Memory strided im2col

memory_strided_im2col.py

#from https://gist.githubusercontent.com/anirudhshenoy/5d99c087f0943b1306bbfedf4cc879a0/raw/2fe0cbbd4d70157db39a8eea1cefe77d960f4b06/memory_strided_im2col.py

from skimage.util.shape import view_as_windows

def memory_strided_im2col(x, kernel):
    output_shape = (x.shape[0] - kernel.shape[0]) + 1
    return view_as_windows(x, kernel.shape).reshape(output_shape*output_shape, kernel.shape[0]*2)
        #view_as_windows has an additional step parameter that can be used with different strides
### usage:
# input_matrix = np.array([[3,9,0], [2, 8, 1], [1,4,8]])
# kernel = np.array([[8,9], [4,4]])
# output_shape = (input_matrix.shape[0] - kernel.shape[0]) + 1
# mem_strided_mat = memory_strided_im2col(input_matrix, kernel) 
# mem_strided_conv = np.dot(kernel.flatten(), mem_strided_mat) + biasmem_strided_conv = mem_strided_conv.reshape(output_shape, output_shape)

#PS: x_newview = np.lib.stride_tricks.as_strided(x, shape = (5, 4), strides = (8,8))