flowtools.py 文件源码

def imresize(img, sz):
    """
    Resize image

    Input:
        img: A grayscale image
        sz: A tuple with the new size (rows, cols)

    Output:
        Ir: Resized image
    """
    if np.all(img.shape==sz):
        return img;

    factors = (np.array(sz)).astype('f') / (np.array(img.shape)).astype('f')

    if np.any(factors < 1):               # smooth before downsampling
        sigmas = (1.0/factors)/3.0
        #print img.shape, sz, sigmas
        I_filter = ndimage.filters.gaussian_filter(img,sigmas)
    else:
        I_filter = img

    u,v = np.meshgrid(np.arange(0,sz[1]).astype('f'), np.arange(0,sz[0]).astype('f'))
    fx = (float(img.shape[1])) / (sz[1])     # multiplicative factors mapping new coords -> old coords
    fy = (float(img.shape[0])) / (sz[0])

    u *= fx; u += (1.0/factors[1])/2 - 1 + 0.5    # sample from correct position
    v *= fy; v += (1.0/factors[0])/2 - 1 + 0.5

    # bilinear interpolation
    Ir = ndimage.map_coordinates(I_filter, np.vstack((v.flatten().transpose(),u.flatten().transpose())), order=1, mode='nearest')
    Ir = np.reshape(Ir, (sz[0], sz[1]))
    return Ir