image() slow if auto_write on

[caternuson]

The image() function does a loop and sets the display pixel by pixel:

Adafruit_CircuitPython_HT16K33/adafruit_ht16k33/matrix.py

Lines 145 to 147 in 4eed803

	for x in range(self.columns): # yes this double loop is slow,
	for y in range(self.rows): # but these displays are small!
	self.pixel(x, y, pixels[(x, y)])

If auto_write is on, this will cause the entire display to be updated with each pixel set:

Adafruit_CircuitPython_HT16K33/adafruit_ht16k33/ht16k33.py

Lines 138 to 139 in 4eed803

	if self._auto_write:
	self.show()

This leads to a noticeably slow update.

Could maybe force auto_write off before looping and then back to whatever it was after the loop.

[makermelissa]

That's how I would do it. :) Don't forget to apply the same thing in the Matrix8x8x2 class's image() function.