what is the easiset way of writing pixel_data (RGB or gray-value) into arrays?

I've tried it by scanning the file using pix_data object.
my patch scans and writes y values for each x sequentially:
for x0 from y0 to yn;
for x1 from y0 to yn;
.
.
for xn from y0 to yn.

I believe there should a better and easier way to this job. Could you advise me?

http://www.pdpatchrepo.info/hurleur/pix_data2array.pd

i guess it depends on what you want to do with those values. give a look at the gridflow library, it's the best option for pixel matrix processing.