transform a ArrayBuffer to an array

The issue is that you're using 1 bit per pixel, so 8 bits are in each byte - and you're trying to retrieve bytes. If you used:

var g = Graphics.createArrayBuffer(5,7,8, {zigzag:true});

Then I'm pretty sure that'll work fine. I'm not sure what you're planning but you may find you don't want the zigzag:true either, as that will make alternate scanlines reversed.