'given image index, return full path
Parameters:
index: int
index of a specific image
Returns
path of this image'

def image_path_from_index(self, index):

    name = self.image_set_index[index]
    if self.extension:
        name += self.extension
    if self.root_dir:
        name = os.path.join(self.root_dir, name)
    assert os.path.exists(name), 'Path    does    not    exist:    {}'.format(name)
    return name
