    Call:  y = sparsify(x, percentage)

    Input: x            input ndarray x
           percentage   percentage of nonzero entries in y 

    Output: sparsified version of x            
    --------------------------------------------------------------------------

    Copyright (C) 2011 Michael Hirsch   
    """
    vals = np.sort(x.flatten())[::-1]
    idx  = np.floor(np.prod(x.shape) * percentage/100)
    x[x < vals[idx]] = 0

    return x