I'd love to see your code. In particular, I'd like to see what you did with "I could just directly assign the data I read from the SD card to the internal buffer of the LED library instance and display it."
self._np.buf = column
self._np.write()
Where column is a list of RGB (or RBG) pixel values like [128, 255, 0, 255, 0, 0, 128, 15, 200].