Thank you both very much.
If course I read the P5 documentation, but evidently did not understand the pixelDensity.
When I console log it, it say 2, so my extra factor of 4 is 2x2.
What it’s not clear to me is:
what use has this? I mean, if an image is 2x5 pixels, I have 10 pixels and RGBA for each tallies up to 40 elements of an array. If this is suddendly 4 times as long, what other information do i have in this 160 long array?!