im2col.py 文件源码

def get_im2col_indices(x_shape, field_height, field_width, padding=1, stride=1):
    # First figure out what the size of the output should be
    N, C, H, W = x_shape
    assert (H + 2 * padding - field_height) % stride == 0
    assert (W + 2 * padding - field_height) % stride == 0
    out_height = (H + 2 * padding - field_height) / stride + 1
    out_width = (W + 2 * padding - field_width) / stride + 1

    i0 = np.repeat(np.arange(field_height), field_width)
    i0 = np.tile(i0, C)
    i1 = stride * np.repeat(np.arange(out_height), out_width)
    j0 = np.tile(np.arange(field_width), field_height * C)
    j1 = stride * np.tile(np.arange(out_width), out_height)
    i = i0.reshape(-1, 1) + i1.reshape(1, -1)
    j = j0.reshape(-1, 1) + j1.reshape(1, -1)

    k = np.repeat(np.arange(C), field_height * field_width).reshape(-1, 1)

    return (k, i, j)