where can find documentation this?

i trying option:

-format "%[pixel: u.p{1,1}]"

and gets pixel 1,1.

how pixel @ 100% of image, tried:

-format "%[pixel: u.p{100%,100%}]" -format "%[pixel: u.p{-1,-1}]"

i reading this, difficult understand pixel entry says:

p = pixel use (absolute or relative current pixel)

context

the complete command using is:

color=`convert ~/desktop/my_image.png -format "%[pixel: u.p{-1,-1}]" info:`

and trying color in last pixel of image.

by looking @ documentation suggest try u.p{w-1,h-1}

IO