The Width command returns the width information of the image img.

$\mathrm{with}\left(\mathrm{ImageTools}\right)\:$

$\mathrm{img}≔\mathrm{Create}\left(10..59\,-100..100\right)\:$

$\mathrm{Width}\left(\mathrm{img}\right)$

$201$

$\mathrm{map2}\left(\mathrm{Width}\,\mathrm{img}\,\left[\mathrm{size}\,\mathrm{lower}\,\mathrm{upper}\,\mathrm{range}\right]\right)$

$\left[201\,\mathrm{-100}\,100\,\mathrm{-100}..100\right]$