Faster Array looping

I'm not quite sure I understand what you want to do - you want to just copy the 'old' buffer back into m?

I think the issue is that the image buffer itself has a really strange pixel order (because of the zigzag:true needed when sending to the LEDs, and also the setRotation(1)). You're then using that as data for drawImage which expects the data to be in a simple scanline format, and not rotated.

If you do just want to restore the old data, try:

var m = Graphics.createArrayBuffer(16,8,24,{zigz­ag:true});
m.flip = function(){ SPI2.send4bit(m.buffer, 0b0001, 0b0011); };
var mCopy = Graphics.createArrayBuffer(16,8,24,{zigz­ag:true});

// save data away
mCopy.buffer.set(m.buffer);
// copy it back
m.buffer.set(mCopy.buffer);

That should work, and would be way faster as it just copies the raw data rather than trying to encode/decode it into pixels.