[TYPO3-mvc] Invoke fileadmin in backend module

[alexandros I]

im building an extension using the extension_builder extension on typo3 6.1 for resizing images on-demand 
nothing too complicated i intend to have 

one select box for the selected images
one folder icon button to invoke the fileadmin window 
two fields for width and height 
a submit button 

i would like to use the fileadmin and as much as possible typo3 features but i have been unable to find any up-to-date documentation, tutorials, guides explaining how to achieve the desired result 

is it ok / safe if i just use native php function like opendir and scandir

any pointers are much appreciated 

alex